Fine Mapping of , a Minor Effect QTL for Grain Weight in Rice ( L.).

Grain weight is a key trait that determines rice quality and yield, and it is primarily controlled by quantitative trait loci (QTL). Recently, attention has been paid to minor QTLs. A minor effect QTL that controls grain weight was previously identified in a set of chromosomal fragment substitution lines (CSSLs) derived from Nipponbare (NPB)/93-11. Compared to NPB, the single segment substitution line (SSSL) N83 carrying the introgression exhibited an increase in grain length and width and a 4.5% increase in grain weight. Meanwhile, N83 was backcrossed to NPB to create a separating population, , a QTL distinct from , which was detected between markers G31 and G32. Twelve near-isogenic lines (NILs) from the BCF population and progeny of five NILs from the BCF population were genotyped and phenotyped, resulting in the fine mapping of the minor effect QTL to the approximately 86.2-kb region between markers G72 and G32. Further sequence comparisons and expression analysis confirmed that five genes, including , , , , and , were considered as the candidate genes underlying . These results provide a crucial foundation for further cloning of and molecular breeding design in rice.