IRPS 84 Rapid Generation Advance of Rice at the International Rice Research Institute

8/4/2019 IRPS 84 Rapid Generation Advance of Rice at the International Rice Research Institute

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RAPID CENERATION ADVANCE OF RICE AT THEINTERNATIONAL RICE RESEARCH INSTITUTE 1

A short generation rice cycle helps rice breederswho work with photoperiod-sensitive crosses whereonly one generation is possible per year becauseflowering is delayed if rice is planted off-season.Short generation is also necessary when breedingrice for low-temperature areas where only one cropcan be grown each year. The rapid generationadvance (RCA) method shortens rice plant growthduration by using high temperature-short day treat-ments to make three generations possible each year.The duration from F2 to F5, which generally takes4 years, can be reduced to 2 years.Besides shortening crop duration, RCA allows manycrosses to be processed in limited space and time.Environment can be controlled, and problems such asbad weather, rats, and other disease and insectpests are minimized. Also, limited selection andscreening is possible using RCA.RCA was suggested by Coulden in 1939. Japaneserice breeders began using it in 1958. By 1977 31%of the rice areas in Japan grew cultivars bredusing RCA (Nakane 1979). In 1976 Ikehashi beganusing RCA for photoperiod-sensitive rice breedingat IRRI (Ikehashi 1977). By 1980, IRRI RCA facili-ties were in full operation.

ABSTRACT

RCA can help shorten breeding periods at nationalprograms in rainfed wetland areas where photoperiodsensitivity is important. Few new photoperiod-sensitive rice varieties have been named in thelast 20 years, yet they are grown on more than 20million hectares. Breeding for photoperiod-sensitivevarieties has been neglected because more time isneeded to develop them than is needed for photo-period-insensitive varieties like the new, high-yielding breeds.

In photoperiod-sensitive rice breeding, selectionfor maturity date is site-specific. Strong speci-ficity limits international testing and breedingmaterial exchange because selection for a specificenvironment may result in discarding varietiesbest suited for other areas. RCA solves thesedifficulties. Through RCA, fixed bulk materialsfrom IRRI are sent to different sites where primaryselections, especially flowering dates, are made.

This report describes cultural methods we haveevolved to obtain optimum growth, shortest possiblegrowth duration, and maximum use of space. Variouscharacters that can be screened during RCA and thegeneral breeding procedure are discussed.

1By B. S. Vergara, C. Patena, and F. S. S. Lopez, plant physiologist, research assistant, and research aide,International Rice Research Institute, Los Banos, Laguna, Philippines. Submitted to the IRRI Research PaperSeries Committee July 1982.


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RAPID GENERATION ADVANCE OF RICE AT THEINTERNATIONAL RICE RESEARCH INSTITUTE

Rapid generation advance (RGA) is not a totalbreeding method in itself but a breeding procedurewhere segregating populations are raised in anenvironment using close spacing, high temperature,and short days to rrriLm ize growth duration andmake several generations per year possible.RGA preserves the potential variability of eachcross so genetically fixed materials can be rigor-ously selected under local conditions. However,certain characters can be selected during RGA. Af-ter RGA, the Fs to F6 lines are almost homozy-gous. Trait selection is reliable at this stage,even if low heritability traits such as elongationabili ty , which causes problems if selected at anearly generation, are desired.Because the special RGA environment does not allowresearchers to visually assess plant population,potential performance of crosses cannot be ob-served. To overcome this problem, scientists mayplant a sample of the reserve F2 seed and moni-tor traits essential to the breeding objective.Care should be taken when selecting parents forthe crosses and the breeding objective should bewell defined. Taking notes on individual plants isnot advisable, this defeats one of the major RGAadvantages.Standard steps taken before and during RGA are:1. Hybridization. Specific breeding objectives are

determined and the parents to be used selectedbased on adaptability to the area and specifictraits needed to improve the variety for thatarea. The promising donor or parent may beidentified through field observation, publishedliterature, or the IRRI germplasm data bank. Alocal scientist can make the cross or IRRI canbe requested to make specific crosses (Fig. 1).The cross may be simple or complex, dependingon the objectives and donor availability.

2. Production of F2 seeds. About 100 g of F2 seedsare needed for the first RGA planting. However,if the procedure is strictly followed, 300 greserve seed will be needed for other purposes(see Table 1). To produce this amount, grow atleast 20 Fl plants at ordinary spacing. Alsogrow the parents of the crosses as Fl generationreferences.

