Aggressivity of Different Fusarium Species Causing Fruit Rot in Melons in Brazil

Brazil is one of the largest melon (Cucumis melo) producers in the world and most of the production is exported to international markets. Currently, over 15% of Brazilian melon shipments are lost during export transportation due to Fusarium fruit rot, which is jeopardizing the livelihood of Brazilian melon producers. We focused on understanding the aggressivity of five species of Fusarium causing fruit rot on the main types of melon produced in Brazil. We also investigated the correlation between pathogenicity and fruit quality. Experiments were performed under a completely randomized experimental design, in a 5 x 8 factorial scheme, using two methods for inoculation: deposition of discs of culture media containing fungal structures and deposition of spore suspensions in needle-punctured lesions. The fungal species used were Fusarium falciforme, F. sulawesiense, F. pernambucanum, F. kalimantanense, and Fusarium sp. Fruits of two hybrids from four types of melons, canary (Goldex and Gold Mine), piel de sapo (Grand Prix and Flecha Verde), galia (McLaren and DRG3228), and cantaloupe (SV1044MF and Bonsai), were used. Disease severity was assessed by measuring the lesions, disease severity index, fruit firmness, and degrees Brix of fruits. The five Fusarium species caused rot in the fruits of all melon hybrids studied and the aggressivity of those fungal species varied with the type and hybrid. Fruits of the hybrids McLaren and Bonsai presented the largest lesions among all melon hybrids, and hybrids of canary type (Gold Mine and Goldex) were the most tolerant to rot caused by the Fusarium species investigated. Furthermore, the greater the severity of Fusarium fruit rot, the lower the pulp firmness of the fruits, but degrees Brix did not correlate with the onset of the disease.