Male Sterility System for Hybrid Rice Breeding and Seed Production

Abstract

Heterosis has been exploited for production of commercial hybrid seed, and rice is the most significant model crop plant where seed production has occurred through multiple types of male sterile lines. Rice being a staple crop throughout the world, cultivation of rice hybrid varieties is escalating. Isolation and identification of male sterility-related genes and proteins will help in acquiring information about the reasons and mechanism behind occurrence of male sterility and key players involved in microspore abortion. Recently, through the experimental studies involving genetics or proteomics, genes and proteins associated with cytoplasmic male sterility (CMS), photoperiod-sensitive male sterility (PSMS), self-incompatibility and microspore deterioration have been identified. In plants, mitochondrial genes along with nuclear genes or nuclear genes alone can induce male sterility, and consequential conditions known as CMS and genetic male sterility (GMS) occur, respectively. CMS and GMS assist in hybrid seed production and as a result permit breeders to exploit yield gains connected with hybrid vigour. The communication between mitochondrial and nuclear genes regulates male specificity, occurrence and restoration of fertility under CMS system. Genes of nuclear restorer of fertility (Rf) helps in suppressing CMS. Thus, CMS/Rf systems present a typical model for evaluating mitochondria-nuclear genes interactions in plants. CMS/Rf scheme proved to be cost-effective and efficient tools for the production of hybrid seeds. However, environment-sensitive GMS (EGMS) mutants engage epigenetic control through noncoding RNAs and are capable of regressing fertility beneath diverse growth conditions, making them valuable breeding materials in the hybrid seed industry. In this chapter, our focus is on the phenomenon of male sterility along with recent progress in studies of the three major CMS/Rf systems in rice.