Molecular regulation and breeding prospects of second-generation hybrid rice

Second-generation hybrid rice breeding, using two-line systems also called Environment-sensitive Genic Male Sterility (EGMS), represents a significant advancement in hybrid rice. By eliminating the need for a maintainer line, this method simplifies hybrid seed production and reduces associated costs, thereby offering promising solutions for yield improvement and food security. EGMS encompasses various systems, including Temperature-sensitive (TGMS), Reverse TGMS (RTGMS), Photoperiod-sensitive (PGMS), Photoperiod and Temperature-sensitive (PTGMS) and Humidity-sensitive (HGMS), each of which is regulated by specific environmental cues. This review highlights the evolution, genes associated with and classification of EGMS systems, as well as their roles in hybrid rice production. The different methods of production and selection of location for the EGMS lines are also discussed. Advances in biotechnology, such as CRISPR/Cas9 gene editing, mutation breeding and speed breeding, have significantly improved the stability, adaptability and faster development of EGMS lines. Furthermore, gene pyramiding and marker-assisted selection (MAS) enhance trait integration, facilitating the creation of hybrids with superior agronomic traits, disease resistance and environmental stress tolerance. India’s contributions in two-line breeding, especially the development of several TGMS lines suitable for regional climatic conditions, demonstrate the potential of TGMS in hybrid rice technology. This will help meet the demands of a growing population while enhancing climate resilience.