Drought and limited availability of water serve as the serious limitation for rice production in rainfed ecosystems. Among the major rainfed rice-cultivating areas, states of eastern India occupy one of the largest drought-prone ecologies in the world. Cultivating drought tolerant rice varieties can serve as the most coherent approach to ensure food security in these areas. International Rice Research Institute (IRRI), along with its national collaborators, has developed drought tolerant rice varieties possessing high yield along with desirable grain quality. One such conventionally bred line, IR74371-70-1-1, has been released with different names in the different countries: in India as Sahbhagi Dhan, in Nepal as Sukha Dhan 3, and in Bangladesh as BRRI Dhan 56. This indicates the suitability of this line to show better performance across the wide range of environments. Sahbhagi Dhan is a short duration variety that has genetic drought tolerance and is more efficient at extracting available moisture from the soil. During drought years, farmers cultivating Sahbhagi Dhan obtained the yield advantage of 0.8 to 1.6 t ha−1 over currently grown long duration as well as traditional varieties. In 2012, when the paddy crop was hit by drought, Sahbhagi Dhan revealed the yield advantage of more than a t ha−1, which reduced to 0.78 and 0.56 t ha−1 during non-drought years of 2013 and 2014, respectively. Data taken from head to head trials during 2017 showed that Sahbhagi Dhan exhibited better performance over the existing rice varieties grown by farmers even under non-drought conditions. The important feature of Sahbhagi Dhan is its evident impact under drought and no yield penalty under favorable conditions over the counterfactual varieties of the same duration. Along with better yield under drought, the important advantage of Sahbhagi Dhan is the short maturity duration of this variety. This allows the farmers to advance the succeeding crop and creates an opportunity for accommodating an additional crop under favorable rainfed ecology, thereby enhancing the cropping intensity. Since the majority of the farmers living in drought prone ecologies are socio-economically under privileged, Sahbhagi Dhan, along with other drought tolerant varieties, can serve as one of the most viable and deliverable technologies for eradicating poverty from these ecologies dependent on rainfed rice.

Flash floods leading to complete submergence of rice plants for 10-15 days is one of the major constraints for rice production, mainly in rainfed lowland areas. In India, 30% of the rice growing area (12-14 M ha) is prone to flash flooding with average productivity of only 0.5-0.8 t ha −1 .

Abstract:The experiment was conducted to estimate combining ability and heterosis for yield, yield attributing traits and few grain quality parameters in rice. The crosses were made among three CMS lines i.e., IR58025A, Pusa6A and IR68897A and seven pollen parents viz., Sarjoo-52, Jaya, Sasyashree, Swetha, HUR 5-2, PR-106 and BPT 5204. Twenty one hybrids were generated in line x tester design. The superior hybrids were identified on the basis of combining ability effect and heterosis. Cross combination IR68897A/Jaya and IR68897A/BPT 5204 exhibited good x good parental GCA effects suggesting that there is additive x additive type of gene action. The cross IR68897A/Jaya showed highest positive SCA effect. The higher magnitude of heterosis for all the yield and quality traits were not expressed in a single hybrid combination. It varied from cross to cross due to diverse genetic background of their parents. The two crosses IR68897A/Jaya and IR68897A/BPT 5204 were found to be heterotic for yield and yield traits as well as the grain quality characteristcs.

Flooding is one of the major constraints for rice production in rainfed lowlands, especially in years and areas of high rainfall. Incorporating the Sub1 (Submergence1) gene into high yielding popular varieties has proven to be the most feasible approach to sustain rice production in submergence-prone areas. Introgression of this QTL into popular varieties has resulted in considerable improvement in yield after flooding. However, its impact under non-flooded conditions or years have not been thoroughly evaluated which is important for the farmers to accept and adopt any new version of their popular varieties. The present study was carried out to evaluate the effect of Sub1 on grain yield of rice in different genetic backgrounds, under non-submergence conditions, over years and locations. The study was carried out using head to head trials in farmer’s fields, which enable the farmers to more accurately compare the performance of Sub1 varieties with their recurrent parents under own management. The data generated from different head to head trials revealed that the grain yield of Sub1 varieties was either statistically similar or higher than their non-Sub1 counterparts under non-submergence conditions. Thus, Sub1 rice varieties show no instance of yield penalty of the introgressed gene.

Twenty F1 hybrids from three CMS lines and eight pollen parents were evaluated to study the heterosis for various yield and quality traits in rice (Oryza sativa L.). The findings suggested that the magnitude of heterosis differed from character to character and cross to cross. Majority of the hybrids recorded desirable heterosis for grain yield. Among the rice hybrids exhibiting high heterosis for grain yield, IR-68897A x Pusa Sugandh-3, IR-58025A x HUR-JM-59221 and IR-58025A x Pusa Sugandh-5 were top performers. The hybrid, IR-68897A x Pusa Sugandh-3 recorded highest yield per plant, and was among the best three performers for traits, days to 50% flowering, days to maturity and number of effective tillers per plant. Thus, IR-68897A x Pusa Sugandh-3 may be considered as the best heterotic combination for yield and yield traits. Among the three high yielding hybrids, IR-58025A x Pusa Sugandh-5 was found to be relatively better performing for majority of the quality traits. Thus, IR-58025A x Pusa Sugandh-5 may be considered as the best cross combination if both yield and quality traits are taken into consideration.