Métodos de detecção de infecção quiescente de Colletotrichum musae em banana "Prata Anã"

Abstract

The anthracnose, caused by the quiescent fungus Colletotrichum musae, is considered the most severe disease in post-harvest conditions being distributed in all of the producing areas. Order to detecting quiescent infections in tropical fruits, some techniques have been studied and used, seeking to quantification of the infection level on the fruit's surface before the ripening. The study aimed to evaluate the Ethanol, Paraquat and Ethephon methods in different concentrations and age of maturation of the fruits to detecting quiescent infections of C. musae in "Prata-Ana" banana. Initially methods in different concentrations of the products were evaluated in unripe fruits, with 3 weeks antecedents to commercial harvest time being: Ethanol in the concentrations: 40%; 50%; 60%; 70% and control (being control 1 fruits with 3 weeks antecedents to harvest without immersion in product, and control 2 fruits in commercial harvest time without immersion in product); Paraquat in the concentrations 3 mL⎺¹, 6 mL⎺¹, 9 mL⎺¹; 12 mL⎺¹ and control (being control 1 fruits with 3 weeks antecedents to harvest without immersion in product and control 2 fruits in commercial harvest time without immersion in product) and Ethephon in the concentrations 1.2 mL⎺¹ 1.45 mL⎺¹; 2.1 mL⎺¹; 2.4 mL⎺¹ i.a and control (being control 1 fruits with 3 weeks antecedents to harvest without immersion in product and control 2 fruits in commercial harvest time without immersion in product). Later, the effect of the age of unripe fruits was analyzed with 2, 3, 4 and 5 weeks before the harvest time and fruits in commercial harvest time on the efficiency of the methods in the selected concentrations: Ethanol (40%); Paraquat (3 mL⎺¹ ) and Ethephon (1.2 mL⎺¹ i.a). In all of the experiments, the fruits were maintained in refrigerating chamber to 25 °C ± 1° and 85% ± 5% of relative humidity for 12 days for the Ethanol and Ethephon methods and 18 for the Paraquat one. Every three days, the fruits were appraised, according to incidence and severity of the disease. The Ethanol method is not efficient in the detection of quiescent infections in "Prata-Anã" banana in any fruits age. The fruits' age that provided the highest disease incidence was the one of 2 weeks antecedents to commercial harvest when they were submitted to the Ethephon method in the dose 1.2 mL⎺¹. It is concluded that the Ethephon method was the most appropriate in detecting quiescent infections of C. musae, in advance of 15 days before the harvest. That result is constituted, therefore, in alternative of great applicability in the precocious detection of anthracnose.