QTL Mapping Of Leaf Senescence Phenotype In Wheat DH Population And Response Of Premature And Greening Plants To Salt Stress

Wheat is one of the most important food crops in the world,and increasing its yield is crucial for solving the global food problem.Leaf senescence is an important process in the life cycle of wheat,and its main function is to transfer nutrients to developing grains,which is closely related to wheat yield and quality.Therefore,studying leaf senescence is of great significance for cultivating high-yield and high-quality wheat varieties.Our laboratory created a doubled haploid（DH）population using CASL7AS and ZNL12 as parents.During the planting process,some DH lines were found to have significant premature senescence.In order to clarify the genetic basis of these premature senescence DH lines,this study used this DH line population as the material for observation of leaf premature senescence after multiple years of planting and QTL mapping.The research results are as follows:1.The leaf senescence phenotype of wheat DH population was observed under multiple environments.The results showed that the phenotype was normally distributed under five environments,the absolute values of skewness and kurtosis were basically less than 1,and the coefficient of variation was 23.2%-38.5%,indicating that the phenotype was a continuous variation with rich phenotypic variation.The correlation analysis of DH line leaf senescence phenotype,yield traits,and seedling phenotype showed that there was a highly significant positive correlation between leaf senescence phenotype and thousand grain weight at the 0.01 level in the five environments,with correlation coefficients of 0.208,0.196,0.346,0.253,and 0.233,respectively.2.Using a 55K SNP gene chip,association analysis was conducted on the leaf senescence phenotype of DH populations under multiple years of environmental conditions.A total of 61 QTL loci related to wheat leaf senescence were identified,with a phenotypic variation contribution rate of3.31%-20.27%.Among them,25 main QTLs with a contribution rate greater than 10%were identified,and 10 stable QTLs were repeatedly detected in multiple environments.Using BSR-Seq technology to analyze the hybrid offspring population of DH70（premature aging）×DH106（normal）,it was found that there may be QTL loci related to leaf aging within the 700Mb-740Mb interval of 4A chromosome.3.The seedlings of the premature aging strain DH70 and the green holding strain DH106 were planted under normal conditions,salt treatment,salt treatment with calcium chloride,and other conditions.It was found that under normal conditions and salt stress,the antioxidant enzyme activity of DH70 was lower than that of DH106,while the MDA content was higher than that of DH106.This suggests that low levels of antioxidant enzyme activity and excessive MDA content in the body may be the reasons for premature aging of DH70 leaves.Exogenous application of Ca Cl₂ can improve the antioxidant enzyme activity of wheat seedlings,and the best alleviation effect is achieved at a concentration of 40 mmol/L Ca Cl₂,and the alleviation effect on premature senescence plants is greater than that of green plants.This indicates that spraying Ca Cl₂ may delay the senescence of wheat leaves.In summary,QTL loci related to wheat leaf senescence were identified and their physiological characteristics were preliminarily explored,laying a theoretical foundation for cultivating delayed senescence,high yield,and high-quality wheat varieties in production.