response of iranian local and improved genotypes of melon and musk melon to charcoal rot disease caused by macrophomina phaseolina

melon and musk melon are grown widely in warm and moderate climate regions of the world as well as iran. these crops are attacked by several fungal pathogens including macrophomina phaseolina which causes charcoal rot disease at different growth stages and reduces the yield remarkably. fungicide application and other control methods have not been successful in control of charcoal rot and utilization of resistant cultivars seems to be the most effective way for control of disease. to evaluate the resistance of melon and musk melon genotypes grown in iran, several isolates of the pathogen were collected from infected fields in tehran province. after pathogenicity tests, two highly virulent isolates, mp-123and mp-146 were selected for resistance evaluation. forty five local and improved genotypes of melon and musk melon were grown in greenhouse in completely randomized design with three replications and inoculated separately with each isolate. disease severity and infection index for each genotype were assessed 28 days after inoculation. based on the results, infection severity and response of genotype to both isolates were similar. none of genotypes was resistant to disease but genotypes ananas meanh mni and melon genotype mahalli mazandarani had the lowest infection index. melon gentyes haj mashallahi, shahabab, jajoo, sooski sabz eyvanaki and musk melon genotypes semsoori varamin and khoshkerood with high infection indices (5.71-9) were susceptible. the remaining genotypes were moderately susceptible or moderately resistant. based on these results farmers are recommended to use relatively resistant genotypes which are adapted to their local environmental conditions.