RESISTANCE OF MUSKMELON TO FUSARIUM WILT

In Italy Fusarium oxysporum f.sp. melonis induces an important disease of muskmelon. Four races of this pathogen are currently known, i.e. 0, 1, 2 and 1-2. Varietal resistance of the only reliable approach for preventing wilt induced by race 0, 1 and 2, which were studied in this work. Investigations carried out between 2008 and 2010 aimed first at verifying the resistance of the cultivars certified as "resistant" by seed companies. To this aim, 3 "resistant" cultivars (Bingo, Giusto and Sweetness) were compared with three susceptible ones (Cantalupo, Harper and Retato degli Ortolani), by infection plants with each of the three pathogenic races (spore suspension: 106 conidia/ml). Among the resistant cultivars, one resulted totally resistant (Bingo) whereas Giusto and Sweetness showed a partial resistance (disease severity: 10%). Similar differences were observed among the susceptible cultivars for disease severity which was close to 100% in Retato whereas for Cantalupo and Harper it ranged between 80 and 85%. Differences in pathogenicity were also observed among the pathogenic races tested: race 0 and 2 caused the highest disease severity in Bingo and Retato. Attempts were made to investigate the mechanisms involved in plant resistance. We found that root exudates did not affect neither conidia germination rate nor mycelial growth. Currently, studies on the development of promycelium are carried out. Further investigations will aim at highlighting possible differences between resistant and susceptible cultivars in post infection root morphological modifications, by means of fluorescence and microscopy techniques.