3. F2 planting. When a cross is submitted for RGAat IRRI (Plant Physiology Department), a RGAnumber is assigned and information about thecross is listed (see Table 2 for the form).Generally, 1,000 to 1,500 F2 plants are grownfor each cross. At least 3,000 seeds areneeded. Before beginning the process, seed

RGA screenhouse at IRRI.

dormancy must be broken. To break dormancy,fresh seeds are dried for 2 to 3 days and sub-jected to 50C for 5 days.Seeds are soaked for 24 h, then incubated for24 h. Wooden boxes or metal trays are preparedfor planting by adding 1 g ammonium sulfate,0.5 g of solophos, and 0.5 g of muriate ofpotash per liter of soil. A stick with nailsat 3-cm intervals is used to make guide holesin the soil surface. Standard spacing is3 x 3 cm, but optimum spacing depends on con-tainer depth and soil fertility. Using forceps,a germinated seed is placed in each hole andcovered with 1 to 2 mm soil. Only uniformlygerminated seeds should be planted so evengrowth and competition are maintained.

Direct sowing of pregerminated seeds using 3 x 3 cmspacing.


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4 IR PS No. 84, D ecem ber 1982

Table 1. Amount of seeds needed for a RGA programwith 3,000 initial F2 plants per cross.

Operation Amount ofseeds ( )Main planting 100Short-term 100

reserve

Long-term 100reserve

Monitoring 100

Remarks

For RCAIn case population is

reduced by unexpectedstress.

For future use.

To check the potentialof the cross.

If vegetative growth is vigorous and insideplants are heavily shaded, leaf pruning may benecessary 20 days after sowing. Pruning at 15cm above the ground will prevent plants fromgrowing too tall, but will not delay flowering(Eunus et al 1980). During pruning, plants canbe inoculated for bacterial blight using theclipping technique. Premature lodGing can beminimized by spraying B995 at 4,000 ppm on 35-day-old seedlings. Carts used at IRRI havemetal posts at each corner so strings can beattached to support plants.

Inoculating for BLB screening during pruning atvegetative stage.

Photoperiod treatment is started 20 days aftersowing for crosses using photoperiod-sensitiveparents. Carts are placed inside the darkroomat 1700 h, and removed the following day at0700 h. This process is continued until 50%of the plants have headed. Many photoperiod-sensitive plants will start flowering 60 to 70days after seeding. Some plants with longbasic vegetative phase (BVP) need 100 days toflower. The longest sowing tu flowering dura-tion recorded for a RGA population is 134 days-- a DA29/IR42 cross (Bardhan Roy et at 1982).Delayed flowering in certain crosses usually

Table 2. Entry form used in RGA. Information foritems one to six and nine must be supplied by thecooperator.

RGA No.RAPID GENERATION ADVANCE

1. Name of cooperator2. Address3. Designation of cross4. Female parent Male parent5. Hybridization (Yr/Season)6. Institution where hybridization was made

7. Breeding objectives:Deep water rice / /!/ubmergence tolerance

/ / elongation ability/ / photoperiod sensitivity/ / other agronomic characters

Cold tolerance / // / at seedling stage/ / at panicle initiation/ / at flowering/ / earliness of flowering/ / other agronomic characters

Disease and pest resistance / /RTV / / ShB / /Bl / / SB / / BB / /GLH / / RSV / / BPH / /GSV / / CM / / BLS / /

Other objectives such as drought and problemsoiIs / /

8. Generation of the seedDate submitted

9. RGA from F to FNo. of No. ofseeds 121ants Sowing

F2FF3F45Data to be collected

Flower-ing Harvest

10.11. Special treatment made12. Data collected13. No. of lines returned14. Remarks

Date returned

is the result of a long BVP. A plant with a60-day BVP will take more than 100 days tomature. These crosses diminish the value ofRGA because growing three generations per yearis difficult. BVP should be considered whendetermining crosses for RGA. Crosses with longBVP and photoperiod insensitivity should beplanted in the field because growth duration inRGA is not shortened and is sometimes delayed.


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National Program I R R I

Fig. 1. General scheme for rapid generationadvance (RGA).

