Genetic Analysis And Mapping Of QHd3-1 For Heading Date And GW3 For Grain Weight In Rice

Heading date is responsible for the regional and seasonal adaptation, which is a major target trait in the breeding, improvement and extension of rice varieties. 1000-grain weight is determined by grain length, grain weight and grain thickness which has an effect on both grain yield and quality. In this research, we selected a BC3F2 line segregating with heading date from chromosome segment substitution lines (CSSLs) derived from the cross, Nippanbare /Minghui63. genetic analysis and molecular mapping were done to the main QTL qHd.3-1 in the BC3F2 segregation population. Besides, We conducted effect analysis and fine mapping to a QTL GW3 for grain weight in the NIL background which is originally detected in F₂ population from the cross, Minghui63/Teqing. The major results were as follows:1) The frequency distribution of heading date showed bimodal in the segregation population of 327 plants and the ratio of late heading individuals to early heading individuals showed 3:1, suggesting that heading date was controlled by a single major QTL qHd.3-1. The strategy of bulked segregant analysis (BSA) was used to quickly locate the QTL. SSR marker, RM416, was identified polymorphism between two DNA bulks consisting of early and late heading plants, respectively. One-way ANOVA was performed to confirm the linkage between RM416 and qHd3-1.2) To mapping qHd3-l in a smaller region, linkage map for the target region was constructed. qHd3-l was located to a region between InDel marker IDL01 and SSR marker RM5995 using interval mapping method. qHd3-l was 5.3 cM and 1.5 cM from loci IDL01 and RM5995 respectively, accounting for 62.9% of phenotypic variance. Besides, two minor QTLs, qSpp3 and qTn3,controlling spikelets per panicle and tillering number respectively were detected in the same region with qHd3-l.3) The genetic effect of GW3 was re-estimated in NIL background, analysis of a random population confirmed that the GW3 locus was located between RM186 and MRG4995, explained 50.4% of the variation for the grain weight, and had effect on grain length, width and thickness. Recombinant plants were selected using GW3 flanking marker from 600 individuals with extreme phenotype. GW3 was mapped to a DNA fragment approximately 600 kb in length.