International Rice Research Notes Vol.19 No.3

International Rice Research Notes

The International Rice Research Notes (IRRN) expedites communication among scientists concerned with the development of improved technology for rice and rice- based systems.

to help scientists keep each other informed of current rice research findings. The concise scientific notes are meant to encourage rice scientists to communicate with one another to obtain details on the research reported.

The IRRN is published quarterly in March, June, September, and December by the International Rice Research Institute; annual subject and variety indexes are also produced.

The IRRN is divided into three sections: notes, news about research collaboration, and announcements.

The IRRN is a mechanism

ISSN 0115-0944

Contents September 1994

Germplasm improvement

Breeding methods 4 Heterotic hybrid combinations identified for

commercial exploitation of hybrid vigor in rice 4 Tropical japonica lines as Improved sources of

wide compatibility trait in rice ( Oryza saliva L.) 5 Natural outcrossing potential In cytoplasmic

male sterile Iines of rlce 6 Evaluation of cytoplasmlc male sterile and

maintainer lines in Cuu Long Delta, Vietnam 6 A specific esterase band found in Annong-1S 7 Effect of maltose and hormones on callus

formation and plant regeneration in Isolated microspore culture of japonica rlce ( Oryza sativa L.)

8 Restorers and maintainers for four cytoplasmic male sterile lines of rice

8 Improvement in anther culture of japonca/indica crosses of rice

Pest resistance 9 Evaluation of selected cultures for resistance to

rlce tungro disease and its vector, green leafhopper

pests in Raipur, India

Pest resistance—diseases 11 Analysis of bacterial blight resistance genes in

11 Screening rice varieties for reslstance to rlce

12 ldentifying reslstance genes for bacterlal blight

13 Analysis of reslstance gene for blast in Chengte

three japonica rice varieties

yellow mottle virus in Kenya

in Chengte 232

232

Pest resistance—insects 14 Screening of rice hybrids for resistance to

whitebacked planthopper, Sogatella furcifera (Horvath)

thrips

with different resistance genes

14 Screenlng rice accessions for resistance to

15 Reslstance to green leafhopper in rice varletles

Pest resistance—other pests 16 New ufra-resistant rice lines

Integrated germplasm improvement 16 Twelve new rice varieties released for Orissa

State, lndia

Integrated germplasm improvement—irrigated 18 Rajavadlu and Sagar-Samba released in Andhra

18 Pakhal: a high-yielding, short-duration rice variety

18 ADT42: a new high-yielding, early-duration rice

19 CORH1: the first rice hybrld for Tamil Nadu, India

Pradesh, India

for Hazara division in Pakistan

for Tamil Nadu, lndla

Integrated germplasm improvement— rainfed lowland 20 Performance of lowland transplanted sali

(winter) rice varletles under late planting in Assam, India

Crop and resource management

Fertilizer management 21 Integrated N management in irrigated lowland

21 Evaluating Sesbania and urea supergranules vs rice

prilled urea in rice and their residual effect on the succeeding wheat crop

amelioratlng highly sodic soil and on yields of rice and wheat

22 Effects of gypsum, farmyard manure, and N on

Fertilizer management—inorganic 24 Modified urea forms evaluated in lowland rlce 24 Fertilizer scheduling and economics of varietal

25 Resldual effects of P on wheat in a rlce - wheat mixtures of rice

sequence

Crop management 26 Stand establishment practices affect

performance of intermediate deepwater rice

Integrated pest management— diseases 27 Widespread ufra disease incidence in different

28 Effect of temperature and light on growth and rice ecosystems in Bangladesh

sporulation of fusarium rice sheath rot

Integrated pest management—insects 29 Effects of Beauveria bassiana Vuill. and

Metarhizium anisopliae Sorok on brown planthopper (Nilaparvata lugens Stål) in Vietnam

29 Whitebacked planthopper feeding on rlce seedlings treated with uniconazole

Integrated pest management—other pests 30 Aphelenchoides besseyi in irrigated upland and

lowland rice during dry and wet seasons 30 The combination of nematodes, Sesbania

rostrata, and rice: the two sides of the coin

page 30

10 Reactions of advanced IET rice varieties to major

Environment

31 32 32 33

33 34 35 36 37 38

39

39

40

41

43

44

45

46

Methane emission from ricefields Measuring methane emission Effect of rice cultivars on methane emission Diel and seasonal patterns of methane fluxes in ricefields Effect of fertilization on methane emission Effect of cultural practices on methane emission Dissolved methane in soil solution Ebullition of methane Methane production potential of soils Predicting methane production in wetland rice soils A simple process-based model to predict methane emission from flooded fields Possibilities for reducing methane emission from ricefields in China Effects of heat balance on methane emission in rice plant canopy Impact of gypsum application on methane emission from a wetland ricefield Effects of carbon dioxide and temperature on methane emission of rice Control and monitoring of rice experiments in closed environmental chambers using a distributed network of dataloggers Environmental factors affecting rice responses to elevated carbon dioxide concentrations Responses of rice to elevated levels of carbon dioxide

in response to carbon dioxide and temperature 48 Carbon dioxide and nitrogen fertilizer effects on

rice canopy carbon exchange, growth, and yield 49 Effects of carbon dioxide on competition

between rice and barnyard grass 50 A very simple model of crop growth. derivation

and application 52 Climate change and rice production in India 52 Photosynthesis and stomatal conductance in rice

53 Impact of global warming on rice production in

47 Modeling leaf and canopy photosynthesis of rice

as affected by drought stress

Egypt

54 Lipid peroxidation and superoxide dismutase activity in rice leaves as affected by ultraviolet-B radiation

abscisic acid and indoleacetic acid content of rice leaves

associated with effects of enhanced ultraviolet- B and temperature changes in the Philippines

56 Effect of elevated ultraviolet-B radiation on

57 Risk analysis of rice leaf blast epidemics

Research methodology

58 How to adjust grain yield to 14% moisture

58 A new method for transporting Azolla culture content

collections

News about research collaboration

59 59 59 59

60 60

60 60

Forest-friendly stove a success using free fuel Training center opens in Lao PDR Understanding rice yield potential Former Soviet states request rice research support from IRRI Vietnam awards IRRI with Friendship Order Rice training network proposed by Asian countries First-time release of hybrid rice in lndia Rice germplasm exchange program proposed for the Mediterranean and West and Central Asia

Announcements

61 61 61 62 62 62 62 62

page 31

Rice dateline Postdoctoral research fellowship at IRRI New IRRI publications New publications IRRI group training courses for 1994 Rice literature update reprint service IRRI address Call for news

page 32

~

Rice and climate change: a glimpse into the future

In the next century, food will

be produced amid the

uncertainty of changes in the world's climate. How will rice, the world's most

important food crop, respond to these changes?

In March 1994, IRRI convened an international

sumposium that reviewed the broad issues of global climate change and its effect on rice growth and production. Based on research conducted by

scientists at IRRI and other

institutions, participants assessed how rice may be affected by ultraviolet-B radiation, increases in carbon dioxide, and

potential increases in global temperature. They also discussed the possible contribution of rice cultivation to climate change through the emission of

methane and other greenhouse gases.

The key papers pre- sented at the Climate Change and Rice Sympo-

sium are being published as a book by Spring-Verlag. The posters displayed at

the symposium appear in a slightly modified form in the Environment section of this issue of IRRN. We hope you

find these notes to be a

valuable information source.

We attempted to identify some elite hybrid combinations by crossing three cytoplasmic male sterile (CMS) lines, V20 A, IR58025 A, and IR62829 A, with 33 known restorer lines from Indian germplasm. The 99 F 1 s produced using line × tester design were evaluated along with 36 parental lines during 1992 wet season (WS) at the Directorate of Rice Research (DRR), Hyderabad.

The experiment was laid out in a completely randomized block design. Each entry was replicated three times. Hybrids and parents were transplanted in rows of 20 plants at 20- × 15-cm spacing and fertilizer applied at 100-60-40 kg NPK/ha following recommended practices. We recorded days to 50% flowering for each replication of each culture. Grain yield per plant was assessed by taking the mean yield of five randomly selected plants in each replication.

Twenty-two of the cross combinations exhibited standard heterosis of >20% over the check, Jaya (see table). Among the hybrids tested using V20 A as the female, V20 A/UPR254-85-ITCA showed high standard heterosis (42.4%) over Jaya. We identified 13 heterotic cross combinations using IR58025 A as

Germplasm improvement

the female (see table). IR62829 A/ Chianungsenyu, IR62829 A/Mahsuri, and IR62829 A/Vajram were the best among the crosses using IR62829 A as the female.

Heterotic hybrid combinations identified for commercial exploitation of hybrid vigor in rice P. V. Satyanarayana, Hybrid Rice Division, Agricultural Research Station, Maruteru 534122, Andhra Pradesh, India; I. Kumar and M. S. S. Reddy, Genetics and Plant Breeding Department, College of Agricul- ture, Andhra Pradesh Agricultural University, Rajendranagar, Hyderabad 500030, lndia

Performance of elite rice hybrids showing yield heterosis of >20% over Jaya. DRR, Hyderabad, lndia 1992 WS.

Days to Grain yield/plant (g)

flowering X Standard

Jaya (%)

V20 A/Vajram (MTU5249) 91 19.6 24.2**a

V20 A/lri 316 R 91 19.2 21.5**

Cross 50%

X heterosis over

V20 A/lR2797-125 93 21.8 37.9** V20 A/UPR254-85-ITCA 81 22.6 42.4** lR58025 A/IR9761-19-1 R 101 22.4 41.1** lR58025 A/Vajram (MTU5249) 92 24.0 51.8** lR58025 A/IR13419-13-10 R 100 19.6 22.8** lR58025 A/lR28178-70-2-3 101 21.9 38.7** lR58025 A/Chianungsenyu 90 20.4 29.1** lR58025 A/Suweon 318 R 96 24.0 51.8** lR58025 A/ARC 11353 R 101 23.0 45.6** lR58025 A/Suweon 287 R 108 27.8 75.9** lR58025 A/HKR119 93 20.9 32.3** IR58025 A/NST200 99

lR58025 A/T1154 79 lR58025 A/IET9188 100 lR62829 A/Vajram (MTU5249) 92 lR62829 A/IR13419-13-10R 94

lR58025 A/BR51-91-7 84 24.1 52.5** 19.5 23.4** 22.3 41.3** 22.8 44.3** 22.3 40.8** 20.5 29.8**

lR62829 A/lR35366-40-3-3 lR62829 A/Chianungsenyu lR62829 A/Mahsuri Jaya (check)

87 20.8 31.6** 87 26.9 68.4** 98 25.7 97 15.8

62.8**

a ** = Significant at the 1% level.

IR58025 A/IR9761-19-1 R, IR58025 duration hybrids. The rest are short- A/IR13419-13-10 R, IR58025 A/ duration. Commercially exploiting these IR28178-70-2-3, IR58025 A/Suweon 287

because of their >20% mean grain yield R, and IR58025 A/IET9188 mature in 22 F 1 hybrids should be quite worthwhile

advantage over Jaya.

Tropical japonica lines as crossed to both indica or japonica lines. improved sources of wide They are called wide compatible varieties compatibility trait in rice (WCVs). During the past decade, several ( Oryza sativa L.) WCVs—mostly traditional varieties—

have been identified in Japan, at IRRI, and in China. T. S. Bharaj, S. S. Virmani, R. C. Aquino,

and G. S. Khush, IRRI

Indica/japonica or indica/tropical efforts are being made to develop a new japonica F 1 hybrids, though heterotic plant type involving crosses with tropical exhibit high spikelet sterility that hinders japonica (previously known as bulu ) their commercial exploitation. Allelic germplasm. interaction at the S 5 locus, which leads to Experiments at IRRI have shown that partial elimination of female gametes tropical japonica lines, when crossed with carrying japonica alleles, causes indica/ semidwarf indica rices, exhibit stronger japonica sterility. Some rice cultivars, yield heterosis than do indica/indica however, exhibit normal fertility when hybrids provided that either of the

To break the present yield plateau,

4 IRRN 19:3 (September 1994)

Breeding methods

about 130 d, making them medium-

–

Spikelet fertility of lR64446-7-3-2-2, lR65598-112-2, and their testcross F 1 s with indica and japonica lines with an indica tester showed partial testers. IRRI. fertility (42.6-68.3% spikelet fertility).

Difference in spikelet Testcross F 1 s involving IR64446-7-3-2-2 Line/F 1 Spikelet fertility fertility (%) from a (MD2/Pakisan) and IR65598-112-2 (Shen

(%) Indica × japonica F 1 Tester parent

Nung 89-366 Gendjah Wangkal), mean spikelet however, showed spikelet fertility either

similar to or higher than that of the parental and tester lines (see table), lR64446-7-3-2-2 57.8 ± 4.5 +21.9** –26.6**

(lR64446-7-3-2-2/1R36) F 1 89.1 ± 4.3 +53.2** 4.7

lR65598-112-2 79.6 ± 5.6 +43.7** –4.8 than normal fertility (57.8%). (lR65598-112-2/IR36) F 1 87.5 ± 5.6 +51.6** 3.1

(IR64446-7-3-2-2/Taichung 65) F 1 84.3 ± 6.6 +48.4** –0.1 although IR64446-7-3-2-2 showed less

(IR65598-112-2/Taichung 65) F 1 83.7 ± 7.7 +47.8** Lines IR64446-7-3-2-2 and IR65598-

IR36 81.2 ± 5.3 112-2 are therefore considered to possess Taichung 65 87.6 ± 6.5 the WC trait. Both lines are semidwarf and (IR36/Taichung 65) F 1 35.9 ± 6.5 possess the characteristics of IRRI’s new a ** = significant at the 0.01% level. plant type: fewer tillers and larger panicles

parental lines possesses the wide compa- Parental lines, testers (IR36 and varieties. tibility (WC) gene(s). Taichung 65), and their F 1 s were grown at IR65598- 112-2 was also found to be a

We screened 10 improved tropical IRRI during 1993 WS. Each F 1 was grown maintainer for the wild abortive cyto- japonica lines (IR64446-7-1-2-3, in a plot of two rows (12 plants each) and plasmic male sterile (CMS) line; testcross

IR64446-7-10-2-2, IR64454-6-8-5-3, Two rows of IR36/Taichung 65 F 1 were all plants to have complete pollen sterility.

IR65597-25-1, IR65597-134-2, and each plant of every F 1 or parental line were line and are also incorporating the IR65598-112-2) for WC trait by crossing sampled to determine spikelet fertility. thermosensitive genic male sterility these, on a single plant basis, with indica All 10 tropical japonica lines exhibited (TGMS) gene into the two lines. The CMS (IR36) and japonica (Taichung 65) normal fertility in crosses with japonica and TGMS lines may be useful for testers. Selfed seed of the parental lines (Taichung 65) tester. Testcross F 1 s developing indica/tropical japonica rice and testers was also collected. involving 8 of the 10 tropical japonica hybrids.

–0.7

than current modern high-yielding

IR64446-7-3-2-2, IR64446-7-8-2-2, each parental line in a single-row plot. F 1 (IR62829 A/IR65598-112-2) showed

IR64454-36-1-5-3, IR64454-81-1-3-2, also grown. Two healthy panicles from We are converting this line into a CMS

Natural outcrossing potential their promising restorers. A crossing block in cytoplasmic male sterile was raised with four CMS lines (V20 A,

lines of rice ZS97 A, IR58025 A. and IR62829 A) and five restorers (IR24, IR54742-22-19-3,

J. Ramalingam, N. Nadaralan, IR29723-143-3-2-1, IR9761-19-1, and C. Vanniarajan. and P. Rangasamy, Agricul- ARC11353) in a randomized complete tural Botany Department, Agricultural

625104, Tamil Nadu, lndia College and Research Institute, Madurai

block design with two replications during 1993 kharif (Jun-Sep). Seed setting percentage was calculated for 20 cross

We studied the outcrossing potential of combinations. An A to R row ratio of 4:2 cytoplasmic male sterile (CMS) lines of was adopted; 10 plants for both A and R wild abortive (WA) origin along with lines were maintained in each row at a

Natural outcrossing (%) on four A lines planted along with five R lines. Madurai, Tamil Nadu, India. 1993 kharif.

Outcrossing rate (%) in CMS lines Restorer (Pollen source) V20 A ZS97 A lR58025 A lR62829 A

spacing of 20 × 10 cm. Three rows of Purple Puttu served as pollen barriers around the crossing block and between each cross combination. Rice was planted across the wind direction and allowed to pollinate naturally. Seeds were collected for individual A × R combinations at maturity. We used the mean of 40 plants in each A line replication for analysis.

Seed setting percentage was significantly different among cross combinations using analysis of variance. Mean outcrossing was high in V20 A (16.4%) and IR58025 A (16.4%) when interplanted with different restorers (see table), meaning that these lines can be used in hybrid rice breeding programs.

Individual combinations IR58025 A/ IR29723-143-3-2-1 R (20.5%), IR58025

IR24 18.9 12.2 18.9 2.2 A/IR24 R (18.9%), V20 A/IR24 R lR54742-22-19-3 13.1 16.1 16.6 lR29723-143-3-2-1 18.8 18.2 20.5 11.5 lR9761-19-1 15.5 10.2 9.5 5.5

1.2 (18.9%) V20 AAR29723-143-3-2-1 R (18.8%), and ZS97 A/IR29723-143-3-2-1

ARC11353 15.6 9.3 16.4 12.0 R (18.2%) showed the highest outcrossing. Mean CD (0.05)

16.4 13.2 16.4 6.5 These crosses can produce more hybrid 0.4 seed in a unit area than the others.

IRRN 19:3 (September 1994) 5

- -

- -

Evaluation of cytoplasmic male sterile and maintainer lines in Cuu Long Delta, Vietnam Pham Trung Nghia, Bui Ba Bong, and Nguyen Van Luat, Cuu Long Delta Rice Research Institute (CLRRI), Omon, Can Tho, Vietnam

We evaluated 18 cytoplasmic male sterile (CMS) A lines (Table 1) and their corresponding maintainers (B lines) in

1993 wet season (WS) at CLRRI. The A lines were planted in two rows and the B lines in four rows, with 25 plants per row. Single seedlings were transplanted at 20- × 2-cm spacing. We evaluated A lines for pollen and spikelet sterility, panicle exsertion, and flag leaf length and width. Panicle length, grains/panicle, and grain shape were recorded for B lines. Days to 50% flowering, plant height, panicles/ plant and disease reaction were recorded for both A and B lines. To determine

pollen sterility, we collected five florets from five plants before flowering; pollen grains were stained with KI. Spikelet sterility was recorded for five panicles (bagged before emergence) from five plants. Other traits were recorded for five randomly selected plants.

CMS and maintainer lines were evaluated for field reaction to ragged stunt virus and agronomic characteristics (Table 2).

IR62829 A had spikelet fertility of 2% and IR58025 A of 5% in this experiment (Table l), although in previous seasons at CLRRI, they showed complete pollen and spikelet sterility.

CMS lines IR58025 A and IR62829 A are being used to develop F 1 hybrids for multilocation yield testing in Vietnam. Based on these results, however, CMS and maintainer lines of IR58025, IR62829, and IR64608 must be purified using the pair crossing method. CMS lines IR66707 A, Pragathi A, Madhuri A, PMS8 A, and PMS10 A have good agronomic traits and are suitable for use in the Cuu Long Delta.

Table 1. Characteristics of CMS lines in Cuu Long Delta, Vietnam. 1993 WS.

CMS Origin Pollen Spikelet Panicle Flag leaf (cm) CMS line source sterility (%) sterility (%) exsertion

(scale) Length Width

IR58025 A WA a IRRI 95 95 7 lR62829 A WA

30.7 IRRI 95 98 5

1.5

lR64608 A WA IRRI 97 28.5 1.0

99 7 lR67684 A WA

31.0 IRRI

1.7 100 100 7

lR64607 A WA 19.0

IRRI 1.3

98 100 7 32.0 1.3 lR66707 A O. perennis IRRI 100 100 3 PMS1 A WA

31.0 1.4 India 100 100 7 35.5

PMS8 A 1.9

WA India 100 100 7 41.5 1.7 PMS10 A WA India 100 100 7 46.0 Madhuri A MS 577

1.8 India 95 100 7 32.0

Pragathi A MS 577 1.6

India 97 100 7 39.5 1.7 Pushpa A MS 577 India 95 100 7 35.0 1.7 Krishna A WA India 93 100 7 21.5 1.7 Krishna A Kalinga I India 100 100 7 29.7 1.6 CNTPR10 A WA Thailand 100 100 7 29.5 1.8 RD25 A WA Thailand 100 100 1 37.5 RD21 A

1.5 WA Thailand 100 100 1 37.0

V20 A 1.8

WA China 100 100 7 25.0 1.6

a WA =wild abortive.

Table 2. Agronomic traits and disease reaction of CMS (A) and maintainer (6) lines. Cuu Long Delta, Vietnam. 1993 WS.

Days to Plant Panicles/ Panicle Grains/ Grain Disease b

50% height plant length panicle shape a reaction c

Line flowering (cm) (no.) (cm) (no.)

A B A B A B B B B A/B

lR58025 81 84 68 85 11.2 6.0 21.0 72.0 LS S lR62829 72 72 68 77 16.6 8.2 15.8 49.0 LS R lR64608 73 73 69 80 11.0 6.0 17.0 82.0 M S lR67684 78 78 69 80 16.0 7.8 21.0 96.0 LS S IR64607 84 84 71 91 9.0 7.0 17.8 103.0 LS MR lR66707 81 81 71 91 12.5 6.8 17.8 99.6 LS R PMSl 87 83 73 85 12.0 7.6 19.6 95.0 LS S PMS8 83 79 66 84 17.0 11.0 27.0 113.0 LS S PMS10 83 83 65 86 13.0 5.0 23.6 126.0 LS S Madhuri 74 74 54 92 16.5 10.2 20.3 72.0 M R Pragathi 63 63 54 69 10.0 5.8 26.1 166.0 M R Pushpa 74 74 90 95 10.0 7.8 16.8 64.0 M R Krishna (WA) 67 67 57 76 13.0 9.8 16.6 48.0 M S Krishna (Kalinga) 63 63 54 69 13.0 9.2 19.3 36.6 M S CNTPR10 88 88 95 117 6.0 6.0 27.3 120.0 L R RD25 68 66 78 85 11.0 9.0 17.3 38.0 L R RD21 90 88 113 117 6.6 7.8 22.3 130.0 L R V20 62 62 61 73 15.5 8.6 19.0 72.0 M S

a LS = long slender, L = long, M = medium. b Ragged stunt virus. c R = resistant, MR = moderately resistant. S = susceptible.

A specific esterase band found in Annong-1S Li Ren-hua, Cai Hong-wei, and Wang Xiang- kun, Agronomy Department, Beijing Agricul- tural University, 100094 Beijing, China

Isozymes have a noteworthy impact on regulating plant growth and development. To determine the spicific proteins of isozymes in thermosensitive genic male sterile (TGMS) rice, we performed vertical polyacrylamide gel electrophoresis at different plant growth stages.

Annong-1S is a natural mutant from indica line Annong-1. Its male sterility by environmental temperature is conditioned. Under high temperatures (daily mean > 26 °C), it has a stable sterile stage. The higher the temperature, the earlier the pollen development stage, which results in sterility. When temperature falls below the thershold, partial or normal fertility occures. Studies indicate that a pair of recessive nuclear genes controls sterility and that segregating generations have goodness of fit to the Mendelian rules with respect to the trait.


a M1 = MS salts + 100 mg/liter myoinositol + 1.0 mg/liter thiamine-HCI + 500 mg/liter glutamine + 0.5 mg/liter 2,4-D + 30 g/liter sucrose, pH 5.8; M2 = M1 + 30 g/liter sucrose: M3 = 60 g/liter maltose in place of 60 g/liter sucrose in M2: M4 = M3+ 0.5 mg/liter 2.4-D: M5 = M4 + 1.0 mg/liter NAA. b Values are means of three replications. c MS agar medium supplemented with 1 mg/liter vitamin B 1 , 0.5 mg/liter vitamin B 6 , 2 mg/liter glycine. 0.5 mg/liter nicotinic acid, 100 mg/liter myoinositol, 2 mg/liter kinetin, and 0.5 mg/liter indole-3-acetic acid (IAA), pH 5.8.

We used an improved method to conduct an esterase isozyme assay based on our prior work, adopting the discon- tinuous separating system. The staining method of M. Nakagahra was used.

Seven isozyme bands can be separated under our system of electrophoresis. We detected Est-1 and Est-2 isozyme bands at both the geminated seed stage and at all other growth stages and Est-3 band at only the mature-leaf stage. A specific esterase band (s band) was discovered in Annong- 1S and N422S, a photoperiod-sensitive genic male sterile (PGMS) line derived from Nongken 58S (Fig. 1). Annong 1 and 2 10 other normal rice varieties did not have this s band. Its stable expression in mature leaves and unstable expression in young leaf blades are detectable in some PGMS and TGMS lines derived from Nongken 58S and Annong-1S (Fig. 2). We are conducting further studies on linkage analysis in segregating generations and its genetics.

Effect of maltose and hormones on callus formation and plant regeneration in isolated microspore culture of japonica rice ( Oryza sativa L. )

1. Strong expression of s band at sterile stage of TGMS and PGMS lines.

Annong-1S; 45 Bodat Mayang (check).

1-3: N422S; 68

2. S-band at four- leaf-old seedling stage of Annong-1S. 1-3: Annong-1S; 4-6: Annong-1 (check).

and washed with the same medium. The extract was filtered through a nylon sieve (1 00 µm pore size) and the filtrate was precipitated for 20 min, then centrifuged at 100 x g for 2 min, The 2 ml of medium containing microspores in the bottom of

Xie Jiahua, Gao Mingwer, Cal Qihua, Cheng Xiongying. Shen Yuwei. and Liang Zhuqing, Institute of Nuclear Agricultural Science, Zhejiang Agricultural University, Hangzhou 310029, People's Republic of China

Microspore culture provides an ideal system for genetic manipulation in plants. Its efficiency in rice, however, is quite poor. We studied the effects of maltose, 2,4-dichlorophenoxy acetic acid (2.4-D), and naphthalene acetic acid (NAA) on callus formation and plant regeneration from microspore culture of rice.

Three japonica cultivars and five liquid media were used (see table). The anthers with microspores at the middle to late uninucleate stage were pretreated at 6° ± 1°C for 17 d, then precultured onto liquid medium for another 5 d at 27° ± 1°C. After that, the microspores were isolated from the anther with a glass rod

the tube was cultured in petri dishes at a density of about 4.0 x 10 4 pollen grains/ml and kept in the dark at 27° ± 1 °C for callusing. Number of calli was recorded after 35 d.

were transferred to medium of the same composition, solidified with 0.6% (w/v) agar. When calli became about 2 mm long, they were transferred to plant regeneration

Only a few microspores in M1 and M2

Calli as large as 1.0-1.5 mm in diameter

medium.

media, which contained sucrose, divided without any callus formation. A high frequency of callus induction occurred, however, when microspores were cultured on media with maltose as the carbon source (Fig. 1a, b). All three genotypes responded well to the M3 medium, producing many calli. The frequency of callus formation could be raised by increasing the concentration of 2,4-D from

a) Microspores started to divide after 5 d of culture (X60). b) Microcalli derived from microspore after 7-10 d of culture (X50). c) Green plantlet.

Effect of maltose and hormones on callus formation and plant regeneration of isolated rice microspore

Genotype induction anther regeneration Green Albino medium a (no.) b (no.)

02428 M1 0 M1 0

Taipei 309 M1 0 02428 M2 0

Taipei 309 M2 M2 0

0 024287 M3 1.48 178 50 28.6 Xiushu 117 M3 1.38 145 1 Taipei 309

0.7 M3 1.24 269 26 9.7 63 23.4

Taipei 309 M4 1.66 155 9 5.8 35 22.6 Taipei 309 M5 0.46 148 18 12.2 69 46.6

culture.

Plant regeneration c

Callus Calli/ Calli for

no. % no. %

Xiushu 117


Xiushu 117 - - - - - - - - - - - -

- -

- - - - - - - - - - - -

- -

- - - - - -

0.5 (M3) to 1.0 mg/liter (M4) callus induction medium (see table).

Green plant regeneration ranged from 0 to 12.2% and was greatly dependent on genotype; Taipei 309 was the most responsive (Fig. 1c). Although the callus formation per anther could be increased

with increased 2.4-D concentration from 1.24 (M3) to 1.66 (M4) mg/liter, most calli on M4 were smaller and more difficult to regenerate than those on M3. MS had low callusing (0.46 per anther) but high regeneration capacity of green and albino plants. The results indicate

that the high frequency of callus induction and green plant regeneration from isolated microspore culture could be obtained by using maltose as a carbon source and 2,4-D and NAA as hormone in the induction medium.

Restorers and maintainers for four cytoplasmic male sterile lines of rice P. Jayamani, K. Thiyagarajan, and M. Rangaswamy, Paddy Breeding Station, School of Genetics, Tamil Nadu Agricultural University, Coimbatore 641003, lndia

We evaluated 84 hybrids, their pollen parents, and four isogenic maintainers (B lines) during Jul-Oct 1993 to identify maintainers and restorers for cytoplasmic male sterile (CMS) lines. The experiment was laid out in a randomized block design with two replications. Each genotype was planted in three rows with 10 plants each at a spacing of 20 × 20 cm. Fertilizer was applied at 120-60-60 kg NPK/ha and other recommended cultural practices were followed.

florets in the upper part of the panicles before dehiscence. Pollen grains were stained with IKI. Cultivars with <5% pollen fertility were classified as potential maintainers, those with 6-20% as partial maintainers, 21-95% as partial restorers, and >96% as potential restorers (see table).

We are using the maintainers identified in this experiment in a backcross program to develop new CMS lines. The restorers are being used to develop new hybrid combinations.

Pollen fertility was determined from

Improvement in anther culture of japonica/indica crosses of rice S. M. Ibrahim, Seong-ah-Han, Xiamao Lei, P. M. Colowit, and D. J. Mackill, Agronomy and Range Science Department and USDA- ARS, University of California, Davis, California, USA

We conducted a study to generate an anther culture-derived population for use in molecular mapping of genes for cold


Restorers and maintainers for four CMS lines. Coimbatore, India. 1993.

CMS line Potential maintainers Partial maintainers Partial restorers Potential restorers

lR58025 A Akinishiki, Pada- ASD16 Kundalika, Oozora, IR50, IR62, IR70, IR72, shabag, J. Samba Black Puttu, Co 41, AS781/5, ADT2, IR74, W. Ponni, (VTS), 03866, 03891,03898,

Basmati 370, C12, ADT36, Co 29, AS781/3, C19, C36 C15, C24, C37, AS781/1,

C29, C32, C33, C39, C40, C41 AS781/4, Dular TNAU831520,

03860, 03862, 03877, 03880, 03881, 04001, C1, C2, C6, C7, C10, C13, C20, C22, C35, C40

lR62829 A – TNAU88013, Thalisamba, Ponni, Co 44, Zhuhio, TNAU831520, C18, TNAU92093 TNAU841434, TNAU802293

IR20, Co 41, Co 29, Co 43, ASD18

V20 A – – ASD18, Co 41 IR64, IR62, IR70, W. Ponni

MS37 A – TNAU89093, TKM 6. IR62, IR42, Ponni, J. Samba (VTS) ARC6650, IR20

Bhavani

tolerance. Anther culture efficiency was from calli subcultured three times each at studied in two F 1 hybrids, M201/IR50 biweekly intervals followed by a and M202/IR50, and their respective preculture treatment with abscisic acid parents. M201 and M202 are cold- (ABA) at 5 mg/liter (treatment 2). tolerant japonicas and IR50 is a Regeneration medium (N6 medium, 2 mg susceptible indica. kinetin/liter, 1 mg IAA/liter, and 1 mg

and were cultured in the dark on N6 treatments. callus induction medium supplemented Callus induction and regeneration, with 6 g agarose/liter, 2 mg 2.4-D/liter regardless of treatments, followed the and 60 g sucrose/liter. Plant regeneration order of japonica>indica>japonica/indica. from calli receiving no treatment M201 recorded greater callusing (35%) (treatment 1) was compared with that and regeneration efficiency (12% in

Table 1. Callus induction in parents and F 1 crosses.

Anthers were pretreated at 9°C for 7 d NAA/liter) was similar for both

Anthers plated Anthers producing Callus production Genotype (no.) calli before subculturea

(no.) (X)

M201 720 M202 720 IR50 720 M201/IR50 (F 1 ) 10836 M303/IR50 (F 2 ) 11880

Total 24876

252 244 169

1150 1224 3039

35.0 33.9 23.4 10.8 10.4 12.2

a Anthers producing calli = Total anthers plated

× 100.

treatment 1 and 2.1 % in treatment 2) Table 2. Green plant regeneration of parents and F 1 crosses in different medium treatments. (Table 1 ). Japonicas generally have a higher efficiency of callus formation than Genotype

Callus Embryogenic Nonembryogenic Embryogenic Plant

do indicas. Differences in callusing ability plated calli calli calli regeneration (no.) (no.) (no.) (%) (%) a

and regeneration efficiency between parents and hybrids may depend on factors Treatment 1 (without subculture and preculture)

such as differences in combining ability of M302 M201 112 18 94 16.1 1.2

107 15 92 14.0 1.4 parents and varying degrees of heritability.

after subculturing in media with ABA Total 1423 97 1326 6.1 (F 1 ) medium without ABA (Table 2). The calli

(F 1 ) higher in medium containing ABA than in

IR50 77 7 70 9.0 0.9 0.3

M202/IR50 508 20 488 3.9 0.4

The amount of embryogenic calli was M201/IR50 619 37 582 5.9

- generally appeared whiter, and the embryogenic calli were more defined and developed compared with calli without subculture and ABA preculture treatment.

