QTL Mapping For Kernel Nutritional Quality Traits Using The Chromosome Segment Substitution Lines From G.mustelinum

Cotton is one of the world’s largest cash crops,and cotton fiber,the main raw material for textiles,is the main acquisition target for cotton production.With China’s huge cotton cultivation area,a large number of cotton seeds are produced.Cottonseed is rich in edible fatty acids and proteins,and cottonseed oil also has great potential as a next-generation bioenergy material.For a long time,cottonseed has only been used as a by-product of cotton production,and its value for research and economic value has been neglected.In recent years,with the improvement of people’s living standards,the demand for plant oil has also been increasing,especially in China,most of the vegetable oil is still dependent on the reality of imports,and people began to notice the important value of cottonseed,cotton kernel nutritional quality improvement research work began to receive more and more attention.The genetic and QTL localization studies of nutritional quality traits of cotton seeds are of great importance for the improvement of nutritional quality of cotton seeds.In this study,a population of 564 lines of G.mustelinum chromosomal fragment substitution were obtained after three backcrosses and self-crosses with G.mustelinum as the recipient parent and CCRI35 as the donor parent in the pre-laboratory stage,and the BC₃F₂ genetic linkage map was constructed using this population.We further encrypted the genetic map using SSR markers and identified the phenotypic data of six quality traits such as protein and oil content of cotton seeds in four lines using BC₃F_2:3,BC₃F_2:4,BC₃F_2:5and BC₃F_2:6lines,and conducted preliminary QTL mapping for nutritional quality traits of cotton seeds.The main results are as follows:1.150 new SSR primer pairs were screened to the previous study to detect the genotypes of BC₃F₂ population,and together with the previous primers,an encrypted genetic map of 520 SSR markers was obtained.The average genetic distance between markers of the encrypted genetic map was 7.49 c M,the average coverage of 26chromosomal SSR molecular markers was 96.80%,the genetic background recovery rate was 77.6%-99.3%,and the substitution rate was 9.07%.2.The mean values of protein content（PC）,oil content（OC）,linoleic acid content（LA）,oleic acid content（OA）,stearic acid content（SA）,and palmitic acid content（PA）were determined and analyzed for the main nutritional quality traits of cotton seeds from a population of 564 chromosomal fragment substitution lines under four family lines with34.08%-35.72%,27.35%-28.52%,and 48.68%-54.09%,18.32%-21.45%,2.87%-3.11%,and 23.72%-25.73%,respectively.The content of linoleic acid was the highest and the content of stearic acid was the lowest.All six traits showed an approximately normal distribution with skewness and kurtosis approximately less than 1,which is consistent with the genetic characteristics of quantitative traits.3.The correlation analysis of nutritional quality of cotton kernel showed that protein content and oil content showed a significant negative correlation.Oil content showed a highly significant negative correlation with linoleic acid content,and showed a negative correlation with palmitic acid content,but the correlation was not significant.Oil content showed positive correlation with stearic acid content and oleic acid content.The correlation analysis between each fatty acid content,palmitic acid content and linoleic acid,oleic acid and stearic acid content all showed a negative correlation.A highly significant negative correlation was shown between linoleic acid content and oleic acid content.ANOVA showed that environment and genotype had significant effects on nutritional quality traits of cotton kernels,and their phenotypic traits were jointly acted by genes and environment.4.A total of 68 QTL（11 QTL for protein content,12 QTL for oil content,15 QTL for linoleic acid content,7 QTL for stearic acid content,12 QTL for oleic acid content,and 11 QTL for palmitic acid content）were mapped using encrypted genetic maps combined with phenotypic data of nutritional quality of six cotton kernels using Map QTL6.0 software.The range of explained phenotypic variation was 2.04%-14.24%,with 28 positive additive effects.The favorable alleles are from G.mustelinum,with 40negative additive effects.The favorable alleles are from CCRI35.31 QTLs were detected in the A sub-genome,and 37 QTLs were detected in the D sub-genome.A total of 12stable QTLs were located,with 39 QTLs distributed within 16 QTL clusters on 12chromosomes.