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

Abstract

RESUMOA agricultura orgânica busca atender a demanda crescente por alimentos saudáveis, produzidos sem agroquímicos. Este trabalho objetivou: a) caracterizar as doenças pós-colheita em laranjas 'Valência' provenientes de cultivo orgânico e convencional; b) caracterizar a micoflora ambiental nos pomares citrícolas e c) detectar a presença de isolados de Penicillium spp. resistentes aos fungicidas tiabendazol e imazalil nos pomares. Frutos coletados nos pomares e no mercado atacadista de São Paulo (CEAGESP) foram armazenados durante 14 dias a 25ºC e 85% de UR. A incidência de doenças foi avaliada visualmente a cada dois-três dias. A micoflora ambiental foi amostrada com placas de Petri, contendo meio batata-dextrose-ágar acrescido ou não dos fungicidas. As maiores incidências de doenças foram observadas nas laranjas orgânicas em relação as do sistema convencional. A principal doença detectada foi a podridão peduncular de lasiodiplodia. A micoflora total do ambiente, assim como os principais gêneros fúngicos não diferiram significativamente entre os pomares amostrados. Cladosporium foi o gênero fúngico mais abundante nos pomares. A frequência de isolados de P. digitatum resistentes a tiabendazol foi semelhante nos pomares, com média de 47,3% dos isolados. A frequência de isolados de P. digitatum resistentes a imazalil foi baixa (2,6%), não sendo constatados isolados resistentes a tiabendazol + imazalil. Palavras-chave: Citrus sinensis, Penicillium spp., citros, podridões, resistência a fungicidas. ABSTRACT Postharvest diseases in orange fruits and characterization of the fungal population in organic and conventional farmersOrganic 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 25ºC 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...

Transition management for organic agriculture under citrus cultivation favors fungal diversity in soil

“…The CFU count of Penicillium isolates was significantly higher in TM, which may be also associated with the reduced chemical applications (75%), mainly from the second year of harvest. The genus is considered the main threat in citrus post-harvest (Fischer et al ., 2011), but its manifestation also depends on the practices used in the conduction of the crop to the field, harvesting, transportation and storage (Fischer et al ., 2013).…”

Alternative products in the management of green mold in postharvest oranges

“…Fischer et al (2009) conducted studies in the citrus packinghouses of São Paulo and found that 39% of P. digitatum isolates were resistant to fungicides in the benzimidazole group. In organic and conventional orchards in São Paulo, 47.3% of P. digitatum isolates were resistant to benzimidazole (Fischer et al, 2011) phosphite was applied after previously treating the fruit with hydrogen peroxide solution (20 g L -1 ) and copper sulfate (6 mmol L -1 ).…”