Plant regeneration was almost twice as great in treatment 2 as in treatment 1, perhaps because more nonembryogenic calli formed as a result of no subculture and preculture treatments with ABA.

This study reveals that certain refined treatments administered after callus induction and prior to regeneration cause increased plantlet regeneration.

Treatment 2 (with subculture and preculture) M201 140 29 111 20.7 2.1 M202 137 29 112 18.2 2.6 IR50 92 11 81 11.9 1.7 M201/IR50 531 43 488 8.0 0.8

M202/IR50 716 65 651 9.0 0.6 (F 1 )

(F 1 ) Total 1616 177 1443 10.7

a = Anthers producing calli

Total anthers plated × 100.

Reaction of selected cultures for resistance to RTD and GLH.

tungro disease and its vector,

Evaluation of selected Designation Cross Mean reaction to GLH

RTD Onginat a Transformed reaction b

(1-9 scale) (sq root) (0-9 scale)

green leafhopper BPT2217 BPT3329/ARC6650 3.9 2.0 5 BPT4358 BPT3291/ARC6650 1.9 1.4 5

A. Gosh and N. V. Krishnalah, Directorate of RP2333-156-8 BPT329l/Vellathilcheera 3.2 1.8 5

Rice Research, Rajendranagar, Hyderabad RP2337-43-4-1 Ratna/ARC10659 2.9 1.7 6 Ratna/lET6858

500030, India 3.3 1.7 4

RP2541-167-290 Swarnadhan/RP1579-36 2.2 1.5 5 A set of 81cultures possessing resistance RP2547-100-255 ARC5723/ARC665O//RP1579-36 2.6 1.5 4

to at least one insect pest or disease was CRM47 - c 2.3 1.5 6

tested under glasshouse conditions for P2409 2.7 1.6 5 ASD 5.5 2.3 5

resistance to rice tungro disease (RTD) and its vector green leafhopper (GLH) Nephotettix virescens (Distant).

The entries were scored at seedling stage (15-25-d old) on 0-9 scales for RTD and GLH using the Standard evaluation system for rice.

We found 18 entries to be promising against GLH; 6 of these showed some resistance to RTD (scores of 4) (see table).

Bhoban (OR 447-20) Cul 8770 Cul 8756 Pusa 598-17-349 IET10810 IET11047

RP2337-46-5-4 RP2337-202-93-10 IET7302 (resistant

TN1 (susceptible check)

check)

LSD (0.05) CV (%)

3.0 2.2 2.6 2.3

Pankaj/Mahsuri 3.3 Nam Sagui 19/IR5215-301//

Ratna/lET6858 3.1 Ratna/lET6858 3.2

1.0

9.0

lR5853-102 2.0

1.7 1.5 1.6 1.5 1.8

1.4 1.8 1.8

1.0

3.0

0.6 20.1

6 4 4 6 6

5 4 4

3

7

a Av of 4 replications. b Av of 3 replications. c - = not available.


Pest resistance

BPT4363

- -

- - - -

cultures for resistance to rice

-

Rice gall midge (GM), Orseolia oryzae; brown planthopper (BPH), Nilapavarta lugens; and bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae, can create severe problems in rice production. A collection of 58 IET rice genotypes was studied for resistance to some or all of these pests during 1988-92 under field and laboratory conditions.

Five hundred 25-d-old seedlings of each entry were transplanted in the field in two 2-m long rows at 15- × 15-cm spacing during 1988-90 kharif (Jun-Oct) seasons. Each entry alternated with a row of the susceptible check TN1. At maximum tillering stage, entries were inoculated with X. oryzae pv. oryzae using the clip

Reactions of advanced IET rice

inoculation method. Those entries exhibiting consistently a plant damage score below 6 were tested for resistance to BPH using the standard evaluation technique in a glasshouse experiment.

After the final test, BPH-resistant varieties were uprooted from wooden boxes and transplanted in the field, along with TN1, to record GM infestation in 1990-91 kharif season. Seeds of those varieties free from GM infestation were collected and retested again in 1992 kharif season.

Twenty clean, sound seeds of these varieties were exposed to five pairs of newly emerged grain moths in a 6- × 3-cm glass vial covered with black paper, replicated three times. Grain moth emergence was recorded and damaged grains counted at 45-50 d after infestation.

Fifty-six of the varieties were resistant to BPH and two moderately resistant (see table). Only 13 entries, however, were resistant to GM.

In general, ARC and R (Raipur) series were resistant to BPH and GM, but only a few were resistant or moderately resistant to BLB. Overall, 12 varieties were resistant to BLB.

Reaction of IET rice varieties against major insect pests at Raipur, India, 1988-92.

varieties to major pests in Raipur, India

Av plant IET no. Designation/cross damage score a Gall midge Grain moth

D. K. Rana, D J. Pophaly, Entomology Department, Raipur, Madhya Pradesh, India; A. S. Kotasthane, Plant Pathology Depart- ment, IGKVV, and U. K. Kaushik, Entomology Department, IGKVV

12802 12195 12767 12776 11105 12770 12793 12206

11481 2030 11582 12805

12199

12785

12204

12800 12803

Vikramarya/lET6262 Prasanna/lET5688 Ratna/ARC5981 Swarnadhan/RP1579-36

Ratna/ARC10654 Ratna/ARC10654 Ratna/ARC10654

Ratna/ARC19666 IET6315/ARC5984 IR36/MTU4569 Ratna/ARC5981

A302 IR54/Surekha Swarnadhan/RP1579-43

Nagarguna/ARC5984 Salivahana Phalguna/Andrawsali

G453 A689 Phalguna/lR36 Vikramarya/Somasall A705 A81

CR57-392/OR57-21

R650-1820

lR33059-26-2-2

R847-89-1

lR39423-124-3-3-1

BLB b BPH c

6.0 0.2 5.0 0.4 5.0 0.5 5.0 0.5 4.0 0.7 6.0 0.7 5.0 1.1 5.0 1.1 3.0 1.1 3.0 1.1 6.0 1.2 4.0 1.2 2.3 1.3 2.3 1.3 6.0 1.3 5.0 1.6 6.0 1.6 4.0 1.6 3.0 1.6 5.0 1.6

1.7 3.0 1.7 5.0 1.8 5.0 1.8

1.8 6.0 1.9 5.0 1.9 4.0 1.9

1991 1992 Grain damage (% silvershoots) (%)

19.0 9.0

22.0 14.0

0.0 0.34 0.0 1.0 0.1 1.0 0.0 0.0 0.0 1.3 0.0 0.14

0.0 0.34

7.0

8.0

0.0 0.26

10.0 23.0

21.0 10.0

0.0

0.0 7.4

7.4

6.0

0.0

4.2

0.8 2.1

R435-65 5.0 1.9 5.3 5.0 2.0

Jagratri 4.0 2.0 A634 3.0 2.0 R296-133 3.7 2.1 0.0 0.0 2.4

10797 CR149-228/T 142

12173 PR106/OBS528 3.0 2.1 1.0 0.0 13.1 10486 PR106/OBS528 4.0 2.1

R296-110 A635 A688 G703 A580 A707 R435-1209 PR51673-172-1-3

9259 CR316-639 BR203-70-13-2

10849 CR157392/OR 57-21 R649-1715 lR35353-94-2-2-3 AC96 II A384 A411 AC81

A462 A667

R845-89-43

10666 Pankaj/Swarnadhan RP2151-40-1 RP1924/RP9-4 Resistant check Susceptible check g

4.3 2.1 4.0 2.1 5.0 2.1 5.6 2.1 5.0 2.3 6.0 2.3 4.0 2.3 3.0 2.3

2.4 2.4

4.0 2.5 3.0 2.5

2.6 5.0 2.6

2.7 2.8

5.0 2.8 2.0 2.8 4.0 2.9 5.0 2.9 4.3 2.9 3.6 3.3 3.0 4.0 1.5 d 1.3 e

9.0 9.0

0.0 0.6

0.0 39.8 13.0

0.0 0.69 16.0

5.0

0.0 0.0 0.0 0.0 0.0 f 0.0 f

20.6 22.3

6.8 8.8 3.7 5.2 3.1 0.4 6.2 1.1

0.4

5.3

2.1 3.3 0.0 6.2 0.0

10.2 11.0

8.2

10.0

a Reaction rating on 0-9 scale of the Standard evaluation system for rice: 0-3 =resistant, 3.1-5.0= moderately resistant, 5.1-8.0 = moderately susceptible. and 8.1-9.0 = susceptible. b Av of three kharif seasons. c Data based on 4-6 replications in glasshouse. d lR54. e PTB33. f R650-1817. g TN1.


~

- -

-

-

-

-

-

- - - -

- -

- -

- -

- - -

- -

- - - -

- -

-

-

-

-

- - - - -

- - -

- -

- - -

- -

- -

- - - - -

-

-

-

-

-

- -

- - - - - - -

- - -

- -

- - - - -

- - - - -

- - - -

- - - - -

- -

- - -

- -

- - -

- -

-

- -

-

-

Only eight varieties exhibited strong resistance to grain moth, with infestation restricted to only 0.8% of grains; five resistant varieties had damage of 1.1-2.4%.

R650-1820, Ratna/ARC 19666 (IET11481), Ratna/ARC5981 (IET12805), Nagarjuna/ARC5984

(IET12785), and PR106/OBS528 had multiple resistance to BLB, BPH, and GM. They were resistant to GM biotype 1, with ARC10654, ARC5981, ARC5984, OBS528, and RP-9-4 as donors.

Varieties Ratna/ARC 10654 (IET12770), Ratna/ARC10654

(IET12793), Ratna/ARC10654 (IET12206), R296-133, and R296-110 were also resistant to BPH and GM but moderately resistant or moderately susceptible to BLB. R650-1820 was the only variety resistant to BLB, BPH, GM, and grain moth infestation.

Pest resistance—diseases

Analysis of bacterial blight resistance genes in three japonica rice varieties Xu Jianlong, Lin Yizi, and Xi Yongan, Plant Institute, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China

We analyzed inheritance of resistance to bacterial blight pathogen strains W1, P1 (PXO 61, Philippines), and T1 (Japan) in three japonica varieties (Ning 67, Tai 202, and Bing 814). Shennong 1033,

which is susceptible to these isolates, served as the susceptible parent. CBB3, CBB4, and CBB 12, near-isogenic lines with resistance genes Xa-3, Xa-4, and Xa-12, respectively, are resistant to all of these isolates and served as the resistance parents. We made 12 crosses, including resistant/susceptible and resistant/ resistant crosses (Tables 1 and 2).

All materials were planted in the field. Inoculum was adjusted to a concentration of 10 9 cells/ml. Fully expanded leaves at

booting stage were inoculated by the clipping method. A different tiller was inoculated with each isolate, and the tillers were marked with different colors. Disease reaction was assessed at 21 d after inoculation using the Standard evaluation system for rice. Plants scored as 1-3 were classified as resistant and those scored as 4-9 were classified as susceptible.

A single dominant gene controls the resistance of Ning 67 and Tai 202 to the three isolates and two dominant duplicate genes condition resistance in Bing 814 (Table 1). Allelism tests indicated that the genes of Ning 67 and Tai 202 were allelic to Xa-3, as was one of the two genes in Bing 814 (Table 2).

Screening rice varieties for resistance to rice yellow mottle virus in Kenya J. N. Danson, Ahero lrrigation Research Station (AIRS), P. O. Box 1961, Kisumu, Kenya

We screened 60 rice varieties of diverse origins, supplied by IRRI, for their resistance to rice yellow mottle virus (RYMV) during four seasons: 1989-91 long rains (LR) and 1989 short rains (SR). IR2793-80- 1, which is grown commercially in western Kenya irrigation schemes, and local variety Sindano were included as checks.

The trial was laid out in a randomized block design. The natural inoculation method was used. No pesticides were applied to facilitate the spread of the virus by beetles. Fertilizer was applied at 78 kg N/ha, half as basal and half at 42 DAT. Fields were kept clean with three hand weedings.

Test variety seedlings were sown at 20- × 20-cm spacing. Sindano, used as a

Ning 67/CBB12 RR a 240 222 18 15:1 0.4444 0.75-0.50

Table 1. Reactions of progeny of crosses among four parents to W1, P1, and T1 isolates of bacterial blight.

Parent or combination Plants RRR a SSS a Expected P (no.) ratio

Tai 202 13 13 13 13 Ning 67

Bine 814 14 14 Shennong 1033 16 16 Ning 67/Shennong 1033 F 1 14 14

F 2 209 164 45 B 1 F 1 117 66 51

3:1 1.1627 0.50-0.25 1:1 1.6752 0.50-0.25

Ning 67/Shennong 1033 F 1 13 13 F 2 208 165 43 3:1 1.8526 0.25-0.10 B 1 F 1 67 37 30 1:1 0.5373 0.50-0.25

Bing 814/Shennong 1033 F 1 12 12 F 2 206 191 B 1 F 1 62 42 20 3:1 1.3763 0.25-0.10

15 0.2188 0.75-0.50

Combination F 1 ratio P

a The first letter stands for reaction to W1, the second to P1, and the third to T1.

Table 2. Segregation for resistance to W1, P1, and T1 isolates of crosses among three parents and known gene varieties.

F 2 Expected

Total RR SS

Ning 67/CBB3 RR a 209 209 0 Ning 67/CBB4 RR b 116 109 7 15:1 0.0092 >0.90

Tai 202/CBB3 RR a 216 216 0 Tai 202/CBB4 RR a 206 199 7 15:1 Tai 202/CBB12 RR a 219 203 16

2.3935 0.25-0.10 15:1

Bing 814/CBB3 RR a 210 210 0 0.2560 0.75-0.50

Bing 814/CBB4 RR b 210 197 13 63:1 26.3114 <0.005 Bing814/CBB12 RR a 197 192 5 63:1 0.6672 0.50-0.25

a The first letter stands for reaction to W1, the second to T1. b The first letter stands for reaction to W1, e second to P1.


c 2 c

a 1989 SR

Average scores for reaction to RYMV at 90 DT of 60 varieties at AIRS, Kisumu, Kenya. 1989-91.

Variety 1989 LR b 1990 LR a 1991 LR a Av c

Azucena Basmati 370 Basmati 217 BG35-2 BR51-282-8 BR153-28-282-8 BRIRGA409 BW196 BW348-1 C1321-9 C1322-28 CR126-42-2 Eiko Faro 15 Faro 27 Farox 228-3-1-1 Farox 233-1-1-3 Farox 233-7-1-2 Farox 239-1-1-1 IET6279 IR50 lR2793-80-1 lR9202-5-2-2-2 lR9698-16-3-2 IR9758-K2 lR9784-142-1-3-3 IR13260-100-1E-P2 lR19090-136-2-2-3 lR19225-142-1-6 lR19225-289-3-1-3 lR24486-166-2-3 lR25873-22-3 lR27301-154-3 lR27301-62-2 ITA21 ITA222 ITA245 ITA249 ITA302 ITA310 JC99

K143-1-2 KAU166 Ketan1 Kisuke Khao Dawk Mali Malagkit Sungsong Milyang 49

Shin-ai Sindano

TNAU658

TOX902-42-1 TOX902-5-103-3-101 TOX894-28-201-1-5

K39-96-1-1-1-2

RP1125-1526-2-2-3

SI-PI-692033

TOX714-1-204-1-101

TOX894-28-201-1-2 UPR254-35-3-2

Total Mean F-test for variety comparison cv SED LSD (5%) LSD (1%)

5 0 0 7 7 7 6 7 7 7 7 7 8 7 7 7 7 6 7 7 7 5 8 6 8 7 6 7 7 8 5 7 7 7 8 7 8 5 7 4 7 7 4 6 5 2 3 4 6 5 7 9 8 7 7 6 7 8 8 5

378 6

6 2 2 7 8 6 7 6 6 8 6 7 6 7 7 7 4 6 6 7 6 6 8 6 6 6 6 6 6 8 8 6 5 7 9 8 7 6 6 6 7 7 6 6 4 0 0 4 6 5 5 9 7 8 7 4 6 6 9 6

365 6 0.29 %

16 % 0.7 % 1.4 % 1.9 %

6 3 3 5 7 8 6 8 7 6 7 7 6 7 5 7 7 6 5 7 6 6 8 8 5 7 8 5 5 6 6 5 6 7 8 5 7 7 6 3 8 6 3 3 4 2 3 4 7 5 4 9 6 5 6 6 5 5 6 6

350 6

8 3 3 7 8 8 9 7 8 8 8 9 6 8 7 9 8 5 7 8 8 9 9 7 8 7 7 5 7 7 7 8 8 8 7 8

9 7 8 9 8 9 7 3 2 3 4 8 7 5 9 8 8 6 7 8 8 8 8

431 7

8

6.3 MS 2 R 2 R 6.5 S 7.5 S 7.3 S 7 S 7 S 7 S 7.3 S 7 S 7.5 S 6.5 S 7.3 S 6.5 S 7.5 S 6.5 S 5.8 MS 6.3 S 7.3 S 6.8 S 6.5 S 8.3 S 6.8 S 6.8 S 6.8 S 6.8 S 5.8 MS 6.3 S 7.3 S 6.5 S 6.5 S 6.5 S 7.3 S 8 S 7 S 7.5 S 6.8 S 6.5 S 5.3 MS 7.8 S 7 S 5.5 MS 5.5 MS 4 MR 1.5 R 2.3 R 4 MR 6.8 S 5.5 MS 5.3 MS 9 HS 7.3 S 7 S 6.3 S 5.8 MS 6.5 S 6.8 S 7.8 S 6.3 S

a LR = long rainy season. b SR = short rainy season. c R = resistant, MR = moderately resistant, MS = moderately susceptible, S = susceptible, HS = highly susceptible.

spreader variety, was planted at 60- x 20- cm spacing. The test varieties were transplanted in three rows inside the Sindano rows at 21 d after sowing. Plants were inoculated at 18 d after transplanting (DT).

A mixture of 100 g infected leaves ground in 1 liter of distilled water with 5 ml of a phosphate buffer (to maintain pH 7.0) and 2 g of a carborundum powder (an abrasive) was used to inoculate the Sindano plants. The finger rubber technique was used, where fingers were dipped in the inoculum and then rubbed gently on all of the plants’ leaves two to three times. RYMV symptoms were scored systematically using the Standard evaluation system for rice at 42 DT, 56 DT, 70 DT, and 90 DT.

Ketan 1 and Malagkit Sungsong were moderately resistant while Basmati 370, Basmati 217, Kisuke, and Khao Dawk Mali were resistant (see table). Nine varieties were moderately susceptible. Sindano was highly susceptible.

Identifying resistance genes for bacterial blight in Chengte 232 Xu Jianlong, Lin YiZi, and Xi Yongan, Plant Institute, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China

We analyzed the bacterial blight resistance genes and their allelism for Chengte 232 and its resistance donors, using the pathogen strains W1, P1 (PXO 61, Philippines). and TI (Japan). Chengte 232 and its resistant donors, Nongken 58 and Hongkewan, were all resistant to the three isolates; its other donor, Tetep, was resistant to T1 but susceptible to W 1 and P1. Near-isogenic lines carrying known genes, CBB3 (Xa-3) and CBB4 (Xa-4), were resistant to these isolates. Nonghu 6, which is susceptible to the isolates, served as the susceptible parent.

To determine the number of resistance genes effective against the isolates tested, Chengte 232. Nongken 58, and Tetep were each crossed with Nonghu 6. We also crossed Chengte 232 with Tetep and Nongken 58, and Chengte 232 and Nongken 58 with CBB3 and CBB4 to test allelism of resistance genes.


Table 1. Reaction of resistance to W1, P1, and/or T1 isolates in progeny of resistant/susceptible combinations.

F 2

Combination F 1 Total Resistant Susceptible Expected P plants plants ratio (no.) (no.)

Chengte 232/Nonghu 6 RRR a 212 195

Tetep/Nonghu 6 R b 180 168 12 15:1 0.0059 >0.90 Nongken 58/Nonghu 6 RRR a 196 148 48

17 15:1 3:1 0.0068 >0.90

0.8503 0.50-0.25

a The first letter stands for reaction to W1, the second to P1, and the third to TI. b Reaction to T1.

Table 2. Segregation for resistance to W1, P1, or T1 isolates in progeny of resistant/resistant combinations.

F 2

Combination F 1 Total Resistant Susceptible Expected P plants plants ratio (no.) (no.)

Chengte 232/Nonghu 58 Chengte 232/Tetep Chengte 232/CBB 3 Nongken 58/CBB 3 Chengte 232/CBB 4 Nongken 58/CBB 4

RR a 204 R b 306 RR c 188 RR c 204 RR a 195 RR a 210

204 0 300 6 255:1 15.5633 <0.005 188 0 204 0 190 5 63:1 0.7040 0.50-0.25 195 15 15:1 0.1537 0.75-0.50

a The first letter stands for reaction to W1, the second to P1. b Reaction to T1. c The first letter stands for reaction to W1. the second to T1.

All materials were planted in the field and inoculated at the booting stage (after dipping scissors into a bacterial suspension containing 10 9 cells/ml). Different tillers were inoculated with the different isolates and marked with different colors. Disease reaction was assessed after 3 wk using the Standard evaluation system for rice. Plants with scores of 1-3 were classified as resistant and those with scores of 4-9 as susceptible.

Chengte 232 and Tetep each carried two resistance genes for these isolates, while Nongken 58 carried one (Table I). Allelism tests indicated one of the two genes in Chengte 232 was allelic to Xa-3, which was derived from Nongken 58. Apparently, the resistance genes of Tetep were not transferred into Chengte 232 (Table 2). The other gene of Chengte 232, however, was probably derived from Kongkewan

Analysis of resistance gene for blast in Chengte 232 Ku Jianlong, Lin YIZI, and XI Yongan, Plant Institute, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China

We analyzed the resistance genes and their allelism of Chengte 232 and its resistance donors using blast fungus isolates ZB1 (926) and P-2b (Japan). Chengte 232 and its resistance donors, Toride 1 and Tetep, are resistant to ZB1 and P-2b. Nonghu 6, which is susceptible to the isolates, was used as the susceptible parent.

Chengte 232, Toride 1, and Tetep were each crossed with Nonghu 6 to analyze the inheritance of resistance. We also made crosses among Chengte 232, Toride 1, and Tetep to test allelism of resistance genes.

and inoculated at maximum tillering by injecting plants with a spore suspension of 1-2 x 10 5 conidia/ml. Disease reaction was assessed at 7 d after inoculation using the Standard evaluation system for rice. Plants with scores of 1-3 were

All materials were planted in the field

classified as resistant and those with

Table 1. Resistance reaction to ZB1 and P-2 braces in progeny of resistant/susceptible combinations.

F 2 EX- Combination Race F 1 pected P

Total Resistant Susceptible ratio

Chengte 232/Nonghu 6 ZB1 R a 189 143 46 3:1 0.0159 >0.90 P-2b R 189 143 46 3:1 0.0159 >0.90

Toride 1/Nonghu 6 ZB1 R 204 144 60 3:1 1.8889 0.25-0.10 P-2b R 204 144 60 3:1 1.8889 0.25-0.10

Tetep/Nonghu 6 ZB1 R 182 133 49 3:1 0.2637 0.75-0.50 P-2b R 182 166 16 15:1 1.5956 0.25-0.10

a R = resistant.

Table 2. Segregation for resistance to ZB1 and P-2b races in progeny of resistant/resistant combinations.

Combination Race

Chengte 232/Toride 1 ZB1

Chengte 232/Tetep ZB1 P-2b

Toride 1/Tetep ZB1 P-2b

P-2b

F 2 Expected F 1 ratio P

Total Resistant Susceptible

R a 216 216 0 R 216 216 0 R 169 162 7 15:1 0.9471 0.50-0.25 R 169 165 4 63:1 0.2841 0.75-0.50 R 178 168 10 15:1 0.0375 0.90-0.75 R 178 170 8 63:1 8.1330 <0.005

a R = resistant.

scores of 4-9 as susceptible. two dominant duplicate genes for P-2b

resistance to ZB1 and P-2b in Chengte genes of Chengte 232 are nonallelic to 232 and Toride 1. Tetep has one those of Tetep and those of Toride 1 are dominant gene for resistance to ZB1 and allelic (Table 2).

A single dominant gene controls (Table 1). Allelism tests indicated that the


c 2 c

c 2 c

c 2 c

c 2 c

Resistance in Chengte 232 to the two Because Toride 1 carries Pi-z t , it is likely isolates tested is conditioned by a single gene that is allelic or closely linked to a Chengte 232. The resistance genes of Reprint service. All items included in

that Pi-z t controls the resistance in IRRN REMINDER

gene in its progenitor, Toride 1. We Tetep, however, were not transferred into conclude, therefore, that Chengte 232 inherited the gene from Toride 1.

Chengte 232. the Rice literature update are available at the IRRI Library and Documentation Service. Photocopies of original documents (not to exceed 40 pages) are supplied free to rice scientists of developing countries. Rice scientists elsewhere

of a page copied, plus postage. Payment should be in check or money order,

was counted by tapping plants. Damage Service, IRRI. was scored in the glasshouse experiment Address requests to Library and using the 0-9 scale of the Standard evaluation system for rice (see table).

Screening of rice hybrids for are charged US$0.20 for each page or part randomized complete block design. The

resistance to whitebacked

design. furcifera (Horvath) twice using a completely randomized planthopper, Sogatella glasshouse experiment was replicated

Number of insects/10 hills in the field Payable to Library and Documentation J. Singh, K. K. Shukla, G. S. Sidhu, S. S. Malhi, and M. R. Gagneja, Punlab Agricul- tural University (PAU), Ludhiana 141004, India

Twenty-four rice experimental hybrids PERHl88, PERH207, PERH210, and were screened for whitebacked PERH225 were found to be moderately planthopper (WBPH) resistance at the resistant under both conditions and

IN%"[email protected]"

adult plant stage under natural conditions PERH239, PERH288, and PERH690 at Bhupindra Rice Research Substation,

germplasm should be screened for noted in PERH125, PERH229, ments were replicated three times using a the test entries suggests that rice conditions. Differences, however, were glasshouse at PAU. The field experi- PERH577 A. The differential behavior of nearly half of the entries under both stage), and under artificial conditions in a PERH244, PERH353, PERH588, and Similar results were recorded for Rauni (a hot spot of the insect at seedling

were considered to be susceptible.

Screening of rice hybrids under natural conditions at a hot spot in Rauni and under artificial infestation artificia1 conditions. conditions. 1993 kharif.

Documentation Service, IRRI, P.O. Box 933, Manila 1099, Philippines. Fax: (63-2) 817-2087, electronic mail:

reaction to WBPH under both natural and

Insects/10 hills Damage Screening rice accessions for Hybrid Parentage at Rauni score

(no.) (0-9 scale) resistance to thrips PERH1 Pb.CMS 8 A/PAU1106-6-2 66 6.9

PERH38 Pb.CMS 2 A/PR106 25 5.7 PERHS Pb.CMS 1 A/PAU1126-15-3-1 61 6.8 PERH7 Pb.CMS 1 A/PAU1106-6-2 44 6.6

Annamalainagar 608002, Tamil Nadu, India PERH3 Pb.CMS 10 A/PAU1106-6-2 60 5.2 ogy Department, Annamalai University, PERH2 Pb.CMS 8 A/IR31432-6-2-1R 55 7.2 M. P. Parthiban and R Veeravel, Entomol-

Thrips, Stenchaetothrips biformis PERH46 Pb.CMS 4 A/IR31432-6-2-lR 61 6.3 (Bagnall), is a serious pest in rice PERH125 Pb.CMS 8 A/lR13292-5- 3 39 7.9 nurseries in the tropical plains of Tamil PERH134 PERH135 PERH188 PERH207 PERH210 PERH225 PERH229 PERH239 PERH244 PERH257 PERH288 PERH353 PERH389 PERH588 PERH577 A PERH690 PR103 (check) PR106 (check) PR108 (check) PR110 (check)

Pb.CMS 8 A/PAU1126-1-1 Pb.CMS 8 A/PAU1126-15-3-1 Pb.CMS 10 A/PAU1106-5-4 Pb.CMS 10 A/PR106 Pb.CMS 1 A/lR32841-46-1-1 Pb.CMS 2 A/lR32841-46-1-1 Pb.CMS 2 A/PAU1106-21-4 Pb.CMS 3 A/IR31432-6-2-lR Pb.CMS 3 A/PAU1106-21-4 Pb.CMS 3 A/PR103 Pb.CMS 8 A/PAU1126-29-1 Pb.CMS 1 A/lR13292-5-3 Pb.CMS 3 A/PAU1126-15-3-1 Pb.CMS 1 A/lR31802-56-4 Pb.CMS 2 A/lR31802-56-4 Pb.CMS 58025 A/PAU1106-6-2 IR8/IR127-2-2 IR8//Peta*5/Belle Patna Vijay/Ptb21 TN1/Patong 32//PR106

145 77 39 53 34 35

191 138 165 101 193 34 79 27 22

165 76 83 29 72

5.8 6.9 4.5 4.6 3.2 5.0 4.1

3.6 5.8 8.1 6.7

7.5

6.3 6.6 6.8 6.3 8.4 7.2 6.3

Nadu. Both nymphs and adults can cause extensive damage to seedlings by feeding on the leaves, resulting in inward curling along the margins that can lead to scorching, wilting, and death.

In the first phase, we screened 122 accessions for reaction to thrips in the field during August 1992 and September 1993 at the Annamalai University Experimental Farm, Annamalainagar. Each test entry was planted in moist soil in 0.7-m long rows, at a row space of 20 cm. Each entry was replicated three times, with one row per replication. Ptb33, the resistant check, and TN1, the


Pest resistance—insects

6.5

Reaction of rice accessions to thrips. Annamalainagar, Tamil Nadu, India. 1992-93. length of all leaves, pronounced

Field Greenhouse

1992 1993 Reaction a I II Reaction a Accession

1 1 HR 1 1 HR 1 1 HR 1 1 HR

Ptb33 1 1 HR 1 1 HR T235 1 1 HR 3 3.6 R Afaamwanza 1-1-159 1 1 HR 7 7 S Ptb19 3 3 R 3 3 R Ptb20 3 3 R 3 3 R Pokkali 3 3 R 3 3 R

IET6012 3 3 R 3 3 R IET6017 3 3 R 7 7 S IET8833 3 3 R 3 3 R

CO 43 3 3 R 3.6 3.6 R

lR49517-23-2-2-3-3 3.6 3.6 R 7 7 S RP2271-433 3 3 R 7 7 S IET9702 3 3 R 7 7 S IET9709 3 3 R 7 7 S IET9727 3 3 R 7.6 7.6 S T117 3 3 R 7 7 S T258 3 3 R 3.6 3.6 R T401 3 3 R 7 7 S T585 3.6 3.6 R 3 3 R

a HR = highly resistant, R = resistant, S = susceptible.

susceptible check, were sown randomly rolling of terminal third of first leaf only: alongside the test entries and exposed to 3 = rolling of terminal third of first and natural infestation. Damage was rated second leaves: 5 = rolling of terminal half twice, at 14 d and 21 d after sowing, on a of first, second, and third leaves. 0-9 scale where 0 = no damage: 1 = yellowing of leaf tip; 7 = rolling of entire

yellowing; and 9 = complete plant wilting, yellowing, and scorching. Five of the accessions were highly resistant and 16 resistant (see table).

In the second phase, the 21 resistant accessions were screened twice in the greenhouse. Entries were sown in 10-cm long rows in plastic trays (40 cm × 30 cm × 15 cm), filled 10-cm deep with soil. In each tray, 20 rows were sown in two strips. Ptb33 and TN1 were sown randomly with the test entries.

times. Water was added regularly to maintain soil moisture. Leaves infested with S. biformis from the stock culture were collected and evenly distributed until the population reached 5 thrips/ seedling. Seedlings were covered with a mylar film case with a muslin top. Damage was rated on the 0-9 scale 21 d after infestation. Three of the accessions were highly resistant, nine resistant, and the rest susceptible (see table).

Each set of entries was replicated three

Resistance to green leaf- glh 4: ASD8 with Glh 5; Tap1796 with and susceptible check TN1 were sown in Glh 6; Moddai Karuppan with Glh 7: 40-cm rows in wooden trays (60 x 45 x

10 cm) with five replications. At 7 d after 659 with Glh 3 + Glh 5; and monogenic sowing, seedlings were thinned to 15/row,

hopper in rice varieties with Charon Bawla with Glh 1 + Glh 2; Laki different resistance genes R. Velusamy, M. Ganesh Kumar, Y. S. Johnson Thangaraj Edward, and P. C. Sundara Babu, Entomology Department, Tamil Nadu Agricultural University (TNAU), Coimbatore 641 003, lndia

While identifying sources of resistance to the Tamil Nadu populations of green leafhopper (GLH), Nephotettix virescens (Distant), we observed differences in levels of resistance among varieties identified as resistant to GLH at IRRI. Varieties with a known GLH resistance gene or resistance genes and varieties with an unidentified dominant GLH resistance gene were evaluated for damage rating in the seedbox screening test and for their effects on growth of Tamil Nadu GLH populations.

To study varietal reactions, Pankhari 203 with Glh 1; ASD7, Tendeng, Rhissa, Sefa, Badal 2, and Chota Digha with Glh 2; Chiknal with Glh 3; Ptb8 with

varieties Hashikalmi, Ghaiya, ARC10318, infested with 5-6 second-instar nymphs/

Plant damage rating and population growth of green leafhopper on rice varieties with different genes for resistance a . Tamil Nadu, India.

Gene(s) for Damage Population Variety resistance rating b growth (no.)

