Reaction of Melon ( C ucumis melo L .) Cultivars to M onosporascus cannonballus ( P ollack & U ecker) and their Effect on Total Phenol, Total Protein and Peroxidase Activities

Eighteen melon cultivars were screened for resistance to M onosporascus cannonballus under greenhouse conditions. The melon cultivars were grown in pasteurized sand, which had been inoculated with a high level (60 CFU s/g of soil) of M . cannonballus mycelium from culture. Cultivars N abijani, S fidak khatdar, S fidak bekhat, G handak, M ollamosai, C happat, H ajmashallahi and S hadgan were moderately resistant to M . cannonballus but all other melon cultivars were moderately to highly susceptible (HS) to this pathogen. A second screening was performed for resistance to M . cannonballus under greenhouse conditions. In the second screening, cultivars N abijani, S fidak khatdar, S fidak bekhat, G handak, M ollamosai, C happat, H ajmashallahi and S hadgan were moderately resistant to M . cannonballus . To examine the melon resistance mechanism against M . cannonballus, the activities of total phenol, total protein and peroxidase in two melon cultivars N abijani (as resistant) and Khaghani (as susceptible) were determined at 0, 24, 48 and 72 h after inoculation. Inoculated resistant cultivar roots had always higher content of total phenol, total protein and peroxidase than the corresponding inoculated susceptible cultivar roots. The results indicated that there was a relationship between resistance in N abijani and accumulation of total phenol, total protein and peroxidase.