Poor nutrition or overfertilization can retardflowering. Proper fertilization maintains healthygreen plants that are not overvegetative. At 40to 50 days after sowing, 10 g ammonium sulfate/m2 dissolved in 10 liters of water is applied.The box is then flooded with additional water,and nitrogen is dissolved in water to facilitateeven distribution. If the soil N level is low,frequent topdressing may be necessary.Plants should be harvested panicle by panicle asthey mature. Two seeds should be taken fromeach plant. The rest is threshed in bulk andreserved.

4. Planting F:tS seeds. The procedure described insteps 2 and 3 can be used through F4 or FS gen-erations although individual pots 2 1/4 inchesin diameter are better for F3 or F4 plantingsbecause screening is easier and bigger plantswith larger panicles are produced.At IRRI, F4 or FS seeds are given to the PlantBreeding Department for field evaluation duringwet season. Pedigree selection and bulk harvest-ing are made. Selections from the pedigree aregiven to the International Rice Testing Program(IRTP) for inclusion in the International RiceDeepwater Observational Nursery (IRDHON) or theInternational Rice Cold Tolerance Nursery (IRCTN)(Fig. 1). The cooperator who sent the F2 seedsor requested the specific cross to be made isalso supplied with bulk seeds. Seeds are plantedat specific sites and subjected to rigorous area-specific selection pressure.

IRPS No. 84. December 1982 5

OPTIMAL USE OF SPACE fu~D PLANT CONTAINERSUsing large wooden boxes or small individual pots hasadvantages and disadvantages. Hooden boxes canaccom-modate more plants but boxes are occupied until thelast plant is harvested. Small pots take more spacebut half that space may be available 3 months aftersowing. If plants are stressed at an early stage,elimination of susceptible lines provides additionalspace a month after sowing.

Drought screening. A disadvantage of using woodenboxes is that dead plants occupy space untilharvest.

Harvesting each panicle separately.

The number of plants grown per year is the sameregardless of whether wooden boxes (127 x 127 x 10COl) or square pots (5.5 x 5.5 x 5.0 cm) are used.


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6 IRPS No. 84, December 1982

Wooden boxes may be best for early generation mater-ials that are not screened or selected and that re-quire only a small number of seeds per plant. Indi-vidual plant containers are better for screeningthan large boxes. Susceptible plants can be elim-inated immediately after testing and remainingplants can grow to maturity in a smaller space.Square pots are ideal for RCA screening, which isusually done at F4 or FS generation. During the F4and FS generations bigger panicles are needed be-cause larger seed supply is required.

A plastic pot used in RCA.

Closer spacing in wooden boxes results in moredead plants at harvest. There is more competitionfor nutrients and light. Survival is 74% in boxesand 99% in square pots (Peralta et al 1979).

SELECTION PRESSURES DURINC RCASelect ion dur ing RCA is possible to a 1imi ted ex-tent. Poor performers, disease-infected plants,and plants wi th long awns, can easily be removed.If selections are made, population is reduced forthe next generation. To sow the same number ofseeds for the next generation, more seeds shouldbe taken from each surviving plant.If environmental pressure will be applied duringthe growing stage and early selections made, potsshould be used instead of boxes so less space isoccupied after selection.

Screening for bacterial leaf blight resistanceHybrid rice populations can be screened for bacte-rial leaf blight (BLB) resistance during RCA with-out affecting flowering responses (Eunus et al1980c). BLB, caused by Xanthomonas oryzae, is oneof the most serious rice diseases in Asia. Thepopulation can be inoculated with Xanthomonas,using a suspension of 109 cells/ml, 20 to 40days after seeding by the clipping method. Lesions

on leaves can be measured 2 weeks after inocula-tion to give a general idea of resistance. Suscep-tible plants will have decreased vigor and maydie. Inoculation at an early growth stage, espe-cially if one parent is highly susceptible, canreduce the population by as much as SO%.

Screening for drought toleranceScreening for drought tolerance during RCA is pos-sible, but has not been used with actual crosses.Tests of 10 varieties from di fferent geographicareas have been made using plastic pots. Eighteen-day-old seedlings were water-stressed for S days(Eunus et aI 1980a). Seedling survival percentageranged from 22 to 89%. Actual stress measurementis not necessary, because the goal is to eliminatesusceptible plants during RCA.Five days of water stress did not delay flowering,but grain sterili ty was increased and plantheight, panicle length, and panicle weight werereduced, as compared to the control. Howeve~ suchplant characteristics during RCA is relativelyunimportant because they are not part of the se-lection process. In cooler climates, a longerstress period may be necessary.

