PLANT BREEDING AND GENETICS

The Plant Breeding and Genetics division undertakes research on aspects of varietal improvement and fundamental investigations in taxonomy, genetics, cytogenetics, induced mutagenesis and morphogenesis. Collection, maintenance and evaluation of germplasm was one of the activities of this division till a separate division of Genetic Resources was formed in 1983.

PRE-SEMI-DWARF ERA

Until early 1950s, varietal improvement was mainly restricted to pure-line selection. The Working Party Meetings of the International Rice Commission identified the drawbacks responsible for poor yield in local cultivars such as late maturity, poor response to fertilizers, proneness to stem collapse leading to lodging, susceptibility to prevailing insect pests (stem borers and gall midge) and diseases (blast and brown spot) and abiotic stresses caused by drought, flooding and salinity and narrow range of adaptation. Following this, the indica-japonica hybridization programmes - one sponsored by the Food and Agricultural Organization and the other by the ICAR were launched in 1952 at CRRI, Cuttack for the benefit of the countries in tropical Asia and another in 1965 for different rice-growing states in India, respectively. This programme, however, brought limited success. From the crossed seeds sent from CRRI to different countries and Institutions within India, Regional Research Station (Tamil Nadu Rice Research Institute), Tamil Nadu (Madras State) identified a promising culture and released it as ADT 27. In addition, Mahsuri and Malinja in Malaysia and Circna in Australia identified from this programme were released for cultivation.

Recognizing stem collapse leading to lodging in local cultivars as one of the major limitations in restricting their yielding ability, the institute took up breeding for non-lodging types using the stiff-strawed javanica in early sixties. This resulted in the development of CR 1014, a super fine grain variety capable of yielding 3 to 4 t/ha under stagnant water conditions in intermediate depth (0-50 cm) from a cross between T 90 and Urang Urangan in early sixties. This variety became popular with the farmers in the states of Orissa, Andhra Pradesh and West Bengal and is being preferred by them even to-day. However, this variety was released formally only in 1988.

SEMI-DWARF ERA

Varietal improvement

Varietal improvement programme of the Institute took a new turn with the introduction of high-yielding, semi-dwarf, photo-insensitive varieties, Taichung (Native) 1 in 1965 and IR 8 in 1966 from the Philippines to develop short-statured photo-insensitive varieties capable of responding to high levels of nitrogenous fertilizers thereby possessing remarkably high yield potential. The changed scenario in rice cultivation characterized by new threats posed by severe incidence of diseases and insect pests hitherto considered minor in importance such as bacterial blight and tungro virus complex, leaf and planthoppers and leaffolders and resistance from consumers to accept the coarse grain types necessitated incorporation of resistance to these insect pests and diseases and consumer-preferred medium-slender and long-slender grains in the newly bred varieties.

Varieties for irrigated lands

At this period of time, the concentration was to develop varieties suitable for homogenous, relatively risk-free irrigated ecosystem. The following 21 varieties developed by CRRI were released for this ecosystem : Padma, Ratna, Krishna, Vijaya, Vani, Saket 4, Sarasa, Supriya, Jayanthi, Kalinga I, Kalinga II, Kiran, Pallavi, Shakti, Indira, Udaya, Kshira, Ramakrishna, Shaktiman, CR 138-928, and IET 7280.

Till recently, varieties suitable for the ecologically handicapped, rainfed ecosystems, very diverse in nature and associated with high degree of risk for rice cultivation, predominant in eastern India were not available. As a result of increased attention in recent years to develop varieties suitable for each of these harsh environments, 12 varieties for rainfed uplands and 15 for rainfed lowlands, developed at CRRI (listed below) were released for cultivation.

Besides these released varieties, a number of promising cultures (listed below) suitable for different ecosystems with different durations have been developed.

Situation Varieties Duration Yield

(days) poten- tial

(t/ha)

Rainfed upland CR 544-1-1 65-80 3.0-4.5

CR 544-1-3-4

RR 139-1 95-100 3.0-4.0

CR 628-2 90-120 4.0-5.0

CR 666-100

CR 142-3-8

Irrigated land CR 333-6-1 120-140 4.0-6.0

CR 308-408

CR 603-1-14-1

CRM 40

Rainfed lowland CR 95-26-1 Flowering 4.0

Shallow CR 210-1006 Oct 3-4th wk

(0-30) CR 210-1010

Intermediate

(0-50 cm) CR 629-243 Flowering 4.0

CR 629-256 Oct 3rd-

Nov 1st wk

Coastal saline CR 644 Flowering

areas (up to 50 cm) Oct 3-4th wk 4.0-5.0

Varieties like Ratna and Saket 4 (sister line of Ratna) in the early group and CR 1014 in the late group are still extremely popular in many parts of the country for the past 25 and 30 years, respectively. Ratna and Saket 4 are popular in rice-wheat cropping system in northern states and as summer crop in eastern states, while CR 1014 is popular for its good grain quality and suitability for waterlogged areas.

