Exploration of heterosis for yield and morpho physiological traits in hybrid rice (Oryza sativa L.): A comparative study under flooded and aerobic conditions

The global water crisis threatens the sustainability of irrigated rice production in all the rice producing countries. Development of rice hybrids with high yield potential for aerobic conditions would be one of the exciting research to overcome the existing water crisis. Present investigation was carried out to identify the best combining parents and hybrids suitable for aerobic cultivation based on their physiological and yield contributing traits. One hundred and twenty hybrids along with four lines, 30 testers and two check hybrids viz., ADTRH 1 and CORH 2, were raised in randomized block design in three replications under aerobic and flooded conditions. Data were recorded at vegetative (55-60 days), panicle initiation (75-80 days), flowering and maturity stage for physiological and quantitative traits for all the parents and hybrids included in the study. The hybrid COMS 14A x IR55838-B2-2-3-2-3 and COMS 14A x IR 36 showed superiority for number of productive tillers, panicle length, number of filled grains, spikelet fertility, total dry matter production and harvest index; the hybrid IR 68888 A x IR 72875-94-3-3-2 for number of productive tillers, spikelet fertility, relative water content, root dry weight, harvest index, root shoot ratio and IR 68897 A x IR 36 for number of productive tillers, panicle length, spikelet fertility, total dry matter production and harvest index. These four hybrids can be best utilized commercially for both flooded and water limited conditions. The parental lines involved in the above hybrids also had high per se performance for grain yield under aerobic condition. In general, higher yield was obtained in most of the hybrids under flooded condition. A few hybrids had equal performance under both conditions. The female parents IR 68888A and COMS 14A and the male parents IR55838-B2-2-3-2-3, IR 36, WGL 14 and WGL 32100 best suited for irrigated conditions also had good performance for most of the yield contributing traits and physiological parameters under aerobic condition. The hybrids developed from these parental lines were found superior for most of the yield and physiological traits under aerobic condition. Therefore these parental lines could serve as basic materials for developing high yielding hybrids suitable for water limited conditions.