Genetic dissection and validation of QTLs for grain shape and weight in rice and fine mapping of qGL1.3, a major QTL for grain length and weight

Grain shape is a key factor that influences both grain yield and quality of rice (Oryza sativa L.). In order to elucidate the genetic basis of grain shape, an F2 and derived F2:3 populations were developed from a cross between Guangzhan63-4S (GZ63-4S) and TGMS29, and used in a quantitative trait locus (QTL) analysis. A total of thirty-six QTLs were identified for grain shape and weight, and the phenotypic variance explained by each QTL ranged from 0.88 to 35.70%. Given that most of the QTLs were detected in only one population, a BC1F2 and derived BC1F2:3 populations were constructed with GZ63-4S as the recurrent parent to further verify the QTLs. Seventeen QTLs were validated in at least one population. qGL1.3, the major QTL for grain length in both the F2 and F2:3 populations, contributed 41.16% of the variation in grain length and 35.96% of the variation in 1000-grain weight in a random BC1F3 population, and thus was selected for further fine mapping. Based on progeny tests of 31 recombinants, qGL1.3 was delimited to a region of about 350 kb on chromosome 1. These results could lay the foundation for map-based cloning of qGL1.3 and provide genes or QTLs for breeding rice lines with high grain yield and quality.