Aplicação da radiação ultravioleta-C para controle da podridão peduncular do mamão.

A podridao peduncular em mamao e fator limitante na comercializacao, principalmente para exportacao. Os objetivos do presente trabalho foram definir doses de luz ultravioleta C (UV-C) que inibem a germinacao de esporos dos fungos do complexo causador da podridao peduncular, bem como avaliar doses de UV-C no controle da doenca nos frutos. Suspensoes de esporos foram irradiadas com doses variando de 0,25 a 2,00 kJ m -2 plaqueadas e apos 72h avaliou-se a inibicao na germinacao pela contagem de Unidade Formadora de Colonias (UFC). Em teste in vivo irradiou-se a regiao peduncular do fruto com doses de 0,5 a 2,0 kJ m -2 . Apos irradiados, os mamoes foram armazenados durante sete dias em câmara fria e oito dias em temperatura ambiente, avaliando-se, diariamente, a incidencia e a severidade da doenca. A dose de UV-C necessaria para inibir os esporos variou em funcao da sensibilidade da especie fungica. Em frutos, doses ? 0,5 kJ m -2 prolongaram o periodo de incubacao dos frutos e diminuiram a taxa de progresso da podridao peduncular, sendo otima a dose considerada entre 0,5 e 1,5 kJ m -2 . A epiderme do mamao e sensivel a radiacao UV-C, portanto a aplicacao desta radiacao deve ser direcionada apenas ao pedunculo, e o restante do fruto dever ser protegido. -- Abstract: Fruit stem-end rot in papaya is a limiting factor in commercialization, mainly for exportation. The aims of this work were to determine the ultraviolet C light (UV-C) doses to inhibit the spore germination of the fungi complex causing papaya stem-end rot, and to evaluate doses for controlling the disease. Spore suspensions were irradiated with different doses ranging from 0.25 to 2.0 kJ m -2 , plated, and after 72h, the inhibition on germination was evaluated. For in vivo tests, the peduncle region of the fruit was irradiated with doses from 0.5 to 2.0 kJ m -2 . After irradiation, the papayas were stored for 7 days in a cold room and 8 days at room temperature, evaluating daily the incidence and severity of the disease. The dose of UV-C required to inhibit fungal spores germination varied according to the sensitivity of the fungal species. On fruit, UV-C radiation presented an effective result from the dose of 0.5 kJ m -2 , which significantly increased the incubation period and lowered the progression rate of peduncle rot, as the optimal dose falling within the range from 0.5 to 1.5 kJ m -2 . The epidermis of papaya was found to be very sensitive to UV-C, therefore the radiation should be directed only to the peduncle, protecting the rest of the fruit.