Effect of ochratoxin A-producing Aspergilli on stilbenic phytoalexin synthesis in grapes

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 degreesC and 30 degreesC. 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 mug/g and 20 mug/g, respectively.