Screening for submergencetolerance at seedling stageComplete submergence of the rice plant at trans-planting is common in rainfed wetland rice areaswhere photoperiod sensitivity is required. Plantsare most sensitive to submergence 10 days aftersoaking. Screening for submergence toleranceduring RCA is done by planting in individual potsand submerging 10-day-old plants for 7 to 10 days,depending on parent resistance and environmentalconditions before and during submergence (BardhanRoy et al 1980b).

Ten days after the submergence period dead plantscan be removed. In a RCA submergence test, 62% ofthe population died. Seedling submergence duringRCA has little effect on growth duration and pro-ductivity of submergence-tolerant plants but maydelay heading by 5 to 10 days and increase steril-ity in susceptible plants (Bardhan Roy et al1980a) .

IRRI studies show that submergence tolerance haslow to moderate heritability. Because dominanceand nonallelic interactions are present, selectionfor submergence tolerance in the F2 generationwill be ineffective because subsequent progeniesof selected entries will show submergence suscep-tibility. Nevertheless, screening in F2 willeliminate most of the susceptible lines and reducepopulation size. If screening facilities are lim-ited, it may be best to screen in the F3 or F4generations.


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Screening for cold tolerance at seedling stageTo screen for cold water tolerance at F3 seedlingstage, pots should be used and 10-day-old seedlingsshould be subjected to 12C water for 10 days.Water depth should be 1-2 cm from the soil surface.Susceptible lines usually die or turn brown.In 1 RGA cross, 14% of plants died, 17% floweredearly, 23% flowered normally, and 46% floweredlate. Plants severely damaged by low water tem-perature headed later than the tolerant plantswhich showed little delay.In 2 RGA crosses screened for cold tolerance atseedling stage, removing susceptible lines (scoreof 7 to 9) eliminated 87 and 58% of the F3 plants,freeing greenhouse space for other u~es 30 daysafter sowing (Patena et al 1980a).

Selection for earliness or short growth duration

In low-temperature areas growth duration is animportant factor determining varietal suitability.When using RGA for low-temperature rice varieties,eliminating plants with long duration should bestandard practice (Bardhan et al 1982).For a plant to have 130-150 day growth duration inlow-temperature areas, it should flower within 70days under RGA conditions. To select for shortgrowth duration, plants flowering later than 70days are removed.Earliness selection in the F2 generation assuresthat 72-84% of the F3 population have growth dura-tion less than 70 days (Patena et al 1980b). Selec-tion for earliness does not double as a selectionfor cold tolerance at seedling stage. If selec-tion for earliness is to be made at F2 generation,a minimum of 2,000 plants should be grown.An F2 cross between Silewah and Hokkai 241 fromJapan was selected for earliness (Fie. 2). Only245 plants of 2,965 seedlings grown had growthduration less than 70 days. Ten seeds, instead oftwo, were taken from each plant to assure thedesired number of plants could be grown in the F3generation.

Selection for plant heightMany factors affect plant height. High temperatureand close spacing may make plants tall. Low nutri-ent level and short growth duration may grow shortplants. These factors interact during RGA, espe-cially in the F2 when plants are closely spaced.Plant height correlation between RGA-grown andfield-grown plants is low, indicating that selec-tion for height should not be done during RGA(Vergara et al 1980).

Screening for salinity tolerance at seedling stageCoastal wetland areas need photoperiod-sensitive,salt water-tolerant varieties. Preliminary RGA

IRPS No. 84, December 1982 7

experiments show that screening for salinity atseedling stage is feasible. Small pots are used.Ten-day-old seedlings are treated with 0.5-1% saltsolution to a depth of 10 cm. Salt concentrationis chosen depending on donor parent(s) toleranceor level of stress needed for specific areas.

TK5331 (Silewah/Hokkai 241)

Scuds eceived DI!c 1978j8 Jan Sowinq

'6 Apr SowingI22 Jun23 Jul SowinqI1 Oct8 Oct SowingI220!!c

Sl!.:ds rcturn!:d tocooperaTOr (Jail 1980)

Korea planted asbulkpopulation (1980)

IRRIPlant Bn!(!diny forfield plantinu/cva1u(nion

Fig. 2. Rapid generation advance of the crossTK5331 from F1 to F5. Four generations wereplanted in 1 year.

Salinity screening during RGA.


