Identification of QTLs and heterosis loci for grain shape using single segment substitution lines in rice ( Oryza sativa L.)

Abstract QTL and HQTL (heterosis QTL) of grain shape are two important components for grain yield and influence the end-use rice quality. However, limited QTLs of grain shape were detected, with only a few applied in production. In this study, 54 QTLs of grain shape were detected on 10 chromosomes over 2 years,twenty-three of which showing positive additive genetic effects, including some QTLs that were newly found and with large positive effect such as qHGW4-1,qHGW4-2 and qHGW10-2. 26 HQTLs of grain shape were probed, with eighteen of which providing positive dominance genetic effects. 33 QTLs of grain shape were mapped by linkage analysis. Most of grain shape QTLs have pleiotropic effects which control simultaneously the multiple appearance traits of the grain shape, for instance GL, GW, LWR, GS, GC, GR and TGW. Linkage mapping by F2 population deriving from sub-SSSLs further narrowed the interval containing qTGW10-3 down to about 75.124 kb between markers PSM169 and RM25753, where eight candidate genes were predicted. In this study, the finding of grain shape QTL will provide us greater insight into improving rice quality and grain yield in rice breeding.