Screening of Rice Genotypes for Drought-prone Rainfed Environments

This study was undertaken to investigate the responses of rice genotypes in water stress prone rainfed environments and to select drought-tolerant rice genotypes. Thirty rice genotypes were evaluated in the drought-prone rainfed high Barind tract at Godagari, Rajshahi, Bangladesh (24.27 N latitude, 88.21 E longitude, 40 masl) during two wet seasons (WS), from July to December. In both WSs, 25-day-old seedlings were transplanted on August 16 at a spacing of 25 x 15 cm, with three seedlings per hill, using a randomized block design with three replications. To comprehend the drought stress and assess the performance of the genotypes, estimates of precipitation, temperature, drought severity, ground water depth, soil moisture content, soil water potential, phenology, leaf rolling and desiccation, spikelet sterility, dendogram clustering, rooting behaviors, yield, and yield component data were estimated. Yield, yield components, leaf rolling, spikelet sterility, and root properties exhibited considerable variation (p = 0.001) among the rice cultivars. The grain yield and harvest index of the evaluated rice genotypes varied from 1.28 to 4.51 t ha-1 and 0.25 to 0.47, respectively, contingent upon the degree of drought. Across genotypes, 61% of root biomass was found in the upper 0-10 cm soil layer, with a significant decline in the subsequent layers (27%, 9%, and 3% in the 10-20, 20-30, and 30-40 cm layers, respectively). Four rice genotypes (IR74371-70-1-1, IR83377-B-B-93-3, IRRI123, and IR83381-B-B-6-1) were identified as drought-tolerant based on their overall performance under drought-stress, while BR7873-5*(NIL)-51-HR6 was selected as drought-escaping. The genotypes IR74371-70-1-1 and BR7873-5*(NIL)-51-HR6 were released as the drought-tolerant variety BRRI dhan56 and the drought-escaping variety BRRI dhan57, respectively. Consequently, the genotypic variance in our germplasm selection revealed significant potential to generate drought-tolerant varieties through breeding aimed at enhancing rainfed lowland rice.