Caracterização epidemiológica e manejo da podridão pós-colheita por Aspergillus em uva de mesa

Abstract

The grapevine is one of the oldest plants cultivated by human and has significant social and economic importance worldwide. The Submedio San Francisco Valley has a key role in the production and export of the grape, however, the culture has a high susceptibility to postharvest fungal infections generating significant losses from cultivation to marketing. Aspergillus niger is a common fungal species in the region today, especially when harvesting occurs during rainy periods. In general, there is darkening and softening of the berries, in the fruit storage period, resulting in depreciation of the commercial value of the grape. There is a strong need to explore alternative measures in the postharvest that are safe and effective to reduce decay and increase shelf life. Thus, the objective of this study was to evaluate the inoculum concentration (102, 103, 104, 105, 106 e 107 conídia.mL-1), the wetness period (0, 12, 24, 36 e 48 h) and temperature (2, 5, 10, 15, 20 e 25 °C) that are optimal for disease establishment in table grape cv. Italy, evaluate the effect of Ca, K, Cu, Mg and Zn phosphites salts applied at postharvest by dipping the clusters in solutions at different concentrations (0,3; 0,9; 1,25; 1,7 and 2,0 g.L-1) in two inoculation periods of A. niger (12 and 24 h), and in vitro tests, by mycelial growth and conidia germination as well the chemical characteristics of the grape. The highest inoculum concentrations (106 and 107 conídia.mL-1), wetness period 48 h and temperature 25 °C showed the greatest mean lesion size, it means, that these are optimal conditions for the development of Aspergillus rot in Italy table grape. The phosphites inhibit mycelial growth and germination of conidia. Zn phosphite had significantly lower EC50 values to the others, as well as phosphite Ca for micelial growth. The lowest EC50 values are represented by K and Ca phosphite for conidial germination. There was no significant interaction between the salts in the applied concentrations and is not effective in reducing the severity of the disease in table grape. The Ca phosphite showed lower average size values of the lesion when the berries were treated 12 hours before inoculation, and could be relevant in future research.