Effect of Ochratoxin A-Producing Aspergilli on Stilbenic Phytoalexin Synthesis in Grapes

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Abstract
Berries of Vitis vinifera L. cv. Barbera were infected, at veraison and during ripening, by a conidial suspension of A.japonicus, A. ochraceus, A. fumigatus and two isolates of A. carbonarius to control ochratoxin A production and stilbene induced synthesis. The experimental design provided also for intact and punctured berries and incubation temperature of 25 °C and 30 °C. All the tested fungi, except A. fumigatus, significantly increased trans-resveratrol synthesis over the control, while trans-piceid was not affected; only A. ochraceus significantly elicited the berries to synthesize piceatannol. The two isolates of A. carbonarius produced higher amounts of ochratoxin A than did the other fungi. A positive correlation between ochratoxin A and trans-resveratrol synthesis occurred. trans-Resveratrol and piceatannol showed fungicidal activity against A. carbonarius, being able to completely inhibit fungal growth at a concentration of 300 μg/g and 20 μg/g, respectively. Keywords: Vitis vinifera L.; Aspergillus spp.; stilbenes; resveratrol; piceatannol; ochratoxin A.