Pankhari 203 Glh 1 9.0 a 201.8 ab ASD7 Tendeng Rhissa Sefa Badal 2 Chota Digha Chiknal Ptb8 ASD8 Tapl796 Moddai Karuppan Hashikalmi

ARC10313 Ghaiya

Choron Bawla Laki 659 TN1

Glh 2 Glh 2 Glh 2 Glh 2 Glh 2 Glh 2 Glh 3 glh 4 Glh 5 Glh 6 Glh 7 One dominant One dominant One dominant Glh 1 + Glh 2 Glh 3 + Glh 5 None

3.0 b 2.2 bcd 1.4 de 1.8 cde 1.0 e 1.4 de 2.6 bc 2.2 bcd 2.6 bc 1.0 e 1.0 e 9.0 a 9.0 a 9.0 a 1.8 cde 1.0 e 9.0 a

41.9 efg 56.4 d 54.8 d 47.0 def 31.2 ghi 51.0 de 50.0 de 39.6 fg 47.4 def 23.0 l 12.4 j

187.0 c 197.0 bc 190.0 bc

38.8 fgh 8.6

212.8 a j

a Mean of five replications. In a column, means followed by the same letters are not significantly different (P = 0.05) by DMRT. b Damage scored using SES.


Ptb22 IR62

seedling, and covered with a fine fiber glass-mesh cage. Damage was scored on the 0-9 scale of the Standard evaluation system for rice (SES) when TN1 was killed.

Population growth was studied by infesting 30-d-old potted test plants with five pairs of GLH adults. The plants were covered with mylar film cages and arranged in a randomized complete block design, replicated five times. Nymphs

New ufra-resistant rice lines M. L Rahman, Plant Pathology Division, Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh

During 1990-93, we tested and selected 29 F 2 populations and their progenies for ufra ( Ditylenchus angustus ) resistance. One hundred twenty-four selected lines of F 5 populations were further evaluated in 1993. Seeds of each of these entries were sown in pots and inoculated with 100 nematodes/plant at 15 d. Entries were scored 6 wk after inoculation based on leaf symptoms of susceptibility (Fig. 1a) and resistance (Fig. 1b-d).

Ten seedlings from each of the entries with resistance symptoms were transplanted for field evaluation from booting to flowering stages. A few seedlings with primary infestations and resistance symptoms were marked with


and adults on each plant were counted 30 d after infestation.

Thirteen varieties, ASD7, Tendeng, Rhissa, Sefa, Badal, Chota Digha, Chiknal, Ptb8, ASD8, Tap1796, Moddai Karuppan, Choron Bawla, and Laki 659, were rated as resistant in the seedbox screening test (see table). Pankhari 203 with Glh 1 gene, and Hashikalmi, Ghaiya, and ARC103 13 with a dominant gene, were rated as susceptible. Population

increase was significantly higher on TN1. Pankhari 203, Hashikalmi, Ghaiya, and ARC10313 than that on the resistant varieties.

Among the GLH resistance genes identified at IRRI, Glh I and a dominant gene in Hashikalmi, Ghaiya, and ARC10313 do not confer resistance to GLH populations in Tamil Nadu while varieties with Glh 2, Glh 3, Glh 4, Glh 5, Glh 6, Glh 7, Glh 1 + Glh 2, and Glh 3 + Glh 5 do confer resistance.

Rice entries with ufra resistance. BRRI, Bangladesh.

Plant type Entries

Tall IR63142-J6-B-1 IR63142-J8-B-2 IR63155-J9-B-1 IR63174-J1-B-3 IR63188-J8-B-1 IR63188-J8-B-7 IR63225-J2-6-1 IR63225-J2-B-4 IR63225-J2-B-6 IR63645-J3-B-8

Short IR63174-J1-B-2-3 IR63174-J1-B-3-2 IR63174-J1-6-3-1 IR63174-J1-B-4-3 IR63174-J1-6-6-3 lR63174-J2-8-4-2 IR63174-J3-B-1-2

red cellophane tape to record their secondary tillers of susceptible varieties survival. After establishment, five plants survived. Nematode numbers were 0-101/ from each of these entries were dissected plant in resistant entries and 141-3280 in to count nematode populations. Rayada the susceptible ones. Rayada 16-06-1, 16-06- 1 was the resistant check and however, did not have any symptoms or Habiganj Aman II, the susceptible check. nematodes in this experiment.

Sixty-four of the lines survived and flowered successfully. Ten deepwater rice lines (see table) had mild or no resistance symptoms. Seven other resistant entries (see table) were short- stemmed and may be used as resistance sources for rainfed lowland and irrigated rices. These entries had either Bazail 65 Twelve new rice varieties or Rayada 16-06 as a resistant parent. released for Orissa State, India

to maturity in all of the marked lines, but 91-96% of the secondary tillers that

Seedlings with primary infestations and resistance symptoms did not survive H. K. Mohanty, A. T. Ray, S. R. Das, Sri D. N.

Bastia, Rice Research Station, Plant Breeding and Genetics Department, Orissa University of Agriculture and Technology (OUATI,

emerged from them survived and Bhubaneswar 751003, lndia flowered successfully. In contrast, neither seedlings with primary infestations nor The Orissa State Subcommittee

varieties, developed by OUAT, for commercial cultivation in the state. Badami (OR 164-5), Nilagiri (OR 163-

recommended the release of 12 new rice

Symptoms of ufra

pattern chlorosis (a); rainfed and irrigated upland ecosystems; Susceptible: splash Ghanteswari (OR377-85-6) are adapted to disease on rice leaves.

104), Khandagiri (OR811-2), and

resistant: discrete or Birupa (OR253-2), Meher (OR526-2008-

rounded cholorotic 4), Samanta (OR487-30-3) and Bhanja

lesion (b, d), elongated (OR443-80-4), four midseason varieties chlorotic lesion (c). are recommended for irrigated

Integrated germplasm improvement

Pest resistance— other pests

Rice varieties recommended for release in Orissa State, India, during 1992-93.

Variety Designation Parentage Major features Maturity (IET no.) duration

Badami 0R164-5 Suphala/ Semidwarf, golden-colored 90-95 (IET7259) Annapurna hulls and kernels, medium-

bold grains

Nilagiri 0R163-104 Suphala/ Semidwarf, straw-colored hulls. 90-95 (IET10393) DZ192 medium-bold grains, trans-

lucent white kernels

Khandagiri OR811-2 Parijat/ Semidwarf, straw-colored hulls, 90-95 (IET10396) lR13429-94 medium-slender fine grains,

translucent white kernels

Ghanteswari 0R377-85-6 lR2061-628/ Semidwarf, golden-colored hulls 90-95 (I ET9802 j N22 with medium-bold translucent

dull red kernels

Birupa 0R253-2 Adt 27/1R8/// Semidwarf, straw-colored hulls, 130-135 (I ET8620 j Annapurna medium-bold translucent

white kernels

Meher 0RS26-2008-4 OBS6771 Semidwarf, straw-colored hulls, 135-140 (I ET9849) IR2071// medium-bold, translucent white

Vikram/ kernels W1263

Samanta 0R487-30-3 T90/IR8// Semidwarf, straw-colored hulls, 135-140 (IET10451) Vikram/// medium-bold translucent white

Siam29/ kernels, dark green, erect flag Mahsuri leaves until maturity

Bhanja 0R443-80-4 IR36//Hema Semidwarf, straw-colored hulls, 140-145 (IET10738) Vikram medium-bold grains, translucent

white kernels, dark green erect flag leaves until maturity

Mahalaxmi 0R621-6 Pankaj/ Semidwarf, straw-colored hulls. 150-155 (IET10048j Mahsuri

white kernels medium-bold grains, translucent

Manika 0R624-46 CR1010/ (IET9737) OBS677

Semidwarf, straw-colored hulls, 155-160 medium-bold grains, dark green

white kernels erect flag leaves, translucent

Urbashi 0R645-I8 Rajeswari/ Tall, straw-colored hulls, 140-145 (IET10811) Jajati medium-bold grains,


Kanchan 0R609-15 Jajati/ Tall, straw-colored hulls, 150-155 (IET10016) Mahsuri medium-slender grains,


Resistance Av

(t/ha) yield

Gall midge, leaf- 3.7 folder, green leafhopper, bacterial leaf blight and blast Bacterial leaf blight, 3.5 blast, rice tungro virus, stem borer, leaffolder, gall midge 1 Bacterial leaf blight, 3.5 blast, sheath rot, gall midge, brown planthopper, whitebacked planthopper Bacterial leaf blight, 3.5

gall midge, sheath blast, brown spot,

blight, green leafhopper Bacterial leaf blight, 4.2 blast, rice tungro virus, gall midge, stem borer, whorl maggot, leaffolder, and whitebacked planthopper Blast, bacterial 4.4 leaf blight, sheath rot, brown planthopper, whitebacked

blight, gall midge planthopper, sheath

Blast, bacterial leaf 4.4 blight, sheath rot, gall midge 1, gall midge 4, whitebacked planthopper, sheath blight Blast, bacterial leaf 4.0 blight, sheath rot, gall midge 1, gall midge 4, sheath blight Bacterial leaf blight, 5.0 blast, false smut, leaffolder, green

Bacterial leaf blight, 5.0 leafhopper

blast, sheath rot, gall midge 1, gall midge 4, sheath blight, and brown planthopper Blast, sheath blight, 4.8 rice tungro virus, gall midge, leaffolder Bacterial leaf 4.5 blight, sheath

blight, gall rot, sheath

midge

Adaptability

Rainfed and irrigated uplands


Rainfed and Irrigated uplands


Irrigated and rainfed medium lands




Lowlands

Lowlands

Lowlands

Lowlands

ecosystems; and Mahalaxmi (OR621-6), Manika (OR624-46), Urbashi (OR645 18), and Kanchan (OR609-15) are suitable for lowland ecosystems.

The features of these varieties are listed in the table.


Rajavadlu and Sagar-Samba released in Andhra Pradesh, India M. Kashikar, N. V. Nanda, V. Hasan, and N. Kulkarni, Rice Section A, Agricultural Research Institute, Rajendranagar, Hyderabad 500030, India

Rajavadlu (RNR99377) and Sagar-Samba (RNR52147) were released in Andhra Pradesh (AP) for general cultivation during 1993.

Rajavadlu, a derivative of the cross Rajendra/IR30, is a semidwarf, medium- duration variety with multiple resistances and high yield potential.

In yield trials under transplanted irrigated conditions from 1980 to 1991, Rajavadlu yielded an average of 6.5 t/ha, with 21 % higher yields than Tellahamsa, 34% than Saleem, 55% than Prakash, and 24% than Samba-Mahsuri, one of the most popular varieties in AP.

In the All-India Coordinated Trials, Rajavadlu ranked 2nd and yielded an average 21.2% more than check varieties. In farmers’ field trials, it yielded an average of 20% more than the checks.

Rajavadlu is nonlodging, photoperiod- insensitive, and fertilizer-responsive. It has 130-135 d duration in wet season and 145-150 d in dry season due to the region’s low temperatures. It is resistant to blast, brown spot, and sheath rot and moderately resistant to bacterial leaf blight and gundhi bug. Seedlings up to 50 d old may be planted without problems. Grain is long and slender with white translucent kernels and good cooking quality.

Sagar-Samba (RNR52147) is another medium-duration nonlodging variety with multiple resistances and fine grains. It is derived from the double cross IR8/Siam 29//IR8/Ptb21.

It was tested in various yield trials under transplanted irrigated conditions from 1974 to 1991. Yield averaged 5.7 t/ha—13.4% higher than that of Samba- Mahsuri. In All-India Coordinated and multilocation trials, Sagar-Samba yielded an average of 5.6 t/ha, an average of 12.4% more than that of check varieties.

In large-scale demonstration trials from 1982 to 1991, Sagar-Samba yielded an average of 4.9 t/ha. In minikit trials, it averaged 4.5 t/ha, an 8.3% increase over the checks.

Sagar-Samba is a dwarf photoperiod- insensitive, fertilizer-responsive variety

Pakhal: a high-yielding, short-duration rice variety for Hazara division in Pakistan M. Akram, M. Ashraf, F. M. Abbasi, and M. A. Sagar, National Agricultural Research Centre, Islamabad, Pakistan

Pakhal (IR28128-45-2) is a new high- yielding rice variety recommended for cultivation in Hazara division. It is semidwarf and 104 cm tall, compared with local variety JP5, which is 131 cm. Pakhal matures 16 d earlier than JPS. The new variety produced 28% more grain

Table 1. Performance of Pakhal in yield trials. Pakistan, 1988-90.

Yield (t/ha) Percentage Year

Pakhal JP5 increase over JP5

1988 3.7 2.9 29 1989 5.5 4.4 25 1990 5.0 3.9 28

Mean 4.7 3.7 27

Table 2. Comparative characteristics of Pakhal and JP5. Pakistan.

Aeronomic trait Pakhal JP5

Plant height (cm) 104 131 Maturity period (d) 124 140 Yield (t/ha) 4.6 3.3 1,000-grain weight (g) 22.9 24.2

Grain quality (physicochemical characteristics) Rough grain

Length (mm) 10.0 7.8 Breadth (mm) 2.2 4.2

Length (mm) 6.6 5.8 Breadth (mm) 1.9 3.0 L-B ratio 3.5 1.9 Grain size and shape Long/slender Short/

bold Head rice recovery (%) 58.8 55.2 Aroma None None Protein content (%) 8.0 7.8 Amylose content (%) 24.7 17.7

Milled grain

with a 145 d duration in wet season. It is resistant to blast, sheath rot, brown spot, and gall midge and has field resistance to brown planthopper. Grain is medium slender.

than did JP5 in 1989 and 1990 national uniform rice yield trials (Table 1).

Pakhal is resistant to stem borer and leaffolder. Head rice recovery is 58.8% for Pakhal and 55.2% for JPS (Table 2). Pakhal’s grain is long and slender while that of JPS is short and bold. Pakhal’s quality index value is 2.2; that of JPS is 0.84.

ADT42: a new high-yielding, early-duration rice for Tamil Nadu, India A. P. M. K. Soundararaj, S. Giridharan, S. Geetha, P. Narayanasamy, A. Abdul Kareem, S. Palanisamy, and S. Chelliah, Tamil Nadu Rice Research lnstitute (TNRRI Aduthurai 612101, India

ADT42 is a semidwarf indica rice that was developed at TNRRI by pedigree selection from the cross AD9246/ ADT29. It is suitable for cultivating as a transplanted crop in the irrigated ecosystem.

In 91 trials conducted at research stations and in farmers’ fields in Tamil Nadu, ADT42 yielded a mean of 5.5 t/ha, 10% more than the yield of check IR50 (Table 1).

to blast and brown planthopper (BPH) (Table 2).

This variety is 90 cm tall and has a growth duration of 100 d. The grain is long and slender, with good cooking quality. It has hulling recovery of 81.9% and milling recovery of 75.64. Its 1,000- grain weight is 24.8 g.

ADT42 was released in Jan 1994 for cultivation during kharif season (Jun- Sen) in all districts of Tamil Nadu.

ADT42 possesses moderate resistance


Integrated germplasm improvement—irrigated

Table 1. Grain yield of ADT42 in Tamil Nadu, India. 1986-93.

Mean grain yield (t/ha) Increase

(no.) ADT42 IR50 (check) check (%) Trial and year Locations over

TNRRI, Aduthurai, 1986-93 8 6.0 4.5 33 Multilocation trials at research stations, 1990-92 22 5.5 4.8 15 Adaptive research trials in farmers' fields, 1992 61 5.5 5.2 7

Total/weighted mean 91 5.7 4.8 10

Table 2. Reaction of ADT42 to blast and BPH in Tamil Nadu, India. 1990-92.

Mean score a

ADT42 IR50 (check) Disease/insect

Blast 3.4 8.7 BPH 3.7 7.0 a Scored under artificial conditions using the scoring methods in Standard evaluation system for rice.

CORH1: the first rice hybrid for Tamil Nadu, India M. Rangaswamy, M. N. Prasad, S. R. Sree Rangasamy, Tamil Nadu Agricultural University (TNAU), Coimbatore 641003, India; S. S. Virmani, IRRI; E. A. Siddiq, Directorate of Rice Research (DRR), Hyderabad, India; and T. B. Ranganathan, W. Wilfred Manual, K. Thiyagarajan, P. Jayamani, V. Palanisamy, K. Angamuthu, A. S. Ponnusamy, G. James Martin, P. Thangamani, and R. Velusamy, TNAU

CORH1 is a rice hybrid selected at the Paddy Breeding Station, Coimbatore, Tamil Nadu, from hybrids shared by IRRI through DRR, Hyderabad. The hybrid is developed using the cytoplasmic genetic male sterility and fertility restorer system. IR62829 A and IR10198-66-2 R are the parents.

CORH1 matures in 100-115 d and is up to 75 cm tall. It has high-tillering ability, giving up to 20 productive tillers/ hill at 25- × 20-cm spacing. The average grain number is 150/panicle; its 1,000- grain weight is 20 g. Grains are medium slender and straw-colored; kernels are

Yield of CORH1 (t/ha) compared with IR50 and Rasi, Tamil Nadu, India.

Trials Type of trial Year (no.) CORH1 a IR50 Rasi

Research station 1990-92 4 5.2 4.6 Multilocation 1991 kharif 7 5.7 4.4 Multilocation 1992 kharif 6 5.2 4.8 Multilocation 1993 kharif 3 5.4 4.3 Large-scale demonstration 1993 kharif 4 5.2 4.9 On-farm 1992 kharif 14 6.1 5.2 On-farm 1993 kharif 18 6.3 5.4 National hybrid rice 1990-91 18 6.2 5.1

Mean 74 5.9 5.0 5.1 a % over IR50 = 118.8; Rasi = 117.3.

white. CORH1 is best suited for May-Jun sowing in Tamil Nadu.

The mean grain yield for CORH1 at 74 locations in research station, on-farm, and national hybrid rice trials (see table) was 5.9 t/ha compared with 5.0 t/ha for IR50. The mean biological yield of CORH1 was 11.2 t/ha (5.9 t grain and 5.3 t straw). The highest recorded grain yield was 10.1 t/ha (see figure).

Physical, cooking, chemical, and organoleptic characters are all good. CORH1 is moderately resistant to whitebacked planthopper. brown

Average and highest yield of CORH1. Tamil Nadu, India.

planthopper, green leafhopper, sheath rot, brown spot, and rice tungro virus under field conditions.

The Tamil Nadu State Variety Release Committee approved the release of CORHl in Dec 93 and the state government released it for general cultivation during kharif season (Jun-Sep) 1994.

IRRN REMINDER

Routine research. Reports of screening trials of varieties, fertilizer, cropping methods, and other routine observations using standard methodologies to establish local recommendations are not ordinarily accepted. Examples are single-season, single-trial field experiments. Field trials should be repeated across more than one season, in multiple seasons, or in more than one location as appropriate. All experiments should include replications and an internationally known check or control treatment.


Performance of lowland transplanted sali (winter) rice varieties under late planting in Assam, India

Cultivar

Grain yield (t/ha) and duration (d) of some sali rice varieties as influenced by transplanting dates in Assam, India, 1990-92.

Transplanting date (TPD) a

11 Aug 26 Aug (25 DAS)

10 Sep (40 DAS) (55 DAS)

25 Sep (70 DAS)

Mean

J. K. Choudhary, K. Kurmi. R. K S. M. Baruah, and G.R. Das, Regional Agricultural Research Station, Assam Agricultural University, Karimganj 788710, India

In flood-prone areas of Assam, transplanting of sali (tall or semidwarf winter) rice is sometimes impossible at the normal time (Jul-Aug) because of floods, forcing farmers to transplant older seedlings after the floodwater recedes. To compensate for low tillering from the aged seedlings, farmers transplant 4-6 seedlings/hill instead of 2-3 at a closer spacing. But with the monsoon retreating, the crop often suffers from insufficient soil moisture late in the season.

We evaluated yield performance of three photoperiod-insensitive semidwarf cultivars, IET10334, IET9757, and IET7251; two photoperiod-sensitive semidwarf cultivars, Biraj and Kmj 1-52- 3; and two photoperiod-sensitive tall cultivars, Andrewsali and Monoharsali, during 1990-92 under two normal and two late transplanting dates (TPD).

In both years, seeds were sown on 17 Jul. Seedlings were transplanted at 25, 40, 55, and 70 d after sowing (DAS) on 11 and 26 Aug and 10 and 25 Sep, respectively. A split-plot design with four replications was used with TPD as main plots and cultivars as subplots.

For normal transplanting (11 and 26 Aug), 2-3 seedlings/hill were transplanted at 20- × 10-cm spacing; for late transplanting (10 and 25 Sep), 4-6 seedlings/hill were transplanted at 15- × 10-cm spacing.

The soil was a clay loam with pH 5.8, 0.7% organic C, 65 kg available P/ha, and 115 kg available K/ha. Fertilizers were applied at 60-30-30 kg NPK/ha.

Mean yield was greater in 1991-92 than in 1990-91 (see table), perhaps because of a more favorable cessation of the wet season. Rainfall during Nov-Dec was greater in 1991 (120.7 mm) than in 1990 (71.8 mm).

Monoharsali Andrewsali IET10334 IET9757 IET7251 Kmj 1-52-3 Biraj

Mean

Monoharsali Andrewsali IET10334 IET9757 IET7251 Kmj 1-52-3 Biraj

Mean

2.8 (130) b

2.7 (130) 2.2 (138) 2.7 (139) 2.8 (131) 2.4 (131) 2.8 (131) 2.6

4.2 (130) 4.6 (126) 4.0 (137) 3.7 (142) 3.9 (131) 4.0 (130) 3.7 (130) 4.0

1990-91 2.7 (134) 2.0 (137) 2.4 (133) 2.3 (137) 1.7 (149) 1.5 (164) 1.8 (148) 1.5 (175) 2.5 (137) 2.2 (146) 2.2 (134) 2.1 (137) 2.3 (134) 2.1 (137) 2.2 2.0

1991-92 4.0 (131) 3.9 (136) 4.2 (128) 3.9 (135) 3.8 (145) 2.2 (161) 2.3 (150) 0.2 (175) 3.3 (140) 2.9 (151) 3.7 (135) 3.6 (137) 3.9 (134) 3.7 (136) 3.6 2.9

1.9 (137) 2.2 (137) 1.3 (172) 0.1 (178) 1.8 (156) 2.1 (148) 2.0 (143) 1.6

3.2 (142) 3.6 (137) 0.8 (167) 0.1 (177) 0.3 (155) 3.2 (145) 3.2 (145) 2.1

2.3 2.4 1.7 1.5 2.3 2.2 2.3 2.5

3.8 4.1 2.7 1.6 2.6 3.6 3.6 3.7

LSD for yield (0.05) 1990-91 1991-92 TPD 0.08 CV

0.11 0.10 0.22

CV within a TPD 0.21 0.45 TPD within the same or different CV 0.20 0.42

a Sown on 17 Jul. b Duration in parentheses.

The main effects of TPD and cultivars on grain yield were significant (see table). Grain yield decreased significantly with delay in transplanting. Andrewsali significantly outyielded Monoharsali. Kmj 1-52-3, and Biraj, which in turn significantly outyielded the three IET cultivars.

The interaction between TPD and cultivars was significant, with greater yield reduction in the case of photoperiod-insensitive cultivars than for photoperiod-sensitive cultivars. With late transplanting in 1991-92, Andrewsali. Monoharsali, Kmj 1-52-3, and Biraj significantly outyielded the three IET cultivars.

Delay in transplanting significantly increased crop duration (see table). especially for the photoperiod-insensitive cultivars. Extended crop duration resulted in decreased grain yield, presumably because plants were exposed to greater water stress at the grain-filling stage.

Thus, in flood-prone areas of Assam, tall photoperiod-sensitive cultivars, such as Andrewsali, are favored. If floods delay transplanting, such cultivars are less susceptible to delay in flowering and the likely reduction in grain yield due to terminal drought stress.


Integrated germplasm improvement—rainfed lowland

Crop and resource management

Integrated N management in irrigated lowland rice K. S. Rao and B. T. S. Moorthy, Agronomy Division, Central Rice Research Institute, Cuttack 753006, lndia

Using both organic and inorganic fertilizers is a way to save on costs and to maintain soil health, resulting in sustained crop production. We conducted a field experiment at Cuttack from 1988 to 1992 in an alluvial (Inceptisol) sandy loam soil with pH 6.0, 0.5% organic C, 0.058% total N, 36 ppm available P, and 1 meq exchangeable k/100 g soil.

The treatments (see table) combined inorganic fertilizer (prilled urea [PU]) in equal proportion (50:50) with organic fertilizers: farmyard manure (FYM), Azolla compost, water hyacinth compost, and green manures ( Sesbania aculeata and S. rostrata ). A conventional 3-way split application of PU, urea supergranule (USG) placement 7 d after transplanting (DT), and a no-N control were used for comparison. The N rate was maintained at 75 kg/ha.

in a randomized block design. The photoperiod-sensitive, long-duration variety Gayatari (CR1018) was planted in the first fortnight of July, at a spacing of 15 × 15 cm. Green manure crops were incorporated into the field at 40 d.

1.9% for S. aculeata, 1.6% for Azolla compost, 1.5% for S. rostrata, 1.3% for FYM, and 1.2% for water hyacinth compost.

Grain yield in different integrated N application schedules was comparable with that of the conventional 3-way split application of PU and USG treatments during the first 4 yr of the study (see table). During the fifth year, grain yield was significantly lower in the 3-way split of PU compared with the other treatments. Yield declined over time in all the

Treatments were replicated four times

N content, on a dry-weight basis, was

Influences of different integrated N management treatments on grain yield of rice. Cuttack, India. 1988-92.

Treatment a Grain yield (t/ha)

1988 1989 1990 1991 1992

Control (no N) 4.1

FYM + PU (50:50) 6.2

Azolla compost + PU (50:50) 6.2

Water hyacinth compost + PU 6.3

S. aculeata + PU (50:50) 6.4

S. rostrata + PU (50:50) 6.3

Conventional 3-split application 6.3

USG at 7 DT of PU

6.2

LSD (P = 0.05) 0.3

(50:50)

4.0 (2.4) b

5.7 (8.3) 5.6

(10.6) 5.3

(10.9) 5.6

(11.9) 5.7

(10.4) 5.4

(10.4) 5.5

(12.0) 0.5

3.8 (8.5) 5.4

(12.8) 5.4

(13.8) 5.4

(13.4) 5.4

(15.5) 5.4

(15.4) 5.4

(14.6) 5.3’

(15.3) 0.3’

3.8 3.3 (7.3) (19.2) 5.7 5.3

5.9 5.2 (5.5) (15.9) 5.7 5.3

(9.4) (14.6) 5.6

(11.5) 5.2

(17.7) 5.9

(7.3) 5.2

(17.1) 5.5 4.7

(13.8) (25.8) 5.8 5.2

(7.7) (17.0) 0.5 0.4

(7.0) (13.3)

a N application treatments = 75 kg N/ha. b Figures in parentheses indicate yield decline from the first year.

treatments. The decline was, in general. Organic and inorganic fertilizer greater in the conventional 3-way split of applied in equal proportions can be used PU than in the integrated N application to realize higher and sustained yields in schedules and USG treatment in all years irrigated lowland rice. except 1990, when it was similar across treatments.

Evaluating Sesbania and urea supergranules vs prilled urea in rice and their residual effect on the succeeding wheat crop B. S. Mahapatra and G. L Sharma, Agronomy Department, G. B. Pant Univer- sity of Agriculture and Technology, Pantnagar 263145, Nainital, Uttar Pradesh (U.P), India

Much interest exists in ways to exploit renewable N sources that sustain soil fertility in rice cropping. Rice - wheat sequence is an important cropping system in the tarai Mollisol of U.P. We investi- gated how timing applications of urea supergranules (USG) in combination with green manure (GM) ( Sesbania aculeata grown in situ)—compared with best split applications of prilled urea (PU)—affect yield and N uptake of the rice crop.

The succeeding wheat crop yield and N uptake, nitrate production at wheat planting, and available soil N at the end

of the experiment were recorded. The clay loam soil had pH 7.3, 1.35%

(0-20 cm depth) and 0.5% (20-50 cm depth) organic C, 0.12% total N, and 200 m mol (+)/kg cation exchange capacity. Zinc (5 kg ZnSO 4 + 2.5 kg lime in 1000 liters of water/ha) was sprayed on the rice crop at 60 and 90 d after transplanting (DT) to control Zn deficiency. Ammo- nium N of the wet soil was determined by modified Nassler method (Jackson 1973). At wheat planting, nitrate N was determined by chromotropic acid method (Sims and Jackson 1974). Available soil N was determined by alkaline potassium permanganate method (Black 1973). Sesbania was raised in situ using 50 kg seeds/ha and was irrigated once before sowing and once during the growing season in all 3 yr. Average fresh weight of Sesbania was 34.1 kg/ha in 1987-88, 32.9 kg/ha in 1988-89, and 31.7 kg/ha in

Integrated management of Sesbania 1989-90.

GM + 29 kg N/ha as USG applied 2-5 wk


Fertilizer management

after transplanting (WT) gave about the same yield as that of 120 kg N/ha applied as PU. Yields obtained with 120 kg N/ha as PU and Sesbania + USG@ 2-5 WT were significantly more than those with 80 kg N/ha as PU. Yield obtained with Sesbania + USGat 1 WT was equal to that with 80 kg N/ha through PU. Grain yields had significant positive correla- tions with panicle number and with soil ammonium N measured during 1988-89 and 1989-90 at different rice growth stages (Table 1). N uptake by rice showed a trend similar to that of yield obtained.

Integrated management of Sesbania + USG@ 1-5 WT in lowland rice resulted in a significant increase in residual wheat yields compared with the control and with PU applied to rice at 40, 80, or 120 kg N/ha (Table 2). Increase in yield was greater in the second year and N uptake by the residual wheat crop was greater in the third year, and were significantly correlated with soil nitrate at wheat planting. Integrated GM + USG in rice - wheat rotation helped to maintain higher available soil N after 3 yr compared with the control and with PU application to the rice crop (Table 2).

Integrated N management with Sesbania GM and USG@ 2-4 WT can be used instead of PU at the recommended dose in a rice - wheat rotation where there is only time enough to grow a Sesbania crop for 50-60 d before transplanting rice. Using a renewable N source in lowland rice also benefits the succeeding wheat crop in a rice - wheat rotation, is equivalent to 20-30 kg N/ha, and will help to sustain soil N fertility.

Table 1. Grain yield and N uptake (grain + straw) of rice crop. a Pantnagar, U. P., India. 1987-90.

Grain yield (t/ha) N uptake (kg/ha) Treatment b

1987-88 1988-89 1989-90 1987-88 1988-89 1989-90

2.9 3.8 5.0 a 5.9 b 5.0 a 6.0 b 5.9 ab 6.0 b 5.7 b 0.59

2.7 3.8 5.0 a 6.1 b 4.9 a 6.5 b 6.3 b 6.2 b 5.9 b 0.71

56.4 a 78.9 b 94.1 c

103.7 cd 70.4 ab

124.8 e 97.8 cd

111.4 de 110.1 de

15.0

Control PU @ 40 kg N PU @ 80 kg N PU @ 120 kg N S + USG 1 WT S + USG 2 WT S + USG 3 WT S + USG 4 WT S + USG 5 WT CD at 5%

3.9 a 4.0 a 5.3 bc 5.8 cd 5.2 b 6.4 5.8 cd 5.9 d 6.0 d 0.50

49.8 76.8 a 95.8 abc

111.7 bcd 89.5 ab

111.7 bcd 121.5 cd 129.5 d

97.3 ab 26.7

47.8 81.4 a 97.3 ab

107.5 ab 91.3 ab

118.1 b 109.5 b 117.5 b 103.1 ab

27.1

r to panicle number

r to wet soil ammonium N

15 DT 30 DT 45 DT 60 DT

0.943** - 0.893** 0.918**

0.626 0.888** 0.853** 0.928**

0.702* 0.702* 0.807** 0.938**

0.666* 0.662 0.838** 0.936**

0.666* 0.879** 0.823** 0.905**

a * and ** =significance at P = 0.05 and P = 0.01, respectively. Values followed by the same letter in a column do not differ significantly. b PU was applied as split applications (50% at transplanting, 25% at tillering, and 25% at panicle initiation); USG was applied at 29 kg N/ha at 10.12 cm depth; S = Sesbania aculeata grown in situ for 55 d: + N content of 0.49% in 1987-88, 0.51% in 1988-89, and 0.51% in 1989-90.

Table 2. Grain yield and N uptake (grain + straw) of residual wheat, nitrate production at wheat planting, and available soil N at the end of the experiment a . Pantnagar, U. P., India. 1987-90.

Grain yield (t/ha) N uptake (kg/ha) Treatment b

1987-88 1988-89 1989-90 1987-88 1988-89 1988-90

23.5 a 25.4 ab 27.5 abc 30.2 bcd 34.5 d 27.5 abc 33.2 d 29.8 bcd 29.5 bcd

5.41

Control PU @ 40 kg N PU @ 80 kg N PU @ 120 kg N S + USG 1 WT S + USG 2 WT S + USG 3 WT S + USG 4 WT S + USG 5 WT

CD at 5%

0.9 a 0.9 a 0.9 a 0.9 a 1.2 b 1.2 b 1.2 b 1.2 b 1.0 b

0.29

1.0 a 1.0 a 1.0 a 1.1 a 1.9 b 1.7 b 1.6 b 1.7 b 1.9 b

0.34

1.2 a 1.2 a 1.3 a 1.2 a 1.9 b 1.9 b 1.7 b 1.8 b 1.8 b

0.41

28.3 a 28.9 a 31.7 a 32.1 a 42.1 b 48.1 b 45.1 b 47.2 b 46.1 b

7.30

29.8 a 31.4 ab 30.2 a 31.7 ab 37.5 bc 43.6 c 39.5 c 43.5 c 39.5 c

6.12

r to nitrate production at wheat planting in respective years 0.738** 0.943** 0.964** 0.960** 0.920** 0.921**

1987-88

14.2 14.9 15.7 14.9 23.4 20.8 20.1 22.5 20.1

18.51

Effects of gypsum, farmyard manure, and N on ameliorat- ing highly sodic soil and on yields of rice and wheat A. Swarup and K. N. Singh, Central Soil Salinity Research lnstitute (CSSRI), Karnal 132001, India

We explored the possibility of reducing the dose of gypsum application in conjunction with applying farmyard manure (FYM) and at two N levels. The field experiment was conducted from

Nitrate N Available soil N (kg/ha) (1990)

264 270 270 283 295 293 301 286 298

284.4

1988-89

17.1 16.1 19.1 20.1 27.6 29.3 26.5

1989-90

12.8 13.4 13.0 14.1 24.8 22.5 23.1 25.7 25.1

19.38

Control PU @ 40 kg N PU @ 80 kg N PU @ 120 kg N S + USG 1 WT S + USG 2 WT S + USG 3 WT S + USG 4 WT S + USG 5 WT

Mean

27.2 29.1

23.57

a ** = significant at P = 0.01, b All treatments were applied to the rice crop only. Nitrate N and available soil N were determined for each treatment from combined sample of three replications.


