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Breeding approaches for varietal improvement in rice, with special reference to genetic yield enhancement and stability, and reflection on 35 years of rice breeding in eastern India
Dr. S. R. Das
Rice Seminar Series
Current position:• Professor of plant breeding (Emeritus), Orissa University of Agricultural
Technology (OUAT), India• IRRI consultant (2010-2012)
Education and Work experience• PhD in Genetics (1987) Indian Agricultural Research Institute, New Delhi.• Under-graduate and post-graduate degrees (1973 and 1975) in
agriculture, OUAT• Joined department of Plant Breeding and Genetics of OUAT (1976);
became professor in 1999
Achievements:• Released 49 high yielding rice varieties for Orissa during 1980-2012.
These varieties currently cover more than 70% of the rice area in the state. Some of these varieties are widely grown in other states of India
• “Pratikshya” a newly released variety has replaced Swarna
Achievements (cont’d)• “OR 142-99” (“Santepheap-3”) released in Cambodia via INGER• “OR 1128-7-1” (“ADT-44”) released recently in Tamil Nadu. • Contributed to collection, evaluation and maintenance of nearly 100 indigenous aromatic
rices of Orissa• Handled research projects on “Genetic yield enhancement of aromatic short grain rices for
higher productivity and export” which led to the release of two varieties: “Nua Kalajeera” and “Nua Acharamati”.
Awards and distinctions:• Rao Bahadur Dr.Ram Dhan Singh Memorial Trust Award (2003) from Haryana Agricultural
University as the Best Rice Scientist• Dr. R.B. Ekbote Prize from Maharashtra Association for Cultivation of Science, Pune (2006)
for his significant contribution in rice research. • Senadhira Rice Research Award (2012), awarded by IRRI for outstanding contributions to
rice research and international cooperation in rice varietal development.
Breeding approaches for varietal improvement in rice with Breeding approaches for varietal improvement in rice with special reference to genetic yield enhancement and stabilityspecial reference to genetic yield enhancement and stability
andandReflections on 35 years of rice breeding in eastern IndiaReflections on 35 years of rice breeding in eastern India
DEPARTMENT OF PLANT BREEDING AND GENETICSOUAT, BHUBANESWAR, INDIA
PROF. S. R. DASPROF. S. R. DAS
Introduction
• By the adoption of semi dwarf rice varieties coupled with improved management practices, there was spectacular advance in rice production during last four decades.
• Incorporation of a series of resistant genes conferring resistance, tolerance to biotic and abiotic stresses into the breeding populations the yield level has been stabilized.
Growth rates of riceArea, production and yield in India
Period Area Production Yield
70-79 0.87 1.88 1.01
80-89 0.41 3.55 3.14
90-99 0.65 2.00 1.34
2000-2011 0.00 1.72 1.72
Growth rates of rice area production and yield in Asia
Regions Period Area Production Yield
East Asia 60-69 0.81 5.36 4.55
70-79 0.13 2.50 2.37
80-89 -0.58 2.08 2.66
90-99 -0.58 0.81 1.39
2000-2011 0.27 0.98 0.71
South Asia 60-69 1.09 1.67 0.58
70-79 0.93 2.11 1.18
80-89 0.31 3.09 2.77
90-99 0.61 2.11 1.49
2000-2011 0.36 2.11 1.75
Growth rates of rice area production and yield in Asia
Regions Period Area Production Yield
Southeast Asia 60-69 0.91 1.58 0.68
70-79 1.00 2.34 1.33
80-89 0.79 2.94 2.15
90-99 1.71 2.72 1.02
2000-2011 0.87 1.81 0.93
Asia 60-69 0.95 3.29 2.35
70-79 0.69 2.36 1.67
80-89 0.19 2.59 2.40
90-99 0.62 1.70 1.09
2000-2011 0.51 1.60 1.09
The targeted projection of production (mt) and yield (t/ha) in Asia
Regions Period Production Yield
Southeast Asia 2011 117.8 2.55
2020 168.0 3.28
2030 223.0 3.94
East Asia 2011 147.5 4.43
2020 197.0 6.04
2030 231.0 7.30
South Asia 2011 151.3 2.46
2020 188.0 2.89
2030 239.0 3.49
The targeted projection of production (mt) and yield (t/ha) in Asia and India
Regions Period Production Yield
Asia 2011 416.6 2.95
2020 549.0 3.72
2030 682.0 4.43
India 2011 104.3 2.35
2020 133.0 2.85
2030 167.0 3.45
• Important rice improvement programs in India as well as at IRRI, have not made any significant increase in the genetic yield potential of varieties released after IR 8
• If we fail to stabilize the yield growth level at least at where
we stand today, then it may not be possible to sustain the self-sufficiency and surplus in rice.
