Assessing the performance of hybrids developed using iso-cytoplasmic restorers and identification of promising combiners in rice

Iso-cytoplasmic restorers (ICRs) are valuable sources of fertility restoration for three line rice hybrids derived from wild-abortive cytosterile (WA-CMS) lines. They carry a full complement of fertility restorer (Rf) genes and sterile cytoplasm. We have test-crossed a set of 25 ICRs with four WA-CMS lines namely, IR 79156A, IR 58025A, Pusa 6A and RTN 12A following a line x tester mating design. Significant estimates of general and specific combining ability for agromorphological traits revealed the involvement of both additive and non-additive gene effects. The combining ability estimates implied that some of the restorers were good general combiners for traits such as plant height, number of tillers per plant, panicle length, spikelet fertility, grain weight and yield per plant. Four promising ICRs namely, PRR317, PRR354, PRR381 and PRR390 with high general combining ability for yield across different environments were identified based on their hybrid performance. Additionally, location-specific ICRs, namely PRR300 and PRR396 for timely sown conditions of New Delhi, PRR348 for Pusa and Karnal, and Pusa 307 for Karnal and late sown conditions of New Delhi environments were identified. The restorers identified in the current study demonstrates ICRs as potential source for restorer development and can lead to the development of heterotic