- -

- - - -

- - - -

Effect of soil amendments and N on grain yield of rice and wheat in a sodic soil.

Grain yield (t/ha)

Treatment Rice Wheat

1989 1990 1991 Pooled 1989-90 1990-91 1991-92 Pooled

Amendment Control Gypsum @ 25% GR Gypsum @ 50% GR Farmyard manure (FYM) @ 20 Mg/ha Gypsum @ 25% GR + FYM @ 20 Mg/ha Gypsum @ 50% GR + FYM @ 20 Mg/ha

N 100 kg/ha 150 kg/ha

LSD at P = 0.05

LSD at P = 0.05

3.0 5.1 5.4 4.1 5.8 6.1 0.3

4.6 5.3 5.5 5.2 5.8 6.0 0.4

5.2 5.3 5.3 5.3 5.8 5.9 0.4

4.3 5.2 5.4 4.9 5.8 6.0 0.4

0.2 1.7 2.0 1.4 2.1 2.4 0.4

1.0 2.2 2.3 2.0

2.8 0.4

2.8

1.2 2.3 2.4 2.2

2.9 0.3

2.8

0.8 2.1 2.2 1.9 2.6 2.7 0.4

4.7 5.2 5.4 5.1 1.5 2.0 2.2 1.9

0.2 0.2 0.3 0.2 0.2 0.2 0.2 0.2 5.2 5.6 5.6 5.4 1.8 2.3 2.5 2.2

Both crops received N (as per treatments) in three splits: one-third at transplanting of rice/sowing of wheat and the rest in two equal splits at 3 and 6 wk of crop growth. A basal dose of 40 kg ZnSO 4 /ha was applied to rice in the rotation. The soil tested high in available

1989 to 1990 at CSSRI’s Gudha experimental farm on a highly sodic soil with sand + silt 85.4%, clay 14.6%, CaCO 3 3.4%, organic C 0.20%, pH 10.4, exchangeable sodium percentage (ESP) 89, cation exchange capacity (CEC) 10 meq/100 g soil, gypsum requirement 25 t/ha, available N 45/kg ha, Olsen’s extractable P 38 kg/ha, NH 4 OAC extractable K 478 kg/ha, and DTPA extractable Zn 0.42 mg/kg.

The experiment was laid out in a split-plot design with 4 replications of 12 treatment combinations. Treatments were a control (no amendment); gypsum @ 25% gypsum requirement (GR) of soil (6.25 t/ha); gypsum @ 50% GR (12.5 t/ /ha); FYM @ 20 t/ha; gypsum @ 25%

P and K so these elements were not

improved significantly the grain yield of rice and wheat (see table) and substantially decreased pH and ESP of the soil

applied. Results showed that gypsum and FYM

profile (see figure) compared with the control. When gypsum dose was reduced from 50 to 25% of GR, with or without FYM, there was no significant decrease in the yield of either crop except rice during 1989. Gypsum @ 25% GR + FYM was significantly better than gypsum @ 50% GR and at par with

GR + FYM @ 20 t/ha; gypsum @ 50% gypsum @ 50% GR + FYM in decreas- GR + FYM @ 20 t/ha, and two levels of ing soil pH and ESP and improving crop N (100 and 150 kg/ha). yields. Increasing N dose from 100 to

Gypsum and FYM treatments were I50 kg/ha significantly improved the applied in one dose 10 d before trans- yield of both crops. Interaction between planting rice in 1989. Farmyard manure N and other treatments, however, was not contained 0.85% N, 0.35% P, 0.78% K, significant. 0.35% Ca, 0.24% Mg, 0.22% S, 52 ppm

crop was harvested at maturity in April 19 Nov 1990, and 18 Nov 1991. The HD2329 was sown on 25 Nov 1989, October. Subsequently, wheat variety crop was harvested at maturity in production.

soils and to maximize rice and wheat 1989, 5 Jul 1990, and 14 Jul 1991. The mended to successfully ameliorate sodic rice variety Jaya transplanted on 21 Jul with FYM @ 20 t/ha could be recom- were irrigated and 30-d-old seedlings of it is suggested that gypsum @ 25% GR Zn, 125 ppm Mn, and 320 ppm Fe. Plots

Based on pooled analysis of the data,

of the following year.


comparable to it except basal application of PU and LGU. The highest panicle weight was recorded under the NCU two-

basally, or applied in two or three splits way split application in 1991 ; comparable

at 60 kg/ha in the 10 treatments which LGU, and NCU and the three-way split

Modified urea forms evaluated in lowland rice to it were basal applications of MRPU, (see table). The N level was maintained

K. S. Rao and B. T. S. Moorthy, Agronomy Division, Central Rice Research lnstitute were replicated three times in a

panicle weight was recorded with PU. (CRRI), Cuttack 753006, lndia randomized block design. application of PU. During 1992, highest

The main reason for low efficiency of urea N—which generally does not exceed 50%—is due to loss of N through one or more of the well-known channels: runoff, leaching, denitrification, and volatiliza- tion. Several modified and coated urea fertilizers have been developed in recent years. We evaluated three of these, Mussorie rock phosphate-coated urea (MRPU), neem-coated urea (NCU), and large granulated urea (LGU) (6-8 mm diam), against prilled urea (PU) during 1991 and 1992 wet seasons (WS).

sandy loam in texture with a pH of 6.8, CEC 16.3 meq/100 g soil, total N 0.05%, available P 36 ppm, and exchangeable K 1 meq/100 g soil. The water level in the field ranged from 5 to 15 cm during the crop growth period.

Twenty-five-day-old seedlings of variety Gayataru (CR1018) were planted during the first fortnight of July at a spacing of 15 x 15 cm. All the urea fertilizers were broadcast, applied

The soil was alluvial (Inceptisol) and

When the entire N dose was applied basally, MRPU and NCU were superior to PU and LGU in grain yield (see table). Single basal applications of MRPU and NCU were comparable to PU when applied in two and three splits in 1991 and three splits in 1992. A two-way split application of MRPU or NCU was not better than a single basal application. Applying LGU in two splits was comparable to applying PU in two splits. A three-way split of PU had an advantage over a two-way split in 1992 only.

N use efficiency across treatments showed a similar trend. All N applications increased grain yield significantly over the no-N control, up to 54% in 1991 and 39% in 1992.

Panicle number was highest with a basal application of MRPU in 1991 ; all N application treatments, except basal applications of PU and LGU, were comparable to it. In 1992, the most panicles were recorded in the conventional three-way split application of PU; all N application treatments were

Effect of different treatments on grain yield, yield attributes, and N use efficiency in rice. CRRI, Cuttack, India. 1991-92 WS.

N use efficiency

Grain yield Panicles/m 2 Panicle weight (kg grain/ Treatment a (t/ha) (no.) (g) kg N)

1991 1992 1991 1992 1991 1992 1991 1992

Control 4.0 4.1 245 223 2.22 2.15 - - PU. all basal 5.3 5.2 279 258 2.24 2.25 22.2 17.3 MRPU, all basal 5.9 5.6 297 282 2.30 2.35 32.5 24.3 LGU, all basal 5.3 5.2 281 265 2.21 2.27 22.5 17.3 NCU, all basal 5.9 5.5 291 285 2.33 2.32 31.3 23.3 PU, 2 splits (2/3 basal + 1/3 Pl) b 5.9 5.4 292 266 2.67 2.58 31.3 21.8 MRPU, 2 splits

(2/3 basal + 1/3 PI) 6.1 5.7 292 283 2.69 2.50 36.0 26.8 LGU, 2 splits

(2/3 basal + 1/3 PI) 5.9 5.5 290 276 2.66 2.50 31.3 22.3 NCU, 2 splits

(2/3 basal + 1/3 PI) 6.1 5.8 291 284 2.71 2.52 35.2 27.0 PU, 3 splits (1/2 basal + 1/4 21 DT c +

1/4 PI) 6.1 5.8 293 286 2.66 2.55 35.7 27.2 LSD (P=0.05) 0.3 0.2 15 20 0.20 0.27

a N content in fertilizers: MRPU = 36%; PU, LGU, and NCU = 46%. b PI = panicle initiation. c DT = days after transplanting.

Fertilizer scheduling and economics of varietal mixtures of rice T. K. Bridgit, J. Mathew, and K. Joseph, Regional Agricultural Research Station, Pattambi 679306, Kerala, India

Cultivating mixtures of rice varieties is a prevalent practice in many rice-growing regions. In this system, seeds of a photoperiod-insensitive variety and a photoperiod-sensitive variety are sown as a mixture in a 70-30 (wt/wt) ratio at the beginning of the wet season (WS). The varieties are successively harvested at the end of the WS and dry season (DS). We evaluated the fertilizer requirements to determine the economic productivity of the system.

The experiment was conducted during 1988-90 WS and DS. The soil at the site is lateritic loam, acidic, and of medium fertility. Aryan (Ptbl) for WS and Chettadi (local) for DS were the varieties in the mixture. The treatments were combinations of the recommended fertilizer schedule for a single variety (40-20-20 kg NPK/ha) applied in three proportions (100,75, and 50%) for the WS crop and four proportions (100,75, 50, and 25%) for the DS crop, along with a control where varieties were cropped singly in the different seasons

schedule.

recorded higher grain yield than did the mixture during individual seasons as well as annually. Grain yield of the varietal mixture did not vary by season, possibly because of the substantial organic matter buildup in the system. Lowering the nutrient supply to 50% or less significantly reduced grain yield during the DS, attributable to the

under the recommended fertilizer

Cropping the varieties singly

increased mineralization of the large


Fertilizer management—inorganic

We applied 13.1, 26.2, and 39.3 kg P/ha to the rice as either single super- phosphate (SSP) or diammonium phosphate (DAP) at transplanting, or mussorie rock phosphate (MRP) or purulia rock phosphate (PRP) 15 d before transplanting; we also applied 175 kg P/ha as SSP to the wheat at sowing. Both rice and wheat also received 40 kg N/ha and 16.6 kg K/ha. Treatments were replicated three times in a randomized block design. Rice variety Culture 1 and wheat variety Sonalika were used. Wheat was sown at 120 kg seed/ha at a planting depth of 5 cm in rows 20 cm apart.

Significant differences were observed among both sources and levels of P in their residual effects on P uptake and to a lesser extent on grain yield (see table). Differences among sources were greater than those among levels, with the rock phosphates having the greatest residual effect. In no case did the residual effects match the benefit of directly applying P to the wheat.

Grain yield of rice under varietal mixtures and economics. Kerala, India.

Fertilizer schedule (% of recommended

WS

Grain yield (t/ha) Economics

DS Annual Total Total Profit Benefit-cost income cost ($/ha) ratio ($/ha) ($/ha)

For varietal mixtures 100 100 2.4 2.5 100 75 2.2 2.5 100 50 2.3 2.5 100 25 2.4 2.3

75 100 2.4 2.5 75 75 2.3 2.6 75 50 2.1 2.2 75 25 2.3 2.1 50 100 2.3 2.5 50 75 2.3 2.6 50 50 2.3 2.2 50 25 2.2 2.2

100 For single variety

100 2.9 2.7

LSD (0.05) ns b 0.3

4.9 726 4.7 703 4.8 716 4.7 712 4.9 733 4.9 728 4.3 657 4.4 679 4.8 715 4.9 728 4.5 678 4.4 679

5.6 747

0.4

497 494 489 485 494 491 486 482 489 486 482 478

636

229 209 227 227 239 237 171 197 226 242 196 201

111

1.46 1.42 1.46 1.47

1.48 1.35 1.41 1.46 1.50 1.41 1.42

1.48

1.17

a Recommended fertilizer schedule was 40-20-20 kg NPK/ha. b = not significant.

quantities of crop residue leftover from same as the treatments receiving 100% or the WS crop under high N levels. 75% in either season. A net savings of

With regard to annual yield, the 50% 75% of the dose for a single season, by WS: 75% DS treatment yielded about the 30-15-15 kg NPK/ha occurred, which is

cropping varietal mixtures when compared with monocropping.

narrow increase in annual gross income over varietal mixtures (see table). This was not, however, commensurate with the larger increase in production costs for cultivating single varieties. Savings in cultivation costs of $139-158 were obtained with varietal mixtures compared with single cultivation.

production costs substantially because the DS crop requires no expenditure for field preparation and transplanting. The reduced production cost contributes to a significantly higher net income and benefit-cost (B-C) ratio with varietal mixtures over a single-cropped variety.

Among the fertilizer levels for the varietal mixture, the 50:75 schedule recorded the maximum net income and B-C ratio. This treatment increased the net income to $13 over the 100:100 schedule varietal mixture and $131 over the single variety.

Cultivating a single variety recorded a

The system may bring down

Residual effects of P on We assessed the residual effects of wheat in a rice - wheat fertilizer P sources applied to rice on

sequence subsequent wheat growth. The soil was a loamy sand with pH 5.1. 0.59% organic

J. Goswami, S. R. Baroova, and K.

Agricultural University, Jorhat 785013, Thakuria, Agronomy Department, Assam

C, 90.96 mg available N/kg (extracted in 0.32% KMnO 4 ), 3.39 mg available P/kg

lndia (Bray I), and 20.45 mg available K/kg (extracted in neutral 1 N NH 4 OA c ).

Residual effects of different sources and levels of P applied to rice on subsequent wheat growth.

Treatment P uptake Straw yield Absolute Grain yield (kg/ha) (t/ha) (t/ha) agronomic efficiency a

Control (0 kg P/ha) 3.03 0.8 1.9

SSP Sources

4.25 DAP

1.99 4.22 0.98 2.00

MRP 6.02 PRP

1.05 5.74 1.04

2.02 2.01

LSD (0.05) 0.75 0.02 0.03

P level (kg/ha) 13.1 4.41 0.96 1.94 10.69 26.2 5.09 1.01 2.00 39.3

7.25 1.05 2.08

17.5 kg P applied 11.97 1.46 2.4 36.57 5.95

to wheat

5.68

LSD (0.05) 0.85 0.02 0.04 a Increase in grain yield over control/kg P applied.


WS DS

– –

0.96

–

–

– – –

dose) a

10 Sep and panicles at maturity was not affected in the direct seeded crop (due to the removal of clonal tillers from the plots sown at 600 seeds/m 2 ) when compared with the undisturbed crop sown at 400 seeds/m 2 . Under transplanted conditions, however, tillers and panicles/m 2 were significantly less than under direct seeding, particularly in the late planted crop. This was caused by mortality of seedlings at or immediately after planting and by less tillering because of excess water stagnation.

Panicle weight was highest in the crop planted on 20 Jul. Lower panicle weight

Daily rainfall (vertical lines) and water depth (dotted line) variation in the field during premonsoon, monsoon, and postmonsoon periods. Cuttack, India, 1989.

Seedlings were transplanted on 30 Jul and 10 Aug with 3-4 nursery seedlings or clonal tillers/hill at 20- × 15-cm spacing. Nursery seedlings were raised in beds where 60 g seeds/m 2 were sown on 30 May.

The direct seeded crop with the higher seeding rate was thinned by uprooting some of the plants, including clonal tillers (100- 120/m 2 ), which were transplanted. Water level rose gradually to a peak depth of 60-65 cm at 55 and 80 DE and then receded to 0 cm by crop maturity. A common basal dose of 40 kg N, 8.7 kg P, and 16.7 kg k/ha was applied uniformly. The treatments were arranged in a randomized block design with three replications in 16-m 2 plots.

Plant height of direct seeded rice was similar under various seeding rates. In the transplanted crop, height was greater for clonal tillers than for nursery seedlings (see table). Tiller number on

Stand establishment practices affect performance of intermediate deepwater rice A. R. Sharma, Central Rice Research Institute (CRRI), Cuttack 753006, India

Rice is either direct seeded or transplanted in rainfed lowlands of intermediate water depth (0-50 cm). Tillers removed from the direct seeded crop (clonal tillers) may be used as seedlings for transplanting, provided the parent crop is not adversely affected.

We compared the performance of intermediate rice under direct seeded and transplanted conditions where nursery- grown seedlings and clonal tillers were used. The study was made at Cuttack in 1989 using a semidwarf, long-duration, photoperiod-sensitive rice cultivar, CR1016, on alluvial sandy clay loam soil of medium fertility. Seed was direct sown on 30 May at 400 (normal) and 600 seeds/m 2 at 20-cm row spacing. Germination occurred when the rains came after sowing, with a 45% emergence rate. Water began accumulating in the field at 10 d after emergence (DE) but remained static at <10 cm until 40 DE (see figure).

Effect of direct seeding and transplanting on growth and yield attributes of rice variety CR1016 under intermediate deep water conditions. Cuttack, India 1989.

Seedling vigor a Plant height (cm) Tillers/m 2 Panicles/m 2 Panicle Grain Straw Treatment on 10 Sep (no.) weight yield yield

Height Dry weight 10 Sep Maturity (no.) (g) (t/ha) (t/ha) (g/seedling)

Direct seeding 30 May

400 seeds/m 2

600 seeds/m 2 (a) 600 seeds/m 2 (b)

87 94 262 151 1.99 2.9 5.3 83 92 277 146 1.94 2.9 4.8 82 92 268 152 2.01 3.0 5.0

Transplanting 20 Jul

Nursery seedlings 40 0.48 86 108 130 125 2.54 3.0 5.7 Clonal tillers 43 0.85 98 112 153 144 2.68 3.4 6.0

uprooted from (a) 10 Aug

Nursery seedlings 70 0.64 80 100 76 65 1.76 1.4 2.7 Clonal tillers 80 0.96 96 110 85 76 1.95 1.8 3.5

SE 3 4 12 8 0.12 0.1 0.3 LSD (0.05) 10 12 37 26 0.36 0.3 0.9

uprooted from (b)

a Mean of 25 seedlings.


Crop management

in the direct seeded crop was because of relatively more panicles/m 2 ; in the 10 Aug transplanted crop, it was because of less dry matter accumulation from the shorter growth duration.

The crop transplanted on 20 Jul produced the highest grain yield, significantly more than that of the other treatments. The clonally propagated crop performed better than the others because it was taller, had more dry weight, and could acclimatize more easily to flooded conditions. The direct seeded crop was at par with the 20 Jul transplanted crop of nursery seedlings. Yield did not decrease with the removal of clonal tillers. Late transplanting resulted in the lowest yield because of fewer and lighter panicles. Clonal propagation was superior to nursery-grown seedlings.

Clonal tillers of rice uprooted from a well-established direct seeded crop may be planted for higher productivity under excess water conditions. This practice is promising for use when early flash floods have partially damaged a crop and nursery seedlings are not available for late planting.

Occurrence of ufra disease in different rice ecosystems in Bangladesh, 1991-93.

Sites District Season a visited Affected Infestation Yield Cropping

area (ha) (%) loss (%) pattern b (no.)

Tangail T. aman 2 180 80-100 80-100 4 Boro 2 141 20-100 10-100 4

Gazipur T. aman 16 132 30-100 20-100 4, 5, 6 DWR 1 3 40-100 50-100 2 Boro 13 333 10-100 10-100 2, 4, 5, 6 T. aus 2 3 10-100 10-50 4, 9

Dhaka T. aman 4 50 40-100 30-100 4, 6 Boro 2 40 10-100 20-60 5, 6 T. aus 1 10 10-40 10-40 5

Narayanganj DWR 2 3 10-20 20-60 2, 6 T. aman 2 40 30-100 20-100 4 Boro 4 60 20-100 10-100 2, 5, 6 T. aus 1 20 10-50 10-40 5

Norshingdi DWR 2 12 40-80 20-80 2, 6 Boro 1 5 10-50 10-30 2

Comilla DWR 23 1096 10-100 20-100 1, 2, 3, 6 Boro 8 86 10-60 10-50 2, 6

Chandpur DWR 3 6 50-100 40-100 1, 6 Boro 2 30 10-30 10-20 2, 6

Noakhali DWR 1 4 60-600 40-100 1, 2, 6 Gopalgonj DWR 4 27 50-100 40-100 1, 2, 3, 6 Madaripur DWR 3 12 30-80 40-80 1, 2 Barisal T. aman 17 296 10-100 20-100 4, 7, 8

Jhalkati T. aman 2 25 40-100 50-100 7 Potuakhali T. aman 2 20 40-100 60-100 7 Borguna T. aman 2 20 60-100 50-100 7, 8 Bhola T. aman 3 35 10-70 30-50 4, 7, 9 Pirojpur c T. aman 5 400 40-100 40-100 4, 8 Bagerhat T. aman 2 200 10-100 20-100 9 Norail c DWR 5 400 50-100 50-100 1

147 3772

Boro 10 83 10-100 10-100 2, 4, 5, 6

Widespread ufra disease incidence in different rice ecosystems in Bangladesh M. L. Rahman, A. H. Mondal, and M. A. Bakr, Plant Pathology Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangla- desh

Ufra disease, caused by the rice stem nematode Ditylenchus angustus, is a devastating disease of deepwater rice (DWR) in Bangladesh. It has also been occurring in rainfed lowland rice areas during transplanted aman (Jul-Nov), transplanted aus (Apr-Jun), and irrigated boro (Nov-Apr) seasons.

During 1991-93, we surveyed 147 locations under deepwater, transplanted aman, transplanted aus, and boro rice covering 3,772 ha infected with the disease (see table). Thirty-four thanas loca1 administrative units) in 18 districts

a DWR = deepwater rice. T. aman = transplanted aman, T. aus = transplanted aus. b Cropping pattern: 1 = nonrice crops, 2 = DWR-Boro, 3 = DWR-fallow. 4 = T. aman-Boro. 5 = T. aman-Boro-T. aus. 6 = Boro-fallow, 7 = T. aman- pulse/wheat, 8 = T. aman-fallow, 9 = T. aman-T. aus. c Based on newspaper report.


Integrated pest management— diseases

of southwestern Bangladesh were affected

views with farmers, we identified several boro or boro-fallow patterns compared Based on our observations and inter- the boro crop being least affected under

were susceptible to ufra disease. level for the rice crops was 10-100% with Both local and modern rice varieties affected area much greater. The infection

that we could not visit, making the total crop. its occurrence in many other remote areas and transplanted aman than in the boro

loss, with the proportion higher i n DWR (see figure). In addition, farmers reported (see table). Many fields had 100% crop

seedlings in infected fields. irrigating from 10 to SO% in transplanted aus rice DWR, from 10 to 100% in boro rice, and previously infected with ufra. raising from 20 to 100% in transplanted aman and DWR and transplanted aman fields

aus rice: cultivating of the boro crop in patterns. Yield loss was estimated to range transplanted aman, boro, and transplanted planted aman - boro - transplanted aus reasons for the spread of ufra disease in with transplanted aman - boro or trans-

seedbeds with water from infected fields, exposing fields to irrigation water from infected fields, planting infected seedlings in ufra-free areas, and selling infected seedlings.

learn how to identify its symptoms early, the nature of its devastation and modes of survival and spread, and how to apply different control measures from the seedbed to the main fields. These measures will help to prevent the spread of the disease from endemic to ufra-free rainfed lowland and irrigated rice areas.

To control this disease, farmers need to

Effect of temperature and light on growth and sporulation of fusarium rice sheath rot R. K. Tombisana Devi and N. lboton Singh, Plant Pathology Department, Manipur Agricultural College, Iroisemba, lmphal 795001, India

The main causes of rice sheath rot (ShR) in Manipur, India, — Fusarium moniliforme. F. graminearurn, and F. avenaceum (IMI 342486) — were isolated and maintained on potato

dextrose agar. We studied the effect of temperature and light on their growth and sporulation.

We aseptically cut 5-mm disks from actively growing pure cultures of ShR fungi and transferred each disk to a 100- ml Erlenmeyer flask containing 50 ml of potato dextrose broth. Sets of flasks were incubated in the dark at 5°, 10°, 15°, 20° 25°, 30°, 35°, or 38°C for 7 d. Other flasks were kept at 26-27°C during the day and 18-19°C during the night and exposed to 24 h of light (provided by cool white fluorescent tubes [6500 °K 20

Table 1. Effect of temperature on growth (dry weight) and sporulation of fungi associated with ShR in darkness.

F. avenaceum F. moniliforme F. graminearurn Temperature

(°C) Growth (mg) Spores/ml Growth (mg) Spores/ml Growth (mg) Spores/ml (no.) (no.) (no.)

W]), or 24 h of darkness, or 12 h of light and 12 h of darkness for 7 d. All treatments were replicated three times for growth and three times for sporulation studies. Growth of each culture was estimated on a dry-weight basis; number of spores/ml was calculated using a hemocytometer.

F. avenaceum produced the most growth at 25°C and F. moniliforme and F. graminearum at 30 °C. None of the cultures grew at 5° or 38°C. Maximum sporulation for the fungi was at 30°C, although they did not sporulate at 5°, 10°, 15°, 35°, and 38°C (Table 1).

F. avenaceum and F. graminearum grew best in complete darkness but F. moniliforme grew best in complete light. Alternate light and darkness inhibited growth (Table 2).

F. avenaceum and F. graminearum 5 0 0 0 0 0 0

10 110 0 98 0 88 0 produced the most spores in complete

15 140 0 110 0 97 0 darkness. Complete light markedly

25 284 4 × 10 3 212 16 × 10 3 183 4 × 10 3

30 213 8 × 10 3 317 4 × 10 4 310 4 × 10 3 F. moniliforme produced an appreciable

35 93 0 105 0 121 0 quantity of spores in both complete light

38 0 0 0 0 0 0 and complete darkness, alternate light

20 205 4 × 10 2 118 4 × 10 3 121 4 × 10 2 inhibited their spore production. Though

CD (0.05) 4.4 4.8 4.5 and darkness had a synergistic effect on spore production (Table 2).

Table 2. Effect of light on growth (dry weight) and sporulation of fungi associated with ShR.

Temperature (°C) F. avenaceum F. moniliforme F. graminearum

Night Day Growth Spores/ml Growth Spores/ml Growth Spores/ml Source of lighta

(mg) (no.) (mg) (no.) (mg) (no.)

Complete light 18-19 26-27 257 1 × 10 2 240 4 × 10 3 319 Complete darkness 18-19 26-27 328 3 × 10 3 200 4 × 10 3 345 6 × 10

3

Alternate light (12 h) 18-19 26-27 190 2 × 10 2 210 8 × 10 3 165 4 × 10 2

and darkness (12 h)

2 × 10 2

a Crompton cool white flourescent (2-ft) tube with electric discharge of 6500°K 20 W.


Areas of honeydew excreted by Sogatella furcifera on 30-d-old seedlings of resistant variety Rathu Heenati and susceptible variety TN1 untreated and treated with uniconazole by seed soaking at 100 pprn.

a Columns with the same letters are not significantly different by LSD, P = 0.05. Mean ± SE.

Beauveria bassiana Vuill. and Metarhizium anisopliae Sorok. fungi were collected at different locations in Vietnam and studied at NPPRI from 1990 to 1992 to determine their effects on brown planthopper (BPH).

Fungi were isolated and multiplied using crapek (sacharoza, NaNO 3 , KH 2 PO 4 , MgSO 4 , FeSO 4 , and agar [pH = 6]) and saburo (glucoza, peptone, agar [pH = 5]) media. Results with saburo medium were better than with crapek medium for Beauvaria. Saburo medium supplemented with 1 g/liter each of MgSO 4 · 7H 2 O and KH 2 PO 4 , however, produced the best overall results. Up to 4.8 x 10 8 /g Beauveria spores and 5.6 x 10 8 /g Metarhizium spores were produced. Locally available materials, including maize powder (30%), rice bran (30%), soybean powder (25%), and sugar (15%), also served as satisfactory media.

Optimum growth of the two fungi was at 25-32 °C and 70-85% relative humidity. Filter spores were applied in the greenhouse and field with conventional spray equipment; a hemocytometer was used to determine concentrations.

Results from laboratory and greenhouse experiments on BPH showed that suspension with a spore concentration of 5 x 10 8 spores/ml was optimum and caused a 70% mortality rate for BPH. A higher spore concentration is needed, however, in the field. Suspensions at 6.5 x 10 13 spores/ha were used to control BPH in sticky rice at NPPRI, with Beauveria killing 57.9% of BPH and Metarhizium killing 42.2% 10 d after treatment (DAT).

Pham Thi Thuy, Nguyen Thi Bac, Dong Thanh, and Tran Thanh Thap, National Plant Protection Research lnstitute (NPPRI), Chem, Tullem, Hanol, Vietnam

Effects of Beauveria bassiana Vuill. and Metarhizium anisopliae Sorok. on brown planthopper (Nilaparvata lugens Stål) in Vietnam

Effect of Beauveria bassiana Vuill. and Metarhizium anisopliae Sorok. on BPH. Mortality (%) at different locations in Vietnam. a NPPRI, 1990-92.

Days after treatment Fungus Location

3 5 7 10 12 15 18

Beauveria NPPRI. Hanoi 18.7 30.5 38.8 57.9 47.3 58.8 32.5 Tien Giang 13.6 16.3 15.6 58.3 41.1 40.0 27.1 Minh Hai 5.3 17.5 24.1 35.4 36.7 35.2 18.8

Metarhizium NPPRI, Hanoi 15.0 32.3 37.8 42.2 52.3 56.2 28.5 Tien Giang 4.5 26.7 42.9 67.2 51.4 53.3 59.2 Minh Hai 12.2 23.9 28.8 36.5 35.5 36.1

a Control efficiency calculated based on Henderson-Tillton formula (1955).

In experiments in Tien Giang Province killed 67.20% of BPH 10 DAT (see using variety TG29, we observed that table). Beauveria killed 58.3% and Metarhizium

Whitebacked planthopper feeding on rice seedlings treated with uniconazole Guangjie Liu, China National Rice Research lnstitute (CNRRI), Hangzhou 310006, People's Republic of China

Uniconazole is a new plant growth regulator that is being applied widely to rice, wheat, and rape. Rice seedlings are shorter and stronger when seeds are soaked in uniconazole before sowing. The treated seedlings are more tolerant of low temperature, drought, and salinity. We determined the effect of uniconazole on whitebacked planthopper (WBPH) feeding by measuring honeydew excretion on seedlings from treated seeds.

Heenati and susceptible variety TN1 were soaked in uniconazole solution at 100 ppm for 2 d. Unsoaked seedlings served as the control. Roots of 30-d-old seedlings were washed in preparation for use in the feeding chambers. Filter paper disks, Regardless of variety susceptibility, pretreated with 0.5% bromocresol green in honeydew excretion of WBPH was signi- ethanol, were placed around the base of ficantly lower on the uniconazole-treated each seedling inside the chambers. Two seedlings than on the control within a newly emerged macropters, starved but variety (see figure). Honeydew excretion water-satiated for 3-4 h, were introduced was reduced on treated Rathu Heenati into a chamber, representing a replicate. seedlings by 66.7% and on TN1 seedlings The filter papers were collected after by 45.9% compared with untreated insects had fed for 24 h. The honeydew seedlings. spots on the papers were measured using a Resistance of rice seedlings to WBPH transparent sheet marked with a 1-mm 2 seems to be improved after being treated grid. Each treatment was replicated 10 with uniconazole by seed soaking, which times. Data were analyzed using least could possibly encourage the reduction of significant difference test (P = 0.05). insecticide applications at seedling stage.

Seeds of resistant variety Rathu


Integrated pest management— insects

Aphelenchoides besseyi in irrigated upland and lowland rice during dry and wet seasons C. C. Huelma, J. C. Prot, S. D. Merca, and T. W. Mew, IRRI

Aphelenchoides besseyi, the causal agent of white-tip disease, is the only seedborne rice parasitic nematode. According to quarantine regulations, seed lots used for international germplasm exchange must be free of A. besseyi; those found positive during phytosanitary certification are destroyed. It is essential to produce seeds free of A. besseyi to prevent loss of valuable seed materials. A. besseyi infestation can be avoided by using nematode-free seeds and planting in nematode-free fields.

To determine the field conditions

the coldest. Annual rainfall (1979-92) averaged 2090.7 mm and the average humidity, 88%. Wet season (WS), from June to November, and dry season (DS), from December to May, are the major seasons. On the upland farm, upland rice is rainfed during WS and irrigated using sprinklers during DS.

of the 1989 and 1990 DS and WS crops to estimate frequency and abundance of A. besseyi. Two hundred thirty samples (one/field) were collected during 1989 DS, 1, 192 samples during 1989 WS, 1,019 during 1990 DS, and 1,044 during the 1990 WS. Each sample was made of 25 panicles collected at random. Panicles were threshed. Thirteen grams of seed for each sample were incubated for 5 d at 28°C in a Baermann funnel for nematode extraction. Average number of A. besseyi per sample and frequency of occurrence as a percentage of infested samples were calculated.

irrigated lowland and upland rice in both

We collected seed samples at maturity

A. besseyi was detected on both

seasons (see table). Frequency of A. besseyi occurrence during WS on the upland and irrigated lowland farms was similar. Except for the upland rice farm where the nematode was not detected during 1989 DS, the average number of A. besseyi per sample under either condition and under either season was not significantly different when compared using ANOVA. A. besseyi, however, appears to be less frequent on the upland rice farm during the DS crop than on the irrigated farm during DS and WS crops and on the upland farm during WS.