• Plant breeders today argue that, there is no evidence of yield plateau for any crop including rice
• A perfect variety has yet not been evolved
• Still there is an unexploited genetic variability for improving the direct and indirect components of yield through utilization of untapped germplasm
• There is still scope to develop and use more efficient breeding and selection techniques for yield improvement in rice.
Mating system• Biparental crosses are widely used in rice varietal
improvement programmes to serve the purpose of combining simply inherited traits from two parents
• The recombination possible from biparental crosses are too restrictive to make rapid improvement in a selfing species like rice.
• The use of multiple crosses as suggested by Harlan, Martini and Stevens (1940) involving 16-32 parents which are crossed in successive generations until the final hybrid involve all the parents
• Theoretically the multiple crosses provide an opportunity for recombination of genes from many parental strains by intermating F1s in successive generations.
• It is practically not possible to get enough F1 seed in later generations of mating cycles to retain all the parental genes in the final hybrid.
• Assuming a multiple cross with 16 parents each of which carrying one favourable gene the number of hybrid seeds in each generation ensuring a 50:50 probability of retaining all the 16 genes in one plant in the final generation would be 8, 64, 131000, 640004 in the 1st, 2nd,3rd and final generations respectively
• The second practical limitation was suggested by Mackey (1954) that by using 16-32 parents in a multiple crossing programme will force the inclusion of number of unadapted strains, which are likely to disrupt the good genetic background of varieties that took several years even decades to assemble
• therefore suggested modified backcrossing programmes to obtain optimum parental lines and each unadapted parent should be crossed and backcrossed to an adapted variety before its use in a multiple crossing programmes.
Mating system (cont’d)
• Three way crosses were tried in many selfing species where the third parent is another adaptable germplasm, serves the purpose of increasing the proportion of adaptable germplasm and simultaneously widen the scope for combining desirable genes from another good parent.
• It has been observed that the breeding populations of three way crosses had relatively large genetic variance and produced more superior recombinants than two way crosses.
• Such crosses also provide an element of gamete selection, since the superior performance of test cross F1 plant reflects the combination of superior gametes from the segregating single cross with genotypes of the non-segregating variety as the third parent.
Mating system (cont’d)
• As argued by Stadler (1944) the frequency of superior gamete is much higher that the frequency of superior zygote, therefore, three way crosses provide a more efficient mating system for obtaining lines with better performance
• Besides three way crosses, double crosses using four different parents were also useful in extending the range of parents and achieve recombination of desirable alleles from diverse parents.
• The different mating systems as suggested was limited to a great deal by the requirement of large number of F1 seeds.F1 generation serves itself as the segregating population similar to F2 of single crosses and set the limit of possible recombination of genes available in the population.
Mating system (cont’d)
• Never the less, these multiple crosses are expected to create an array of genotypic variability which never existed earlier in any breeding population.
• Many rice breeders have not used multiple crossing programmes for varietal improvement in rice because they got adequate success through careful manipulation of biparental progenies. However, the limited success achieved through various mating schemes employed in rice is primarily due to
• the requirement of large number of F1 seeds • relatively small sample size in F2, where the full range of yield is
not realized.• A majority of breeders have restricted their selection to known
material and have made intense efforts for local adaptation as a result certain gene blocks are rapidly fixed along with correlated response which in many cases are adverse in direction.
• Therefore, it is suggested to chose the parent on the basis of wide genetic base with acceptable level of productivity high general combining ability before their use in a multiple crossing programme for realization of high
and stable yields in rice.
Mating system (cont’d)
Gene pool concept and use of weedy relatives
• The gene pool concept for plant breeding was conceived by Harlan and de wet (1971) which divides the total array of genetic variation within the reach of plant breeders into
• primary, secondary and tertiary gene pools.