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8 IRPS No. 84, December 1982

After 10 days of treatment, the salt solution isdrained and susceptible plants are discarded. Potsare continuously flushed with tap water for at least1 hand topdressed with 10 g ammonium sulfate pertray. Treatment with 0.5% salt solution has resultedin 100% survival for tolerant Pokkali and 32% sur-vival for susceptible Ml-48. Forty-seven per centof the tolerant check survived in a 1% salt solutionand all plants of the susceptible check died.

Screening for other plant traitsScreening for resistance to brown planthopper, leaf-hopper, blast, other diseases, and adverse soilstolerance during RCA may be possible but no trialshave been made. Crain size and shape, little af-fected by environment, can be selected. Althoughawn length is determined by environment, selectionfor awnless grains is routinely practiced during RCA.Screening for photoperiod sensitivity, the mostimportant trai t for ra Inf ed lowland and deepwaterrice areas, is difficult during RCA. Photoperiodsensitivity must be selected when varieties areplanted in the field during monsoon season. DuringRCA some plants wi thin a population are late inheading. These plants have long BVP. Selection forlong BVP within a photoperiod-sensitive cross canbe made by choosing plants that headed late.TIMINC OF RCA PLANTINCAlthough it would be easier, for comparison andrecord keeping, to plant all varieties in the RCAgreenhouse at the same time, the method is not prac-tical because it would sometimes leave the greenhouseempty and because the peak harvest for individualcrosses would come at about the same time. Sowing

BR1014RR(Digha 489/BR4)ql

ei.s susceptible C : : : : : : = _ ]and long awn s - - - iernoved TI F. I

Made at BRRI

Seeds received7 Feb 1979

75 days RG A

88 day s RGA

F4 seeds returned tocooperator 1 Sep 1979

Fig. 3. Flow diagram of a cross received from anational cooperator and processed through rapidgeneration advance. BRRI = Bangladesh Rice ResearchInstitute, BLB = bacterial leaf blight.

RCA varieties at staggered times maximizes use ofgreenhouse space and optimizes labor use.

If F2 seeds are started in early February, F4 seedscan be returned to the cooperator or breeder bySeptember the same year (Fig. 3). F4 seeds can beplanted in the field for evaluation although photo-period sensitivity cannot be selected for accurately.In crosses for low-temperature areas, receiving Flseeds in December and sowing in January has enabledthe system to return F5 seeds to the cooperator byJanuary the following year (Fig. 2). For a crossmade during the 1978 growing season in Japan, Flseeds were sent to IRRI in December. Without RCAFl seeds would have been planted in 1979 and F2 seedsin 1980. With RCA, F5 seeds were planted in Japanin 1980. Selection for awnless grains and shortgrowth duration had also been made so chances of ob-taining better lines from a bulk population werehigher.Planting F2 seeds later in the year would have pro-vided F4 seeds for field planting the following year.If the F4 seeds can be planted in Mayor June, selec-tion for photoperiod sensitivity is possible.

IRRI RCA FACILITIESIRRI RCA facilities can accommodate about 200,000plants/planting or 600,000 plants/year using woodenboxes and pots. To grow 200,000 plants in the fieldrequires more than 1 ha at normal spacing but only825 m2 in the RCA greenhouse. Labor and space areminimized and insect and disease control is easier.At IRRI, plant physiologists and plant breeders sharmanagement responsibilities for the RCA system. ThePlant Physiology Department supervises facilities anthe Plant Breeding Department manages field plantingsand evaluation (Fig. 4). Five crosses are planted anharvested each week. Harvesting is daily. Betweenplanting and harvesting operations harvested seedsare bulked and/or sampled for the next planting.

Plant PhysiologyDepartment

L____c_,c_Cn_in_g_O_f_m_at_CC_ia_IS_ ~~------.IL-----H-Yb-'_idriz_at_io_n ~

I Registrat ion of mater ia ls J ------1_ F,_o_ ,_F_2_sc_ed_s - -- '1 Growiny of populat ion

i n t he fi el dISelectionI Gr ow in? i n t he RGA f aci li ti es 11-------1Im pOSing selection pressure I '-----l,--~Dispatch of processed materials

Fig. 4. Management of the IRRI rapid generationadvance system.


