Mapping Of Major QTL For Grain Shape And Weight Traits In Rice(Oryza Sativa L.)

Studying special germplasm resource is an important way to reveal rice genomic function.Grain shape traits including grain length(GL),grain width(GW) as well as length/width ratio(GS) and 1000-grain weight(KGW) are closely associated with rice appearance quality,yield and market value.In this study,we selected large grain parent(JF171 and JF178) and small grain parent(JF222 and Samba) to establish two F₂ populations(JF171/Samba population and JF222/JF178 population),and genetic linkage maps were constructed based on SSR(simple sequence repeats) marker and BSA(bulk sergeant analysis) method.The QTL mapping analysis of related traits was conducted by MICM(mixed-model based composite interval mapping) method in the two F₂ populations.Main results showed as follows:(1) Correlation analysis in both F₂ populations indicated that GL was a highly significantly positive correlation with GW,GS and KGW,GW showed a closely significantly negative correlation with GS and GS had a highly significantly positive correlation with KGW.(2) Local genetics maps in both F₂ populations were constructed by SSR marker and BSA method.For JF171/Samba F₂ population,four linkage groups were located on chromosome 1,2,6 and 8 respectively,and for JF222/JF178 F₂ population,five linkage groups were located on chromosome 2,5,6,8 and 10 respectively.(3) Major QTL conferring GL,GW,GS and KGW in the two populations were all detected in the interval of RM263-RM318 on the long-arm of chromosome 2, which mainly showed additive effects.Their additive H^2 was between 18%and 60%.In the JF171/Samba F₂ population,one GL QTL(qGL-2-1),one GW QTL(qGW-2-1) and one KGW QTL(qKGW-2-1) were identified on RM221-RM573, RM318-RM525 and RM318-RM525 of chromosome 2 respectively.Their additive H^2 were 22.47%,40.02%and 23.62%respectively.Similarly,in the JF222/JF178 F₂ population,one GL QTL(qGL-2-2),one GW QTL(qGW-2-2),one GS QTL (qGS-2-2) and one KGW QTL(qKGW-2-2) were located on RM13838-RM13840, RM263-RM13838,RM263-RM13838 and RM263-RM13838 of chromosome 2 respectively.Their additive H^2 were 60.46%,31.49%,17.94%and 59.66% respectively.Furthermore,several minor QTL of related traits were also detected on chromosome 5,8 and 10 in both F₂ populations.(4) Major QTL conferring grain shape and weight which were mapped on RM263～RM318 of chromosome 2 in this study has not yet been isolated and pyramided,which will facilitate marker-assisted selection for new large grain and high quality rice varieties and map-based cloning in the future.