• Often the primary gene pools include the
– progenitor of cultivated species
– that can easily be crossed with cultivated type
– produce fertile hybrids and
– exhibit normal segregation.
Gene Pool Concept• The interspecific oat matings between. A. sativa and A. sterilis
showed a considerable amount of yield improvement ( 3 to 29 %) Frey,1976
• Introgression of germplasm from H. Spontaneum into cultivated barley also increased productivity to the extent of (29 to 46 %) and good levels of agronomic traits were realized in BC3 to BC5 generations. Rodgers,1982
• The interspecific matings take advantage of nuclear genes from A. sterilis/ H. Spontaneum and add a quantum increase in yield potential of cultivated oat and barley varieties in USA
• The expected proportion of germplasm from wild species is 6.25 % or less and both oat and barley can tolerate about the same percentage of wild germplasm for expression of improved productivity.
Gene Pool Concept in rice• Both the cultivated species O. sativa and O. glaberrima
and their related wild species such as O. nivara, O. rufipagon, O. breviligulata and O. longistaminata have the same AA genome and they share a common gene pool.
• These weedy species can be easily crossed with cultivated types and their F1 hybrids have normal chromosome pairing but show varying levels of sterility.
• More often the wild species in rice have been used for transferring resistant genes into cultivated type but never been systematically exploited for increasing higher productivity in rice.
• Therefore, it is suggested to make use of weedy and wild species from the primary gene pool and examine the feasibility of wild germplasm for improving yield potential, like oat and barley, in rice.
Disruptive Matings in Plant Breeding• When the breeder uses germplasm from exotic and especially wild or weedy
sources the repulsion phase of linkage do not express a portion of potential genetic variation for a trait. To overcome this undesirable genetic limitation it has been suggested to use of disruptive mating in cereals.
• Generally samples of individuals or progenies are selected from plus and minus portions of the frequency distribution and only plus and minus matings are made.
• Over cycle of disruptive matings, it is seen that the population mean remained unchanged but the variance and range of the frequency distribution is increased many fold
• Theoretically disruptive mating via mating unlike --leads to greater opportunity for creating heterozygosity in selfing generations,
--enhance rapid crossing over and
-releases latent variations which are locked up by repulsion phase of linkages.
• It has been pointed out that disruptive mating is considered to be an effective plant breeding procedure as more exotic germplasm sources would be used in future plant breeding programmes for improving the direct and indirect components of yield.
Disruptive Matings in Plant Breeding
Male Sterile facilitated Composite• Another method of increasing genetic variation is the composite
method of breeding which has been extensively applied in barley breeding by Suneson (1956). In this method F2 of several crosses are bulked into a composite population and subjected to natural selection in diverse environments.
• But the introduction of male sterility into the hybrid population helped to enhance recombination through natural crossing and Suneson showed that natural selection had caused the bulk population to become higher yielding in later generations.
• Several composites developed by means of the male sterility factors were investigated by Jain and Suneson (1966) for quantitative genetic changes in variability and productivity. These composites exhibited a very high degree of genetic variability and the increase genetic variability was not accompanied by a corresponding increase in productivity.
Male Sterile facilitated Composite• The proportion of good recombinants from undesirable
linkages can be increased up to F4 and F5 through additional recombination and can be isolated in later generations,(Ikehasi,1977)
• The advantage of bulk breeding is to handle large genotypic variation available from multiple crosses or composite populations with least cost and time. Nevertheless by artificial selection the bulk population may be shifted towards agriculturally desirable types.
• Natural selection is crucial for the evolutionary process which
facilitates strong selection pressure for characters of very high adaptation
• Higher recombination by breaking up parental linkage groups may help to form a better base population for the development of best yielding, highly homozygous and homogeneous lines
Monogenic recessive male-
sterile IR-36
Donors of pest and disease resistance,
tolerance for drought, adverse soils, and good
agronomic traits
F1 all fertile
Distribution to interested breeders
Self-pollinating Fertile portion
F2
Male sterile portion
F2
Donors of pest and disease resistance,
tolerance for drought, adverse soils, and good
agronomic traits
Normal F3
Out cross F3
F3 F1
Ordinary pedigree
Further recombination
Composite population
Monogenic male sterility facilitated composite populations in rice (Singh and Ikehashi,1981)
Recurrent selection and Population Improvement
• Recurrent selection is primarily used to promote recombination and to increase the frequency of favourable genes for quantitatively inherited traits in population of plants. It is cyclic and in each cycle the two phase of plant breeding.
