Screening SSR Candidate Molecular Markers Related To Gummy Stem Blight Resistance Genes In Melon

Melon is an annual herbaceous plant,which is widely cultivated around the country,loved by the people.Melon gummy stem blight caused by Didymella bryoniae belongs to fungal disease.It influences the crop production and quality by damaging melon leaves,stems and roots.In this study,by using pathogenic strains preserved in our laboratory,we identified pathogen by its morphological structure,pathogenicity and molecular sequencing.Fourteen melon germplasms and Hami413 were tested for resistance to Didymella bryoniae by inoculating with conidiophor.F2 separation group derived from the cross between Iran H(resistance)and Hmi413(susceptible).By using BSA to screen SSR markers which showed polymorphism between resistant pool and the susceptible pool.Providing foundation for the localization of the resistance gene in Iran H.The result showed that:(1)By inoculating with conidiophor on Hami413 showed it was a highly pathogenic strain.Fungal identification by comparing conidial morphological between Didymella bryoniae strains and analyzing of ITS showed that the strain identified as a strain of D.bryoniae.(2)Only one melon germplasm showed resistance to Didymella bryoniae by the way of inoculation on seedlings.Resistant germplasm showed stable resistance in different seasons.The activity index of POD was measured after inoculation.The results showed that the POD activity in resistant melon was significantly higher than susceptible melon,Which can be used as a reference in selection of resistant germplasm in melon.(3)F2 separation group derived from the cross between Iran H and Hmi413.The segregation ratios for resistance/susceptibility observed in the different populations and the result of the progeny test indicated that resistance to gummy stem blight was governed by one recessive gene.(4)Using BSA,10 SSR primers were screened between resistant pool and the susceptible pool.