Fine Mapping of qTGW7b , a Minor Effect QTL for Grain Weight in Rice ( Oryza sativa 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 BC F population and progeny of five NILs from the BC F 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.