--Selection of a group of genotypes that posses favourable genes
--mating among the selected genotypes to obtain genetic recombination
• The obstacles to genetic recombination among alleles at closely linked loci in self fertilizing species could be eliminated by the use of male sterility
Male-sterile facilitated recurrent selection for rice breeding
Flowchart of development RS population using IR 36 ms and manual crossing
IR 36 msms × P1…N
P1…N × F1 (MSms)
BC1F1 BC1F1
BC2F1 BC2F1
BC2F2 (6.25% msms)BC2F2 (6.25% msms)
3 times recombination
Half-diallel crosses
Double crosses
8-way crosses
C0 populations (15,000 plants)
Progeny yield testSSD
Single plant selection Recombination
Fixed lines
C0 populations (15,000 plants)
3 populations including 26 elite parents
32 BC2F142 BC1F1
Single plants selection
Feed into breeding programs
Yield testing, new varieties
Guoyou Ye
Step 1
Step 2
Step 3
Step 4
Steps 5 - 9
Steps 10
IR36 ms/ARC10451
IR36 ms/WC1263
IR36 ms/F1IR36 ms/F1
Bulk population with 3 staggered plantings to synchronize flowering
Bulk population with 3 staggered plantings to synchronize flowering
Repeat steps 3 and 4 at least 2 more cycles
Select fertile plants purify by pedigree method and test
BC1 F2
Mixed seed
Make crosses with donors
Interplant F1 with IR36 ms. Coincide F1 and IR36 ms flowering. Harvest seed separately.
Use all seed harvested from IR36 ms plants and about 30 g from each F1 to prepare bulk.
Grow at stem borer hot spot to coincide with peak population. Select for desired characteristics, including a number of male sterile plants.
Grow under pest pressure. At maturity, select resistant plants and bulk.
Select for elevated level of resistance.
Male sterility has a selection disadvantage in the population and its frequencies decreases to a very low value within few generations and
The effectiveness of this mechanism in promoting heterozygosis for increased crossing over would be ephemeral.
There is also some evidence that too much crossing over in selfing species can be detrimental to fitness
, Male-sterile facilitated recurrent selection projects
• An extensive recurrent selection project was initiated using the recessive male sterile gene of IR 36 in1984 under the auspices of CIRAD-CA, CIAT, WARDA and IRRI for broadening the genetic base of gene pools in
• tropical upland japonica, lowland tropical indica, upland and irrigated tropical high altitude and irrigated temperate japonica rices.
• Several gene pools and populations were developed which have been used as genetic base population for recurrent selection in different Latin American countries like Brazil, Chile and Colombia and in several African countries viz. Ivory coast, Mal, and Madagascar.
• In 1989, the basic gene pools CAN IRAT-4 and 5 for tropical indica irrigated and tropical japonica upland conditions were made available to the international scientific community.
• In 1990, at CIAT a hand crossed recurrent selection project began focusing on the development of gene pools and populations targeting blast resistance in rice (Chatel and Guimaraes, 1994).
• New gene pools CIRAD-CA and CNPAF developed the indica and japonica basic gene pools CAN-IRAT 4 and CAN-IRAT-5; CIRAD-CA and IRRI developed indica-japonica CPI 22L and indica CP 126 gene pools and CIAT developed the indica-japonica gene pool GC 91 by hand crossing.
DSM system & Population Improvement
• The success of recurrent selection has led to several population improvement schemes. Recurrent selection has been applied to closedclosed genetic systems
• Jensen (1970) proposed the ‘diallel selective mating’ (DSM) system which was designed primarily for autogamous species which worked as a dynamic gene pool
• This system providesConventional bulk population breeding for the biparental diallel crosses
Mass selection in each population series Recombination of selected genotypes Introgression of new germplasm into breeding population at any time.
• DSM seems to be formidable due to large number of crosses and requirement of enough F1 seeds in each crossing cycle
• Jensen (1978) suggested use of male sterility factor to facilitate crossing and growing of breeding populations in a specialized environment to maximize genotypic expression of the trait under selection.