The nematode needs high canopy humidity to infest the aerial part of the plant, a condition present in irrigated lowland with standing water. Multiplying seeds for international exchange under upland conditions during DS may reduce the risk of A. besseyi contamination. Using gravity flow irrigation instead of sprinkler irrigation may further reduce the occurrence of A. besseyi under upland conditions during DS.

under which A. besseyi development is The combination of limited, we conducted a survey on the irrigated lowland and upland IRRI experimental farms during four consecutive rice-growing seasons. The sides of the coin

nematodes, Sesbania rostrata, and rice: the two

IRRI fields have the Maahas (Guadalupe) J. C. Prot, IRRI series of soil profile. Irrigated lowland fields have clay to silty clay soil texture with pH of 5.7-7.2. Upland fields have silty clay to silty loam soil texture with pH 5.5-7.1. The temperature from 1979 to 1992 averaged 27°C (15.2-38.2°C). April is the hottest month and December,

Samples analyzed, average number of Aphelenchoides besseyi per 13-g seed sample, and frequency of occurrence (F = % of infested samples) of the nematode in 1989 and 1990 DS and WS rice crops on the IRRI irrigated (IR) and upland (UR) rice farms.

Samples Average Frequency (no.) number/

sample

IR 1989 DS UR 1989 DS IR 1989 WS UR 1989 WS IR 1990 DS UR 1990 DS IR 1990 WS UR 1990 WS

204 26

973 219 733 286 747 297

0.9 9.3 0 0 1.8 21.2 2.7 18.7 0.7 14.9 0.5 0.7 1.1 7.1 0.7 8.1


Sesbania rostrata has tremendous potential as a green manure crop for improving soil fertility in permanently or intermittently flooded rice ecosystems. An additional benefit of growing S. rostrata in lowland rice is the control of rice root nematodes, Hirschmanniella spp. Since 1983, five papers have been published reporting that S. rostrata could be used in rotation with rice to reduce field populations of Hirschmanniella mucronata and H. oryzae, which damage irrigated rice. The coin, however. has two sides.

Rice root nematodes are not the only nematode pests of rice. More than 200 species of plant-parasitic nematodes have been reported to be associated with rice. Among these, the root-knot nematodes. Meloidogyne spp.. are major pests of rainfed rice, causing swelling and galla throughout the root system. Although

Number of second-stage M. graminicola juveniles obtained from 3 g of roots of rice cultivar UPLRi- 5 and S. rostrata grown under upland and irrigate conditions 60 d after plants were infested with 5,000 nematodes.

Condition under which plants were grown

Crop Upland lrrigated

Rice (UPLRi-5) 20,424 3,104 S. rostrata 20,165 3

Galls of M. graminicola on roots of S. rostrata

Integrated pest management— other pests

they do not cause specific symptoms on the aboveground parts of the plant, they can cause severe growth reduction, chlorosis, wilting of plants, and 20-70% yield reduction in infested fields. M. graminicola, the rice root-knot nematode, is widely distributed in rainfed upland and lowland ricefields in South and Southeast Asia, especially in light- textured soils. It is considered to be an important pest in rainfed lowland areas in India and northeast Thailand.

Environment Climate change and rice

Methane emission from ricefields H. U. Neue, R Wassmann, R. S. Lantin, M. C. Alberto, and J. B. Aduna. IRRl

The increase in atmospheric CH 4 concentration has been recognized during the past decade. The current amount of methane in the atmosphere is 4700 Tg. The total annual global emission of CH 4 is estimated to be 500 Tg, about 70% of which is biogenic in origin. Flooded ricefields are probably one of the largest agricultural sources of atmospheric CH 4 .

Flooding a ricefield cuts off the oxygen supplied by the atmosphere to the soil; this results in the fermentation of soil organic matter. CH 4 is a major end product of this process. Flooded ricefields release CH 4 to the atmosphere by diffusion, ebullition, or through the

S. rostrata, unfortunately, is a very good host for M. graminicola when grown in nonflooded soils (see figure and table). Cropping it before rice in nonflooded soils infested by rice root- knot nematodes may increase their number tremendously. This increase in M. graminicola may cause increased yield losses, eliminating the benefit expected from cultivating the green manure crop. This is the other side of the coin.

S. rostrata has tremendous potential as a green manure crop. Under rainfed conditions, however, it must be used with caution. It is hazardous to grow S. rostrata in rainfed ricefields where M. graminicola is present. Leguminous crops resistant to M. graminicola should be identified as alternatives to S. rostrata in rainfed lowland rice areas infested with the nematode.

Regional distribution of harvested rice area (million ha) in major rice growing, less developed countries in 1985. IRRI, 1989.

Region Irrigated Rainfed Deepwater Upland Total rice rice rice rice

South Asia East Asia Southeast Asia Latin America Africa

Total

19.2 32.2 12.0 2.2 1.0

66.6

24.3 1.9

12.6 0.4 1.3

40.5

8.8

3.6

0.2 12.6

7.9 0.7 3.3 4.5 2.1

18.5

60.2 34.8 31.5 7.1 4.6

138.2

rice plants, which mediate the transport of CH 4 from the reduced soil to the atmosphere (see figure). Much of the CH 4 formed in the anaerobic soil may remain entrapped in the soil and is oxidized to CO 2 .

is grown almost exclusively for human food. One hundred forty million ha of rice are harvested annually. In developed countries, ricefields are irrigated because it increases production potential. In less

Rice is the only major grain crop that

Scheme of methane production, oxidation, and emission in a flooded ricefield.

developed countries, only 50% of the harvested rice area is irrigated but it accounts for more than 70% of yield. Rainfed ricefields, which are prone to droughts and floods, make up 30% of the rice area, and upland rice, 13% (see table). It is estimated that irrigated and rainfed ricefields emit annually up to 100 Tg CH 4 .


In March 1994 IRRI convened an inter-

national symposium that reviewed the

broad issues of global climate and its

effect on rice growth and production.

The posters displayed at the sympo-

sium appear in a slightly modified form

in this section. We hope you find these

notes to be a valuable source of

information.

Measuring methane emission H. U. Neue, R. Wassmann, R. S. Lantin, M. C. Alberto, and J. B. Aduna, IRRI

Recent estimates of annual global CH 4 emission from ricefields range from 20 to 100 Tg, with a best estimate of 60 Tg. Global and regional estimates vary greatly, with assumptions based on the understanding of processes and data currently available. Reducing these uncertainties and predicting future emission trends — as well as developing mitigation technologies that do not negate gains in rice production — require information about processes and geo- graphic distribution of factors controlling CH 4 fluxes in ricefields.

Methane fluxes from ricefields are highly variable, with distinct diel and seasonal patterns. Continuous measurements are essential to monitor and evaluate CH 4 fluxes. We employed a system that allows continuous and simultaneous measurements at 16 plots for an entire growing season. Soil at the experimental site is an Aquandic Epiaqualf (Guadalupe clay, pH 6.4, organic C 1.57%, total N 0.174%, CEC 37.3 meq/100 g).

Flooding and puddling wetland ricefields render the soil an ideal growth medium by buffering it and increasing nutrient availability. Flooding drastically reduces the oxygen supply, thereby inducing anaerobic fermentation of organic matter in the soil. A pH of around 7 and a redox potential below -150 mV favor methanogenesis. In the irrigated wetland soil monitored, we found a constant pH of 7 soon after flooding soil and solution Eh varied from 0 to -100 mV (corresponding to a soil Eh of -150 to -250 mV) and soil temperature ranged from 26 to 30 °C.

Integrating continuous CH 4 flux measurements with respective climate, soil, and crop data provides the essential base to identify controlling factors and processes that are required to predict future emission trends and to develop mitigation technologies.


Effect of rice cultivars on methane emission H. U. Neue, R. Wassmann, R. S. Lantin, M. C. Alberto, and J. B. Aduna, IRRI

Rice plants play an important role in the flux of CH 4 . Up to 90% of the CH 4 released from ricefields into the atmosphere is emitted through the rice plant. Well-developed intracellular air spaces (aerenchyma) in leaf blades, leaf sheaths, culm, and roots provide an efficient gas exchange medium between the atmosphere and the anaerobic soil (see figure).

Atmospheric oxygen needed for respiration is supplied through the aerenchyma to the roots. Gases formed in the soil, such as CH 4 , diffuse from the reduced soil through the aerenchyma to the atmosphere. Production and transport

depend on the rice plant’s properties. The rice plant does not only mediate CH 4 flux; root exudates and degrading roots are important sources of CH 4 , especially at later growth stages.

of CH 4 to the atmosphere appear to

The flux of gases in the aerenchyma depends on concentration gradients and diffusion coefficients of roots and the internal structure of the aerenchyma. Tillers/m 2 , root mass, rooting pattern, total biomass, and metabolic activity influence gas fluxes. These traits and related emission rates vary widely among cultivars and rice crops in the field, making it possible for breeders to develop rices with low CH 4 emission potential.

Large cultivar differences in emission rates have been reported (see table). We found that traditional variety Dular emitted about 30% more CH 4 per day than did the new plant type IR65597. The traditional variety has more tillers and longer roots, and these appear to enhance CH 4 emission. To compare the emission potential of rice under field conditions, actual crop parameters, such as tillers/m 2

for optimum yield, are as important as characteristics of the cultivar itself. Keeping the number of productive tillers/m 2 and eliminating unproductive tillers while developing new plant types

will result in lower field emission potentials even if other CH 4 -related traits remain the same.

W = root, AB = aerenchyma of culm, BS = culm, Aw = aerenchyma of root.

Tillers/m 2 at optimum crop development and methane emission of 3 cultivars.

Tillers/m 2 (no.) Methane emission (g) Cultivar

Total Productive per tiller per g biomass

New plant type 300 300 12 3 Improved variety 1000 600 5 Traditional 1200 500 13

Intersection of shoot and root aerenchyma, which highly affects the diffusion of gases. Root and shoot aerenchyma are separated by cell layers (Butterbach-Bahl 1992).

4 8

Diel and seasonal patterns of Emissions usually increase rapidly methane fluxes in ricefields after sunrise, peak in the early afternoon,

H. U. Neue, R. Wassmann, R S. Lantin, M. C. Alberto, and J. B. Aduna, IRRI

then decline rapidly and level off at night. Cutting the rice shoot above the water level has no immediate effect on diel

Methane fluxes in ricefields show cating that plant metabolism does not distinct diel and seasonal variations emission patterns and amplitudes, indi-

tude of fluxes correlates with the diel soil processes are poorly understood. directly affect CH 4 flux. The diel ampli- (Fig. 1a, b), but controlling factors and

1a. Diel variation of CH 4 emission. IRRI, 1992 DS.

1b. Methane emission during two seasons under urea fertilization. IRRI, 1992 DS and WS.

2. Methane emission and air temperture in urea- treated plots. 1992 WS, 1993 DS.

temperature changes. The relationship between temperature and CH 4 flux changes with crop development stage (Fig. 2). At the later growth stage, the slope is steep because of greater partial pressure of CH 4 in the soil, higher root biomass, and increased plant-mediated gas transport and capacity (greater aerenchyma volume and tiller number).

the dry season than in the wet season. If ricefields are kept flooded during the entire growing season, up to three distinct seasonal maxima are observed (Fig. 1b): the first develops shortly after flooding, the second during the later vegetative period, and the third—being the highest- during the grain-filling and maturity stages. The first peak reflects the initial flux of fermenting easily degradable soil organic matter present after flooding. If the amount of easily degradable soil C is low, no initial peak of CH 4 flux develops. The increasing capacity of plant-mediated CH 4 emission and probably the increase in release of plant-borne C sources cause the increasing peaks. CH 4 production and CH 4 oxidation over the entire cropping season will be quantified in future research to elucidate the net flux of CH 4 .

Generally, CH 4 emissions are higher in

Effect of fertilization on methane emission H. U. Neue, R. Wassmann, R. S. Lantin, M. C. Alberto, and J. B. Aduna, IRRI

Nitrogen, although crucial in achieving high yields in wetland rice, is the most deficient nutrient in the ecosystem. Most farmers apply N fertilizer in two or three splits as urea or (NH 4 ) 2 SO 4 . Part of the fertilizer is incorporated into the soil during the final land preparation stage or broadcast shortly after planting. The remainder is applied at midtillering and at panicle initiation.

The effects of N fertilization on CH 4 production and emission are incon- sistent. The complex interrelationships between fertilization and biochemistry of flooded soils, plant growth, and CH 4 fluxes, however, still need to be elucidated.

N fertilizers and modes of fertilizer We evaluated the effects of different


1. Methane emission rates, IRRI, 1992 DS.

2a. Methane emission under two N sources. IRRI, 1992 WS.

2b. Methane emission from ricefields under two sources of organic matter. 1992 WS.

(DS). Differences in fluxes were not significant between additions of (NH 4 ) 2 SO 4 and urea.

to flooded soils, CH 4 production and emission are increased by lowering the Eh and providing more C sources. Adding 5 t rice straw/ha increased CH 4 emission tenfold compared with mineral fertilizers (Fig. 2a). Quality and quantity of added organic materials influence CH 4 formation. Green manure incorporation showed higher CH 4 emission than did adding rice straw (Fig. 2b). Green manure has a C-N ratio of 10 compared with 60 for rice straw.

Because organic substrates are added during the preflooding period before transplanting, the initial emission peak may be missed if CH 4 fluxes are monitored only during crop growth. Small differences in sources of C and its fermentation highly affect emission

When organic amendments are added

patterns and emission levels.

Effect of cultural practices on methane emission H. U. Neue, R Wassmann, R. S. Lantin. M. C Alberto, and J. B. Aduna, IRRI

Cultural and agronomic practices have been developed to suit the physical, biological. and socioeconomic conditions of the different rice-growing regions and environments. While the effects of agronomic practices on rice growth and yield are well-documented, their relation- ships to CH 4 emission are not well- established.

Water control is one of the most important factors in rice production. Short aeration periods at tillering and at heading may improve yield in irrigated rice. A constant water level is maintained during the growing season except where midseason drying is practiced. Large portions of CH 4 formed in an anaerobic soil may remain trapped while the soil is flooded. Entrapped CH 4 may be oxidized when the floodwater is drained during the rice- growing season or when the soil dries at

application on CH 4 emission. Improved Methane emissions were similar the end of the season. But a lot of the plant and root growth in CH 4 -enriched regardless of application method (Fig. 1) entrapped CH 4 escapes into the atmosphere soil layers—as a result of fertilization- at rates of 90 kg N/ha in the wet season immediately after the flood-water recedes will obviously increase CH 4 emission. (WS) and 120 kg N/ha in the dry season and macropores become aerated (Fig. 1).


Soil-entrapped CH 4 can be released into the atmosphere as a result of soil disturbances, such as puddling, harrow- ing, transplanting, weeding, fertilizer/ pesticide application, and harvesting. Even if cultural practices do not disturb fields, up to 90% of the CH 4 released into the atmosphere is emitted through the aerenchyma of the rice plant.

In a field experiment using micrometeorological techniques in combination with a tunable diode later, CH 4 emission greatly increased during

1. Effect of soil drying on methane fluxes. IRRI.

2. Effect of weeding on methane emission from ricefield. IRRI, 1992 DS.

weeding (Fig. 2). The emission declined to previous levels after weeding. Cultural practices may account for 10-20% of the overall seasonal CH4 emission.

Dissolved methane in soil solution

H. U Neue. R. Wassmann. R. S. Lantin. M. C. Alberto, and J. B. Aduna. IRRI

Methane that is produced but does not escape into the atmosphere remains entrapped in the soil. This entrapped CH 4 may be oxidized, reducing net CH 4 emission to the atmosphere. Determining the amount of soil-entrapped CH 4 is time- consuming and laborious.

An alternative method is to determine the amount of CH 4 dissolved in soil solution. Floodwater and soil solutions at different depths were sampled using porous tubing. About 5-ml samples were collected in 10-ml vacutainers. The samples were shaken vigorously for 30 s and headspace gas was analyzed for dissolved CH 4 . Field sampling was done weekly in plots planted to IR72 and treated with urea (low C input) and organic amendment (high C input).

solution over time followed the same pattern as that of soil-entrapped CH 4 . A close linear relationship exists between dissolved CH 4 and entrapped CH 4 ( r = 0.916**). This allows monitoring en- napped CH 4 using the easier measurement of dissolved CH 4 .

Dissolved CH 4 remained at very low levels at low C input during the early growth stages (Fig. 1). Organic amendment at high C input increased dissolved CH 4 tenfold (Fig. 2). At later growth stages, dissolved CH4 started to increase (Fig. 1.2). The dynamics of CH 4 production rate at affected by C input was similar to that of dissolved CH 4 .

Dissolved CH 4 in the floodwater was negligible. The concentration of dissolved CH 4 in the soil solution increased with increasing depth below the soil- water interface. Maximum concentrations were recorded at 15 cm (the deepest layer sampled) (Fig. 1, 2). Methane movement from this depth was hindered by the plow pan, and the lower soil temperatures decreased CH 4 solubility.

The dynamics of dissolved CH 4 in soil


1. Changes in dissolved CH 4 under low C input.

2. Changes in dissolved CH 4 under high C input.

Ebullition of methane growing period enhance ebullition of

H. U. Neue, R. Wassmann, R. S. Lantin, M. C. Alberto, and J. B. Aduna, IRRI

Up to 90% of the CH 4 released into the atmosphere from ricefields is attributed to the rice plant, but another release mechanism is ebullition as gas bubbles. Ricefields are usually prepared flooded with at least 4 wk passing before rice is transplanted. If bare mud is flooded, CH 4 is entrapped in the soil, and ebullition becomes the only major pathway for CH 4 release. Cultural practices during the

soil-entrapped CH 4 . To quantify the contribution of CH 4

ebullition to total fluxes, we installed Plexiglas boxes between rice hills and measured the collected gas after 24 h throughout the growing season. We monitored CH 4 ebullition and total fluxes

ments.

in plots planted to IR72 and treated with mineral fertilizers and organic amend-

1. Variability of methane in urea plot.

~

Methane ebullition varied greatly in all plots (Fig. 1). The variability increased as the growing season progressed. Ebullition is higher during the day than at night and the seasonal pattern was similar to that of emission. Organic amendments increased the ebullition of CH 4 (Fig. 2).

The maximum amount of CH 4 ebullition was observed 2 wk after flooding the soil, followed by a decrease during the crop’s vegetative growth. Ebullition increased again during the reproductive phase, with a final peak at harvest. Ebullition contributed 20% of the total CH 4 emission.

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2. Methane ebullition from ricefields. 1992 WS.

Methane production potential of soils H. U. Neue, R. Wassmann, R. S. Lantin, M. C. Alberto, and J. B. Aduna, IRRI

Soils in which rice is grown vary from

in terms of nutrient contents, from low organic carbon (OC) to peat soils, from sand to clay, and from ones with low base status to ones with high cation exchange capacity.

We studied the effect of soil properties in CH 4 production using 20 soils from different rice-growing areas in the Philippines. Soil properties govern the electrochemical and chemical changes that occur upon flooding and the pattern of CH 4 formation. We found that soils can be grouped into four classes according to the amount of CH 4 produced during anaerobic incubation for 10 d: I< 1 µg CH 4 / g soil, II<10, III<100, IV>100. Each group has a distinct pattern of CH 4 formation and differs significantly in the total amount of CH 4 produced (Fig. I), though final Eh and pH values were similar.

Soils categorized under class IV had the highest average OC (2.2%) while those in classes I and II had average OC (1.4%). Soils with >2% OC produced

acidic to alkaline, from deficient to toxic

more than 300 µ g CH 4 /g. The OC

content is the only soil property that shows a significant correlation with CH 4 production. But CH, production and soil OC are not correlated in soils with C content of less than 2%. Sandy soils high in OC produce more CH, than do clay soils. With similar OC content, the negative impact of clay is probably because of the formation of organo- mineral complexes where C becomes less degradable. Clay soils may also entrap

1. Effect of soil properties Eh and pH on CH, production.

more CH 4 , thus increasing the probability of oxidation.

Adding rice straw increased CH 4 production but did not affect the grouping of the CH 4 production potential of the soils (Fig. 2). This implies that degradable C is an important-but not the only- limiting factor for CH 4 production.

Soils that produced the highest CH 4 had low pH when air-dried. This appears to contradict the hypothesis that acidic soils produce less CH 4 . The reduction of soils upon flooding converges any air- dried soil pH at about 7, which is the optimum level for CH 4 production. In acid soils, substrates that can be catabolized by methanogens may be conserved during the fallow periods and the initial reduction phase, leading to higher total CH 4 production.

The effects of soil properties on CH 4 production and oxidation are not well- understood at present. Further research is needed to elucidate the dynamic and


2. Effect of adding

production 20 d after flooding. 1992 WS.

straw on CH 4

complex interaction of microbial metabolism of the whole fermentation chain and soil properties to determine mechanis- tically the CH 4 production potential of soils.

Predicting methane tion in wetland rice

produc- soils

J. L. Gaunt, Natural Resources Institute (NRI), Central Avenue, Chatham Maritime, Chatham, Kent ME4 4TB, UK; H. U. Neue, IRRI; K. E. Giller, Wye College, University of London, Wye, Nr Ashford, Kent, UK, I. F. Grant, NRI; and J. Bragais, IRRI

Methane is an important greenhouse gas with a relative potential for thermal absorption 30 times greater than that of CO2. It plays an important role in the chemistry of the troposphere. Methane production in soil is a microbiological process that occurs under strict anaerobic conditions. Soil oxidation - reduction (redox) characteristics are the key soil parameters that control CH 4 production.

Laboratory incubation studies were conducted using 10 wetland rice soils from the Philippines to measure patterns of soil reduction upon wetting. The following logarithmic function was used to quantify soil reduction patterns of soil redox potentials (Eh):

y = a + b ln x

The reduction capacity of the soil was defined as the difference between the fitted initial Eh and equilibrium Eh values. (See Figure 1 for the fitted and observed Eh values for the soils). Given the excellent description of Eh, the fitted data were used in subsequent analysis. The rate and capacity of soil on wetting strongly influenced CH 4 production (Fig. 2).

The C-N ratio of labile organic matter controlled the reduction rate upon

where y = Eh at a given time, a = equilibrium Eh for the system, b = rate of reduction, and x = days after flooding.

1. Measured soil redox potentials (Eh, mV) compared with fitted values obtained using a logarithmic function.

wetting, whereas the reduction capacity of the soils was negatively correlated to the active iron, cation exchange capacity, and clay, silt, and sand content.

wetting depends on the rate and capacity for reduction in soils when melted. Initial results suggest that the nature of labile organic matter, buffering due to iron compounds, and soil texture control the soil reduction process.

Predicting CH 4 production upon

2. Methane production (log, µg CH 4 /g soil) during a 30-d incubation predicted from the rate and capacity of soil reduction.


A simple process-based model to predict methane emission from flooded fields

J. Arah, K. Bronson, M. C. Alberto, E. Abao, and H. U. Neue, IRRl

Making reliable predictions of CH 4 fluxes in a changing environment calls for understanding of the processes and interactions involved. This understanding can best be expressed as a mathematical model. We set up a simple model of CH 4 production, consumption, and transport in flooded soil and tested it against data measured in the field (Fig. 1). We hoped to be able to simulate diurnal flux variations over periods of a few days: success would indicate that the essential features of the system have been captured in the model, which could then be refined.

(oxygen and CH 4 ) and makes the following assumptions: the area of the system is homogeneous: transport occurs only by diffusion; all microbial reactions obey dual-substrate Michaelis-Menten

oxygen; and temperature affects reaction kinetics; methanogenesis is inhibited by

potentials, solubilities, and diffusion

Our model considers only two species

Possibilities for reducing methane emission from ricefields in China Sicui Liang, National Environmental

Agricultural Technology Extension Center, Protection Agency, and Geng Yang, National

Beijing, China

This discussion on possible ways to reduce CH 4 emission from irrigated rice in China is based on data from Sino-

cooperation (1990-92) and studies by American scientific and technological

Wang (1993).

ricefields make up 92% of the total in International irrigation. Irrigated

China. Using intermittent irrigation saves 30% of the water required for conventional flood-irrigation and increases production by about 10-20%, CH 4 emission could be reduced in different soil conditions by 15.59% with intermittent irrigation (Table 1). Even when

1. Measured and modeled methane fluxes over time.

constants. Potential rates of oxygen consumption, CH 4 production, and CH 4 oxidation were measured in the laboratory by incubating segmented core samples. Michaelis constants and inhihition thresholds were taken from the literature.

depths over 4 d were used to drive the Temperatures measured at different

organic fertilizer was three times that of the control field in Nanjing, for example, intermittent irrigation still lowered CH 4 emission by 12%.

ing ridge culture for rice production in

decreased. Ridging could reduce CH 4

1983 because the area under water is

emission by 39-43% (Table 1). Even when organic fertilizer was doubled, the rate was still reduced by 31%.

Although furrowing requires relatively more labor, ridge culture can generally increase production by 20- 30% and raise farmers’ income by 15%. The area under ridge culture has been expanding rapidly in recent years.

seeded rice has been introduced to some Dry seeded rice. Since the 1970s, dry

ricefields in northern China to save 30- 60% of the water normally used. Tests showed that dry seeding could reduce CH 4 emission by 59-74% (Table 1).

Ridge culture. China began introduc-

2. Modeled methane concern- trations at different soil depths.

model. Apparent activation energies were adjusted to optimize the fit between measured and modeled fluxes. (See Figure 2 for the simulated CH 4 concentration profiles.) The model appears to behave reasonably well, although peak

a useful basis for future elaboration. fluxes are not reproduced. It should form

of transplanted rice, dry sccding showed Although yield was 10% lower than that

great potential for reducing CH 4 cmis- sion.

varieties. An experiment at Nanjing Selecting CH 4 emission-reducing

compared CH 4 emission from hybrid and conventional rices in 1991 (Table 2). The hybrid reduced CH 4 emission by 28% and raised yield by 45% compared with conventional rice. Wang (1993) found that hybrid rice reduced CH 4 emission by 13.4%.

a) Organic fertilizer: The quantity and Rational fertilizer application.

type of organic manure is the dominant

(1993) found that using fermented and factor affecting CH 4 emission. Wang

“old” sludge from biogas pits could reduce CH 4 emission by 26.7%. More than 5 million rural households are using biogas pits: this technology is being popularized in other areas.


Table 1. Comparison of CH 4 emission between different rice cultivation methods and different Effects of heat balance on irrigation systems. methane emission in rice

Fertilizer application CH 4 emission flux Reduction plant canopy Year Site a Cropping system (kg/ha) (mg/m 2 per h)

Organic Inorganic Jeong-Taek Lee, Moon-Eon Park, Seong-Ho Yun, and Byong-Lyol Lee, Agricultural

Conventional lntermittent Sciences Institute (ASI), Suwon, irrigation irrigation Korea 441-707

1990 BJI

1991 BJll

1990 NJI

1992 BJlll

1990 NJll

Rice after wheat Horse manure

Spring rice Pig manure

Rice after wheat Pig manure

15,000

15,000

15.000 Spring rice Pig manure

7,500 Rice after wheat Pig manure

45,000

NH 4 HCO 3 610 Urea 500 Urea 188 Urea 300

35.9 14.6 59 b

10.0 8.7 15 c

10.8

8.5 5.6 34

9.5 12

Dry seeded Conventional

1991 BJll Spring rice Pig manure Urea 2.6 10.0 74

1992 BJlll Spring rice Pig manure Urea 3.5 8.5 59 95,000 300

75,000 300

Ridge culture Conventional

1990 NJI Rice after wheat Pig manure Urea 6.6 10.8 39

1991 NJll Rice after wheat Pig manure Urea 11.3 19.8 43

1991 NJll Rice after wheat Pig manure Urea 13.7 31 d

15,000 188

12,500 200

25,000 200

a BJ = Beijing, NJ = Nanjing. b Poor soil permeability. c Good soil permeability. d Organic fertilizer doubled.

Table 2. Comparison of CH 4 emission between different rice varieties. 1991.

Fertilizer application Site a Variety Cropping (kg/ha) CH 4 emission Yield

system flux (mg/m 2 (t/ha) Organic Inorganic per h)

NJI Conventional Rice after wheat Pig manure Urea 34.8 4.7

NJI Hybrid Rice after wheat Pig manure Urea 25.2 6.8 15,000 150

15,000 150

a NJI = Nanjing.

b) Adjusting inorganic fertilizer

inorganic fertilizers may reduce CH 4

20%. More studies are needed to confirm ing the application time of the different possible to reduce CH 4 emission by about application time: Data show that adjust- will occur by the year 2000 and that it is

are needed to verify this observation. cover the two emission peaks; more tests application are reasonably delayed to controlled if ammonium sulfate and urea

Wang M X (1993) Adv. Earth Sci. [Chinese] revealed that CH 4 emission may be REFERENCE CITED Academy of Environmental Sciences

emission. Research at the Chinese these methods.

Since 1985, China has maintained its rice area at 32 million ha. It is estimated that no remarkable increase in this area

8(5).

Methane emission from agricultural wetlands, although a direct result of soil bacterial activity, should be a function of temperature, water regime, root exudates, organic residues, plant metabolism, and physicochemical and biological properties of soils (Conrad 1989). Diurnal fluctuation of CH 4 emission is strongly dependent on the temperature changes of the upper soil layer, with maximum CH 4 emission under high soil temperature (Shútz et al 1989).

Various micrometeorological elements related to the heat balance within the rice plant canopy and CH 4 emission rates were monitored at different growth stages in ricefields into which organic matter had been incorporated.

The experiment was conducted at Suwon Weather Station (37' 16" N, 126' 59" E, 39 m) in 1993. Twenty-day-old seedlings of the rice variety, Ilpoom- byeo, was transplanted on 20 May. Fertilizers were applied at 110-30.8- 66.4 kg NPK/ha along with 7.4 t rice straw/ha.

Micrometeorological elements measured within the rice plant canopy were hourly solar radiation, net radiation, soil heat flux, relative humidity, air temperature, water temperature (average over 4 cm depth), and soil temperature (at 5 cm depth). Heat balances within the rice canopy were determined by Bowen ratio method. Three types of chambers, with dimensions of 30 × 60 × 125 cm, 15 × 30 × 45 cm, and 30 × 60 × 85 cm, were used to measure CH 4 emission

CH 4 emission rates from the rice canopy were highly correlated with water temperature, soil temperature, latent heat flux, and sensible heat flux (see table). This indicates that incoming energy flux and evapotranspiration from the plant canopy influenced CH 4 emission rates at the canopy level. CH 4 emission rates per unit leaf area showed

rates.


Correlation matrix between CH 4 emission rates and micrometeorological elements. Suwon, Korea, 1993.

Air Relative Temperature Radiation Heat flux Element temperature humidity

Water Soil Total Net Soil Latent Sensible

Canopy Emission (E) –0.05 –0.23 0.57** 0.67** –0.08 –0.04 –0.39 0.70** 0.36 E/LAI –0.18 0.06 0.51* 0.60** 0.01 0.47 –0.77** 0.57* 0.56**

Water Emission (E) 0.53* –0.44 0.85** 0.77** 0.38 0.36 –0.74** 0.79** 0.81** surface E/LAI 0.20 –0.07 0.62** 0.63** 0.26 0.28 –0.87** 0.59** 0.74**

Impact of gypsum application on methane emission from a

the highest correlation with soil heat flux (r = 0.77**) compared with the other elements. This finding suggests that solar energy plays an important role as a thermal energy source for CH 4 emission, and that the amount of energy reaching the ground where methanogenic bacteria live may be more important than previously thought in determining CH 4 emission. (See the figure for temporal changes in daily means of water and ground temperatures along with CH 4 emission rates estimated as a function of these temperatures.)

We determined the estimation models by combining the respective estimation formulas developed under either bright or dark conditions. CH 4 emission were estimated by using one of two regression equations: Y = -2347.12 + 221.5488x - 3.75347x 2 as a function of water temperature or Y = -3205.08 + 27.501x - 1.29756x 2 as a function of ground temperature. During the early growing

Seasonal changes in water temperature, ground temperature, and CH 4 emission estimated as a function of these two temperatures. Suwon, Korea, 1993.

season (from May to early June), CH 4 emission fluctuated greatly, depending strongly on the temporal variations in water and ground temperatures.

REFERENCES CITED Conrad R (1989) Exchange of trace gases

between terrestrial ecosystems and the atmosphere. Pages 39-58 in M. O. Adreae, and D. S. Sehimel eds. Wiley, Chichester.

Processes involved in formation and emission of methane in rice paddies. Biogeochemistry 7(1):33-53.

Schútz H, Seiler W, Conrad R (1989)

wetland ricefield H. A. C. Denier van der Gon, Soil Science and Geology Department, Wageningen Agricultural University, P. O. Box 37, 6700 AA Wageningen, The Netherlands; and H. U. Neue, IRRI

A frequently suggested option to mitigate CH 4 emission from ricefields is use of sulfate-containing fertilizers, such as (NH 4 ) 2 SO 4 , because sulfate reducers (in the presence of SO 4 2- ) can outcompete methanogens for substrates (Martens and Berner 1974, Lovley and Klug 1983). Methanogens may coexist with sulfate reducers, however, when there are zones or spots with low sulfate content (Mar- tens and Berner 1974). CH 4 emission measurements in ricefields fertilized with (NH 4 ) 2 SO 4 gave contradicting results, presumably because of variations in in situ SO 4 2- concentrations in the different field experiments.

