The Effect of Environment on Combining Ability and Heterosis in Hybrid Rice

Study was undertaken to estimate the combining ability and heterosis for yield and yield contributing characters over environments. Environment, Crosses, GCA and SCA, and their various interactions with environment were significant suggesting that the hybrids did not have the same relative performances among environments. An evaluation of combining ability across the environment indicated that both general and specific combining ability effects are important but predominance of non-additive genetic variance indicated the presence of heterozygosity in the population. As such this type of genetic variance is non-fixable hence; heterosis breeding is effective for crop improvement. Line IR-79156A, IR-68897 and tester R-51 during both the seasons and testers R-47, R-48, R-49, R-52, IR-64 and IR-10198 during kharif and line R-42, IR-66, R-43, R-46, R-56 and IR-13419 during rabi were the promising general combiners for grain yield per plant and other traits. These parents used as testers and lines in the cross combinations would be able to realize good hybrids. Considering high physical grain quality parameters as well as per se performance, sca effects (High x high or high x low gca effects of each cross) and standard heterosis, hybrids viz., IR-80555A x R-51 and IR-79156A x R-44 during kharif and IR-79156A x R-43, IR-68897A x R-51 and IR-68897A x R-52 during rabi have been identified as promising rice hybrids