Unraveling the genetic basis of fertility restoration in hybrid rice: insights from CMS lines and male restorer analyses

Rice (Oryza sativa L.) serves as the staple food for over half of the global population. To address the pressing need for increased rice production, hybrid rice technology leverages the concept of hybrid vigor, or heterosis, achieving a 15–20% yield advantage over traditional varieties. This study focuses on developing hybrid varieties through the cytoplasmic genetic male sterility (CGMS) mechanism. It explores the genetic inheritance of fertility restoration in two distinct CMS lines, IR58025A (WA) and RTN13A (Gambiaca), using 165 diverse male lines. The study successfully generated F1 hybrids and evaluated them for pollen and spikelet fertility, identifying NVSR 2965 and NVSR 3280 as effective restorers, with fertility rates surpassing 90%. Analysis of the F2 generations from these crosses revealed that fertility restoration is controlled by two dominant genes, Rf3 and Rf4, which interact epistatically. The cross IR58025A × NVSR 2965 exhibited a 12:3:1 segregation pattern, suggesting simple dominance with a masking effect, while RTN13A × NVSR 3280 showed a 15:1 ratio, indicating duplicate dominance. These findings enhance our understanding of the genetic mechanisms underlying fertility restoration and provide valuable insights for applying marker-assisted selection and breeding strategies to develop high-yield hybrid rice varieties.