Diallel selective mating system
F1(Plant)
Parent diallel
series (F1)
F2(Seed)
Diallel cross
F2(Plant)
F3
F3
F4
F4
F5
F5 line selection
F6 head rows
F1(Plant)
Diallel series (F2)
F2(Seed)
F2(Plant)
F3
F3
F4
F4
F5
F5 line selection
F1(Plant)
1st selective mating series
(P3)
F2
F2
F3
F3
F4
F1
2nd selective mating series
(P4)
F2
F2
F3
Selectivemating
Selectivemating
Mass selection
Mass selection
Mass selection
Mass selection
(Ps)
End productLine variety or parent line
Line variety, Composite variety or parent line
1
2
3
4
5
6
7
History of stay green indica germplasm in Colombia
• Taiwanese japonicas were selected as donors for resistance to hoja blanca virus during 1958.
• These parents had dark green foliage and little or no leaf senescence at grain maturity.
• Many virus resistant stay-green lines were developed were used repeatedly over 40 years in the crossing program, resulting in typical indica germplasm having hoja blanca resistance and stay-green leaves.
• With the exception of the release, Fedearroz 50, none of the many varieties produced during the past decades in Colombia has dark green, non-senescing foliage, indicating that breeders paid little attention to these traits.
History of stay green indica germplasm in Colombia
• It is rarely observed any dark green, stay-green indicas in other tropical breeding programs.
• There is a general correlation that pale leaves senesce early while dark green is invariably stay-green. In rice all leaves, including the flag leaf, of stay-green lines remain functional past grain maturity.
• Typical sensitive indica types exhibit leaf deterioration and drying soon after flowering and well before grain filling. Intensity of leaf colour is constant in all growth stages of a given line.
• Leaf colour and degree of senescence are inherited independently of maturity period in rice.
Physiological evidence associating stay-green with yield capacity
• Early senescing indica varieties with a senescence inhibition gene from Arabidopsis were transformed with extraordinary increases in photosynthetic rates and chlorophyll content which resulted
--gains in tiller number,
--seed set,
--plant yield and biomass• The flag leaves of stay-green Fedearroz 50 at grain
maturity showed large advantages in
--chlorophyll content,
--photosynthetic rates and
--nitrogen content.
Senescing (left) and Stay-green (right) rice lines.Jennings et al.
Field observations on Fedearroz 50• Fedearroz 50, quickly occupied a large part of Colombia’s rice area and is
planted in other tropical countries since its release during 1998.
• It is a typical indica that has Taiwan and West African japonicas in its remote parentage. It differs from all of the nearly 300 semi-dwarf varieties released in Latin America during the last 35 years in having extremely
-- dark green leaves
-- an unusually long and erect flag leaf and
-- non-senescing foliage.
• The stay-green trait,
-- involving an unusually high photosynthetic rate, and
-- enhanced chlorophyll and nitrogen content
• All plant leaves appear normal and functional at physiological grain maturity.
contribute to
-- maximum yield capacity
-- extraordinarily high ratoon crop yields ranging from 7 to 10 t/ha
-- superior milling quality by enhanced carbohydrate translocation
-- tolerance to stress related diseases
.
Observations and proposed research on stay-green
• Stay-green is frequently found in japonica types, both temperate and tropical and contributes substantially to their historically good yielding potential despite their relatively poor culms and overall plant type. Stay-green in indica backgrounds is uncommon.
• There are many stay-green materials with poor yielding capacity and the trait must be combined with excellent plant type. Additionally, average size panicles in a stay-green background will not confer maximum yield potential. Therefore, large panicles are required to store the increased production of carbohydrates resulting from stay-green foliage combined with superior plant type.
• Selection for the stay-green trait combined with large, erect flag leaves is a valid and potentially valuable breeding objective for increased yield potential.
• It is not possible to estimate at present the potential genetic advance that might accrue from this strategy, and it is hoped that genetic gain will be at least equal that provided by heterosis.
• Basic studies on the inheritance of stay-green, its physiology and its relation to yield potential and other economic traits, to increase the efficiency in breeding.
• Selection of parents and elite lines should be rated for leaf nitrogen at maturity, chlorophyll content, and photosynthetic rate.
Development of heterogeneous population• The use of intensive monoculture in the agricultural ecosystem
Heterogeneous crops and cropping systems in subsistence developed to maximize yield potential.
