Study On Genetic Analysis And Molecular Markers Of Resistant Gene To Powdery Mildew In Cucumber

In China, Cucumber (Cucumis sativus L.) was one of the most important fruit vegetablecrops grown in greenhouse. Powdery mildew disease had been a very serious disease since thedevelopment of cucumber production, it often causes rather disease losses in cucumber. To selectmore efficiently for powdery mildew resistance, seeking markers linked to the powdery mildewresistance related genes was the main aim in this project.The'WIS2757' and '19032' was used to construct a F₂ population including 597 individules.'WLS2757' is an inbred line from American open field ecotype, which was resistance to powderymildew disease. '19032' was an inbred line from European greenhouse ecotype, which wassusceptible to powdery mildew disease. Two parent lines and F₁,F₂ populations were inoculatedfor disease resistance screening during seedling stage, the genetic analysis to powdery mildewdisease resistance was first carried out, and then SSR and SRAP markers were adopted to identifythe resistance related genes.This project had led to the following results:1. Resistance to powdery milde was controlled by a major recessive gene s, a dominantgene R and an recessive gene I. The gene s was the major gene, it decided the hybicalresistance, R was basis of leaf resistance, it was expressed when s was homozygous. Whenrecessive gene I was working, plants only expressed some parts of resistance, but I didn'tinfluenced the expression of s.2. The optimum SRAP-PCR reaction system on cucumber was established with orthogonaldesign. 900 SRAP primers were used to screening the polymorphism between resistant andsusceptible parents, 210 primers showed polymorphism, polymorphic percentage was 23.3%.Unfortunately, the tightly SRAP marks were not found.3. Using BSA and SSR technique, 439 SSR primer were used to screening the polymorphismbetween resistant and susceptible parents, 25 primers showed polymorphism, the SSR markers SSR 97-200 and SSR273-300 are linked to powdery mildew resistant gene and the geneticdistance between them are 5.0 cM and 13.0 cM, respectively.4. The resistant and susceptible parents possessed the 193bp and 173bp fragment respectively,and the difference of the two fragments lied in the insert-deletion of 20 bases. It show that theDNA fragment was new found cucumber DNA sequence from Genebank.