65 Potential Use of Bioagents in the Control of Postharvest Rot in Melon D. Terao 1 , C. Forner 2 , A. de H.N. Maia 3 and W. Bettiol 3 1 Embrapa Semiárido/Embrapa Meio ambiente, Petrolina, PE, Brazil 2 Universidade Estadual Paulista “Júlio de Mesquita Filho” - UNESP, Botucatu, SP, Brazil 3 Embrapa Meio Ambiente, Jaguariúna, SP, Brazil Keywords: Cucumis melo, Fusarium pallidoroseum, Bacillus, yeasts, biocontrol Abstract Rot caused by Fusarium pallidoroseum has had a severely negative impact on the export of melons from Brazil. Uncertainty regarding the health of the fruit due to the quiescent infection of the pathogen has led producers to use fungicides in the postharvest treatment of the fruit, thereby causing contamination and risking the health of consumers. Consequently, there is a demand for clean and safe natural technologies for the postharvest treatment of melons, including biological control. The present study aimed at evaluating bioagents for use in controlling Fusarium rot in ‘Galia’ melon. The following bioagents were evaluated: two isolates of Bacillus subtilis, B. licheniformis and a mixture of B. subtilis and B. licheniformis, as well as the yeasts Sporidiobolus pararoseus, Pichia spp., Pichia membranifaciens, P. guilliermondii, Sporobolomyces roseus, Debaryomyces hansenii and Rhodotorula mucilagenosa. Treatment with imazalil and water were used as controls. Two experiments were conducted in a completely randomised design with 10 replicates per treatment with four fruit per replicate; the disease incidence was evaluated in the first experiment, and the disease severity was evaluated in the second. Similarity analysis of the temporal evolution profiles of rot incidence caused by F. pallidoroseum allowed the evaluated treatments to be clustered into four groups. In the first experiment, the yeasts P. membranifaciens and D. hansenii produced results similar to that of the fungicide imazalil. The second experiment highlighted the yeasts P. guilliermondii and R. mucilaginosa. Electron microscopy studies confirmed that once applied to the fruit, the yeasts colonised the skin and damaged the pathogen mycelium; the action of the yeasts affected the mycelium of F. pallidoroseum, which had infected wounds on the fruit’s surface. Bacillus spp. did not provide good disease control. These results demonstrated that yeasts have the potential to control postharvest rot caused by F. pallidoroseum in ‘Galia’ melon. INTRODUCTION The results of a study performed during a cooperative project between Denmark, Estonia, Finland, Norway, and Sweden (the Nordic project) revealed the presence of high levels of pesticide residues in fruits from South America. Analyses of 724 samples of 46 fruit and vegetable species imported from eight South American countries indicated that, on average, over 80% of the samples contained pesticide residues. Multiple residues in a single fruit were detected in 71% of the samples. For example, samples of table grapes were found to contain up to nine different pesticides. A total of 83 different pesticide molecules were detected; among them, the fungicides used for postharvest treatment (thiabendazole, imazalil and prochloraz) appeared most often. The findings of this project drew attention to the need for the continuous monitoring of pesticide residues in fruits and fresh vegetables (Hjorth et al., 2011). Brazil is a major producer, consumer and exporter of melons. However, much of the production is lost due to the high incidence of rot caused by Fusarium pallidoroseum. The long storage periods required for the transport of fresh fruits from the site of production to the consumer market, together with the occurrence of quiescent infections that are not detectable at the time of shipment, have led to the application of fungicides for postharvest treatment. Such applications are usually empirical and indiscriminate and cause chemical contamination in the product. Proc. II nd IS on Discovery and Development of Innovative Strategies for Postharvest Disease Management Eds.: M. Wisniewski et al. Acta Hort. 1053, ISHS 2014