Evaluation Of Local Wheat Germplasm Resources And Genome Wide Association Study Of Important Agronomic Traits In Shanxi Wheat

The inductive selection of high-yield breeding targets has led to a more and more single genetic background of wheat cultivars,which makes wheat varieties more susceptible to sudden diseases and even lose their productive potential when dealing with environmental threats such as drought.Landraces have excellent characteristics such as abundant genome variation,strong adaptability and stable heritability,which are ideal gene resources for exploring new genetic variation.Shanxi wheat landraces have rich genetic diversity,especially drought resistance.In order to make full use of the excellent traits and drought resistance characteristics of landraces,the genetic mechanism of favorable allele variation in landraces was revealed.In this study,Shanxi wheat landrace germplasm was used as the basic material.Through the identification of the germplasm resource of the same name,after eliminating the redundancy of germplasm resources,a genetically representative core germplasm of Shanxi wheat landrace was constructed.Association analysis of natural population of materials with long genetic distances.Phenotypic traits and 55 K SNP markers were used to analyze the genetic diversity and phenotypic variation characteristics of Shanxi wheat landraces.Identify the drought resistance of wheat landraces at maturity stage.We analyzed the population structure of natural population,mined excellent allelic variation associated with main agronomic traits and drought resistance traits,screened and annotated related candidate genes,which laid a theoretical foundation for subsequent functional gene verification and gene cloning.The main findings are as follows:1.Genetic relationship analysis of wheat landraces with the same name in Shanxi Province.The phenotypic traits and genotypic analysis of the main landraces Heshangtou,Hongtumai,Jinguoyin,Siyuehuang and Xiaobaimai with the same name.The results showed that the coefficient of variation and genetic diversity index of the five groups of materials with the same name varied widely,with obvious differences in agronomic traits and morphology,and rich genetic variation.Combined with 55 K SNP markers,the whole genome of the cultivar with the same name was scanned.Through genotype clustering and genetic similarity analysis,there were similar cultivars with less genetic background differences among the landraces with the same name.The overall comparison of phenotype and genotype identification results showed that there is still a high genetic diversity among the landraces with the same name,especially the genetic similarity between the materials with the same name among various groups is low,but the genetic similarity between the materials of the same group is relatively high.Through the identification of the genetic relationship of the landraces with the same name,the landraces with close genetic relationship can be eliminated,which provides more efficient and accurate basic materials for the subsequent innovative utilization of landraces.2.Construction of primary core germplasm of wheat landraces.According to field agronomic traits,the primary core germplasm was constructed by combining genetic distance,phylogenetic clustering method,sampling ratio and sampling method,and the primary core germplasm was evaluated and tested.The results showed that the strategy of "multiple clustering preferential sampling method+19.27% sampling ratio+Mahalanobis distance+intermediate distance method" was the best construction method,and a total of 79 wheat landraces were selected into the primary core collection.Among them,the evaluation parameters VD,MD,VR and CR values of the primary core collection were 69.57%,0,133.93% and 100.00%,respectively,and the t-value test of the total genetic diversity index of the primary core collection and the basic sample was not significantly different.The difference is only 0.07.The maximum,mean,genetic diversity index and minimum coincidence rates of the primary core collection and basic samples were 92.96%,96.25%,90.24% and 92.98%,respectively.The cumulative contribution rate of the principal components of the primary core collection was 6.49% higher than the basic sample.which indicated that core collection retained the genetic diversity of basic collection and could represent the phenotypic variation characteristics of basic collection.3.Identification of phenotypic and quality traits and evaluation of drought resistance in mature stage of wheat landrace.The phenotypic variation and grain quality of population materials were preliminarily evaluated by the coefficient of variation,correlation analysis and genetic diversity analysis.1 landrace with strong gluten,9 landraces with medium gluten were screened out.At the same time,combined with the phenotypic variation under normal irrigation and drought stress conditions,the effects of drought stress on phenotypic traits were discussed.The drought resistance coefficient was used to analyze the sensitivity of natural population to drought resistance at maturity.66 landraces with strong drought resistance were screened out.Comparing the results of quality and drought resistance identification,1 landrace with strong drought resistance and medium gluten,2 landraces with medium drought resistance and medium gluten,1 landrace with drought sensitivity and strong gluten,6 landrace with drought sensitivity and medium gluten.4.Association analysis and candidate gene annotation of wheat landraces.The 55 K SNP markers were used to analyze the main agronomic traits of the population materials.Under irrigation conditions,17 SNP loci were detected and significantly associated with major agronomic traits.8 functional candidate genes were annotated.32 loci were identified to be significantly associated with 8 target traits under drought stress and irrigation conditions,among which 3 SNPS were detected to be significantly associated with multiple traits.1 SNP was detected to be significantly correlated with spikelet length under multiple environments.24 functional candidate genes were annotated.Using the gene-wide association analysis of drought resistance coefficients of yield-related traits at maturity,154 loci that were significantly associated with drought resistance-related traits at maturity in wheat were identified,50 candidate functional genes were annotated.6 candidate genes were screened out that may be involved in wheat maturation.The acquisition of these candidate genes provided theoretical references for subsequent gene function verification,cloning and molecular marker-assisted drought resistance breeding.