Combining ability and molecular marker approach for developing early maturing high yielding hybrid rice

Hybrid rice breeding is an important strategy for enhancing grain yield. The development of high yielding and early maturing hybrid rice is vital in order to enhance rice production and ensure global food security. Combining ability analysis is one of the most effective tools used to understand gene action effects and help to identify promising parental lines for crosses necessary to breed high yielding and early maturing hybrid rice. In this study, fourteen rice genotypes were crossed in a line × tester mating design to generate breeding populations, evaluate general and specific combining ability effects, heterosis, and the gene action governing eight yield and yield-related traits. In addition, the research aimed to assess parental genetic distance (GD) using 25 simple sequence repeat markers, and to determine its association with hybrid (F1) performance, heterosis, and specific combining ability (SCA) effects. Both additive and non-additive gene actions were involved in regulating the inheritance of all the studied traits; however, non-additive gene action was predominant for most traits. The parental genotypes SH-3A, SH-4A, BUR and SH-802R were identified as excellent general combiners for developing high-yielding and early maturing genotypes. Moreover, the hybrids SHD-1 (SH-3A × BUR), SHD-2 (SH-3A × BDU-1R), SHD-4 (SH-3A × SH-802 R), SHD-16 (SH-3A × SHRX- 34R), SHD-33 (SH-4A × BUR) and SHD-36 (SH-4A × SH-802 R) were the most favorable combinations for improving grain yield with earlier maturity. The parental genetic distance (GD) varied from 0.36 to 0.72, with an average of 0.55. Positive and significant correlation was found between GD and heterosis for days to fifty percent flowering and days to maturity (DTM). For all the other studied traits, it showed lower association with hybrid performance, heterosis, and combining ability effects. However, SCA revealed a significant positive correlation with both hybrid performance and heterosis. This indicates that SCA, alongside heterosis, serves as a primary determinant of F1 performance across the evaluated traits. This comprehensive study highlights the importance of both GCA and SCA in early maturing, high yielding hybrid rice breeding. Furthermore, integrating molecular markers could enhance heterosis prediction for certain traits through GD.