Mapping Of QTLs For Grain Shape And Grain Weight In Rice（Oryza Sativa L.）

Rice is an important food crop.The yield of rice is determined by the number of effective panicles,the number of grains per panicle,and the grain weight.The grain weight traits are directly affected by the grain shape.Studying the grain shape and weight of rice plays an important role in improving rice yield and quality.In this study,the large grain glutinous rice variety Zhuyunnuo and the slender grain indica rice variety Aoguizhan 1 were used as parents to construct the F2 population and its genetic map.;Select the interval of QTL with higher contribution rate in the initial positioning,and verify the positioning results in the F2:3 population;the three reported granulose genes near the positioning interval,FUWA,LG1 and GW2,clone sequencing The coding region sequence of the parent allele.The following results were obtained:1.Select 102 pairs of molecular markers that have specificity between the two parents to construct a genetic map,which is evenly distributed on 12 chromosomes in rice.The total genetic distance of the genetic map is 2288.16 cM,and the average genetic distance is 22.43 cM.A total of 20 QTL sites with 5 traits were detected in the initial mapping,namely,2 QTLs for grain length,7 QTLs for grain width,3 QTLs for grain thickness,6 QTLs for aspect ratio and 2 QTLs for 1000 grain weight.Among them,there are 8 sites with a LOD value greater than 10,qGW2,qGW8-1,qGW8-2,qGT2,qL WR8-1,qLWR8-2,qLWR8-3,qTGW2.There are 3 main effect sites with contribution rate over 20%,qGL2,qGT2,qTGW2.There are QTL sites controlling different traits in the same interval on chromosomes 2,5,8,and 12,respectively,indicating that there is a multiple effect or trait linkage in these intervals.2.The initial positioning results show that there are 4 QTLs affecting the grain length,grain width,grain thickness and thousand grain weight in the physical interval of about 5 Mb between marker K6 and K120.Select the heterozygous F2 single plant in this interval and develop into F2:3 segregating population for further positioning and verification.A total of 108 recombinant plants were screened in this interval.After polymorphic marker development and QTL detection,there was a grain length QTL qGL2 between marker C452 and C495 with a LOD value of 4.60 and a contribution rate of 17.35%;The main effect QTL that affected the grain width,grain thickness and thousand grain weight at the same time was detected between marker C496 and RM71,and the phenotype contribution rate exceeded 50%,which was tentatively named qSW2.Using the close linkage marker C495 as the genotype reference,the distribution of the number of grain width,grain thickness and thousand-grain weight traits confirmed that the plants with different genotypes conformed to the separation characteristics of quantitative traits,and the traits were semi-dominant.3.There are three reported granule-shaped genes FUWA,LG1 and GW2 near the positioning interval.Primers were designed according to the reference sequence of Nipponbare,and the allele coding sequences were cloned in the two parents for sequencing and comparison.It was found that the coding sequences of these three genes in the parent Zhuyunnuo were completely consistent with the reference sequence of Nipponbare;the coding sequences of FUWA and LG1 in parent Aoguizhan 1 were also consistent with the reference sequence of Nipponbare.The single-base substitution of C→T resulted in the mutation of arginine（Arg,R）at position 262 of the amino acid sequence to cysteine（Cys,C）.The mutation occurred in an unknown functional region at the C-terminus,so this mutation Not enough as a basis for functional variation.In this study,related gene expression analysis and further fine positioning of qSW2 are needed.