Genetic Analysis Of Rice Shape And Weight And Fine Mapping Of QTGW7.2

Rice is one of the main food crops in the world.The population is increasing rapidly now,and the area of cultivated land is decreasing.Therefore,increasing rice yield per unit area has become the most serious problem faced by rice breeders.Rice yield is controlled by complex agronomic traits,including the number of panicles per panicle,number of grains per panicle,and 1000-grain weight.The three factors are controlled by multiple genes,and the phenotype exhibits a normal continuous distribution,called quantitative traits.(Quantitative traive loci,QTLs).Generally,increasing the number of panicles per plant will decrease the number of grains per panicle,and increasing the number of grains per panicle will reduce the 1000-grain weight which three factors are closely related.Grain weight is a comprehensive reflection of grain storage capacity(length,width,thickness)and grain plumpness.The grain weight mainly depends on the grain storage potential and the degree of grain filling.The formation of sufficient grain storage capacity(increasing grain size,grain width and grain thickness)is the basis for increasing grain weight.How to increase the 1000-grain weight and improve the yeild is a problem faced by breeders.At the same time,1000-grain weight will cause changes in grain shape and quality.Therefore,exploring the genetic mechanism of rice grain weight,grain shape and grain-weight-related genes are important for improving rice yield and quality.(1)In this paper,108 recombinant inbred lines constructed by 9311(genetic background)and C418(infiltrated fragment)were used to investigate the traits of 1000-grain weight,grain length,grain width and grain lengh-to-width ratio of each family.QTL detection of 1000-grain weight,grain length,grain width and grain lengh-to-width ratio traits for 2016 and 2017 data use the stepwise regression similarity ratio test(RSTEP-LRT)method by QTL IciMapping 4.1 software.A total of 19 QTLs with LOD>2.5 were detected.It includes 6 thousand-grain weight QTLs distributed on chromosomes 2,3,7,8,11 and 12,explaining the genetic variation of 7.35%-14.4%;Six grain lengh-to-width ratio QTLs were distributed on chromosomes 2,3,7,8,11 and 12,explaining a genetic variation of 7.35%-14.4%;Three grain length QTLs were distributed on chromosomes 1,3 and 7,explaining the genetic variation of 9.45%-26.6%;Four grain width QTLs distributed on chromosomes 2,3 and 5,explaining genetic variation of 7.43%-15.5%.Among them,qTGW2,qTGW7,qTGW12,qLWR2,qLWR7,qLWR12,qGLl,qGL3,qGL7 were detected within two years.(2)qTGW7 has stable effect in the detected QTL as the research object.The NIL-C418 and NIL-9311 were constructed to investigate their traits.The 1000-grain weight,grain shape,plant height,ear length,primary branch,secondary branch,and number of grains per panicle were significantly different,the effective number of tiller is difference.There was no difference in quality traits including white grain rate and chalkiness between NIL-C418 and NIL-9311.(3)Using the F2 population,the qTGW7 is positioned between RM22020 and RM22034,and verified by generations.The qTGW7 was decomposed into two subQTLs,including qTGW7.1 and qTGW7.2 by F3 population and progeny verification.We use 2024 individuals of F4 population and progeny verification by designing markers based on Gramene and Rice3k database that qTGW7.1 was located in the 868 kb between VF2081-GH-seq-19,and qTGW7.2 was located in the 4.74 kb between IN-NEW-4-RM8261.