Assessment of heterotic potential and combining ability of immortal 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 immortal restorer lines [consisting of two recombinant inbred lines (RILs) and two doubled haploid lines (DHLs)] developed from an elite rice hybrid, KRH-2 by crossing them with three popular WA-CMS lines, IR58025A, CRMS32A and APMS6A through line x tester analysis. The doubled haploid line 1 (DHL-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 novel crosses between the immortal restorer lines derived from KRH-2 and the WA-CMS lines, 66.66% (eight crosses) showed significant and desirable SCA effects for the traits viz., total grain yield per plant, days to fifty percent flowering, plant height, flag leaf length, flag leaf width, number of filled grains per panicle and spikelet fertility. 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. Heterotic yield advantage of IR58025A/RIL-24 and CRMS32A/RIL-24 was 77.05% and 54.74%, respectively over KRH-2 and these can be utilized for developing commercial hybrids. 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.