Mapping Of Major QTLs For Grain Shape And Weight Traits And Construction Of Its Near-isogenic Line In Rice(Oryza Sativa L.)

Rice grain shape, including grain length(GL), grain width(GW), grain length to width ratio(LWR), grain thickness(GT) and kilo-grain weight(KGW) is a key determinant of grain appearance, yield and market values. Identification of major quantitative trait loci(QTLs) for grain traits is an important objective of rice breeding and genetic research. In this work, long-grain mutants of JF178 was crossed with a very short-grain cultivar Samba, generating one F2 populations and one BC2F2 population.Based on the grain traits investigating of F2, correlation analysis showed there are highly significations among grain traits, except that GL and GW did not show significant correlation. Path analysis of grain shape traits(GL, GW, LWR and GT) and grain weight show GL may contribute more to grain weight than other grain shape traits.A molecular marker-based genetic analysis was conducted to investigate the major QTLs associated with grain length, grain width, length to width ratio, grain thickness and grain weight. QTLs for these grain traits were identified on chromosome 2. Analysis of the JF178/Samba F2 population identified a QTL for grain length(26.8% PVE), grain thickness(24.2% PVE) and grain weight(34.3% PVE) and a QTL for grain width(21.7% PVE) on the long arm of chromosome 2, between SSR markers RM13840 to RM525,with a genetic distance of about 10 cM. Analysis of the JF178/Samba BC2F2 population revealed a QTL for grain length(13.7% PVE), grain thickness(11.9% PVE) and grain weight(42.1% PVE) and a QTL for grain width(26.7% PVE) on chromosome 2. Integration of these mapping data suggested the presence of the major QTLs for grain shape and grain weight located between SSR markers RM13838 and RM525, with a genetic distance of about 2 cM on chromosome 2. These two populations mapped grain traits QTLs on the similar location suggest the highly reliable existence of major QTLs for these traits.A near-isogenic line carried the target segments of large grain parent JF178 with Samba background was bred. This work has provided a solid foundation for fine mapping and map-based cloning of the related QTLs.