Basic studies

Origin of cultivated rice

Concerted effort was made to trace the origin of cultivated rice from its wild progenitors. It is generally agreed that the cultivated rice Oryza sativa L. originated in Asia and O. glaberrima Steud originated in Africa. The widely distributed, long-ligulated, long-anthered perennial species designated as O. perennis Moench was established as the ancestral species. The collection of species from various countries showed a wide range of variation, and it is possible that the cultivated rices might have originated by hybridization between such taxa followed by selection. It was also inferred that subspecies formation in O. sativa was interconnected with geographical differentiation of the ancestral species. The role of introgressive hybridization in the origin of cultivated rices was highlighted through critical studies carried out with collection from the Jeypore tract which is considered to be one of the secondary centres of origin of cultivated rices.

Genetics

Exhaustive studies were conducted on inheritance patterns of morphological traits such as plant stature, leaf characters, grain types and pigmentation in different plant parts and information on the number of genes governing these traits and their position in linkage groups has been generated. In addition, inheritance of quantitative traits related to yield and yield attributing characters and their association was examined under different situations which facilitate in enhancing the selection efficiency.

Inheritance patterns and identification of genes for major diseases like blast and bacterial leaf blight and insects such as stem borer, gall midge and planthoppers have been investigated which resulted in the identification of suitable donors. These donors have been utilized in breeding programmes.

Induced mutagenesis

Cultivars such as T 141, Ptb 10, Saturn and Tainan 3 and the wild rices (spontaneas) were subjected to treatments with chemical mutagens. Subsequently, a few more tall indicas were also used. The result indicated that mutagens, EMS, NMU and DES were potent enough to induce a wide range of morphological and physiological variations. The highest frequency of variants were the dwarfs and short culm mutants. A large number of morphological mutants isolated were studied for their genetics and breeding behaviour. Many of the short culm mutants were characterized by stiff straw and longer panicle and high tiller numbers, and consequently were proved to have high yield potential. The dwarfing genes in these short culm mutants were different from those found in Taichung Native 1, thereby offering an alternate source of dwarfing gene in hybridization programme. Several new mutant loci were studied and genetics of some, such as gaping spikelets, zebra, striping, beaked palea, palealess and nude panicle have been reported. Experience with wild rices indicated that chemical mutagens can successfully be utilized in selective elimination of undesirable characters like awning, shattering and red pericarp in wild rices thereby making them mutable for using the wild genotypes in hybridization programme.

Induced mutation as a tool for varietal improvement undertaken in the institute, yielded four varieties, Sattari for rainfed uplands, Indira for irigated lands, Padmini for shallow water regime with superfine grain quality and Lunisree with long slender grain for coastal saline areas where salinity and waterlogging coexist. Besides, a productive mutant CRM 8 with aroma and cooking quality similar to Basmati 370 and CRM 30 was evolved. Employing chemical mutagens, it was also possible to remove the undesirable characters in wild rices prior to their use in hybridization programme.

Development of blast tolerant mutants from IR 50

Three blast tolerant lines, CRM 49, CRM 51 and CRM 53 were developed from IR 50, a blast susceptible variety utilizing mutation breeding (chemical mutagenesis) technique. Of the three lines, CRM 49 and CRM 51 were isolated from sodium azide-treated populations, while CRM 53 was developed from ethyl methane sulfonate (EMS)-treated populations. The three cultures possess semi-dwarf stature, long slender grains and an yield potential of 5 t/ha. These cultures were evaluated for their blast tolerance at Hazaribag (Bihar), Hyderabad and Maruteru (Andhra Pradesh), Jagadalpur (Madhya Pradesh) and at Cuttack (Orissa). These cultures have performed well in yield evaluation trials conducted in Assam and has been proposed for release in that state.

Aneuploid

Two complete sets of simple primary trisomics (2n + 1 = 25) were established in indica varieties, Sona and Ratnagiri. Employing the primary trisomics, a number of genes have been assigned to specific chromosomes and linkage groups.

Wide hybridization

Employing embryo rescue technique, interspecific hybrids were obtained using wild species, O. longistaminata, O. punctata, O. eichingeri, O. officinalis, O. minuta, O. malamphuzhaensis, O. australiensis, O. alta and O. latifolia.

Cytological behaviour of the interspecific hybrids, O. sativa (AA) / O. latifolia (CCDD) and O. sativa / O. minuta (BBCC) revealed that 36 univalents with occasional 1-3 bivalents were formed indicating genetic incompatibility between the species.

