Incidência e controle de fungos do gênero Aspergillus Seção Nigri em uvas viníferas cultivadas na região tropical do Brasil

Abstract

The Aspergillus section Nigri is reported as the main contaminant species of wine grapes. The production profile of OTA can be changed under different fungus cultivation conditions, such as availability of water, nutrients, pH and temperature. Thus the prevention of growth of mycotoxin-producing fungi is the most effective strategy for controlling the presence of mycotoxins in foods. In this sense, the present study aimed to evaluate the occurrence of Aspergillus section Nigri in different grapes varieties cultivated in tropical vineyard of Brazil, and evaluate the impact of the application of several fungicides on A. carbonarius growth and OTA production. The Aspergillus Seção Nigri were isolated from five grape cultivar and moforlogical identified. OTA was quantify by HPLC. A total of 272 isolates of Aspergillus section Nigri was isolated and identified in the following species A. carbonarius, A. niger, A. niger Agregado, A. foetidus, A. aculeatus and A. japonicus. Among them, A. niger Agregado was the most common specie in all grape samplings (42%), followed by the A. carbonarius (38%). All isolates of A. carbonarius (103) were OTA producers. The other species were not ochratoxigenic. These data suggest that the potential risk of OTA contamination in grapes was associated with A. carbonarius, due to the high frequency of occurrence and the OTA levels produced in vitro. Five fungicides used in Brazilian grapes were screen in CYA media and then incubated at 25°C. The colony diameter was measured every day during ten days of incubation period. OTA was quantified after period of incubation by HPLC. Then, the minimum inhibitory concentration (MIC) of each fungicide for A. carbonarius growth on semi synthetic grape medium at 15, 20 and 30°C was found. The effect of fungicides on A. carbonarius-inoculated grapes was investigated. At the doses recommended by manufacturers the majority of fungicides tested reduced A. carbonarius growth rate and OTA production. This effect was affected by fungicide, dose and temperature. The temperature was the main factor that affected the fungicides effectiveness again A. carbonarius growth and OTA production. The reduced growth and OTA levels were higher at 15°C than 20 and 30°C. The fungicides doses tested on grapes were not effective.