• The use of planned heterogeneity in modern crop varieties was first implemented by Suneson (1968), by releasing ‘Harland’ barley variety in USA.
• Jenson(1952) proposed the use of multiline varieties. Norman Borlaug who has been instrumental in developing a comprehensive programme for producing multiline varieties of wheat
no consistent relationship a strong positive relationship a strong negative relationship • A homogeneous composite variety constituted by mixing phenotypically
similar but genotypically different related lines helps to maintain substantial amount of genetic diversity give longer varietal life with higher yield greater stability of production through residual heterozygosity positive intergenotypic interaction between the component lines • IR 8 is believed to be its limited heterogeneity at the time of its release.• The cultivar “Gamenya” which has enjoyed great popularity among farmers
for a long time in many areas in Australia,
Heterogeneous populations in rice
Major constraints• Lowland rice is the major crop of the coastal region.
Photosensitive varieties of maturity duration from 145 to 165 days with strong seed dormancy and plant height of 100 to more than 120 cm are grown in lowlands.
• Lack of suitable rice varieties with high yield, tolerance to submergence and stagnant flooding and resistance to stem borer and bacterial leaf blight, are the major constraint to high productivity in these ecologically handicapped semi deepwater and deepwater lands of the eastern India
• The lowland direct-seeded crop often suffers
-- poor seedling establishment due to weed competition,
-- early drought, or occasional submergence;
-- suppressed tillering due to prolonged water stagnation;
-- premature lodging and reduced light intensity;
-- flash-flood submergence and postflood drought.
Varietal Improvements for Low lands• In 1969, Pankaj (a sister selection of IR5) along with Jagannath and Mahsuri
were being increasingly used in rice breeding work for rain fed shallow and semi-deepwater lowlands.
• One significant achievement in lowland breeding was release of the short, photosensitive, late-maturing variety Savitri (CR 1009)
• Both at CRRI and OUAT, the lowland rice breeding program was intensified in the late 1970s with major objectives such as
-- short to intermediate plant height (90–100 cm), photosensitivity
-- with maturity duration of 145 to 155 days, panicle weight type,
-- tolerance of flood submergence for shallow-water areas;
-- intermediate to tall plant height (110–130 cm), photosensitivity
-- with maturity duration of 150–165 days, panicle weight type,
-- adaptability to both submergence and stagnant flooding
-- tolerance of drought and anaerobic germination for semi-deepwater• In both ecosystems, resistance to stem borer, leaf folder, brown plant
hopper, bacterial leaf blight, sheath blight, and sheath rot was an important breeding objective.
Although efforts towards this goal began in the 1980s (Mohanty and Khush 1985; Mohanty and Chaudhary 1986; Haque et al. 1989),
it was not until the mid-1990s that submergence tolerance from the FR13A-derived breeding line IR49830-7-1-2-2 was successfully introduced into productive short to intermediate stature lines
Fifty-day-old plants of these breeding populations showed prolonged submergence tolerance under greenhouse and field conditions.
Early breeding of submergence tolerant rice
Until the mid-1990s, the genetic control of submergence tolerance remained ambiguous.
Several studies suggested that it was a typical quantitative trait
Molecular mapping allowed the identification of the major QTL SUBMERGENCE 1 (SUB1) on chromosome 9, contributing up to 70% of phenotypic variation in tolerance
Other minor QTLs that accounted for less than 30% of the phenotypic variation were also identified
Mapping and molecular characterization of SUB1
The identification of the SUB1 QTL its transfer by marker-assisted backcrossing (MABC) into the farmer preferred varieties;
Using MABC, a small genomic region containing SUB1A has been introgressed into modern high-yielding varieties, such as Swarna, Samba Mahsuri, IR64, Thadokkam 1 (TDK1), Ciherang, CR1009, BR11, PSBRc 18
Exhibit greater tolerance to complete submergence as compared with their original parents
Comparative analysis of the three Sub1 varieties and their original parents revealed that introgression of SUB1 does not negatively affect agronomical performance including yield and grain quality under regular growth conditions.
