In vitro effect of some fungicides on growth and aflatoxins production by Aspergillus flavus isolated from Capsicum powder
Résumé
The aim of this study was to determine the effect of some pre-harvest fungicides on growth and aflatoxins (AF) production of three A. flavus strains found in Capsicum powder. Each isolate, previously isolated from paprika, chilli and smoked paprika, was inoculated on Yeast Extract Sucrose agar and on a 3% paprika extract agar medium supplemented with different fungicides and incubated at 20 and 30 ºC during 7 days. Growth measurements were obtained on the days 3, 5 and 7, and the AF production was determined on the day 7. The significance of the effects of the factors (strain, medium, temperature, time and fungicides) and their interaction over colony diameter and AF production was determined. Temperature constrained the effectiveness of fungicides in reducing growth, being the fungicides more effective at 20 ºC. The efficacy of the fungicides over AF production depended on the medium used and temperature. The most effective fungicides in inhibiting growth and AF production, regardless of the strain tested or applied conditions, were tebuconazole 25% and mancozeb 80% applied at a concentration of 0.75 and 3.5 g L-1, respectively. Care should be taken in the choice of a suitable fungicide, because their effectiveness may depend on intraspecific variation and temperature. Moreover, it is necessary to take into account that not always the most efficient fungicide in reducing growth is the best choice for pre-harvest treatments, because it may promote AF production. Thus, the best fungicide is the one which can simultaneous prevent growth and AF production.
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