Identification of stable restorer lines developed through inter-sub-specific hybridization in rice (Oryza sativa) using multi-trait stability index

Inter-sub-specific hybridization between indica and tropical japonica rice germplasm is the most efficient approach for broadening the genetic base of hybrid rice parental lines and enhancing the heterotic potential of hybrids in a tropical country like India. In the present study, 106 indica/tropical-japonica derived lines were developed through inter-sub-specific hybridization and screened using functional markers with respect to the major fertility restorer genes, Rf3 and Rf4, and the wide compatibility gene, S5n. The fertility restoration ability of newly developed restorers was validated through test cross nursery performance. The functional markers were observed to accurately predict the trait of fertility restoration. From the present study, the decreasing order of efficiency of different gene combinations on fertility restoration ability are as follows: Rf4/S5n > Rf4/Rf3/S5n > Rf4 > Rf4/Rf3 > Rf3/S5n > Rf3. Based on multi-trait stability index (MTSI) analysis, the four newly identified restorers, that is, RP6388-90, RP6382-49, RP6375-81 and RP6368-38, were selected as the top best performing genotypes with high stability for multiple traits, and these genotypes will be useful for the development of superior rice hybrids in India.