Doenças pós-colheita em laranja 'Valência' e caracterização da população fúngica em pomares orgânicos e convencionais

Abstract

Organic farming aims to meet growing demand for healthy foods, produced without the use of pesticides. The purposes of this work were a) to characterize postharvest diseases in 'Valencia' oranges grown under organic and conventional conditions; b) to characterize the environmental mycoflora in citrus orchards and c) to detect the presence of Penicillium spp. isolates resistant to fungicides thiabendazole and imazalil in the orchards. Citrus fruit collected at the orchards and at the wholesale market of São Paulo (CEAGESP) were stored during 14 days at 25°C and 85% UR. The incidence of postharvest diseases was evaluated visually every two-three days. The environmental mycoflora was sampled according to the gravimetric method, using Petri dishes containing potato-dextrose-agar medium, supplemented or not with fungicides. The highest incidence of diseases was observed in oranges sampled in organic orchards in comparison to the conventional system. The most frequent postharvest disease was lasiodiplodia stem-end rot. The environmental mycoflora and the population of the major genera of fungi did not differ significantly among the sampled orchards. Cladosporium was the most prevailing genus in the orchards. The frequency of P. digitatum isolates resistant to thiabendazole was similar in orchards, with an average of 47.3%. The frequency of P. digitatum isolates resistant to imazalil was low (2.6%), and resistance to thiabendazole + imazalil was not observed. © Brazilian Phytopathological Society. Printed in Brazil.