Assessment of heterotic potential and combining ability of novel iso-cytoplasmic restorer lines derived from an elite rice hybrid, KRH-2, for the development of superior rice hybrids

Present investigation was carried out to assess the heterotic potential and combining ability of novel iso-cytoplasmic restorer lines [consisting of two recombinant inbred lines (RILs) and two doubled haploid lines] developed from an elite rice hybrid, KRH-2 by crossing them with three popular CMS lines, IR58025A, CRMS32A and APMS6A through line x tester analysis. The doubled haploid line 1 was observed to be a good general combiner for total grain yield per plant (YLD) and other yield component traits and among the CMS lines, IR58025A was observed to be the best combiner as it showed positive significant values for the traits viz., total grain yield per plant, panicle length and spikelet fertility. Higher preponderance of the variance associated with specific combining ability (SCA) as compared to general combining ability (GCA) variance was observed for most of the traits indicated the predominant role of non-additive gene action in the expression of the traits. Out of twelve crosses between the novel iso-cytoplasmic restorers and the CMS lines, 66.6% (eight crosses) showed significant and desirable SCA effects for seven agro-morphological traits. Two crosses IR58025A/RIL-24 and CRMS32A/RIL-24 were observed to be the most promising cross combinations showing standard heterosis of > 50% for YLD trait (as compared with KRH-2) with higher prevalence of GCA and SCA, respectively. The present study also indicates the potentiality of RILs in providing useful parental lines for developing heterotic hybrids which are hard to get from outside sources in the new intellectual property regime.