To elucidate the impact of sulfate availability on CH 4 emission, field experiments with gypsum (CaSO 4 ) application were carried out during the 1991 and 1992 wet seasons (WS) (Jul- Nov) in a wetland ricefield at Los Baños, Philippines. CH 4 emission rates were monitored with an automatic measurement system based on the closed chamber technique described by Schutz et al (1989), with minor modifications. CH 4 emission rates were calculated with linear regression from the temporal increase of the CH 4 concentration in the chamber (Y 2 > 0.95). The SO 4 2- concentration in the soil solution was measured on a dionex ionchromatograph at the beginning and end of thc 1991 growing season.

CH 4 emission from fields with green manure (GM) was strongly enhanced


Average daily CH 4 flux from wetland ricefields in the Philippines with and without gypsum application. 1991-92.

Year Fertilizer Av CH 4 flux (mg/m 2 per d)

Without gypsum with gypsum a

1991 1992

Urea (55.2 kg N/ha) GM b + urea (30 kg N/ha)

40.2 443 c

18.6 128

a 6.66 t/ha CaSO 4 . 2H 2 O. b GM - 20 t/ha ( Sesbania rostrata ). c Av flux calculated without extreme CH 4 emission rates (Fig. 1a).

compared with urea-fertilized plots (see table). The difference between CH 4 emission in the 1991 and 1992 WS cannot be attributed solely to GM application, because plant spacing, N fertilizer rate, and year were also different. The CH 4 emission from gypsum-amended plots was reduced by 55-70% compared with nonamended plots (see table).

CH 4 emission from the GM-treated plot reached a peak value of 4.5 g/m 2 per d (Fig. 1a), probably caused by the quick turnover of easily decomposable organic C from the GM incorporated 1 wk before transplanting. No peak CH 4 emission was observed in the gypsum-amended plot. After the first week, the emission from both plots followed the same pattern. but emission levels differed significantly (Fig. 1b). The relative reduction in CH 4 emission upon gypsum application was independent of GM addition.

Competition for substrate between sulfate reducers and methanogens explains the lower CH 4 emission as a result of applying gypsum. In gypsum- treated soils. sulfur oxidation and a number of anaerobic thiobacilli were

In the first week after transplanting. the

Metahane emission from GM-fertilized ricefields, with and without gypsum amendment, In 1992 a) during the first week after transplanting and b) from the second week after transplanting onward.

found to be significantly higher than in control soils (Freney et al 1982). Dis- solved SO 4

2- in the control plot was below concentrations where sulfate reducers can outcompete methanogens. but after gypsum was applied, dissolved SO 4

2- was well above concentrations necessary for such competition. Initially high SO 4

2- . concentrations will decrease with rime through percolation of dissolved SO 4

2- and reduction by sulfate reducers. Cycling of S through oxidized zones. however. could maintain the inhibition of CH 4 production over a long time. CH 4 emission levels from the gypsum-amended plots never reached the level of the plots without gypsum addition (Fig. 1). indicating that methanogenesis was being inhibited throughout the season.

Despite clear evidence of sulfate- inhibiting methanogenesis. appreciable CH 4 emission still occurred in the gypsum- amended plots. The existence of zones or spots with low sulfate content where methanogenesis occurs implies that removal of sulfate by SO 4

2- reducers is quicker than its supply by dissolution of gypsum (or that the solid gypsum source was quickly depleted). and that cycling of S occurred in special zones (the oxidized rhizosphere) and the regenerated SO 4

2- . is consumed before it is evenly distributed in the bulk soil.

The amount of gypsum in our study was within the normal range of gypsum amendments used to reclaim alkaline or sodic soils (Abrol et al 1985). In India alone, for example, several million ha of the Indo-Gangetic plain are alkaline soils on which rice is the major WS crop (Abrol et al 1985). The data from our study provide a base for reducing the estimates of CH 4 emission from rice grown on high sulfate-containing soils or gypsum- amended soils (by deriving a correction factor from Table 1). A small but significant part of the total area where rice is grown consists of soils that may be low producers of CH 4 because of competition between sulfate reducers and methanogens. In global budgets for CH 4 emission from rice production, these soils should be treated accordingly. Further research on other soil types covering a significant part of the world's rice area is needed to improve estimates of the contribution of rice cultivation to global CH 4 production.

REFERENCES CITED Abrol I P. Bhumbla D R. Meelu O P (1985)

Influence of salinity and alkalinity on properties and management of ricelands. Pages 183- 198 in Soil physics and rice. International Rice Research Institute. P. 0. Box 933. Manila. Philippines.

Frency J R. Jacq V A. Baldenspergcr J F (1982) The significance of the biological sulfur cycle in rice production. Pages 271-313 in Microbiology of tropical soils and plant productivity. Y. R. Dommerques and H. G. Diem. eds. Nijhoff/Junk. Boston, USA.

Lovley D H. Klug M J (1983, Appl. Environ. Microbiol. 45:187-192.

Martens C S. Berner R A (1974) Science

Shutz H. Holzapfel-Pschom A. Conrad H. 185:1167-1169.

Rennenberg H. Seiler W (1989) J. Geophys Res. 94:16045-16416.


days after transplanting

Effects of carbon dioxide and temperature on methane emission of rice L. H. Allen, Jr., S. L. Albercht, W. Colón, and S. A. Covell, United States Department of Agriculture, Agricultural Research Service (USDA-ARS) and University of Florida, Gainesville, FL 32611, USA

Rice cultivation may be the largest anthropogenic source of CH 4 emission (Hogan et al 1991). Factors such as irrigation, organic matter, fertilization, temperature, and season affect emission from ricefields (Lindau et al 1990, Khalil et al 1991). The objective of this study was to determine the effects of elevated CO 2 and temperatures on CH 4 emission of tropical lowland rice grown under flooded conditions.

outdoor, controlled environment plant growth chambers. Daytime atmospheric CO 2 was maintained at 330 (four chambers) or 660 (four chambers) µmol CO 2 / mol air. Air temperature was controlled to follow a natural, diurnal, sinusoidal pattern between daily minimum and maximum temperatures of 32/23, 35/26, and 38/29 °C in each CO 2 treatment.

Carbon dioxide treatments were replicated once at the 30/29 °C temperature treatment.

Preplant fertilizer (80 kg P and K/ha ) was applied on 8 Jul 1992. Rice seeds, pregerminated for 4 d, were planted 20 Jul in 20- × 20-cm hills. Nitrogen was applied as urea in three split applications on 27 Jul (8 d after planting [DAP]), 20 Aug (32 DAP), and 21 Sep (64 DAP).

Soil redox potential and irrigation water pH were measured three times a week during the first two-thirds of the season and once a week thereafter. Final harvest samples were collected on 17-20 and 23 Nov (122-125 and 128 DAP).

For whole-chamber CH 4 measurements, air was pumped sequentially to a gas chromatograph with flame ionization detector. First, daily CH 4 emission was determined from the slope (mg CH 4 /m 2 per h) of four samples measured every 27 min from about 0800 to 1000 h. Second, several times during the season, diurnal CH 4 emission rates were measured at 4-h intervals after flushing each chamber with

Rice cultivar IR72 was grown in eight

Methane emission (mg CH 4 /m 2 per h) at 54, 64, 101, and 136 d after planting (DAP) taken from a hill containing 4 plants and from stubble at 136 DAP after the plant shoots were cut at 5 cm and removed.

CO 2 concentration (µmol/mol)

DAP 330 660

32 °C 35 °C 38 °C 32 °C 35 °C 38 °C

54 1.5 1.2 1.0 0.7 0.6 1.6 64 2.2 0.9 3.1 1.9 2.0 6.1 101 7.1 2.9 3.4 6.5 7.8 13.3 136 4.4 4.1 9.2 3.2 12.6 16.1 136 Stubble 4.7 3.9 8.1 3.7 9.8 15.2

Emissions clearly increased with increasing CO 2 , temperature, and DAP. Methane efflux was very similar between the plants and stubble (see table). Emissions from the stubble plants were obtained about 1 h after clipping the canopy to 5 cm above the water level.

Methane effluxes may be related to plant or root biomass (Sass et al 1990) and photosynthetic rate (Whiting et al 1991). Baker and Allen (1993) pointed out that CO 2 enrichment increased rice photosynthesis, total aboveground biomass, root biomass, tillering, and final grain yield. Since root exudate may be more than 1.7% of photosynthate (Feldman 1988), the increase in methane efflux may be because of higher soil substrate levels obtained under high CO 2 . Tiller number, photosynthetic rates, and root biomass seem likely to exert a significant role in increasing CH 4 emission.

In summary, these data are the first to show a direct relationship between increased atmospheric CO 2 concentration and CH 4 emission in a flooded rice-culture environment.

REFERENCES CITED Baker J T, Allen L H, Jr. (1993) Vegetation

Feldman L J (1988) Bio. Sci. 38(9):612-618 Hogan K B, Hoffman J S, Thompson A M

104/105:239-260

(1991) Methane on the greenhouse agenda. Nature 354:181-182.

Khalil M A K, Rasmussen R A, Wang M X, Ren L (1991) Methane emission from rice fields in China. Environ. Sci. Technol.

Lindau C W, Patrick W H Jr., Delaune R D, 25:979-981.

Reddy K R (1990) Rate of accummulation and emission of N 2 , N 2 O, and CH 4 from flooded rice soil. Plant Soil 129:269-276.

Sass R L, Fisher F M, Harcome P A, Turner F T (1990) Global Biochem. Cycles 4:47-68.

Whiting G J, Chanton J P, Bartlett D S, Happell J D (1991) J. Geophys. Res. 96:13067- 13071.


outside air. Third, several times during the season, CH 4 was measured using closed PVC tubes placed over plants, bare soil, or plant stubble. Methane emissions were determined from the slope of four to five air samples taken by syringe every 10 min.

Daily methane efflux was small up to 40 DAP, although all deep platinum electrodes registered -200 mV by 24 Aug (36 DAP). Methane emission increased soon afterward, with the highest rates observed from the high CO 2 and high temperature treatments. Soil-water samples taken at the end of the season at 5 cm showed little CH 4 at 32, 35, and 38 °C, but at the 17 cm depth, CH 4 content decreased with increased air temperature. Analysis of variance (model R 2 = 0.97) showed a significant CO 2 , temperature, and DAP effect on daily CH 4 efflux (P < 0.001), and a significant interaction between CO 2 × temperature, CO 2 × DAP, and temperature × DAP (P < 0.001).

Diurnal methane efflux from the whole canopy was obtained at 78, 99, 121, and 139 DAP (data not shown). Greatest methane efflux was from 0800 to 1000 h, followed by a gradual decline with minimal rates at 2000-2400 h. At 78 DAP, diurnal methane efflux was greater at the highest CO 2 (660 µmol/mol) and temperature (38 °C) treatment, with no differences among the other five combinations. By 99 DAP, diurnal methane efflux was greatest in the high CO 2 treatments regardless of temperature. Diurnal effluxes at 121 DAP with full canopy and those at 139 DAP with stubble were similar.

Methane efflux was measured from hills with plants and adjacent bare soil- water surfaces at 54, 64, 101, and 136 DAP (see table). Effluxes from the bare surfaces were very low (data not shown) compared with the vegetated surfaces.

Control and monitoring of rice experiments in closed environmental chambers using a distributed network of dataloggers N. B. Pickering, L. H. Allen, Jr., J. T. Baker, and K. J. Boote, United States Department of Agriculture, Agricultural Research Service (USDA-ARSI and University of Florida, Gainesviile, Florida 32611, USA

Environmental chambers provide accurate environment control and measurements for plants exposed to natural levels of

(Jones et al 1981) were used primarily to solar radiation. Our previous chambers

study the effects of CO 2 and temperature on soybean and rice (Baker and Allen 1993). Combinations of environmental set points (dry bulb temperature, dew point, CO 2 concentration) and other factors (nitrogen, variety) allow many different

ously over the experiment. Our chambers treatments that are maintained continu-

are patterned affer the Soil-Plant-Atmos- phere Research (SPAR) units (Phene et al

1985). The chambers consist of a soil (or, 1978, Parsons et al 1980, Acock et al

ricefield water) zone (2 × 1 × 0.67 m), a transparent film-covered canopy zone (2 ×

control box. 1 × 1.5 m), an air-circulation duct, and a

Host system and dataloggers. The host computer is a 486-33 Mhz PC compatible (16 Mb RAM) running IBM’s OS/2 multitasking operating system and Campbell Scientific’s (CSI) beta-release of its Real Time Monitoring System (RTMS). The four software programs (Edlog, NetCom, RTM, Database) that comprise the RTMS allow one to create and download programs, monitor ob-

collect data from the CR10Ts (CSI’s latest served variable values in real time, and

CR10). Voltage inputs (thermocouples, radiometers, tipping buckets) are moni-

The AO4 analog output device regulates tored by the AM416 input multiplexer.

the voltages to the proportional controllers. The CD16 control-port expansion

chamber venting. module controls on/off functions, such as

The nine CR10Ts (8 chambers plus ambient) are linked in a network to the

communication interfaces. Each CR10T host PC using a coaxial cable and MD9


program also calculates gas exchange rates. Data are collected every 2 s; 5-min averages are saved. The CR10T system is battery-powered, thus main power failure

loss of data. results in loss of chamber control, but no

Disadvantages of the CR10 system are the limited input and output voltage ranges and the low AO4 output current, which requires the use of voltage dividers and amplifiers. The RTMS software needs further debugging and it lacks utilities for plotting historic data.

External air ducting is used to circulate Control and measurement system.

air over the cold- and hot-water heat

The coldhot water system (chiller/heater. exchangers and electrical resistive heater.

constant supply of cold/hot water tank, pump, and piping) provide a

1. Relative enhancement rate of nearly doubled CO 2

crop weight of

maturity as a rice at

function of N application levels and averaged temperatures over the entire growth period. Pot experiment, 1990.

(840 ppm) on

2. Relative responses of

weight at maturity to the nearly doubled CO 2 as a function of N levels. Vertical

the standard bars indicate

deviation calculated by

obtained from using the data

4 temperature regimes.

crop dry

(6/50 °C) to each chamber. Dew point/dry bulb temperatures are controlled by regulating the cold/hot water flow through the heat exchangers using proportional valve controllers (Belino KM24-SR). A proportional controller (Electronmatic RE2450AD06) governs the electrical

gas cylinder info the chamber is regulated resisfance heater. Injection of CO 2 from a

by a mass flow controller (Brooks 5850i). Chamber venting, required when CO 2 concentration exceeds the set point (at night), is performed by activating two dump valves and an exhaust fan. Photo- synthetic photon flux density (PPFD) for control purposes is measured at each chamber using a calibrated photocell (Panasonic).

ben requires strong feedback control and Control of small outdoor plant cham-

minimal lag time (Jones et al 1984). All control parameters use proportional- integral (PI) algorithms, and a feed- forward algorithm based on PPFD is used to minimize lag effects. The control performance, based on 5-min averages, is usually within 0.25 °C for dry bulb temperature, 0.5 °C for dew point, and 5 µL/L, for CO 2 concentration. The errors are 2-3 times higher on a 2-s basis. An example of control for highly variable PPFD is illustrated in Figure 1. The daytime PPFD levels are shown in Figure 2. Both nighttime venting and venting due to low PPFD are evident.

Gas measurements (CO 2 , N 2 O, CH 4 ) use a common sampling system with infrared gas analyzers (IRGAs) and a gas chromatograph (GC). Chamber gas (pressurized, heated, dehumidified) is circulated through polypropylene lines between each chamber and the control building. There are two additional lines for ambient air and calibration gases (N 2 O, CH 4 ). Each chamber has its own CO 2 IRGA (Siemens, Ultramat 22P) while the N 2 O IRGA (CID, CI350) and GC (Varian Aerograph 2400) are shared among chambers. Dry bulb temperature is measured with an aspirated, shielded, thermocouple while canopy temperature is monitored with an infrared sensor (Everest Interscience 4000DL). Dew point is monitored using a dew point hygrometer (Dew-10, General Eastmen Instruments) and evapotranspiration or condensate rate is measured by a tipping bucket rain gauge. The CO 2 injection rate is monitored by the mass flow controller and leakage rates are determined from N 2 O loss curves. Ambient PPFD is measured with radiometer (Eppley 8-48) using a factor for PPFD.

Data collection and calculations. The carbon exchange rate is calculated from the change in CO 2 concentration and CO 2 injection rate, then corrected for leakage. Tipping bucket rate and calibrated volume per tip are used to compute ET. Other continuous measurements include dew point; dry bulb; soil (or ricefield water); canopy temperatures; ambient CO 2 , N 2 O, and CH 4 concentrations; and PPFD. (See Figures 1 and 2 for examples of measurements.) Leaf photosynthesis and light interception are measured

weekly using a small access door fitted with a body glove. Other weekly plant measurements include development, biomass, leaf area, leaf N, carbohydrate, and Rubisco activity levels using minimal sample sizes. Root length density is measured at the end of the season.

REFERENCES CITED Acock B, Reddy V R, Hodges H F, Baker D N,

McKinion J M (1985) Agron. J.77:942- 947.

Baker J T, Allen L H, Jr. (1993) Vegetatio 104/

Jones P, Jones J W, Allen L H, Jr., Mishoe J W

Parsons J E, Dunlap J L, McKinion J M, Phene

105: 239-260.

(1985) Trans, ASAE V:879-888.

C J, Baker D N (1980) Trans. ASAE

Phene C J, Baker D N, Lambert J R, Parsons J E, MacKinjon J M (1978) Trans. ASAE

23(3):589-595.

21(5):924-930.

Environmental factors affecting rice responses to elevated carbon dioxide concentrations H. Nakagawa, T. Horie, and H. Y. Kim, Kyoto University, Kyoto 606, Japan

Enriched CO 2 levels improved crop growth and yield, with a range of responses depending on species and other environmental factors (Kimball 1983). The combined effects of CO 2 and other environmental factors on crops must be clarified to assess the impact of global climate change in different regions and under different crop management conditions. We conducted this study to determine the combined effects of CO 2 , temperature, and N level on dry matter production of rice under different radiation and underground environments by using the newly developed temperature gradient tunnel (TGT) (Horie et a1 1991).

Rice cultivar Akihikari was grown to maturity in two TGTs for three cropping seasons (1990-92). Air was ventilated through the long axis of the TGT (25 x 2.5 x 1.7 m) during the day; the direction of air flow was reversed at night. The TGT provided a temperature gradient along the long axis for solar radiation during the day and natural cooling of the heat produced by an oil heater at night. The temperature difference between the air inlet and outlet was maintained at about 4 °C throughout the growth period while maintaining natural daily and seasonal variations. The daytime CO 2 in one TGT was kept at ambient level (350 ppm) in all three seasons, and the level in the other at about twice the ambient level (840 ppm in 1990 and 690 ppm in 1991 and 1992).

Rice plants in 1990 and 1991 were raised in 1/5000a Wagner's pots and spaced evenly in the TGTs; those in 1992 were raised on the ground in TGTs in an underground condition similar to that in a field. Pots in 1990 were rotated twice a week to give the same environment to each plant, while those in 1991 were fixed. The edges of the rice populations in 1991 and 1992 were shaded to create a canopy condition and lessen radiation penetration.

Three N plots (0.3, 1.2, 2.4 g N/pot in 1990 and 1991, and 4, 12, 20 g N/m 2 in 1992) were created at each of four distances from the air inlet in TGTs. The N levels in 1991 could be converted into 6, 24, and 48 g N/m 2 by considering the pot density of 20 pots/m 2 .

Air temperature at four distances from the air inlet was measured during the growth period. Crop dry weight and leaf area were periodically measured.

CO 2 effects on isolated plants. The plants in the 1990 experiment were subjected to a radiation environment similar to that for an isolated plant. Figure 1 shows the percent increase in total dry weight at maturity in 1990 for doubled CO 2 (840 ppm) treatment over the ambient CO 2 control as a function of N rate and temperature, The increase ranged from 10 to 122%, with a longer increase at high temperature at all N levels. This is consistent with the results of Imai et al (1985). While nearly doubled CO 2 did not produce any significant effects on leaf area at heading in the low and intermediate N levels, it gave appreciable effects at high N levels, especially under higher temperature regimes (18% increase at 29.50 °C and 43% increase at 30.5 °C). These results suggest that nearly doubled CO 2 raised the optimum temperature for photosynthesis.


1. Percent increase in total dry weight of rice at maturity for doubled CO 2 (840 ppm) treatment over the ambient CO 2 control as a function of N rate and temperature averaged over the growth period. Pot experiment, 1990.

2. Relative responses of crop dry weight at maturity under doubled CO 2 as a function of N level. Vertical bars indicate the standard deviation calculated using the data obtained under 4 temperature regimes.

Increase in crop dry weight by doubling CO 2 was higher at higher N and higher temperatures due to increases in both leaf area and photosynthetic rate.

The results obtained in 1991 and 1992, when plants were maintained under canopy conditions, were different from the results with single plants. No consistent trend could be seen in the temperature effects on rice response to the elevated CO 2 under canopy conditions, as was reported in an earlier study (Horie

CO 2 effects on plants in a community.


1993). The average values of relative increases in crop dry weight by doubling CO 2 across temperature treatments as a function of N application rate were plotted in Figure 2. The relative increase was greater at higher N levels and reached a maximum at around 24 g N/m 2 . CO 2 had

24%, being less affected by temperature. Our analysis indicates that this enhancement in total dry weight by doubling CO 2 increases with increased N levels up to 30% at optimum N level.

REFERENCES CITED little effect on leaf area at heading for all Baker J T, Allen L H Jr, Boote J K, Rowland- N × temperature plots. The enhancement Bamford A J, Waschmann R S, Jones J W,

Jones P H, Bowes G (1990) 1989 Progress rates of crop dry weight at maturity report of response to vegetation to carbon obtained from pot experiments were much dioxide. Report No. 060 Plant Stress and lower than those of field experiments. Protection Research Unit, USDA-ARS,

When collecting data to assess impact of global climate change on the rice crop,

University of Florida, Gainesville. 70 p.

experiments should be done under canopy

Hone T, Nakano J, Nakagawa H, Wada K, Kim H Y, Seo T (1991). J. Crop Sci. 60 (Extra issue 2): 127-128.

conditions and underground environments Horie T (1993) J. Agric. Meteorol. 48(5):567- similar to those of field conditions. By 574.

analyzing data from long-term CO 2 Imai K, Coleman D F, Yanagisawa T (1985)

enrichment experiments on rice, which satisfy these conditions (our TGT experiments and Baker et al 1990), Horie 54(4):413-418.

( Oryza sativa L.). Jpn. J. Crop Sci.

(1993) concluded that the relative increase Kimbal B A (1983) Agron. J. 75:779-788.

Increase in atmospheric partial pressure of carbon dioxide and growth and yield of rice

in rice dry weight by doubling CO 2 was

Responses of rice to elevated tion rate of the chamber was maintained levels of carbon dioxide covered by polyethylene film. Ventila-

Kezhi Bai, and Tingyuan Kuang, Institute of Botany, Academia Sinica, Beijing 100044, China

at 3 exchanges/min throughout the growing season. Rice was planted in fertile soil in pots (25 cm diameter × 30 cm tall), and a 3-5 cm water depth

Rice is the major crop in China in terms of cultivated area and total yield. The aim of this study was to determine the effects of elevated levels of CO 2 concentration on a Chinese rice variety, Aixiangnuo, and to generate basic parameters for developing global change-crop reaction models.

The experiments were conducted at the Botanical Garden of the Institute of Botany in 1993-94. Ambient or CO 2 - enriched (plus 350 ppm CO 2 ) air was introduced through the bottom of cylindrical open-top chambers (2.2 m diam × 1.7 m tall) with aluminum frames

was maintained. The dry matter partitioning in the

young seedlings under elevated CO 2 levels was measured (Table 1). Total dry weight increased by 15%, compared with seedlings grown under ambient atmospheric condition. Shoot dry weight increased only 4%, but with the major increase in dry matter occurring in the roots. Elevated CO 2 influences C metabolism and dry matter partitioning between shoots and roots in the rice plant even at early growth stages.

Elevated CO 2 also affected growth at maturity: compared with the control,

Table 1. Influences of CO 2 enrichment on dry matter (mg) partitioning between shoots and roots in 3-4 leaf stage rice seedlings.

Whole seedling Shoot Root Root-Shoot

Treatment Dry (%) Dry (%) Dry (%) Ratio (%) weight weight weight

(g) (g) (g)

Ambient air 24.7 100 18.4 100 6.3 100 0.34 100 Ambient air plus 28.5 115 19.1 104 9.4 149 0.49

350 ppm CO 2

Table 2. Effects of elevated CO 2 level on the growth of rice at maturity and on the reproductive characteristics of rice.

Treatment Culm length Root dry weight Shoot dry weight Root-shoot Grain yield Panicles/plant Filled grains/ 1,000 grain (cm) (g/plant) (g/Plant) ratio (t/plant) (no.) panicle (no.) weight (g)

Ambient air 61.35 ± 0.9 1.63 ± 0.35 6.52 ± 0.92 0.25 6.35 ± 0.31 3.8 ± 0.2 52.7 ± 1.6 31.7 ± 0.8 Ambient plus 68.4 ± 1.1 2.00 ± 0.24 6.47 ± 0.61 0.31 8.98 ± 0.41 3.9 ± 0.1 67.9 ± 1.4 33.9 ± 1.0

350 ppm CO 2 ± (%) + 11.8 + 23.0 - 0.7 + 24 + 41.4 + 2.6 - 28.8 + 6.9

plant culm length increased by 11.8%, root dry weight increased by 23%, and root-shoot ratio increased by 24%. Almost no change in shoot dry weight was observed (Table 2).

Grain yield per plant increased by 41.4% under elevated CO 2 levels. Increases in filled grains per panicle and 1,000-grain weight contributed to the higher yield. No significant change in panicles per plant occurred (Table 2).

Results of this study are similar to those of previous studies (Imai et a1 1986,

Baker et a1 1990, Ziska and Teramura 1992). Baker et a1 (l990), using IR30, observed that panicle number per plant was almost entirely responsible for differences in final grain yield among CO 2 treatments. Doubling the CO 2 concentration from 330 to 660 ppm resulted in a 32% increase in grain yield. Ziska and Teramura (1992) described differences in reproductive characteristics between IR36 and Fujiyama 5 cultivars. Considering the large diversity of growth and developmental properties in different

rice cultivars, more cultivars need to be studied under elevated CO 2 .

REFERENCES CITED

Baker J T, Allen L H, Jr., Boote J K (1990) Growth and yield responses of rice to carbon dioxide concentration. J. Agric. Sci. 115:313-320.

Iami K, Coleman D F, Yanagisawa T (1985) Jpn. J. Crop Sci. 54:413-418.

Ziska L H. Teramura A (1997) Physiol. Plant. 84:269-276.

Modeling leaf and canopy photosynthesis of rice in response to carbon dioxide and temperature K. J. Boote, N. B. Pickering, J. T. Baker, and L.H. Allen, Jr., University of Florida and United States Department of Agriculture, Agricultural Research Service (USDA-ARS), Gainesville, FL 32611, USA

Model equations were developed to predict leaf and canopy assimilation of rice as a function of CO 2 , temperature, photosynthetic active radiation (PAR), time of day, leaf traits, and canopy leaf area index (LAI) as described by Boote and Pickering (1984). Predictions were compared with canopy assimilation measured on rice grown in sunlit, controlled-environment chambers under season-long treatments of CO 2 and temperature (Baker et a1 1990, 1992). Apparent assimilation, CO 2 , air temperature, and PAR were recorded at 5-min intervals throughout the day.

The model accounts for diffuse and direct beam interception of PAR, computes irradiance on sunlit and shaded leaf classes, and computes photosynthesis of sunlit and shaded leaf classes with asymptotic exponential equations (Boote and Pickering 1994). Temperature and CO 2 effects on quantum efficiency (QE)

1. Gross assimilation vs photosynthetic active radiation (PAR) at 160,330, and 660 vpm CO 2 .

and light saturated leaf photosynthesis (Pmax) are computed using equations 16.60 a, b of Farquhar and von Caemmerer (1982), assuming limiting RuBP and temperature effects on the specificity factor of rubisco for CO 2 vs O 2 . The equations are scaled to a QE of 0.0541 mol/mol and a relative effect of 1.0 Pmax at 30 °C and 350 vpm CO 2 . Actual QE and Pmax depend on intercel- lular CO 2 concentration (C 1 ), temperature, and oxygen.

2. Gross assimilation vs temperature at 350 or 700 vpm CO 2 .

The canopy assimilation model was used with nonlinear regression to solve for single leaf Pmax for individual rice canopies grown at a range of CO 2 levels and temperatures. For these regressions, we entered observed LAI, and 5-min averages of CO 2 , air temperature, and PAR measured throughout the day for each chamber. Measured plants were 60 d old and LAI ranged from 5 to 11 in the two experiments. A spherical leaf angle distribution was assumed.


We hypothesized that there should be no trends in the solved values of Pmax for individual treatments, based on the assumption that our equations account for PAR and LAI effects, and that the QE and Pmax terms account for CO 2 and temperature effects. We then solved for one Pmax value to represent all CO 2 treatments, based on the same assumptions. Pmax thus reflects light-saturated rate at 350 vpm CO 2 and 30°C.

The trend for solved Pmax (of individual chambers) was to increase with increasing CO 2 : 17.1, 16.3, 21.9, 29.3, 28.9, and 27.1 µmol Co 2 /m 2 per s at 160, 250, 330, 500, 660, and 900 vpm CO 2 , respectively. One solved Pmax (24.0) was adequate to predict canopy response at all CO 2 treatments, except at 160 and 250 vpm. The CO 2 -related increase in Pmax and the fact that a single Pmax for all treatments was overpredicted at subambient CO 2 indicated a problem with the assumption that the complete response to CO 2 can be modeled on the basis of energy limitation only.

reported to be inhibited as C i falls below 300 vpm (Sharkey et al 1988). An asymptotic equation was added to rice Pmax as a function of C i . This function describes CO 2 substrate limitations upon RuBP regeneration and upon rubisco activity. The 50% response of Pmax to C i was achieved at 137 vpm CO 2 . Figure 1 illustrates how well predicted canopy assimilation matched observed values for 160, 330, and 660 vpm CO 2 treatments using one value for Pmax (29.8 µmol CO 2 / m 2 per s).

In the temperature experiment, rice canopies showed a trend for Pmax to increase from low to high temperature: 18.9, 24.1, 23.0, 24.7, and 39.6 µmol CO 2 /m 2 per s at 25, 28, 31, 34, and 37°C growth/measurement temperature, respectively. Solving for a single Pmax (24.6) to represent all treatments overesti- mated assimilation at 25 °C and underesti- mated at higher temperatures.

Temperature effects on efficiency of electron use for CO 2 fixation are ac- counted for in QE and Pmax, but the equations had no temperature effect on electron transport capacity per se. Adding a linear temperature effect on Pmax

Electro-transport rate in high light is


(electron transport) improved the fit major differences in canopy assimilation considerably. measurements, meaning there were no

values vs temperature (10 values from two dates). The equation for temperature effect REFERENCES CITED

on Pmax was normalized to 1.0 at 30°C Baker J T, Allen L H Jr., Boote K J, Jones P.

and had a base temperature of Jones J W (1990) Rice photosynthesis and

6.4°C (relative = -0.272 + 0.0424°C). evapotranspiration in subambient, ambient, and superambient carbon dioxide concen-

Model sensitivity analysis to temperature trations. Agron J. 82(4):834-840. was then conducted at midday for Pmax = Baker J T, Allen L H Jr, Boote K J (1992)

24.0 µmol CO 2 /m 2 per s, LAI = 5.0, and Temperature effects on rice at elevated

linear increase in electron transport from Boote K J, pickering N B (1994) Hort. Sci. (in 6° to 37°C, predicted canopy gross press) assimilation was within 98% of maximum Fartquhar G D, von Caemmerer S (1982)

from 24° to 32°C at 350 vpm CO 2 , and Pages 549-587 in Physiological plant

from 28° to 40°C at 700 vpm CO 2 (Fig. 2). ecology II. O. L. Lang, ed. Springer-

The broad temperature optimum for Sharkey T D, Berry J A, Sage R F (1988) Verlag, Berlin.

Linear regression was done for Pmax from 25° to 37°C.

PAR = 1500 µmol/m 2 per s. Despite a CO 2 concentration. J. Exp. Bot. 43(252): 959-964.

canopy assimilation is consistent with our Planta 176:415-424.

Carbon dioxide and nitrogen fertilizer effects on rice canopy carbon exchange, growth, and yield J. T. Baker, L. H. Allen, Jr., K. J. Boote, and N. B. Pickering, University of Florida, Gainesville, and United States Department of Agriculture - Agricultural Research Service (USDA-ARS), USA

The current global rise in atmospheric CO 2 is now well-established and is largely attributed to the continuous burning of fossil fuels and large-scale deforestation. The Green Revolution in the tropics was made possible by the development of semidwarf, high-yielding cultivars that were fertilizer-responsive and resistant to lodging (Jennings et al 1979). Nitrogen fertilizer is an important limiting nutrient in the production of modern rice cultivars in Asia (De Datta 1981). The objectives of this study were to determine the effects and possible interactions of CO 2 and N fertilization on the growth, grain yield, and canopy gas exchange (photosynthesis, respiration and evapotranspiration) of rice.

irrigated conditions in six sunlit controlled-environment plant growth chambers (aboveground dimensions 2 × 1 m cross section × 1.5 m high). Daytime CO 2 concentration was maintained at 330 (three chambers) and at 660 (three chambers) µmol CO 2 /mol air. Rice was

Cultivar IR30 was grown under

direct seeded by hand into 11 rows in each chamber, 0.18 m apart, on 8 Jun 1990. Temperatures were controlled at 28/21/25 °C (daytime dry-bulb air temperature/ nighttime dry-bulb air temperature/flood water temperature). In each CO 2 treatment, N fertilizer (as urea) at 0, 100, or 200 kg/ ha was applied to a loamy sand in three splits (1/2, 1/4, and 1/4) at 9, 35, and 59 after planting (DAP). Initial or preflood soil pH was 4.8; the NH 4 -N 3.5 mg/kg; the NO 3 -N, 0.5 mg/kg; and the organic matter content, 4.3%.

