Screening And Identification Of Cucumber Mutant Resistant To Powdery Mildew

Cucumber is an important vegetable crop.It is susceptible to disease in production.Powdery mildew is one of the most serious diseases,especially in greenhouses.In recent years,the gradual expansion of the facility cultivation area has made powdery mildew increasingly serious.The application of fungicides is the main way to control the powdery mildew disease in production.However,the widespread application of chemical pesticides will lead to the continuous variation of pathogenic bacteria,and the difficulty of prevention and control increases year by year.Therefore,obtaining excellent materials resistant to powdery mildew and cultivating new varieties of disease-resistant cucumbers can fundamentally solve the problem of powdery mildew.Resistant materials are currently obtained by interspecific hybridization,but genetic stability is poor.In this study,cucumber "Changchunmici" mutant library was used to select some materials for the identification of powdery mildew.The resistance for all materials in seedling stage were evaluated based on phenotypic observation of the disease index,combined with superoxide dismutase(SOD),peroxidase(POD),catalase(CAT)activity,and chlorophyll content,soluble protein content.On this basis,in the natural pathogenesis of the field,we observed the disease phenotype in the adult stage,analyzed the photosynthetic index,endogenous hormone content and related signal pathway gene expression,and finally screened out the materials with better resistance to powdery mildew.The details and results are as follows:1.Screening of cucumber mutant resistant to powdery mildew at seedling stageThrough the inoculation of powdery mildew in the seedling stage,the phenotypic combined disease index was observed,and 400 mutant materials were divided into four types:resistance,medium resistance,medium sensitivity and sensitivity.Among them,3 anti-disease materials,8 medium resistance materials,30 medium-sensitive materials,and the rest were 359 susceptible materials.Eleven materials including resistant and medium resistant materials were used for further physiological test materials.The determination of chlorophyll content,superoxide dismutase,peroxidase,catalase and soluble protein content showed that the related indexes of Mu-58-9 and Mu-86-2 were higher than those of Changchun.The physiological indicators of the medium resistant materials are not the same.2.Screening of cucumber mutant resistant to powdery mildew at adult stageThe resistant mutant material screened at the seedling stage was used to conduct natural disease test in the field of adult stage.The phenotypic observation showed that the surface of the disease-resistant material had less white powder than the susceptible material,while the other medium-resistant materials had thick white powder and serious disease.Photosynthetic indicators of endogenous materials,analysis of endogenous hormone content and related signal pathway gene expression,comparison of susceptible materials,Changchun Mickey and disease resistance material IL-52,found that in the disease resistance mutant materials,photosynthesis indicators and endogenous sources The contents of hormones such as ethylene,salicylic acid and jasmonic acid were higher than those of susceptible materials,and the difference was small with IL-52.The expression of the related signal pathway gene showed high expression of resistant mutants.Two powdery mildew resistance materials Mu-58-9 and Mu-86-2 were finally screened out by analysis of seedling stage and adult stage.