Efeito da quitosana sobre a antracnose e características físicas e químicas de frutos de cultivares de bananeiras

Abstract

Amongst the main phytossanitary problems that occur in the banana culture, anthracnose, caused by fungus Colletotrichum musae, is distinguished as the most important post-harvest one in all the producing regions. Alternative forms of control that minimize or substitute the use of chemical products have been intensified. The use of natural products with antimicrobial properties, like chitin, chitosan and its derivatives have shown itself sufficiently effective in the control of a large range microorganisms that cause post-harvest disease, reducing losses and prolonging the useful life of the plant products. The objective of this work was to evaluate the use of the chitosan in the anthracnose's management in 'Prata-Ana banana; e varieties resistant to Black Sigatoka in different concentrations and pHs of the product and also physical-chemical characteristics of the treated fruits. The assays was set separately and at different times for each one of the evaluated varieties. The assays were carried out in experimental design entirely at random in factorial project 6x2x2 (six concentrations of chitosan (0; 5; 10; 15; 20 and 30 g/L) x two pHs (6,0 and 6,5) x two moments of application of the product (preventive and healing)). For each treatment four repetitions were used, each repetition composed of a bouquet contend three fruits. The evaluations were carried through every 72 hours for twelve days. In the evaluations of the physical and chemical characteristics the fruits were submitted only to healing method, being evaluated as for the variables: loss of fresh mass, total titratable acidity, solid soluble and firmness. The experiment was carried out in entirely at random in split-plot design, having in the parcels the six concentrations of chitosan (0, 5, 10, 15, 20 and 30 g/L), two pHs (6,0 and 6,5) and in the subparcels the 5 times of evaluation after the harvest, in interval of 48 hours, for the 'Caipira', Galil and Thap Maeo varieties, and four periods of evaluation, in interval of 72 hours, to 'Prata-And cultivar. The chitosan did not reduce the disease's incidence in any of the tested varieties. The trend of dose- dependent was well definite only for the 'Caipira' variety, being that the others presented irregular answers in the disease's severity with the addition of the concentration of the product. Different answers between the tested varieties also were observed in the physical and chemical analyses of the fruits. In the fruits of the Thap Maco variety, the chitosan provided the maintenance of firmness and reductions of the acidity, mass loss and soluble solid content. In the 'Prata-Ana, it was observed significant effect of the product in the maintenance of firmness and reductions in the soluble solid content and fresh mass loss. However, for the 18 Galil and Caipira varieties, it was observed significant effect only in the reduction of mass loss and in the total soluble solid content, respectively.