Sub1 rice minimizes the reduction of these reproductive traits by a submergence event and produces three- to six fold more grain weight than the non-Sub1 varieties in Farmers’ Fields
Breeding of Sub1 mega-varieties
In contrast to Sub1 rice, deepwater rice escapes stagnant partial flooding by promoting elongation of internodes
Because the deepwater rice genes SK1/SK2 and the submergence tolerance gene SUB1A regulate ethylene-mediated GA responsiveness in an opposing manner, it seems unlikely that they can be combined to generate genotypes resilient of both stagnant flooding and submergence.
Targets that may aid in this objective include the generation of rice genotypes that combine submergence tolerance with tolerance of other abiotic and biotic stresses and grain quality attributes that match local consumers’ preferences.
The successful combination of submergence tolerance with other traits is likely to involve recognition of landraces with trait attributes that are unraveled at the genetic and molecular levels before their return to the farmer’s field in improved varieties
IR49830Swarna-Sub1
BR11-Sub1 FR13ATDK-Sub1
Samba Mahsuri-Sub1FR13A IR64-Sub1
Swarna-Sub1 Ciherang-Sub1
IRRI 119(PSB Rc68)
IR 10F365(IR 87436-BTN-145-2-1)
IRRI 154(NSIC Rc222)
IR 09F291 IR 09F211IR 09F504
S.M.-Sub1FR13A IR64-Sub1 CR1009-Sub1
IR 49830 IR 09F504Swarna-Sub1
Vegetative vigor: Vegetative vigor: to compete with weeds in both submergence and deepwater areas.
High tillering ability: some tillers may serve as energy tanks for survival
Erect leaves, Longer, wide and thick leaves : efficient utilization of light for better carbon assimilation
Inter mediate height and lodging resistance:
Length and weight of panicles: better yield but with a balance of culm strength
High fertility: for better yield and less risks in unfavorable conditions
Maturity: reducing loss during harvest and pre/post harvest et environment.
Photoperiod sensitivity and tolerance to low light intensityGrain dormancy: advantageous when water lodging or high humidity prevail just before harvesting
Tolerance to major pests and diseases: depends on prevailing pests and diseases in target sites
Target traits for breeding
CONVERGENT BREEDING METHOD
Evaluation of elite lines under stagnant water
Evaluation of elite lines in stagnant water
Giant rice
Many elite lines integrating tolerance to submergence and stagnant flooding may not similar to the Giant rice, but have intermediate plant height, moderate tillering ability, well exerted long panicles, high grain number with improved fertility, long and erect flag leaf with drooping panicles, moderately stiff straw and mid-late in maturity duration.
Majority of these entries have been used as parents in single and three way crosses
Giant rice is a temperate Japonica variety exclusively used for livestock feeding. The name of this variety is "MOKWOO". It has very stiff and sturdy stem and the flag leaf remains green till maturity. It has long panicles bearing about 250 MB grains and has very poor panicle exertion.
As it is a temperate japonica rice it should be crossed and backcrossed to an adaptable variety before its use in practical breeding programes to transfer some of its desirable traits.
Giant rice
Figu
IR 09 F 166 IR 09 F 171
IR 09 F 175 IR 10 F 190
Advice to the next generation of plant breeders
• While there are indeed many difficult challenges ahead in the 21st century, it is important to remember the importance of minor yield increases: 1% yield increase of a widely-grown variety will have a huge impact.
• Even in the advent of new promising technologies such as DNA markers, the time-tested conventional breeding and selection approaches will still account for significant improvement in increasing rice yields.
• A sound theoretical knowledge coupled will considerable hard work and long hours in the field are the secrets to breeding success, and this is likely to be the case for many years to come.
• The success and sustenance of rice breeding tells that there is no easy way to improve rice production, it demands patience, dedication, continuity and our total physical and mental commitments to field work.
My revered teachers
Life for both of us was just like DICED= Dedication, I= Integration, C= Concentration, E= Erasing ego
Dr. Das
Dr. Collard
which is a gentle reminder that life is a cycleThat what is sown must be reaped
Harvesting joy
Farmers and workers…. make India. Their poverty is India’s curse and crime. Their prosperity alone can make India a country fit to live in.
Mahatma Gandhi
Our salvation can only come through the farmer. Neither the lawyers, nor the doctors, nor the rich landlords are going to secure it.
Mahatma Gandhi
Plant Breeder never retires in life
His stories remain untold without you all
My best wishes and kind regards
