ASSESSMENT OF COMBINING ABILITY AND HETEROSIS IN RICE (ORYZA SATIVA L.) UNDER IRRIGATED ECOSYSTEMK. Parimala, Ch. Surender Raju and S. Sudheer KumarAbstract The study was carried out to estimate the combining ability and heterosis for grain yield and its components in rice hybrids. Crosses were effected in line x tester design by using four CMS lines and five restorers as testers and produced twenty hybrids. Analysis of variance for combining ability revealed that variances of SCA were higher than the GCA variances for the traits studied except for 1000 grain weight and spikelet fertility (%) which indicated the predominance of non-additive gene action in the inheritance of traits. The line IR-68897A and the testers IR-79597-56-1-2-1 and WGL-347 were found to be promising general combiners for grain yield per plant and some of its attributes. Estimation of specific combining ability effects revealed that the crosses APMS-6A x IR-79597-56-1-2-1 and IR-79156A x IR-71218-93-1-4-3 had favourable genes for grain yield per plant. The cross IR-68897A x WGL-347 exhibited superior heterosis for number of productive tillers per plant, panicle length, number of filled grains per panicle, spikelet fertility and grain yield per plant over standard check. The cross combinations such as IR-79156A x IR-71218-93-1-4-3, IR-79156A x WGL-347, IR-68897A x IR-79597-56-1-2-1 and APMS-6A x IR-79597-56-1-2-1 showed positive significant heterosis for grain yield. Based on sca effect and standard heterosis the crosses IR-79156A x IR-71218-93-1- 4-3 and APMS-6A x IR-79597-56-1-2-1 were found to be promising for grain yield and its components. Hence these cross combinations could be utilized for exploitation of heterosis in rice. |