Unveiling a half-century mystery of molecular bases for three-line hybrid rice breeding system.

Rice (Oryza sativa L.) is a staple crop for half the world's population and an important contributor to world food security. The discovery and application of cytoplasmic male sterility (CMS) and fertility restoration (Rf) genetic materials have allowed the production of three-line hybrid rice (Kim and Zhang, 2018), successfully harnessing heterosis in crops. Three major CMS and/or Rf systems are commonly used to produce three-line hybrid rice: Wild Abortive (CMS-WA), BoroⅡ (CMS-BT), and Honglian (CMS-HL). Among these, the CMS-WA system is the mostly widely employed (Sattari et al., 2007; Chen and Liu, 2014; Huang et al., 2014). Several Rf genes from different CMS systems have been cloned in rice, including Rf4 for CMS-WA (Tang et al., 2014), Rf1a and Rf1b for CMS-BT (Wang et al., 2006), Rf5 (Rf1a) and Rf6 for CMS-HL (Hu et al., 2012; Huang et al., 2015), and Rf19 for CMS-FA (Jiang et al., 2022). This article is protected by copyright. All rights reserved.