Fine Mapping of Five Grain Size QTLs Which Affect Grain Yield and Quality in Rice.

Grain size is a quantitative trait with a complex genetic mechanism, characterized by the combination of grain length (GL), grain width (GW), length to width ration (LWR), and grain thickness (GT). In this study, we conducted quantitative trait loci (QTL) analysis to investigate the genetic basis of grain size using BCF and BCF populations derived from two lines, Guangzhan 63-4S (GZ63-4S) and TGMS29 (core germplasm number W240). A total of twenty-four QTLs for grain size were identified, among which, three QTLs (, , and ) controlling GL and two QTLs ( and ) controlling GW were validated and subsequently fine mapped to regions ranging from 128 kb to 624 kb. Scanning electron microscopic (SEM) analysis and expression analysis revealed that influences cell expansion, while affects cell division. Conversely, , , and promoted both cell division and expansion. Furthermore, negative correlations were observed between grain yield and quality for both and . Nevertheless, exhibited the potential to enhance quality without compromising yield. Importantly, we identified two promising QTLs, and , which simultaneously improved both grain yield and quality. In summary, our results laid the foundation for cloning these five QTLs and provided valuable resources for breeding rice varieties with high yield and superior quality.