Caracterização de isolados de Colletotrichum musae de Minas Gerais e avaliação de táticas de controle da antracnose da bananeira

Abstract

Anthracnose is one of the major post-harvest diseases in bananas. The objective of this work was to characterize Colletotrichum musae isolates of 'Prata-Anã' banana from different regions in the North of Minas Gerais and to evaluate postharvest control tactics for anthracnose. In order to characterize the isolates of C. musae from the region, fruits of commercial 'Prata-Anã' banana plantations were collected in different producing municipalities in the North of Minas Gerais, evaluated by measurements of mycelial growth and sporulation of the fungus. The pathogenicity test of these isolates was performed by assessing the size of the anthracnose lesion in the fruits. To evaluate the sensitivity of the isolates to the fungicide, different concentrations of imazalil were tested for mycelial growth and fungal sporulation. The concentration of conidia for the development of anthracnose in 'Prata-Anã' banana was also evaluated. In order to determine the time of banana bagging to reduce anthracnose, polypropylene bags were used as a physical barrier method. The fruits were evaluated as for the incidence and severity of anthracnose and analyzed for post-harvest conservation. In the evaluation of the time of year of highest occurrence of anthracnose in banana and the effect of registered fungicides, monthly evaluations of the disease intensity were carried out on the fruits during one year and the Area Under the Severity Progression Curve (AUSPC) was calculated. It was observed that the isolates of Nova Porteirinha, Capitão Enéas, Verdelândia and Janaúba showed the smallest averages of mycelial growth. Higher sporulation was observed in the isolates of Pirapora and Matias Cardoso. There was no relationship between mycelial growth and sporulation of the isolates. It was observed a difference in relation to the aggressiveness of the isolates, demonstrating pathogenic diversity within the species of collected C. musae. The anthracnose severity as a function of the concentration of C. musae conidia in 'Prata-Anã' banana was gradual, but the concentration 107 spores mL-1 provided a higher disease severity. From the concentration of 5 ppm, the fungicide inhibited mycelial growth and conidia production in all isolates of C. musae, proving its potential in higher concentrations. With the use of bagging of bunches on the field, the incidence of the anthracnose in 'Prata-Anã' banana was reduced by up to 66.75% compared to the bunches without the bagging protection. Bunches bagged at a lower phenological stage reduced post-harvest disease severity. The period of bunch bagging did not interfere in the post-harvest conservation of 'Prata-Anã' banana. Rainfall distribution significantly interfered with the development of anthracnose. Treatment with the Imazalil fungicide presented the lowest AACPS values along the year.