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SPECIAL USE OF RGA FOR RICE COMPOSITES


al 1982) to increase the elongation ability ofprogenies and create genotypes with wide adaptabi-lity. The method is illustrated in Figure 6.enetic male sterility in indica rice makes it pos-

sible to combine more than 4 parents to develop apopulation. Chaudhary et al (1982) outlined a methodfor using RGA facilities to produce a composite crossof outcrossing rice plants if genetic male sterilityis maintained in 50% of the individuals. RGA isimportant in male-sterile-facilitated composites be-cause flowering can be synchronized by manipulatingphotoperiod and planting seeds closely to allow crosspollination. Free flow of genes can take place as itdoes in cross-pollinated crops.

Field

By allowing the plants to complete BVP beforeinducing flowering, a very high percentage of thepopulation flowers within a short time and out-cross. In a trial involving 5 male-sterile F2populations, 75% or more of the plants in eachpopula tion flowe red wi thin 4-9 days when p.lantswere grown for 40 days under long day length be-fore subjecting to flower inductive short days(Fig. 5). Shorter flowering range permits a plantthat flowers at 0 day to be pollinated by otherplants heading 2 days before and 2 days after 0day.

Yea, 1RGA

Recombination phase

Close spacing allows maximum outcrossing. In thefield, 50 m2 accommodates 1,000 F2 plants,lessening the chances that 1 plant at 1 end of thefield intermates with another at the opposite end.In RGA the farthest distance between 2 plants in apopulation is 1.5 m. The flowering panicles can beshaken, using a stick to stir pollen and promoteoutcrossing.

Yea r 2RGA

F ix at io n pha se

Composites for photoperiod-sensitive deepwaterrice using IR36(ms) have been made (Chaudhary et

l Pno tcoenod- scos tu vc donor sIR36 (msl with submergence tolerance,male sterile jX elongation ability. resistance to'----------',~ ~pe.",."c.D it te re nr F, s IF, fertileI~F'~

25%

c,

Reserve

S el ec ti on andevatuation

Fig. 6. Scheme to develop and handle male-sterile-facilitated composite.

% population involved in autcrossing~ r - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - '45 40 davs

20 dayst \ _ MeanI "I\ .. . ..,/ \, \I \I \I \I \,

I ', \~._----~--~ \I \/ \I \

I \.I "I ' - " . . . . . . . . . ._J "_/

Mean

55 57 59 61 63 65 67 69 71 13 75 77 79 81 83 85 87 89 91 93 95Davs after seeding

Fig. 5. Period of long day treatment before floral inductiveshort day treatment and percentage of composite populationinvolved in outcrossing.


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10 IR P S No. 84, December 1982

A salt tolerance composite has also been developedthrough RCA. The composite cross seeks to increasethe level of salinity tolerance beyond that of thebest parents and to obtain salinity tolerance in agenotypically diverse background to allow wideada ptabil ity.

STATUS OF RCA AT IRRI -- 1979-82By June 1982, about 600 RCA crosses involving 745generations and a million plants had been grown Lnthe IRRI RCA facilities. Most crosses were forlow-temperature, deepwater, and rainfed wetlandareas.In 1980, five RCA lines were included in the IRCTN.In 1982, 9 entries, 5.4% of all IRRI entries, camefrom RCA. In the Cold Tolerance Nursery atChuncheon, Korea, about 50% of the IRRI entrieswere from RCA. In the IRDWON, 11 entries, 20.7%of all IRRI entries, were generated through RCA.Bulk seeds from RCA crosses have been sent toBangladesh, Burma, Australia, Columbia, China,India, Indonesia, Japan, Korea, Liberia, Malaysia,Nepal, Thailand, Turkey, the West Africa RiceDevelopment Association, and the InternationalInstitute of Tropical Agriculture.

It is too early to expect a variety from the RCAfacilities at IRRI although the effectiveness ofRCA in Japan has been clearly demonstrated. How-ever, the increasing number of entries in theIRDWON and IRCTN indicate that RCA facilities haveindeed shortened the breeding cycle and have madeavailable fixed bulk populations within a shorttime.

INTERNATIONAL COOPERATIONParticipants in the 1978 International DeepwaterRice Workshop in Calcutta, India, recommended thatbreeders working with photoperiod-sensitive ricesshould utilize IRRI RCA facilities (Ikehashi andHilleRisLambers 1979). Participants agreed thatbreeders could send five crosses per year to IRRIfor RCA, or suggest crosses for IRRI to make andrun through the RCA. Researchers at the 1978International Cold Tolerance Workshop at Suweon,Korea, have also decided to use RCA to acceleratecold tolerance breeding for high-elevation andhigh-latitude areas where only one rice crop peryear is possible (Vergara and Coffman 1979).

