Drought Tolerance Evaluation And SNP Molecular Markers Of Cucumber Germplasm Resources

Drought resistance is a complex feature that involves adaptation to different levels,from plant morphology and anatomical structures,to physiological and biochemical reactions.Cucumber(Cucumis sativus L.)is a year of herbaceous plants,is China's important main vegetables,play an important position in the vegetable cultivation.Cucumber is a typical drought-resistant vegetables,lacking of water will cause the hollow melon,bitter fruit,impacts flavor,nutrition and merchandise of the cucumber,it become the main factor limit cucumber production.Cucumber always need water,but too much water will cause waste of water resources,especially in the cultivation of protected areas,therefore,breeding drought-resistant with excellent traits of cucumber varieties,it becomes main problems that the breeder should be faced.In this study,the drought resistance of three stages of cucumber seed germination,seedling stage and fruit ripening stage was identified and evaluated,and the molecular markers of drought tolerance were tested.A total of drought-resistant materials(649)and one drought-resistant material(D0432)were selected to construct 649 × D0432 F2 population.F2 population was used as the experimental material,and the separation group was analyzed by the combination method(BSA)and SLAF-seq And the molecular markers,candidate regions and genes,which were closely related to the target trait,were screened for polymorphism SNP and Indel markers,and the subsequent molecular markers assisted breeding to lay the foundation.The main results of this study are as follows:(1)Relative germination index is an important index to evaluate the drought tolerance of cucumber varieties during germination period.The reduction rate of fresh weight,the rate of MDA increase and the decrease of chlorophyll were the best indexes to evaluate the drought tolerance of cucumber seedlings.Five drought-resistant germplasm resources,six non-drought germplasm resources and five medium drought-tolerant resources were screened out at seedling stage,which could be used for identification of drought resistance at seedling stage.(2)The root dry weight and leaf area were the main indexes related to drought tolerance by evaluating the morphological and physiological indexes.The 16 varieties of cucumber were identified,5 drought tolerant varieties,8 medium drought tolerant varieties and 3 drought tolerant varieties were selected.Drought resistance at seedling stage was significantly correlated with drought resistance at adult stage,and drought resistance of cucumber germplasm resources could be evaluated by drought stress index.(3)Location and validation of candidate genes: A gene containing Csa6M104640.1 and a candidate gene Csa6M106790.1 were obtained by SNP marker and In Del marker association analysis.Csa6M106790.1,Csa6M104640.1 These two genes are involved in signal transduction gene expression,metabolism,ion and water transport through membrane,cytoskeleton kinetics,stomatal movement and growth and development and plant growth,flower development,fruit development,Seed development,damage,pathogen defense,high salt,drought and other environmental stress response.After quantitative verification,it was proved that related to drought stress.