Nitrogen fertilization treatments did not significantly affect plant development rates in this experiment while CO 2 treatment effects on development were small. Logistic regression estimates of the day of 50% panicle appearance (near anthesis) indicated no N treatment effects on the number of days to anthesis while CO 2 enrichment tended to decrease the number of days to 50% panicle appearance by about 4-6 d.

Tillering, final biomass accumulation, and grain yield increased with both CO 2 enrichment and increasing N treatment. (See table for final grain yield, yield components, final aboveground biomass, and harvest index.)

kg/ha, grain yields increased from 6.0 to 8.1 and 7.9 to 10.1 Mg/ha for the 330 and 660 mol/mol CO 2 treatments, respectively, because more grain-bearing

As N treatment increased from 0 to 200

panicles were produced with both CO 2 enrichment and increasing N treatment (see table). Similar trends in individual seed mass were observed while filled grains/panicle were apparently unaffected by either CO 2 or N treatment. These vends in grain yield and final aboveground biomass resulted in a decline in harvest index with increasing N treatment (especially in the 660 µmol/mol). Harvest index tended to be higher in the CO 2 enrichment treatments.

Canopy gross photosynthesis and canopy light utilization efficiency were increased by both CO 2 enrichment and increasing N fertilizer throughout the growing season. Canopy dark respiration rate expressed on a ground area basis followed seasonal trends that were similar to those observed for canopy photosynthesis. Canopy dark respiration rates expressed on a plant dry weight basis declined exponentially throughout the growing season and were little affected by either CO 2 or N fertilizer treatments. After complete canopy closure, CO 2 enrichment reduced canopy evapotranspiration and increased canopy photosynthetic water use efficiency. The effects of CO 2 enrichment at N levels of 100 and 200 kg/ha on growth, grain yield, and canopy gas exchange are similar to our previous CO 2 enrichment studies (Baker et al 1990, 1992a, b). The relatively small plant responses to N fertilizer treatments are attributed to the high native fertility and organic matter content of the soil used in this experiment.

REFERENCES CITED Baker J T, Allen L H Jr., Boote K J, Jones P,

Jones J W (1990) Rice photosynthesis and evapotranspiration in subambient. ambient and superambient carbon dioxide concentrations. Agron. J. 82:834-840

(1993a) Effects of daytime dioxide concentration on dark respiration on rice. Plant Cell Environ. 15:(2)231-239.

Raker J T, Allen L H Jr., Boote K J (19993b) Temperature effects on rice at elevated CO 2 concentration J. Exp. Bot. 43:959-964.

De Dana S K. (1981) Principles and practices of rice production. p. 618. John Wiley and Sons. New York.

Jennings P R. Coffman W R. Kaufman H E (1979) Rice improvement. International Rice Research Institute, P. O. Box 933.

Baker J T. Laugel F. Boote K J. Allen L H Jr.

Manila, Philippines.

Grain yield, components of yield, total above-ground biomass, and harvest index for rice grown in controlled environments chambers.

CO 2 (µmol/mol)

Nitrogen (kg/ha)

Grain yield

(mg/ha)

Panicles (no./plant)

Filled grains (no./panicle)

lndividual grain mass (mg/seed)

Aboveground biomass (g/plant)

Harvest Index (g/g)

330

660

SE a

0 100 200

0 100 200

CO 2 N CO 2 × N

6.0 8.2 8.1 7.9 7.9

10.1

1.46

7.5** 8.0** 3.1*

2.8 3.3 4.0 3.4 3.7 4.4

0.39

48.2 53.4 47.4 49.2 49.4 53.4

7.56

F value b

15.4** 0.2 ns 26.7** 0.5 ns

0.5 ns 1.6 ns

18.7 20.3 18.5 20.6 19.6 19.2

0.97

4.1* 5.0** 6.5**

5.5 7.3 8.1 6.4 7.2 93

1.02

4.8* 27.1**

1.6 ns

0.47 0.48 0.43 0.54 0.49 0.47

0 044

8.9** 6.5** 16 ns

a SE in each column is for each of the means and was obtained by pooling each of the within-chamber variances. b *, ** = significant at the 0.05 and 0.01 probability Ievels. respectively. ns = not significant.

Effects of carbon dioxide on competition between rice and barnyard grass D. M. Olszyk. US Environmental Protection Agency, Corvallis, Oregon, USA, and L. L. Ranasinghe, Oregon State University. Corvallis Oregon, USA

Effects of elevated CO 2 on rice production could occur not only through direct impacts on rice (Baker et al 1990) but also indirectly via ecosystem responses (Bazzaz et al 1985). Preliminary experiments were conducted to test the hypothesis that a C3 crop, rice, and n C4 weed, barnyard grass, respond differently to CO 2 , affecting competition between them when grown at different relative densities in the same container.

Rice cultivar IR72 and barnyard grass were grown from seeds obtained from IRRI. Four-day-old seedlings were transplanted into white plastic pots (7.5 cm high × 16.5 cm inner diameter) filled with soil. Plants were arranged in a circle in each pot. with one in the center for the one-plant pots. Plants were watered periodically to maintain standing water with nutrient solution.

Carbon dioxide treatments were provided in individual small-exposure chambers located in a greenhouse with rough temperature and light intensity control but no dewpoint control. Average conditions over two experiments were photosynthetically active radiation (PAR). average daily at 388 µmol/m 2 per

s; 12 h light period; temperature, average daily maximum of 25.4 °C, average daily minimum of 26.3 °C; and relative humidity, average day period minimum of 42%. average night period maximum, 698.

Carbon dioxide treatments were ambient (average 374 µL/L), and ambient + continuously added CO 2 , resulting in elevated levels of 563, 724, and 895 µL/L. Each CO 2 level occurred in each of two blocks of chambers. Plants were exposed to CO 2 for about 28 d. Seven planting mixtures/densities were examined per chamber (split/plots): 8 barnyard grass, 2 rice and 6 barnyard grass, 4 rice and 4 barnyard grass, 6 rice and 2 barnyard grass, 8 rice, 1 rice, and 1 barnyard grass, with two replicate pots per density per chamber. The experiment was repeated. Both experiments were evaluated together because no significant (at P< 0.05) experiment × CO 2 interactions and few experiment × density interactions were found. Rice and barnyard grass data were analyzed separately (per plant).

Rice plants tended to have increased shoot growth under elevated CO 2 levels. Across densities, elevated CO 2 produced a statistically significant increase in rice leaf number (P < 0.05) (see table), but increases for tiller number and leaf, stem, and total dry weight (Fig. 1) were significant only with P = 0.05-0.16. Few lower P values may be because of, in part, a lack of difference in response among higher CO 2 levels. Density across CO 2 levels had a highly significant effect on ail param-


Effects of CO 2 and plant density on total shoot dry weight of a) rice and b) barnyard grass. Data are per plant and averages of eight plants, two from each of two experiments. Coeffi- cients of variability across CO 2 levels, densities, and experiments were 44.7% for rice and 26.0% for barnyard grass.

that intraspecific competition among barnyard grass plants was more important than interspecific competition with rice.

Results from statistical analysis (P values) of effects of experiment, CO2, and density on rice and

competition) and 1 vs all multiple plants (2-8)/pot (includes interspecific competition). barnyard grass (BVG). The density comparisons are for 1 vs 8 plants/pot (only intraspecific

With increasing CO 2 concentrations, however, there was a trend toward decreased barnyard grass growth in the

Leaf Stem Total mixtures, suggesting that rice plants were becoming more competitive. Source df Tiller no. Leaf no. dry weight dry weight dry weight

Rice BYG Rice BYG Rice BYG Rice BYG Rice BYG

Experiment 1 0.14 0.04 0.36 0.03 0.02 0.04 0.02 0.01 0.02 0.01 Block 2 0.07 0.79 0.10 0.43 0.05 0.47 0.08 0.07 0.12 0.05

Experiment × 3 0.33 0.52 0.27 0.11 0.12 0.25 0.19 0.56 0.16 0.92

Density 4 <0.01 <0.01 <0.01 <0.01 <0.01 0.11 <0.01 <0.01 <0.01 <0.01 (1 vs 8 plants) 1 <0.01 <0.01 <0.01 <0.01 <0.01 0.03 <0.01 <0.01 <0.01 <0.01 (1 vs 2-8 plants) 1 <0.01 <0.01 <0.01 <0.01 <0.01 0.02 <0.01 <0.01 <0.01 <0.01 Experiment ×

density 4 0.08 0.34 0.36 <0.01 <0.01 <0.01 0.03 0.07 0.01 0.22 CO2 × density 12 <0.01 0.43 <0.01 0.88 <0.01 0.50 0.07 0.66 0.06 0.62 Chamber (Expe-

riment × CO2) 7 0.09 0.38 0.28 0.85 0.40 0.48 0.11 0.24 0.07 0.52 Error 124 (123 for leaf dry weight) Total 159 (158 for leaf dry weight)

CO2 3 0.05 0.42 0.04 0.48 0.12 0.29 0.08 0.18 0.16 0.01

CO2

eters (P < 0.01), largely because of the shoot growth with elevated CO 2 , either increase in growth at 1 plant/pot vs other

table), and there actually was a significant densities. with or without plant competition (see

Rice plants showed significant (P < decrease in total dry weight primarily at 0.05) CO 2 × density interactions for leaf low densities (Fig. lb). Density by and tiller numbers and marginally signifi- itself—across CO 2 levels—significantly cant interactions (P = 0.06-0.07) for stem

weight (P< 0.01), with less growth when and total shoot dry weight (see table). In affected all parameters except leaf dry

terms of interspecific competition, rice tended to compete better with barnyard grass under elevated CO 2 levels compared with ambient CO 2 ; the mixtures with more rice and fewer barnyard grass plants per pot showed greater increases in growth (Fig. 1a). In terms of intraspecific competition, CO 2 stimulated rice plant growth more with one rice plant/pot compared with 8 plants/pot for all parameters.

As expected for C4 plants, barnyard grass showed no significant increase in

more plants were present in a pot.

show any significant (lowest P = 0.43) CO 2 × density interactions (see table), likely because of the lack of a general CO 2 response for this species. In terms of general competition, (across all CO 2 concentrations), barnyard grass growth tended to be less with more barnyard grass compared with rice plants in the mixtures. This (coupled with greater growth with 1 vs. 8 barnyard grass plants/pot) suggested

Barnyard grass shoot growth did not

REFERENCES CITED Baker J T, Allen L H. Jr.. Boote K J (1990)

Growth and yield responses of rice to carbon dioxide concentration. J. Agric. Sci. 115:313-320.

Bazzaz F A, Garbutt K, Williams W E, (1985) Direct effects of increasing carbon dioxide on vegetation. Pages 155-170 in B. R. Strain and J. D. Cure, eds. U. S. Department of Energy, Washington, D.C.

*The information in this document has been funded wholly (or in part) by the U. S. Environ- mental Protection Agency. It has been subjected to the Agency's peer and administrative review, and it has been approved for publication as an EPA document. Mention of trade names or commercial products does not imply endorse- ment or recommendation for use.

A very simple model of crop

cation growth: derivation and appli-

K. Kobayashi, National lnstitute of Agro- Environmental Sciences, 3-1-1 Kannondai, Tsukuba, lbaraki 305, Japan

Crop growth models are powerful tools to improve understanding of global climate change and to predict crop yield changes caused by these changes. The problem, however, is that models are often so complex that it is difficult to understand them. We have a very simple model (VSM) for determining crop growth. The


model can be written in only one line, hence it is easy to interpret the outputs.

Derivation of the VSM. The VSM is based on the following assumptions of crop growth processes: 1. The leaf area index (LAI) changes in

a triangular pattern (see figure) as

where L is LAI, t is days after emergence, a is daily LAI increase, TO is days from emergence to linear increase of LAI, Lf is maximum LAI around time of flowering (Tf), b is daily LAI decrease, and Th is days from emergence to harvest.

The LAI change may be better described by a trapezoidal pattern (see figure), but the triangular pattern usually gives a good approximation. If the LAI change is greatly affected by temperature, the LAI change may be better based on accumulated temperature rather than on the number of days. As this can be easily incorporated into the VSM, if necessary, the simplest case as noted above is assumed here. 2. Biomass is accumulated propor-

tionately to the intercepted solar radiation as

where d W /d t is daily biomass accumulation, E is the light use efficiency, /o is incident shortwave radiation, and k is the light extinction coefficient.

biomass at harvest multiplied by the harvest index

3. Yield is denoted as the total

LAI change assumed in the VSM.

mations, the integral can be simplified as

where Tv = Tf-T0, Tr = Th-Tf, /v and /r are the mean daily shortwave radiation for Tv and Tr, respectively, and e v and e r are the light use efficiency for Tv and Tr, respectively. The factor C accounts for the approximation error. The LAI at flowering (Lf) is not really a parameter, yet it can be easily obtained by measurements or even by guesses.

The crop yield at harvest can,

where Y is grain yield, Wh is total dry weight at harvest, and HI is the harvest index.

Total dry matter is calculated by integrating the daily biomass accumulation. By some approxi-

therefore, be expressed as

where Y is yield (g/m 2 ), HI is the harvest index, k is the light extinction coefficient, Lf is LAI at flowering, /v and /r are the mean daily solar input (MJ/d per m 2 ) before and after flowering, respectively, Tv is days from the initiation of the linear LAI increase to flowering (d), e v and e r are the light use efficiency (g/MJ) before and after flowering, respectively, Tr is

Rice yield in Don Daeng village, Thailand. 1981-83.

Yield (g/m 2 )

Kaida et al Miyagawa et al VSM Year (1985) (1985)

1981 118 182 189 1982 60 NA 154 1983 219 236 266

days from flowering to harvest (d), and C is the correction factor, the full description of which is rather lengthy and, hence, omitted here. An application: analysis of field

survey data. The VSM was applied to the rice yield in Don Daeng Village in northeast Thailand from 1981 to 1983. Most of the VSM parameters, including LAI at flowering, and duration of vegetative and reproductive growth, were estimated from field survey data (Miyagawa 1985, Kaida 1985, Miyagawa and Kuroda 1985), but some were set rather arbitrarily because the data were lacking.

Results of the VSM estimation are in the table. Because of the arbitrariness of setting some parameters, the absolute values of the VSM yield estimate should not be focused upon. The year-to-year variation in yield, however, showed a pattern similar to that of the survey data, with 1983 having the highest yield followed by 1981 and 1982. Further analysis of the survey data suggested poor leaf area development and delayed transplanting as factors contributing to the lower yields in 1981 and 1982 when compared with those in 1983.

REFERENCES CITED Kaida Y, Hoshikawa K, Kohno Y (1985) Don

Daeng village in northeast Thailand: instability of rice culture. [ in Japanese with English summary]. Southeast Asian Stud. 231252-266.

Miyagawa S, Kuroda T (1988) Variability of yield and yield components of rice in rainfed paddy fields of northeast Thailand. Jpn. J. Crop Sci. 57527-534.

Miyagawa S, Kuroda R, Matsufuji H, Hattori T (1985) Don Daeng village in northeast Thailand: typology of rice cultivation [ in Japanese with English summary]. Southeast Asian Stud. 23:235-251.


Climate change and rice production in India S. Mohandass, A. Abdul Kareem, and T. B. Ranganathan, Tamil Nadu Rice Research Institute, Aduthurai 612101, India; and M. J. Kropff, IRRl

Rice is India's most important cereal in terms of area and production. By about the year 2020, 65% more rice than the amount produced in 1989 will be needed in the world to meet the demands of the expanding human population (IRRI 1989).

Elevated CO 2 in the atmosphere will affect agricultural production by stimulat- ing photosynthesis (Lemon 1993, Cure and Acock 1986) and improving water use efficiency of crops (Goudriaan and van Laar 1976, Sionit et a1 1980). Increased CO 2 can also induce changes in climate, resulting in increased global average annual mean surface air temperature (IPPCC Report, Houghton et a1 1990). Such global warming is likely to affect agricultural production all over the world.

A crop growth simulation model, ORYZA 1 (Kropff et a1 1993), was used to study the effect of temperature rise and elevated atmospheric CO 2 concentration on rice yields in India. The model was validated for the current climate conditions.

Effects of several combinations of temperature increases and atmospheric CO 2 concentrations on simulated yields were studied. The model simulated potential production, which is growth with ample nutrient supply and in the absence of damage by pests, diseases, and weeds.

A temperature increase of up to 2°C over the current level only marginally affected the length of the growing season (from 126 to 125 d). Grain yield, however, declined with a temperature increase of 7°C from 8.0 t/ha to 7.1 t/ha. Regard- ing locations, places such as Patancheru Bijarpur experienced comparatively greater yield decline (up to 20%) while Kapurthala and Madurai were affected only a little by the increase (see table).

An elevated level of atmospheric CO 2 generally led to an increase in the mean simulated potential yield. With the given weather data, the average increase for India was 11, 20, 28, 40, and 48% for 390, 444, 490, 590, and 680 ppm of atmos-


Effect of temperature rise on simulated grain yield (t/ha) of rice at 9 sites, India.

Temperature rise (°C) Site

0.0 0.5 1.0 2.0 3.0 4.0

Aduthurai 7.94 7.85 7.80 7.70 Bijapur 6.74

7.57 7.35 6.47 6.32 6.03

7.70

Coimbatore 8.66 8.33 5.93 6.22

Cuttack 6.72 7.81

6.48 7.64 7.58 8.02

6.31 6.09 Hyderabad 8.91 8.93

5.99 8.61

6.07 6.28 8.30 8.10

Kapurthala 9.74 8.14

9.54 8.50

9.18 9.07 9.03 Pattambi 6.29 6.03

8.98 9.26 5.76 5.38

Madurai 8.64 8.61 5.20

8.53 5.27 5.66

8.37 Patancheru 8.20 7.92 7.22 6.91

8.18 7.62

7.89 8.37 6.72

Mean 7.43

7.99 7.80 7.58 7.33 7.16 7.10

Mean

5.86 8.11

pheric CO 2 , respectively, compared with the current level of 340 ppm.

The combined effect of doubled CO 2 (680 ppm) and temperature increase (4°C) led to an increase of about 2.5 t/ha (see figure) over current rice yields. In locations such as Kapurthala, Cuttack, and Madurai, the combined effect of doubled CO 2 and temperature increase had the beneficial result of offsetting the yield reduction caused by the temperature increase.

The Impact of climatic change (680 ppm CO 2 and/ or 4°C increases) on rice yield at 9 locations in India.

REFERENCES CITED Cure J D, Aoock B (1986) Crop responses to

carbon dioxide doubling: a literature survey. Agric. For. Meteorol. 38: 127-145.

Goudriaan J. van Laar H H (1978) Photo- synthetica 12:241-249.

Houghton J T, Jenkins G J, Ephraums J J (1990) Climate change. The IPPCC Scientific Assessment. Cambridge University Press, Cambridge.

IRRI — International Rice Research Institute (1989) IRRI towards 2000 and beyond. P. O. Box 933, Manila. Philippines. 80 p.

Kropff M J. Van La H H. and ten Berge H T M (1993) ORYZA1 : an ecophysiological model for irrigated rice production. P. O. Box 933 Manila, Philippines. p. 5.

Lemon E R (1983) CO 2 and plants, the response of plants to rising levels of atmospheric carbon dioxide. Westview Press, Boulder, Colorado.

Sionit N H, Hellmers H, Strain B R (1 980) Crop Sci. 20:456-458.

Photosynthesis and stomatal conductance in rice as affected by drought stress Md. Jalaluddin and M. Price, School of Agriculture and Home Economics, Univer- sity of Arkansas at Pine Bluff, Arkansas, USA; and R. H. Dilday, United States Department of Agriculture - Agricultural Research Service (USDA-ARS), Stuttgart, Arkansas, USA

Agricultural activities, including rice production, may contribute to increased levels of greenhouse gases, such as CH 4 and N 2 O, that lead to global warming. Methane emission from ricefields could be reduced if improved rice varieties

having high yield potential under upland or nonflooded conditions are adopted.

Upland rice often experiences drought stress. Even a partial closure of stomata restricts gas exchange considerably and reduces assimilation rate (Dingkuhn et al 1989). For upland or nonflooded irrigated rice, elevated CO 2 may mitigate, in part, the adverse effects of water deficit. The objective of our study was to test rice cuttivars of different origins and growth habits to determine varietal differences in rates of photosynthesis and stomatal conductance under upland conditions compared with lowland conditions.

with four rice cultivars grown under We conducted two field experiments

irrigated and rainfed conditions: Dular, a tall upland cultivar from Bangladesh; Sufaida Pak. a tall rainfed lowland cultivar from Pakistan; and Newbonnet

and Katy. modem semidwarf irrigated rices from the USA. Irrigated plots were flooded to a depth of 5-10 cm throughout the growing season, and nonirrigated plots were watered only once in mid-July when the drought period exceeded 15 d and plants were severely wilted. Plants received 39 cm of rainfall from seeding to maturity.

In experiment one. three-row plots with 40-cm row and hill spacings were handseeded with 15 single-plant hills per row. Six plants wen pulled from the middle of the center rows of the irrigated plots at 40 d after seeding (DAS) to measure root pulling resistance (RPR) as a measure of deep root density (Ekanayake et al 1986: Price et al 1990). We used a LI-6200 photosynthesis system (LiCor. Lincoln, Nebraska. USA) to measure pholosynthetic rate (Pn) and Stomatal conductance on the second fully opened leaf of five plants from the center row of each plot at 40 DAS. Gas ex-

change data were taken before noon when plants in dry plots showed mild

stress, but the leaves were not rolled yet. In the second experiment, six-row

plots. 4.75 m long, with a 20-cm row

spacing, were drill-seeded with 110 kg seed/ha. Grain yield and other plant characters were observed.

The four cultivars differed in plant height, tiller number, panicle number. growth duration. and RPR values (Table 1). Based on RPR, Dular and Sufaida Pak had larger deep-root systems than Newbonnet and Katy, and Newbonnet had a significantly larger root system than Katy. Significant interactions between cultivars and water regimes in Pn occurred (Table 2).

Dular and Katy had the highest Pn under nonstressed conditions, whereas Newbonnet had the highest under stressed conditions. Stomatal conductance was highest in Katy followed by Newbonnet and Dular under nonstressed conditions (Table 2). In two of our previous experiments, Sewbonnet produced higher biomass and grain yields than the other three varieties under drought stress. Although we do not fully understood why, it is possible that Newbonnet can maintain a greater leaf water potential by osmotic adjustment and a greater sink capacity for continued photosynthesis than the other three varieties.

Our study confirms the finding of Fukoshima et al (1985) that cultivars differed in photosyothetic efficiency

Table 1. plant height, tillers/m2, panicles/m2, days to heading, and root-pulling resistance in four rice cultivars. Pine Bluff, Arkansas, USA, 1992.

Cultivar Plant height (cm)

Tillers/m2

(no.) Panicles/m2

(no.) Days to heading

(d)

Root-pulling resistance

(kg)

Dular Katy Newbonnet Sufaida Pak

CV (%)

120 a a

97 b 95 b

124 a 5.1

590 b 587 b 492 c 622 a

7.7

553 a 495 b 418 c 505 b

7.2

42 a 14 c 23 b 39 a

9.2

71 b 91 a 90 a 88 a

3.1

a Means with the same letters in a column are not significantly different at the 0.05 probability level: av of 4 replications.

Table 2. Photosynthetic and stomatal conductance rate of four rice cultivars, Pine Bluff, Arkansas, USA, 1992.

Photosynthetic rate (µmol/m2 per s) Stomatal conductance (mol/m2 per s) Cultivar

Irrigated Nonirrigated lrrigated Nonirrigated

Dular Katy Newbonnet Sufaida Pak

CV (%)

a Means with the same letter in a column are not significantly different at the 0.05 probability level: av of 4 replications.

22.9 a a

23.5 a 19.9 b 17.3 c

20.43

15.0 c 17.9 b 22.4 a 10.9 d

3.0 b 4.1 a 3.2 b 2.3 c

24.11

1.8 2.5 2.4 2.2

under drought stress. Rice cultivars possessing better photosynthetic efficiency and larger deep-root systems exist in the germplasm. They can be used as parents for breeding improved upland cultivars that will more efficiently use increased levels of atmospheric CO2 in photosynthesis and may contribute io reduced CH4 emissions under upland conditions. thus reducing the degree of potential global warming due to greenhouse gases.

REFERENCES CITED Dingkuhn M, Cruz R T, O'Toole J C.

Dorffling K (1989) Set photosynthesis. water use efficiency. leaf water potential and leaf rolling as affected by water deficit in tropical upland rice. Aust. J. Agric. Res. 40(6): 1171-1181.

Ekanayake I J. Garrity D P. O''Toole J C (1986) Influence of deep root density on roof pulling resistance in rice. Crop Sci.

Fukoshima M T. Hinata K. Tsunoda S (1985) Varietal comparison of the responses of photosynthetic rate of leaf water balance at different soil moisture tensions in rice. Jpn.

26: 1181-1186.

J. Breed. 35(1):109-117. Price M. Jalaluddin W. Dilday R H (1990)

Proc. AR. Acad. Sci. 44:91-93.

Impact of global warming on rice production in Egypt A. Tantawi Badawi. M. S Balai, and R. L. Tinsiey. Rice Research end Training Center. Sakha, Karf-Sheiko. Egypt

Egypt has an arid, subtropical climate in which rice is grown as one of several summer crops following winter crops. Rice was introduced in Egypt in the northern delta near the Mediterranean Sea, at the end of the irrigation system. for controlling salinity. If global warming occurs. the major concerns in Egypt would be the impacts on water supply. sea level. and growing season.

essentially no rain; the Nile River is the country's only water source. This water originates in the headwaters of the Blue Nile in the highlands of Ethiopia. some 4000 km upstream from Egypt's ricefields. If a change in climate reduces the rainfall in Ethiopia, Egypt's water supply will be reduced, which will affect the area of irrigated land. If Ethiopia

Water supply. Egypt receives

lRRN 19 3 (September 1994) 53

receives more rain, Egypt can expand its agricultural land outside of the delta.

Raised Mediterranean Sea level. The low elevation of the lands in the northern delta make them the most vulnerable in Egypt to inundation from rising sea levels. It is estimated that a 2-m rise in sea level would inundate about 50% of the ricelands and a 4-m rise would inundate almost all. Infrastructure to protect the delta is in place, but extensive renovations may be required to accom- modate a rise in sea level, including salt water intrusion barricades across the Nile branches, a network of deep drains with pumps to discharge drainage water into the sea, and even construction of a seawall along the 250 km of the delta coast.

A more pressing problem may be reversing the hydrostatic pressure on soil salts. With the current sea level, the flooded ricefields provide a positive hydrostatic pressure to leach salts from the soil. If the sea level rises above the ricelands, the hydrostatic pressure would be reversed and the natural pressure would be for salts to move up in the soil profile. If this happens, rice may become

rotation and have to be grown more frequently, increasing the water required to protect the land from salinity.

Cropping season. The subtropical climate, with full irrigation, supports an intensive fully double-cropped system, with distinct summer and winter growing seasons. Rice is planted in the spring, as the increasing mean temperature exceeds 20 °C, and is harvested in the fall, when the declining mean temperature returns to 20 °C (Fig. 1). Although the mean temperature is above 20 °C and maximum temperature approaches 35 °C, the mean night temperature is always below 20 °C. These cool temperatures delay maturity in rice by up to 30 d compared with tropical areas. The effect of these seasonal temperatures is a marked decline in yields because planting is delayed (Fig. 2). This is attributed to plants maturing with progressively cooler temperatures. Along with the decline in yield, a significant deterioration in grain quality occurs as the head rice yield declines and broken rice increases.

a more important component in the crop


If a 5 °C uniform increase in temperature occurs, the following may happen.

• The potential growing season may increase by 10 d in both spring and fall.

• The warmer temperatures during maturity could reduce the rate of yield decline associated with late planting, thus providing higher and more stable average yields. Temperatures exceeding 40 °C, however, could cause sterility and grain shriveling.

• Fewer nights when the minimum temperature drops below 20 °C could reduce the maturity time of rice, allowing earlier planting of winter crops but not double- cropping rice.

• Higher temperatures may result in increased evapotranspiration and water requirements.

Rice production in Egypt could be very sensitive to global warming. While a

1. Average minimum and maximum temperatures at Sakha, Egypt.

2. Impact of date of sowing on GZ4120.

warmer climate may increase potential rice yields, there are risks and concerns about Egypt’s water supply, inundation if sea level rises, and increased soil salinity.

Lipid peroxidation and superoxide dismutase activity in rice leaves as affected by ultraviolet-B radiation Xiaozhong Liu and Qiujie Dai, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China; S. Peng and B. S. Vergara, IRRI

Enhanced UV-B radiation affects many processes in plants, such as growth, flowering, pigmentation, respiration, photosynthesis, and stomatal behavior. Recent experiments have demonstrated that UV-B treatment had significant effects on lipid peroxidation and superoxide dismutase (SOD) activity (Krizek et al 1993) in cucumber leaves.

No study had been conducted, however, on changes in lipid peroxidation and the enzymatic defense system of rice plants under UV-B treatment. The objectives of this study were to determine the effect of enhanced UV-A on SOD activity and lipid peroxidation in the rice plant and to characterize the role of SOD in modulat- ing rice plant response to UV-B.

Seeds of IR74 and Naizersail rice cultivars were pregeminated at 30 °C for 24 h and then sown in 1-liter plastic pots containing 1.7 kg of coil fertilized with 0.4 N, 0.1 g P, and 0.3 g K. The plants were grown in a greenhouse for 10 d and then subjected to UV-B radiation in a temperature- and humidity-controlled phytotron (day/night temperature = 27/ 21 °C; RH = 70%). Photosynthetic photon flux at the top of the rice canopy under the UV-B lamps was about 940 µmol/m 2 per/s. UV-B radiation was supplied by pre-aged UV-emitting fluorescent lamps that were enclosed in either presolarized 0.13-mm thick cellulose acetate (transmission down to 290 nm) for the UV-B treatment or 0.13-

mm thick clear polyester film (optically equivalent to Mylar D, absorbing almost all radiation below 320 nm) for the control treatment. The level of biologi- cally effective UV-B radiation (UV-B BE ). when weighted according to the general plant-action spectrum and normalized to unity at 300 nm, was 13.0 kJ/m 2 per d. Control plants received no UV-B. The SOD activity was assayed by the method of Stewart and Bewley (1980). The level of lipid peroxidation in the tissue was measured as malondialdehyde (MDA, a product of lipid peroxidation) content, determined by the method of Heath and Packer (1968).

The MDA content in the leaves of both IR74 and Naizersail was increased after exposure to UV-B radiation. The percent increase of MDA in Naizersail was greater than that in IR74 (Fig. la and c). Initially, SOD activity based on protein content in the two cultivars was stimulated significantly by enhanced UV- B radiation (Fig. 1b and d). SOD activity started to decrease on the 20th day and the 15th day in IR71 and Naizersail.

respectively, under elevated UV-B radation. The activity based on fresh weight had the same trend (data not shown).

Varietal differences in sensitivity to UV-B radiation, in terms of many growth and physiological parameters, have been reported (Dai et al 1992, He et al 1993). The present study shows that Naizersail, a UV-B-sensitive cultivar, had greater concentrations of MDA than IR74, which is less sensitive to UV-B. This indicates that more lipid peroxidation occurred in Naizersail upon UV-B irradiation which was consistent with the results obtained in cucumber (Kramer et al 1991). SOD activity in IR74 was not only much greater than that in Naizersail, but it also decreased later. This finding is different from the results in cucumber leaves, in which SOD activity decreased in leaf 1 but increased in leaf 3 (Krizek et al 1993). Although SOD activity in rice leaves increased under UV-B radiation, it might not be able to scavenge all the active oxygen induced by UV-B. This suggests that UV-B-induced cell injury was, at least partly, the result of decreased enzymatic defense ability.

The results of the present study show that genotypic variation in UV-B sensitivity may be because of differences in enzymatic defense ability to lipid oxidation activity and concentration of defense enzymes among genotypes. Further research is needed to determine if enhanced UV-A radiation stimulates active oxygen production in rice plants.

REFERENCES CITED Dai Q, Coronel V P, Vergara B S, Barnes P W,

Quintos A P (1992) Ultraviolet-B radiation effects on growth and physiology of tour rice cultivars. Crop Sci. 32:1269-1274

He J, Huang L, Chow W S, Whitecross M I, Anderson J M (1993) Effects of supplemen- tary ultraviolet-B radiation on rice and pea plants. Aust. J. Plant Physiol 20:129-142.

Heath R L, Parker L, (1986) Arch. Biochem. Biophys. 125:189-198.

Kramer G F, Norman H A, Krizek D T, Mirecki R M (1993) Phytochemistry

Krizek D T, Kramer G F, Uphadyaya A,

Stewart R C, Bewley J D (1980) Plant Physiol.

30:2101-2108.

Mirech (1993) Physiol. Plant. 88:350-358

65:245-24R.


MDA content and SOD activity in rice leaves as affected by enhanced UV- B radiation.

