QTL Mapping Of Cold Tolerance At The Booting Stage And Mapping Verification Of Grain Width Gene QGW5.2 In Rice

Chilling injury is one of the usual stress in the growth process of rice,which can affect the production of rice.The losses brought by chilling injury at the booting stage are the most serious,comparing with orther growth stages.The researchers have carried out many works related to cold tolerance,arounding mapping and genetic analysis at the booting stage.R727 was cold-tolerant strains selected from the recombinant inbred lines which came from Kunmingxiaobaigu(KMXBG),the cold-tolerant Yunan japonica landraces at the booting stage,and Towada,the cold-sensitive Japan japonica varieties.One F3 segregating population and one BC1F2 backcrossing population derived from R727 and 93-11 were used for QTL mapping by constructing genetic linkage map.Nine QTLs were detected in F3 population,while five QTLs were detected in BC1F2 population.Among these QTLs,four major locus were simulataneously detected in two different generation populations,namely,the QTL qCTB4.2 between SSR markers Y33 and RM7187 on chromosome 4,the LOD value were 8.21(F3)and 10.18(B1-F2),explaining 25.77%and 29.37%of the phenotypic variation,and it was in the same interval as the cloned gene Ctbl;the QTL qCTB2.1between SSR markers Y16 and Y17 on chromosome 8,the LOD value were 6.15 and 5.74,explaining 23.42%and 19.13%of the phenotypic variation;the QTL qCTB8.1 between SSR markers W66 and RM3702,the LOD value were 10.88 and 9.18,explaining21.98%and 18.67%of the phenotypic variation,it was a new major QTL;the QTL qCTB11.1(qCTB11.2)between SSR markers W77 and Y82(Y81),the LOD value were 5.11 and 6.40,explaining 18.22%and 20.07%of the phenotypic variation.Others 7 QTL locus were separately detected in two populations,among these QTLs,the LOD value of qCTB12.1 detected in F3 population was 5.94,explaining 21.29%of the phenotypic variation,while the effect values of others were lower.Accordingly,the strong cold tolerance of R727 was controlled by multiple locus.Grain width belongs to grain shape traits related to rice yield,and is also one of the factors affecting rice quality,the research on grain width has important guaiding significance for rice breeding and production.A large grain variety Pangxiegu(japonica)and a narrow grain variety N-643(indica)were chosed as parent materials in previous research.After hybridization,selfing and backcrossing,the BC2 isolated population was selected to screen for QTLs for grain width,and a major grain width QTL,qGW5.2,was detected between SSR markers RMw513 and RM18068 on chromosome 5,the LOD value was 17.5%,explaining 57.3%of the phenotypic variation.On the basis of previous results,this research selected markers nearby GW5 or GS5 to screen for recombinants and sequenced GW5 and GS5 genes in parents.The result showed that qGW5.2 was detected between RMw513 and L529,which was consistented with previous result.And the result of sequence alignment showed that the effect of grain width increasing for Pangxiegu was no related to the effect of GW5 and GS5,thus we drawed the conclusion that qGW5.2 was a new grain width gene.