Quantitative Trait Locus Analysis for Grain Size Related Traits of Rice

Grain shape and size, which are characterized by grain length, grain width, grain thickness, and length to width ratio, are the key determinants of grain weight. In this study, a 188-individual F 2 population, which derived from a cross between large grain Indica cultivar Nangyangzhan and medium grain Indica cultivar Ce253, were used to analyze grain size related QTLs with 110 molecular markers. Inclusive Composite Interval Mapping (ICIM), was applied to genome-wide detection of QTLs underlying grain size related traits. For grain length, 4 QTLs were detected on chromosome 1, 3, 4, and 9, respectively. qGL-3 , a major effect QTL, explained 27.60% phenotypic variation of grain length. Four QTLs for grain width were detected on chromosome 2, 3, and 5. Among them, qGW-5a was major QTL for grain width, which explained 21.30% of phenotypic variation. Five QTLs for length to width ratio, which were distributed on chromosome 2, 3, 5, and 12, were identified. The range of their phenotypic contribution varied from 8.60% to 16.86%. For TGW QTLs, only two were identified on chromosome 5 and 6, respectively, with which 13.26% and 9.04% phenotypic contribution. In our results, qGL-4 and qGL-9 for grain length were novel loci. They have not seen reported in literature previously. Our results shed new light on further fine mapping and understanding the molecular genetic mechanism of novel grain size QTLs.