Effect of elevated ultraviolet-B radiation on abscisic acid and indoleacetic acid content of rice leaves Jinyu Zhang, Shaobai Huang, and Qiujie Dai, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China; S. Peng and B. S. Vergara, IRRI

The effects of elevated UV-B (290- 320 nm) radiation on plant growth and development have been reported in many plant species (Tevini 1993). Plant height and leaf area are the growth parameters most significantly affected (Barnes et al 1993, Dai et al 1992, Teramura et al 1991). Few studies have been conducted, however, on the mechanisms by which these parameters are influenced by UV-B.

Plant growth and development are closely related to the concentration of some endogenous growth regulators, such as abscisic acid (ABA) and indoleacetic acid (IAA). It is possible that morphological changes induced by enhanced UV- B radiation could be because of its effect on ABA and IAA content. The objectives of this study were to determine the effect of elevated UV-B radiation on the ABA and IAA content of rice leaves and to identify the possible mechanism by which plant height and leaf area are altered by UV-B.

Pregerminated seeds of rice cultivars IR74 and Naizersail were sown in 1-liter plastic pots, each containing 1.7 kg of Maahas clay soil fertilized with 3 g N, 1 g P, and 1 g K. Plants were grown in the greenhouse for 10 d and then subjected to various levels of UV-B radiation for up to 4 wk in a temperature- and humidity- controlled glasshouse (day/night temperature = 27/21 °C; RH = 70%). Photosynthetic photon flux at the top of the rice canopy under UV-B lamps at solar noon on a clear day was about 940 µmol/ m 2 per s. UV-emitting fluorescent lamps supplied the UV-B radiation. Four levels of UV-B were imposed: 0.0.6.0, 13.0, and 19.1 kJ/m 2 per d (weighted according to the general plant-action spectrum and normalized to unity at 300 nm). ABA content was determined by the method of Ross et al (1987) and IAA by the procedure of Weiler et al (1981) at the end of each treatment period.

No difference in ABA content was observed in IR74 under various levels of UV-B treatment for 2 wk, except under 19.1 kJ/m 2 per d. Naizersail showed a slight increase in ABA content under treatments of 13.0 and 19.1 kJ/m 2 per d (Fig. 1a). ABA production was stimulated significantly, however, by 4 wk of UV-B treatment (Fig. 1b). Under 2 wk of UV-B treatment, the amount of IAA in Naizersail was stable at 0.0, 6.0, and 13.0 kJ/m 2 per d of UV-B but declined significantly under 19.1 kJ/m 2

per d. IAA in IR74 decreased under 6.0, 13.0, and 19.1 kJ/m 2 per d of UV-B compared with no UV-B treatment (Fig. 1C). IAA content of IR74 and Naizersail was reduced significantly by 4 wk of exposure to higher UV-B levels (Fig. 1d).

Dramatic effects of enhanced UV-B radiation on plant morphology have been documented (Branes et al 1993, Dai et al

ABA and IAA contents of rice plants subjected to various levels of UV-B radiation.

1992, Tevini 1993). Our results indicate that enhanced UV-B radiation had a significant effect on ABA and IAA content of rice leaves after 4 wk of UV-B treatment. Production of ABA was stimulated while IAA content was decreased. ABA synthesis under stress conditions has been reported in several crops. It is not clear whether this decrease in IAA content under UV-B treatment was

degradation. This study showed that ABA content is negatively related to plant height and leaf area while IAA content is positively associated with these two growth parameters (data not shown).

Tevini (1993) reported that morphological changes in sunflower seedlings

due to lower synthesis or to fast


induced by UV-B radiation was the result of UV-dependent destruction of IAA and the formation of growth-inhibiting IAA photoproducts. Similarly, the growth response of rice plants to elevated UV-B radiation may be associated with the changes in endogenous concentrations of IAA and ABA in UV-B treated plants.

REFERENCES CITED

Barnes P W, Maggard S, Holman S R, Vergara B S (1993) Interspecific variation in sensitivity of UV-B radiation in rice. Crop Sci. 33:1041-1046.

P W, Quintos A T (1992) Ultraviolet-B radiation effects on growth and physiology of four rice cultivars. Crop Sci. 32:1269- 1274.

Ross G S, Elder P A, McWha J A, Pearce D, Pharis R P (1987) Plant Physiol. 85:46-51.

Teramura A H, Ziska L H, Sztein A E (1991)

Dai Q, Coronel V P, Vergara B S, Barnes

Changer in growth and photosynthesis capacity of rice with increased UV-B radiation. Physiol. Plant. 83(3):373-380.

Tevini M (1993) UV-B radiation and ozone depletion: effects on humans, animals. plants. microorganisms, and materials. Pages 125-153 in M. Tevini. ed. Lewis Publishers Boca, Raton. Florida.

Weiler E W, Jourdon P S, Conrad W (1981) Planta 153:561-571.

Risk analysis of rice leaf blast epidemics associated with effects of enhanced ultraviolet-B and temperature changes in the Philippines Y. Luo, D. O. TeBeest, Department of Plant Pathology, University of Arkansas, Fayetteville, Arkansas 72701, USA, P. S. Teng, and N. G. Fabellar, IRRI

Climatic variation and pests, of which rice blast is among the most important, greatly influence rice production in the tropics. The risk of blast epidemics caused by global climate changes is important to consider when developing disease control strategies. Previous work at IRRI has shown that lower temperatures in the tropics promote severe blast and highest yield loss and that elevated UV-B radiation causes more lesions, faster lesion expansion. and reduced spore viability. UV-B effects on rice growth and blast are therefore available for integrating into models to simulate blast epidemics and rice yield.

The objectives of this study were to incorporate UV-B effects into the RICE- BLAST model, and to simulate blast epidemics in the Philippines under a range of temperatures combined with elevated UV-B effects. Risk assessment was based on simulation results.

Model modification. A combination model, RICE-BLAST, was developed from the CERES-RICE model coupled to the BLASTSIM model and used to simulate rice blast epidemics based on rice growth and blast infection on leaves. Relative ratios of lesion number, lesion area expansion rate, and sporulation rate under UV-B exposure were coupled into corresponding subroutines by changing corresponding rates in blast infection. New external data files containing ratios

of effects of UV-B on components were developed. Variety IR30 was simulated under nonlimited water and nitrogen conditions. Estimated weather data under a normal year in Solana, Philippines, were used to simulate rice growth in the first growing season (Jan-May). UV-B effects on rice growth were quantified as a) reduction of net assimilation rate (decrease of dry weight and growth rate of leaf, stem, root, and grain caused by UV-B are the results from this reduction) and b) growth rate reduction for each component. such as reduction of dry weight accumulation rate of leaf, stem, root, and grain.

Two different coupling approaches using four components—leaf area, leaf, stem, and root dry weight—were tested: single coupling. in which only assimilation rate was considered, and multiple coupling, in which components including growth rates of root, leaf, and stem. were considered. We determined that single coupling is better than multiple coupling to simulate UV-B effects on rice growth; UV-B effects on leaf area predicted by multiple coupling is greater than that of observations; single coupling routine is to make the model more explanatory of the effects of UV-B on rice growth; and it is reasonable to use the modified model to simulate blast epidemics occurring under UV-B effects.

Parameter estimation. The relative ratios of UV-R treatments compared with controls were calculated from growth and physiological parameters of rice varieties IR30 and IR74 as affected by 4 wk of UV- B treatment (Q. Daj, IRRI. unpubl. data) and from the effects of UV-B on blast lesion number and lesion size under enhanced UV-B treatment and control on two UV-B-sensitive varieties. IR30 and IR72. infected with blast isolate PO6-6 (Finckh 1993).

Lesion expansion rate was estimated by r = 1/t*log(L2/L1), where r is lesion expansion rate: L1 and L2 are lesion sizes, in mm2, at beginning date of lesion appearance and observation date, respectively; and t is number of days between date of lesion appearance and observation. L1 is assumed to be 5 mm2 and t is 5 d. L2 was obtained from experimental data.

Relative ratio of lesion expansion (RRL) can be calculated from RRL = rt/rc, where R is lesion expansion rate under UV-B treatment and rc is lesion expansion rate under no UV-B control. Effect of UV-B on lesion number can be considered as similar to its effect on infection efficiency. Relative ratio of infection efficiency for the two varieties was calculated by lesion number under UV-B treatment divided by that of no UV- B control. Data of UV-B effect on sporulation were from unpublished data (Leung, Washington State University).

Simulation of global change effects. Thirty years of estimated weather data from seven Philippine locations, produced using either of two programs—WGEN or WMARK—were used in the simulations. Global temperature change treatments were considered by changing the estimated daily temperature data by +3. +1, 0, -1. and -3 °C. Three growing seasons for each location were separately simulated. In each growing season of each simulation year under each temperature change level, four situations were simulated: no blast without UV-B. blast without UV-R, no blast with UV-B, and blast with UV-B. Estimated yield, simulated area under the disease progress curve (AUDPC), and maximum severity of blast were produced at the end of each simulation run. AUDPC and maximum severity caused by blast without UV-B were compared with that caused by blast with UV-B effects. A risk scenario


was produced for each condition of temperature change using GIs.

Simulations of global change effects in the Philippines. Simulation results from each of 7 locations, on yield and disease, were analyzed for each temperature condition interacting with a UV-B treatment. Means and standard deviations were calculated for comparison in different temperature change and UV-B treatments. Results are summarized as follows:

• The yield loss caused by UV-B was normally at 9-10%, independent of temperature change, and its deviation is much smaller than that caused by blast.

• Enhanced UV-B will cause more severe blast epidemics compared with situations without UV-B. In most cases of temperature changes, except -3°C, maximum disease severity and AUDPC were doubled or more under UV-B effect.

blast when the temperature change is -3°C compared with other temperature change levels.

• In most cases, yield loss caused by blast with UV-B is greater than the sum of individual losses caused by blast and enhanced UV-B.

UV-B is generally at 15-20% under most temperature change conditions, except -3°C.

• UV-B will cause much more severe

• Yield loss caused by blast with

In this study, RICE-BLAST model was modified by incorporating enhanced UV-B effects into the individual rice and blast models, using IR30. To further test the model, parameters and complete experimental data from more varieties are needed as are independent data of blast epidemics occurring under enhanced UV-B. These kinds of data, however, are difficult to obtain from field experiments; until they can be, predictions of global change effects on blast must remain tentative.

REFERENCE CITED Finckh M R, Chavez A, Dai Q, Teng P S

(1994) Agric. Ecosyst. Environ. (in press)


Research methodology How to adjust grain yield to 14% moisture content S. Peng, IRRI

Grain yield of rice is usually reported based on 14% moisture content. This allows comparison of yields across locations and years. Grain moisture content of 14%, however, may be expressed on a fresh weight (fw) or dry weight (dw) basis. Moisture content on a fw basis (MC fw ) is generally higher than moisture content based on dw (MC dw ). This difference becomes greater as MC increases.

Moisture percentage on a fw basis (% MC fw ) and dw basis (% MC dw ) can be converted from one to the other using the following equations:

% MC fw = 100 X % MC dw /(100 + % MC dw ) (1)

% MC dw = 100 X 70 MC fw /(100 – % MC fw ) (2)

Electric moisture meters are com- monly used to determine grain moisture content. These meters generally measure the conductivity or capacitance of seeds and express the moisture content as % MC fw , not % MC dw . The correct equation to use in calculating the grain yield adjusted to 14% MC, is

Adjusted weight (14% MC fw ) = W × (1 - 0.01 × % MC f w ) / 0.86 (3)

where W is the weight of the grains and % MC fw is the moisture meter reading. On the other hand, the equation for calculating grain yield adjusted to 14% MC dw is

Adjusted weight (14% MC dw ) = W × (1 - 0.01 × % MC fw ) × 1.14 (4)

The adjusted grain weight calculated with equation 3 is nearly 2% higher than that with equation 4, meaning that the grain yield adjusted to 14% MC dw is almost 2% lower than grain yield

adjusted to 14% MC fw . Therefore, when reporting grain yield, indicate whether the 14% MC is expressed on a dw or fw basis. It is preferable to report grain yield adjusted to 14% MC based on fw using equation 3.

A new method for transporting Azolla culture collections S. Kannaiyan, Agricultural Microbiology Department, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India

Azolla is a free-floating water fern that fixes atmospheric N 2 in association with N 2 -fixing cyanobacteriurn Anabaena azollae that can be used in wetland ricefields.

The survival of Azolla is poor, however, when it is removed from water, making transport difficult. Scientists doing Azolla research transport culture collections in tissue paper soaked with N free nutrient solution in plastic petri dishes. This method is not ideal because the moist tissue paper is conducive to rotting the plants, causing the fronds to die. To overcome this problem, we carried out a laboratory experiment to assess the survival of Azolla fronds stored in polythene bags.

Fresh fronds of A. microphylla and A. filiculoides were collected from culture tanks and washed repeatedly in tap water and then in distilled water. Fronds were placed in tissue paper and gently pressed for 30 min to remove adhering moisture. Ten grams of fronds were packed tightly into polythene bags, which were then sealed or stapled. Two

of the fronds of the species survived and intensity and in the dark. More than 70% wk at 27 ± 1 °C in light at 3000 lux sets were stored in the laboratory for 6

could be revived in N-free liquid medium. The study was repeated three times with the same results.

This easy method is recommended for transporting Azolla cultures.

News about research collaboration Forest-friendly stove a success using free fuel

A stove adapted by IRRI from a Viet- namese design not only cooks rice more quickly but is also environment-friendly and uses low-cost or free fuel.

The stove uses rice hulls, produced when rice is milled. Rice hulls are considered a nuisance byproduct in many Asian countries. The stove is called the Ipa-Qalan, and is an IRRI modified version of a Vietnamese stove called the “Lo Trau” which was introduced to IRRI

by Phan Hieu Hien, previously an IRRI and it can be constructed economically Ph D scholar. from local materials such as recycled oil

One year after its commercial intro- drums, biscuit cans, or used sheet metal. duction in Myanmar, more than 15,000 units have been sold by the San San Industrial Corp., so far the stove’s most enthusiastic promoter in that country.

The Ipa-Qalan requires from 1 to 1.5 kg of rice hulls for 1 h of cooking. A liter of water boils within 5 min of startup, compared with about 11 min for the Vietnam model. The Ipa-Qalan is easy to fire, has a low smoke level, and requires minimal attention. The design is simple

At the very least, a fabricator needs only a tin cutter, a hammer, and a 4-inch nail.

IRRI engineers have calculated that by using rice hulls instead of wood to fuel a stove, a household of 5 or 6 people could save at least 2 t of wood each year or about 1 ha of a typical forest if trees were harvested for fuel in developing countries.

Training center opens in Lao PDR The National Agricultural Training Center of the Lao People’s Democratic Republic was officially opened in March 1994 by His Excellency Blaise Godet, Swiss ambassador to Thailand, and IRRI Director General Klaus Lampe. The center, about 30 km from Vientiane and built at a cost of US$445,000, consists of an auditorium complex and accommodation and dining facilities.

staff and trainees were also officially opened in a separate ceremony at the National Upland Rice Research Center in Luang Prabang Province, northern Lao PDR. It was constructed at a cost of

Accommodation facilities for research

US$80,000.

a three-year, US$3.54 million project aimed at improving rice research in Lao PDR, a country whose rice production is among the lowest in Asia. The project is financed by the Swiss Development Cooperation (SDC) and administered by IRRI.

The National Agricultural Training Center will be used for the training needs of Lao rice research and extension personnel and provide a venue for agricultural meetings and workshops. The first course on basic rice production was offered to Lao technicians in August-

The newly opened facilities are part of

September 1994.

Understanding rice yield potential Scientists at IRRI are collaborating with colleagues at Kyoto University in Japan and the Yanco Agricultural Research Station in Australia to better understand and predict the yield potential of current rice varieties in difficult environments.

This is needed to determine the so- called “yield gap” between farmers’ actual yields and what is potentially possible. It is also essential information for a major IRRI project which is exploring the possibility of increasing the yield potential of future rice varieties.

The yield potential of rice in a tropical environment such as that in Los Baños is about 6 t/ha in the wet season and about 9-10 t/ha in the dry season. In Kyoto, Japan, the yield potential is about 7-8 t/ha. In Yanco, scientists have well-documented data on yields of close to 15 t/ha.

model ORYZA 1 predicted the yield potential of current varieties in these different environments very well. The model indicated that the high yields in Yanco are because of lower temperatures (during the night) which result in a longer spikelet formation period and a longer grain-filling duration. The higher solar radiation in Yanco also results in higher growth rates than in the other environments.

The IRRI-Wageningen crop simulation

Collaborative work with modelers from other countries such as Japan, Australia,

the United States, and seven Asian nations was initiated during the International Geosphere-Biosphere Programme-Global Change and Terrestrial Ecosystems Workshop which was organized at IRRI in March 1994. It was shown in the workshop that rice growth models are capable of predicting yield potential in a wide range of environments.

Former Soviet states request rice research support from IRRI Research institutes in Russia, Uzbekistan, and Kazakhstan have requested assistance from IRRI to strengthen rice research in their countries and to help boost rice production to meet increasing demands.

Dr. Kurmanbek Bakirov of the Kazakh Academy of Agricultural Sciences and Dr. Ishakov Tursunbay of the Uzbek Academy of Agricultural Sciences have visited IRRI to explore possible collaborative activities. They expressed their countries’ interest in seeking assistance in breeding for grain quality, particularly the Rasmati-type rice, and for resistance to rice blast disease. Dr. E P. Alyosin, the director general of the All Russia Rice Research Institute, has also written to seek IRRI’s support in rice research.

Russia has 320,000 ha of riceland; Kazakhtan, 120,000 ha; and Uzbekistan, 100,000 ha.


Vietnam awards IRRI with Friendship Order

The President of the Socialist Republic of Vietnam awarded the Friendship Order of the Vietnamese Government to IRRI in acknowledgment of the Institute’s “very efficient contribution” to food production in Vietnam. The award was received by IRRI Director General Klaus Lampe during the Vietnam-IRRI Rice Confer- ence on 4-7 May.

Rice training network proposed by Asian countries Twelve Asian rice-growing countries have proposed the establishment of an Asian Rice-based Training Network to share expertise and training materials, strengthen relevant training programs, and accelerate research being done to boost rice production.

The proposal came from a conference convened by the Thailand Rice Research Institute, Kasetsart University, and IRRI to share rice-related training activities and experiences among participants and to better understand training constraints of national programs.

Conference participants were heads or directors of rice-related training institutes and programs in Bangladesh, Cambodia, China, India, Indonesia, Myanmar, Lao PDR, Nepal, Philippines, Sri Lanka, Thailand, and Vietnam as well as IRRI staff. Also represented were the Asian Vegetable Research and Development Center, the International Crops Research Institute for the Semi - Arid Tropics, the International Irrigation Management Institute, and the United Nations Development Programme.

would communicate and document information relevant to rice-related training. It would explore and develop new training strategies and coordinate in - country training programs. Membership would be open to rice research organizations or universities.

Based at IRRI, the proposed network


Rice is cultivated on 5.9 million ha, or 80% of the arable land, in Vietnam. Once a major rice-exporting country, Vietnam was a net importer for more than two decades. It became a net rice exporter again in 1988, and now exports approximately 1.5 million t of rice annually.

Planting modern early-maturing rice varieties, improving management resources, and implementing appropriate government policies have been responsible for Vietnam’s recent production increases. Since 1968, 42 breeding lines

have been released in Vietnam. IRRI varieties now cover 60% of the irrigated rice-growing area in the Mekong Delta.

Vietnamese scientists are working closely with IRRI. Some 319 Vietnamese researchers, scholars, and fellows-many now holding key positions in rice research institutes — have received training at IRRI. Researchers at the Cuu Long Delta Rice Research Institute and IRRI have been collaborating to develop hybrid rice technology for farmers in the Mekong Delta provinces since 1983.

First-time release of hybrid rice in India India recently released its first-ever hybrid rices for commercial cultivation, the first in the world for tropical rice cultivation.

India is the fourth country to release commercial hybrid rice, following China (subtropical and temperate rice hybrids), Vietnam (subtropical), and the Democ- ratic People’s Republic of Korea (temperate).

Two of the Indian hybrids — APRH-1 (IR58025A/Vajram) and APRH-2 (IR62829A/MTU9992) — were released by the Andhra Pradesh Agricultural University in Hyderabad. The Tamil Nadu

Agricultural University in Coimbatore released the third hybrid — CORH-1 (IR62829A/IR10198-66-3R). Four more hybrids will be released shortly.

scientists, with technical support from IRRI, have made it possible to release the first set of hybrids in India after only four years of work,” says Dr. S. S. Virmani, IRRI plant breeder and hybrid rice expert.

More than 400 experimental hybrids, either developed in India or introduced from IRRI, have been evaluated in India. About 30 hybrids demonstrated a yield

“The concerted efforts of Indian rice

advantage of one ton or more per hectare over the local varieties.

Rice germplasm exchange program proposed for the Mediterranean and West and Central Asia Researchers in the Mediterranean and West and Central Asia may soon be swapping improved rice germplasm with the rest of the world through the Interna- tional Network for Genetic Evaluation of Rice (INGER). The proposed exchange program will help researchers in these regions broaden the rice genetic base and identify superior varieties.

barriers and the improved communication among countries in these regions provide an excellent opportunity to promote unrestricted exchange and evaluation of rice germplasm,” says Dr. F. A. Bernardo, IRRI deputy director general for interna-

“The recent relaxing of political

The germplasm exchange and evaluation program will involve countries that grow Basmati and fine-grained aromatic rice. They include Afghanistan, India, Iran, Iraq, and Pakistan in West Asia and the Russian Federation, Kazakhstan, Tajikistan, Turkmenistan, and Uzbekistan in Central Asia.

The proposed germplasm exchange program also hopes to link the Mediterra- nean with other countries growing japonica rice, such as Bulgaria, Romania, Ukraine, China, Democratic People’s Republic of Korea, Republic of Korea, and Japan.

“The project, if funded by a donor, will greatly improve and stabilize rice yields in these regions,” says Dr. Bernardo. “Prom- ising varieties and breeding lines will be evaluated to find new superior varieties for release and to identify valuable breeding lines to improve local varieties. The project will also develop scientists’ skills

tional services. through degree and nondegree training.”

Announcements Rice dateline

1994 13-31 Oct Rainfed Lowland Rice Monitoring

Workshop, India, Bangladesh, and Cambodia ................................................... R. C. Chaudhary, IRRI

17-21 Oct Planning Workshop on Biological Control of Rice Disease, IRRI ............................................................................. T. W. Mew, IRRI

1-2 NOV IRRI-UK Day, United Kingdom ............................ R. D. Huggan, IRRI

21-26 Nov IRRI-Japan Day, Japan .......................................... R. D. Huggan, IRRI

28 Nov-2 Dec International Workshop on Flood-Prone Rice, Thailand ...................................................... W. Puckridge, IRRI

28 Nov-2 Dec Postharvest Technology for the Humid Tropics, Vietnam ..................................................... M. Gummert, IRRI

5-8 Dec Annual Workshop of IRRI-EPA and IRRI-UNDP (GEF Methane Projects), Indonesia .................................................................... H. U. Neue, IRRI

1995 13-17 Feb International Rice Research Conference and

Outstanding Young Women in Rice Science Awarding Ceremony ................................................ R. S. Zeigler, IRRI

Postdoctoral research fellowship at IRRI The International Rice Research Institute invites applicants for a postdoctoral position to study resistance management and sustainable deployment for rice genetically engineered with Bacillus thuringiensis ( Bt ) toxins. Experience in simulation modeling, plant-insect interactions, and Bt research is desirable. Send a letter of application and curri- culum vitae to Dr. Michael Cohen, Plant Pathology and Entomology Division, IRRI, P.O. Box 933, 1099 Manila, Philippines. E-mail: IN%”[email protected]” Fax: (63-2) 818-2087. Application deadline is 1 Dec 1994.

New IRRI publications Neem pesticides in rice: potential and limitations. 1994. 69 pages. US$l0.00 in highly developed countries (HDC), US$3.00 in less developed countries (LDC), plus US$3.50 airmail or US$1.50 surface postage.

IRRI started research on botanical pest control in rice and rice-based cropping systems in the late 1970s. The research focused mainly on neem tree products, and involved close collaboration with national institutions in many Asian countries, and with the International Centre of Insect Physiology and Ecology, Nairobi, Kenya.

Special project support for this work was provided by the Asian Development Bank and the Swiss Development Cooperation.

This book reviews the status and prospects of pest control using neem in rice-based cropping systems in developing countries. with special emphasis on its potential and limitations in integrated pest management programs. Results reported in this book show that neem adversely affects some nontarget organisms but does not affect others.

The authors, Dr. Lim Guan Soon and Dr. Dale G. Bottrell, demonstrate that neem has considerable potential in rice, although it also has a number of limitations that reduce its effectiveness and slow its adoption.

A manual of rice seed health testing. 1994. 113 pages. US$30.00 in HDC, US$8.00 in LDC, plus US$6.00 airmail or US$1.50 surface postage.

Intensive collaboration characterizes the international exchange of rice germplasm. Efforts to increase rice yields demand that more germplasm be ex- changed, more often.

Exchanging crop materials involves risks of also exchanging pests and diseases. IRRI, in cooperation with the Plant Quarantine Service of the Bureau of Plant Industry of the Philippines, established a Seed Health Unit to ensure that incoming and outgoing seed lots meet or exceed existing quarantine requirements.

This manual compiles important information relating to common seedborne rice diseases and rice seed contaminants, details of the causal organisms, and methods of detecting their presence.

The manual has three major divisions. Part I discusses the importance of seeds, their health, and the risks involved in seed exchanges; reviews the historical development of quarantine systems; and describes rice plant morphology and ecosystems. Part II describes laboratory equipment needed for assessing rice seed health; samples and sampling methods; dry seed inspection; detection, isolation, and identification methods for fungi,


IRRI provides a limited number of scholarships for participation in its short- term group training courses for 1994. To be considered for an IRRI-funded scholarship, a scientist must be affiliated with a national institution that has an official collaborative agreement with IRRI in a rice-related research and training project. A scientist interested in an IRRI-funded scholarship should apply directly to his or her institution and not to IRRI.

IRRI also accepts scientists from other institutions and agencies for the courses if they are working in rice or rice-related areas. Their applications to participate in courses must be endorsed to IRRI by their employer and specify funding

bacteria, and nematodes; viruses and mycoplasmalike organisms; and methods for field inspection and seed treatment. Part III describes the pathogens and the diseases they cause.

This manual was prepared from materials developed for short courses offered by the Seed Health Unit on seed health maintenance and testing proce- dures. The book should be a useful tool for rice scientists, quarantine personnel, and trainers.

Rice roots: nutrient and water use. 1994. 86 pages. US$12.00 in HDC, US$3.00 in LDC plus US$3.50 airmail or US$l.50 surface postage.

The rice plant invests up to 60% of its energy as carbon in its root system. Our understanding of the rice roots and their function in the capture of nutrients and water lags well behind our understanding of the rest of the plant.

This is particularly so for rice, compared with other cereals, because the rice plant’s ability to grow under waterlogged conditions arises from morphological and physiological adaptations in its roots.

As part of the last International Rice Research Conference, a symposium on rice roots and the uptake of nutrients and water was held to review present knowledge and to make recommendations for future research. This publication contains selected papers from that symposium.

IRRI address International Rice Research Institute P.O. Box 933 1099 Manila, Philippines Tel: (63-2) 818-1926 Fax: (63-2) 818-2087 Telex: (ITT) 40890 RICE PM E-mail: IN%”[email protected]”

Call for news Individuals, institutions, and organizations are invited to tell readers about upcoming events in rice research or related fields in the Rice dateline. Send announcements to the Editor, Interna- tional Rice Research Notes, IRRI.


New publications Dictionary of soil fertility, fertilisers & integrated nutrient management. Dr. H.L.S. Tandon. Order from Fertiliser Development and Consultation Organisation, 204 Bhanot Comer, Pamposh Enclave, New Delhi 110048, India.

World resources 1994-95. A biennial guide to the global environment.

World resources 1994-95 data base diskette. This software program contains extensive economic, population, natural resource, and environmental statistics for 176 countries, compiled from the book World reLsources 1994-95. Both are produced by the World Resources Institute (WRI) in cooperation with the United Nations Environment Programme and the United Nations Development Programme. Order from WRI, P.O. Box 4852, Hampden Station, Baltimore, MD 21211, USA.

IRRI group training courses for 1994

sources to cover costs. IRRI’s group course training fee is approximately US$1,200/month; this does not include participants’ roundtrip international airfare, enroute expenses, or shipping allowance upon return home.

The courses are conducted at IRRI headquarters unless otherwise indicated. For additional information, contact the Head, Training Center, IRRI.

Date Course

10 Oct-2 Dec 3 Oct-4 Nov Rice Seed Health

Rice Production Research (Pathum Thani Rice

Thailand) Upland Rice Breeding

Research Center,

17 Oct-4 Nov

4-25 Nov Research Management 31 Oct-11 Nov Scientific Programming

14-25 Nov Gender Analysis

Rice literature reprint service

update Rice scientists elsewhere are charged US$0.20 for each page or part of a page copied, plus postage. Make checks or

Photocopies of items listed in the Rice money orders payable to Library and literature update are available from the

Address requests to Library and IRRI Library and Documentation Documentation Service, IRRI.

to rice scientists of developing countries. IN%”[email protected]” (not to exceed 40 pages) are supplied free Documentation Service, IRRI. E-mail: Service. Reprints of original documents

Erratum Lioto, a short-duration rice variety suitable for northern Zaire, by B. Mateso et al, 18 (4) (Dec 1993), 19-20. This note should have appeared in the Integrated Germplasm Improvement- Upland section instead of in the Integ- rated Germplasm Improvement-Rainfed Lowland section.

Instructions for contributors

NOTES IRRN categories. Specify the

General criteria. Scientific being submitted should appear. notes submitted to the IRRN for Write the category in the upper

category in which the note

possible publication should • be original work, • have International or pan- national relevance, • be conducted during the immediate past three years or be work in progress, • have rice environment relevance,

right-hand corner of the first page of the note.

GERMPLASM IMPROVEMENT genetic resources genetics breeding methods yield potential grain quality

• advance rice knowledge, pest resistance • use appropriate research diseases design and data collection insects methodology, other pests • report pertinent, adequate stress tolerance data, drought • apply appropriate statistical excess water analysis, and adverse temperature • reach supportable conclu- adverse soils sions. other stresses

Routine research. Reports of ment screening trials of varieties, irrigated fertilizer, cropping methods, rainfed lowland

integrated germplasm improve-

and other routine observations upland using standard methodologies flood-prone (deepwater to establish local recom- and tidal wetlands) mendations are not ordinarily seed technology accepted. Examples are single- season, single-trial field CROP AND RESOURCE experiments. Field trials should MANAGEMENT be repeated across more than soils one season, in multiple soil microbiology seasons, or in more than one physiology and plant nutrition location as appropriate. All fertilizer management experiments should include inorganic sources replications and an internation- organic sources ally known check or control crop management treatment. integrated pest management

Multiple submissions. insects Normally, only one report for a weeds single experiment will be other pests accepted. Two or more items water management about the same work submitted farming systems at the same time will be farm machinery returned for merging. Submit- postharvest technology ting at different times multiple economic analysts notes from the same expen- ment is highly Inappropriate ENVIRONMENT Detection will result in the SOCIOECONOMIC IMPACT rejection of all submissions on EDUCATION AND COMMUNI-

diseases

that research. CATION RESEARCH METHODOLOGY

Manuscript preparation. Arrange the note as a brief statement of research objectives, a short description of project design, and a succinct discussion of results. Relate results to the objectives. Do not include abstracts. Do not cite references or include a bibliog- raphy. Restrain acknowledg- ments.

Manuscripts must be in English. Limit each note to no more than two pages of double- spaced typewritten text. Submit the original manuscript and a duplicate, each with a clear copy of all tables and figures. Authors should retain a copy of the note and of all tables and figures.

Apply these rules, as appropriate, in the note: • Specify the rice production ecosystems as irrigated, rainfed lowland, upland, deepwater, and tidal wetlands. • lndicate the type of rice culture (transplanted, wet seeded, dry seeded). • If local terms for seasons are used, define them by character- istic weather (wet season, dry season, monsoon) and by months. • Use standard, internationally recognized terms to describe rice plant parts, growth stages, and management practices. Do not use local names. • Provide genetic background for new varieties or breeding lines. • For soil nutrient studies, include a standard soil profile description, classification, and relevant soil properties. • Provide scientific names for diseases, insects, weeds, and crop plants. Do not use common names or local names alone. • Quantify survey data, such as infection percentage, degree of severity, and sampling base. • When evaluating susceptibility, resistance, and tolerance, report the actual quantification

of damage due to stress, which was used to assess level or incidence. Specify the measurements used. • Use generic names, not trade names, for all chemicals. • Use international measurements. Do not use local units of measure. Express yield data in metric tons per hectare (t/ha) for field studies and in grams per pot (g/pot) for small-scale studies. • Express all economic data in terms of the US$. Do not use local monetary units. Economic information should be pre- sented at the exchange rate US$:local currency at the time data were collected. • When using acronyms or abbreviations, write the name in full on first mention, followed by the acronym or abbreviation in parentheses. Use the abbreviation thereafter. • Define any nonstandard abbreviations or symbols used in tables or figures in a footnote, caption, or legend.

Tables and figures. Each note can have no more than two tables and/or figures (graphs, illustrations, or photos). All tables and figures must be referred to in the text; they should be grouped at the end of the note, each on a separate page. Tables and figures must have clear titles that adequately explain the contents.

Review of notes. The IRRN editor will send an acknowledgment card when a note is received. An IRRI scientist, selected by the editor, reviews each note. Reviewer names are not disclosed. Depending on the reviewer’s report, a note will be accepted for publication, rejected, or returned to the author(s) for revision.

(continued on back cover)

Documents

International Rice Research Notes Vol.19 No.3