First Report of Root Rot and Vine Decline of Melon Caused by Monosporascus cannonballus in Greece

In June 2017, a severe vine decline of the netted melon (Cucumis melo L.) hybrids Global F1 and Lavigal was observed in a greenhouse of Messara valley, Heraklion, Crete, Greece. Diseased plants exhibited wilting, leaf chlorosis, yellowing and vine collapse. Root rot and necrosis, foot rot and to a lesser extent vascular tissue discoloration at the lower part of the stem were also observed. Numerous perithecia embedded in the root cortex, containing asci and ascospores typical of Monosporascus cannonballus Pollack & Uecker (1974) were observed. Disease incidence in the greenhouse was estimated at 100 and 78% for Global F1 and Lavigal, respectively. The fungus was isolated from the root lesions and the discolored vessels of the basal part of the stem, previously surface-sterilized with 1.5% sodium hypochlolrite for 1 min, on potato dextrose agar (PDA) amended with 0.5 g/l streptomycin sulfate. To obtain single hyphae isolates, hyphal tips were transferred onto new PDA plates and the growth rate of the fungu...