If the best crosses from each national program aresent to IRRI for RCA and sent back to the respec-tive breeding centers for further in situ selec-tion, turnaround time for national breeding pro-grams can be reduced 2 to 3 years. The same seedscan also be sent to other national breeders.Different national programs have different facili-ties to test for environmental and biologicalstresses. A RCA cross may be planted in the deep-

water tanks in Thailand and selected for internodeelongation ability, or tested in West Bengal forsubmergence tolerance and in Bangladesh for uf radisease. A portion of the seed from the selectedlines can be sent to IRTP for future inclusion inthe international nurseries to benefit other areaswith similar varietal requirements. In future, acoordinated testing system may have to be deve-loped to utilize existing capabilities of nationalfacilities and accelerate breeding programs.

REFERENCES CITED

Bardhan Roy, S. K., C. F. Patena, and B. S. Vergara1982. Feasibility of selection for traits asso-ciated with cold tolerance in rice under rapidadvance method. Euphytica 31:25-31.

Bardhan Roy, S. K., B. S. Vergara, and J. Peralta.1980a. Effect of submergence tolerance screen-ing during rapid generation advance on headingduration and productivity. Int. Rice Res.Newsl. 5(5):11-12.

Bardhan Roy, S. K., J. Peralta, and B. S. Vergara.1980b. Submergence-tolerance screening of riceduring rapid generation advance. Int. Rice Res.Newsl. 5(5):3-4.

Chaudhary, R. C., B. S. Vergara, and F.S.S. Lopez.1982. Breeding of photoperiod-sensitive wetlandrices by male-sterile facilitated compOSiteunder rapid generation advance system. Pages307-312 in International Rice Research Insti-tute. Proceedings of the 1981 internationaldeepwater rice workshop. Los Banos, Laguna,Philippines.

Eunus, M., B.Ikehashi.seedlingsgeneration5(4):10.

S. Vergara, J. A. Peralta, and H.1980a. Method for screening ricefor drought tolerance during rapidadvance. Int. Rice Res. Newsl.

Eunus , M., H. Ikehashi, B. S. Vergara, and J.Peralta. 1980b. Prevention of lodging in riceplants during rapid generation advance. Int.Rice Res. Newsl. 5(5):3.

Eunus, H., H. Ikehashi, B.S. Vergara, and J.Peralta. 1980c. Screening for resistance tobacterial blight of rice under rapid gene-ration advance. Int. Rice Res. Newsl. 5(4) :7.

Ikehashi, H. 1977. New procedure for breeding pho-toperiod -sensi t ive deep-water rice wi th rapidgeneration advance. Pages 45-54 in Internatio-nal Rice Research Institute. Proceedings, 1976deep-water rice workshop, 8-10 November,Bangkok, Thailand. Los Banos, Philippines.

Ikehashi, H., and D. HilleRisLambers. 1979. Inte-grated international collaborative program in


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the use of rapid generation advance in rice.Pages 261-276 in International Rice ResearchInstitute. Proc~dings of the Internationaldeepwater rice workshop. Los Banos,Philippines.

Nakane, A. 1979. Present status of rapid genera-tion advancement in rice and its problems [inJapanese]. Recent Adv. Breed. 20:95-101.

Patejia, G., S. K. Bardhan Roy, and B. S.Vergara. 1980a. Selection for cold tolerance atseedling stage during rapid generation advance.Int. Rice Res. Newsl. 5(4):12-13.

Patena, G.,Vergara.S. K. Bardhan1980b. Selection

Roy, and B.for earliness or

S.


short growth duration during rapid generationadvance in rice breeding. Int. Rice Res. Newsl.5(5):4.

Peralta, J., B. S. Vergara, and G. Patena.1979. Optimal use of space and plant containersin RGA. Int~ Rice Res. Newsl. 4(5):5.

Vergara, B.S., and W.R. Coffman. 1979. IRRI's pro-gram for rapid generation advance in ricebreeding. Int. Rice Res. Newsl. 4(5):3-4.

Vergara, B. S., S. K. Bardhan Roy, and G.Pa teiia. 1980. Selection for plant heightduring rapid generation advance in rice breed-ing. Int. Rice Res. Newsl. 5(4):3.


