Genome-wide Association Analysis And Comprehensive Evaluation Of Drought Resistance In Wheat At Seedling Stage

The drought resistance of wheat(Triticum aestivum L.)is controlled by multiple genes.Genome-wide association analysis can enable multiple alleles in a natural population to be detected at the same time,which has the advantages of low cost,high accuracy and strong practicability.In this study,158 wheat varieties(lines)were used as the experimental materials,14 drought resistance related traits were measured,and 114777 SNP molecular markers were used for genome-wide association analysis.The results are as follows:1.Variation analysis and correlation analysisThe coefficient of variation ranged from 8.37%to 30.90%,with an average value of16.07%.The variation coefficient of all characters except the root surface area was greater than 10%.Correlation analysis results of 14 drought-resistance-related traits showed that,under two water conditions,the seedling fresh weight,root fresh weight,total fresh weight,seedling dry weight and root dry weight were very significantly positively correlated with each other.Fresh seedling weight,root fresh weight,total fresh weight,dry seedling weight,root dry weight,total dry weight and total root length were all significantly and positively correlated with D value under drought stress.2.Screening of drought-resistant germplasm resourcesThe results of principal component analysis showed that the cumulative contribution rate of the first six principal components reached 86.24%,which were biological yield,root growth,root material accumulation,and seedling height.The top three items with the highest contribution rate were biological yield,root growth and root material accumulation,which could become important reference indicators for identifying the drought resistance of wheat seedlings.The wheat varieties were screened according to the D value,after comprehensive evaluation of the drought-resistance-related traits at seedling stage,and the K-means clustering method was used to cluster analysis of the D value.The drought resistance of wheat varieties could be divided into five groups:high drought sensitivity(0.28-0.40),drought sensitivity(0.41-0.48),medium(0.49-0.57),drought resistance(0.57-0.68)and high drought resistance(0.71-0.81).3.Genome-wide association analysis114777 SNP markers were used to analyze the correlation between drought resistance traits and drought resistance coefficient of wheat seedlings.A total of 1052 molecular markers were detected at the level of P?0.0001,Among them,47 loci were stably associated with related traits which including 92 single loci,accounting for 8.75%of the total loci.The range of explanatory phenotype variation(R~2)was 8.49%-23.77%,with an average of 13.61%.A total of 27 multiple effect sites were detected distributing on chromosomes chromosomes 1A,1B,2A,2B,3A,4B,5A,7B and 7D.SNP106243 located on chromosome 2A was significantly correlated with 5 traits(SFW,TFW,SDW,TDW and RSA),and SNP310710located on chromosome 5A was also significantly correlated with 5 traits(SFW,RFW,TFW,SDW and TDW).SNP310710,a locus stably associated with seedling fresh weight detected on the 5A chromosome,could be detected in DA,C2,and D2 environments,and had the largest explanatory phenotype variation(R~2),all exceeding 10%,and was the main effect site.