Anatomy amd embryology

Detailed anatomical studies of the genus Oryza and comparative anatomical sutdy of high yielding varieties versus traditional rice varieties revealed the development of better mechanical and conductive tissues in semi-dwarf high yielding types.

Inter-relationship of Oryza species was established based on size and arrangement of cuticular papilae and marginal hairs of the leaf blade. Two genes, Esb-a, Esb-b governing anatomical characters with complimentary reaction for the extra-sclerenchymatous band in flood tolerant variety FR 13-A and Fc for suscoid cells in the leaf blade in a cold tolerant variety Ch 1039 with simple inheritance pattern were identified.

Use of alternate sources of dwarfism

To avoid narrowing of genetic variability resulting in enhanced genetic vulnerability, search for alternate dwarfing gene for utilization was undertaken. Pankaj, sister line of IR 5, and Waikyaku, an indica from main land China were identified as alternate dwarf gene. These have been used for developing semi-tall high yielding varieties such as Savitri (Ponmani), Gayatri, Dharitri (Pankaj x Jagannath crosses) for shallow water ecosystem and Annada (MTU 15 x Waikyaku cross) for uplands.

A local land race named KO with semi-tall plant stature, collected from Koraput district of Orissa was found to have a dwarfing gene non-allelic to De-geo-Woo-gen.

Strategic reserch

Hybrid rice

Work on hybrid rice was initiated at CRRI since 1984 with an objective of developing appropriate parental lines viz., cytoplasmic genetic male sterile lines (CMS), their maintainers and restorers for irrigated as well as shallow submergence condition.

Twenty-five stable CMS limes (from WA, Kalinga I and O. perennis sources) and a number of maintainers and effective restorers for the above CMS lines have been developed. Among these, most promising ones are: Sarasa A, Pusa 33A (WA), Annada A (WA), Kiran A (WA), Deepa A (WA), Monipur A (WA), Moti A (WA), Krishna A(O. perennis), Krishna A (Kalinga I) and Mirai (Kalinga I).

Eleven high heterotic hybrids were developed for shallow submergence condition which have an yield advantage of 1 t/ha over the checks, Swarna and Vajram.

Shuttle breeding

Shuttle breeding approach for development of suitable varieties for rainfed lowlands of eastern India (Rainfed Lowland Consortium) was undertaken. This has resulted in the identification of three specific photosensitive groups, flowering during first week of October, third week of October and first week of November suitable for different regions of Eastern India.

While FR 13-A was found to have high degree of submergence tolerance at early vegetative stage, local cultivars like Khajara and Dhusara from Orissa were found to have submergence tolerance both at early and late vegetative stages. These are better donors for developing varieties for flood-prone lowlands where submergence occurs more than once due to cycles of floods.

Rice biotechnology

A programme on biotechnology was initiated for using recombinant DNA technique for increasing the efficiency of breeding programme, compressing the breeding cycle and transfer of novel genes to the high yielding varieties. Wide hybridization with special reference to diversification of cytoplasm and use of alien genes for biotic and abiotic resistance is also being attempted. Tissue culture techniques such as embryo rescue, anther culture and ovule culture have been standardized to achieve maximum efficiency in wide cross programme.

A large number (>1500) of recombinants from inter-varietal, inter-specific and heterotic hybrid combinations were developed utilizing improved anther culture techniques. The significant improvements to the protocols include the use of: (i) potato-II medium in anther culture of indica rices, (ii) optimal phytoharomone combination in both callus induction (auxin : cytokinin in 4:1 ratio) and regeneration (NAA : kinetin : BAP in 1:1:4 ratio, and (iii) use of supplements like coconut water, casein hydrolysate and sliver nitrate.

A large number of somaclones have been developed from several indica genotypes of: (i) different duration groups (early, medium and late), (ii) salt tolerant genotypes, and (iii) aromatic rices. Wide variation was observed for all the agronomic characters and higher levels of tolerance (score of 3-4) was observed for tolerance to sheath blight in the somaclones of Annada.

Seed production

CRRI is one of the breeder seed production centres for rice under National Seed Project since 1976. The national requirement of rice breeder seed production placed before the institute up till now was 63.28 tones. Against this demand, this centre had produced and distributed 75.21 tones of breeder seeds of 21 rice varieties so far to various seed agencies namely the National Seed Corporation, State Farm Corporation, State Seed Corporations, State Agriculture Departmental Farms,Agricultural Universities and private agencies on the basis of allotments made by Deputy Agriculture Commissioner (Seed), Government of India. The Institute also produced and distributed 4.95 tones of nucleus seeds of 62 varieties for production of breeder seeds.