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The International Rice Research InstitutePO. Box 933, Manila, PhilippinesStamp

O ther papers in th is seriesFOR NUMBERS 1-32. TITLES ARE LISTED ON THE LAST PAGE OF NO. 79AND PREVIOUS ISSUESNo. JJ Determining superior cropping patterns for small farms in a dryla nd

rice environment: test of a methodologyNo. .14 Evapotranspiration from rice f ieldsNo . .15 Genetic analysis of trai ts related to grain characterist ics and quali ty in

two crosses of riceNo . .1() Aliwalas to r ice garden: a case study of the intensificat ion of r ice farm-

ing in Camarincs Sur. PhilippinesNo. J7 Denitrification loss of fertilizer nitrogen in paddy soils - its recogni-

tion and impactNo . .1H Farm mechanization. employment , and income in Nepal: tradi tional

and mechanized farming in Bara Dist rictNo . .19 Study on kresek (wilt ) of the rice bacterial bl ight syndromeNO.40 Implicat ion of the internat ional rice blast nursery data to the genetics

of resista neeNO.41 Weather and climate data for Philippine rice researchNo.42 The effect of the new rice technology in family labor utilization in

I.aguna;>Jo.4.1 The cont ribution of varietal tolerance for problem soi ls to yield stabil -

ity in r iceIR42 a rice type for small farmers of South and Southeast AsiaGerrnplasrn bank information retrieval systemA methodology for determining insect control recommendationsBiological nitrogen fixation by epiphytic microorganisms in rice fieldsQuality characteristics of milled rice grown in different countriesRecent developments in research on ni trogen ferti lizers for riceChanges in community institutions and income distribution in a WestJava village

No. 51 The IRRI computerized mailing list systemNo. 52 Differential response of rice varieties to the brown planthopper in

international screening testsNo. 5.1 Resistance of Japanese and IRRI different ial rice var ieties to patho-

types of Xanthomonas orvzae in the Philippines and in JapanNo. 54 Rice production in the Tarai of Kosi zone, NepalNo. 55 Technological progress and income distribution in a rice village in

West JavaNo. 56 Rice grain properties and resistance to storage insects: a reviewNO.57 Improvement of native rices through induced mutationNo. 58 Impact of a special high-yielding-rice program in Burma

No. 44No. 45No. 46No. 47No. 4HNo. 49No. 50

ISSN 0115386

No. 59 Energy requirements for alternat ive rice production sys tems in thetropics

No. 60 An illustrated description of a traditional deepwater rice variety ofBangladesh

NO.61 Reactions of different ial variet ies to the rice gall midge. Orseolia Orl-zae. in Asia. Repor t of an international collaborative research project

NO.62 A soil moisture-based yield model of wetland rainfed riceNo. 6.1 Evaluation of double-cropped rainfed wet land riceNo. 64 Trends and strategies for rice insect problems in tropical AsiaNo. ()5 Landforms in the rice-growing areas of the Cagayan River BasinNo. 66 Soi l fertil ity, fer til izer management. ti llage, and mulching ef fects on

rainfed maize grown after r iceNo. 67 High-temperature stress in riceNo. 6X Weed-ferti lizer interactions in riceNo. 69 The azolla-anabaena complex and its use in rice cultureNo. 70 An index to evaluate the effect of water shortage on the yield of

wctla nd riceNO.71 The development and diffusion of r ice variet ies in IndonesiaNo. 72 Levels of resistance of rice varieties to biotypes of the BPH, Nilapar-

vata It/gens, in South and Southeast AsiaNo. 73 Growing season analyses for rainfed wetland f ieldsNo. 74 San Bartolome: beyond the green revolut ionNo. 75 Pathotypes of Xanthomonas campestris pv. orvzae in AsiaNo. 76 Focus ing field research on future constraints to rice productionNo. 77 An international survey of methods used for evaluation of cooking

and eating quality of milled r iceNo. 78 Research on algae. blue-green algae. and photot rophic nitrogen f ixa-

tion at the International Rice Research Institute (I%1-81). surnrnari-zation.jiroblems, and prospects

No. 79 Seed-derived callus culture for selecting salt- tolerant ricesNo. 80 Economic limitat ions to increasing shallow rainfed rice productivity

Bicol, PhilippinesNO.81 Irrigation system management research and selected methodological

IssuesNo. 82 Interdisciplinary challenges and opportunities in international agricul

tural researchNO.83 Comparative analysis of cropping systems: an exploratory study of

rainfed sites in the Philippines

Documents

IRPS 84 Rapid Generation Advance of Rice at the International Rice Research Institute