The Research Of Melon(Cucumis Melo L.)Gummy Stem Blight Physiological Characteristics And Molecular Markers Of Resistance Genes

Melon belongs to Cucumis, is one of the favorite fruits of Cucurbitaceae all over the world. The output and consumption of melon in China has ranked top in the world. The production of melon should be increased to fulfilling the ever increasing population. Gummy stem blight (GSB) as one of the soil-fungal diseases was caused by Didymella bryonia. The prevalence of GSB disease often leads to severely losses in melon production. The improvement of GSB resistance has became the main research emphases in melon breeding. The knowledge of relationship between resistance reaction and physiological, biochemical changes among the inoculated melon plants was the based of melon breeding. In this study, the relationship between activity changes of physiological and resistance of melon to GSB were clarified, linked molecular marker to GSB resistance gene was identified and SCAR marker was also explored to facilitate MAS breeding. The main results are as follows:1. Relationship between activity changes of physiological and resistance to gummy stem blight in resistance melon plants after inoculation with Didymella bryoniaeInbred lines PI420145and’baipicui’with highly resistant and susceptible to GSB, respectively, were inoculated with D. bryoniae at three leaf stage. One week after inoculation, the data of the content of materials’chlorophyll, soluble sugar, soluble protein and activity of three defense enzymes (PPO, POD and PAL) were collected. The results showed that:there are no relationships between the content of chlorophyll, soluble sugar, soluble protein and GSB resistance; the activity of PPO, POD and PAL has a positive effect on D. bryoniae infection. The variation of these defense enzymes after inoculation provides reference information for GSB resistance screening in melon.2. A SSR marker linked to Gsb-4loci resistant to gummy stem blight in melon(Cucumis melo L.) Segregating population of F2was generated by crossing the resistant inbred line PI482398)with the susceptible inbred line ’baipicui’, An unique fragment was amplified in resistant materials with the primer CMTA170a. The polymorphic patterns of CMTA170a in the118individuals of F2were scored and then calculated by the software of MAPMAKER/Exp version3.0b. The results showed that the genetic distance between CMTA170a and Gsb-4is5.14cM. This maker can be used for melon resistance to gummy stem blight molecular marker assisted breeding and disease resistant gene pyramiding breeding.3. Development and validation of SCAR markers linked to gummy stem blight of melonBy used same materials as above, specific primer of SCARBBI was designed according to the sequence of the specific fragments from SSR markers which linked to GSB of melon. A polymorphic band was amplified from the DNA of118F2population with the primer SCARGBI.The segregation pattern of the SCAR marker was as same as the original SSR marker with a linkage distance of5.14cM. The results showed that the linked SSR marker with Gsb-4has been successfully converted into SCAR marker.