Impact of fungicides on Aspergillus carbonarius growth and ochratoxin A production on synthetic grape-like medium and on grapes.
Résumé
A study to evaluate the impact of the application of several fungicide treatments used in Spanish vines, on Aspergillus carbonarius growth and ochratoxin A (OTA) production was developed. Three trials were designed in order to: i) screen 26 fungicides at the doses recommended by manufacturers on grape-like synthetic medium (SNM) at 20 şC and 30 şC; ii) find out the minimum inhibitory concentration (MIC) of each fungicide for A. carbonarius growth on synthetic medium, and iii) investigate the effect of several fungicides on A. carbonarius-inoculated grapes. In synthetic medium, nine fungicides significantly reduced A. carbonarius growth rate, meanwhile 13 completely inhibited its growth. In general, growth was faster at 30 şC than at 20 şC, contrary to OTA production. Fungicides that stopped fungal growth also inhibited OTA production, but not all the fungicides that reduced growth reduced the OTA synthesis. In general, fungicides that contained copper or strobilurins reduced both growth and OTA production, contrary to sulfur fungicides. At the optimum temperature for A. carbonarius growth, 30 şC, higher amounts of fungicide were needed to prevent fungal growth than at 20 şC. Among the fungicides that inhibited A. carbonarius growth on SNM at the initial doses, cyprodinil seemed to be the active ingredient more effective to stop fungal growth when testing reduced doses. Fungicide effect on grapes was similar than that on synthetic medium. Both infection and OTA production were reduced when using cyprodinil 37.5% +fludioxonil 25% and azoxystrobin 25%. Penconazole 10% also showed a clear reduction of the OTA production at both temperatures, although infection was only reduced at 20 şC. OTA reduction was strain and temperature-dependent. In general, fenhexamid 50%, mancozeb 80% and copper hydroxide 80%+copper 50% enhanced infection and OTA production.
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