In vitro evaluation of epiphytic vine yeasts activity for biocontrol of ochratoxigenic grapes' molds

One hundred and fourty-four strains of epiphytic micro-organisms, isolated from berries of "Negroamaro ", an apulian grape wine variety, were screened for antagonistic activity against Aspergillus carbonarius and A. niger. These black Aspergilli are considered the main ochratoxigenic species responsible for the accumulation of ochratoxin A in grape. Twenty eight yeast isolates were selected for their inhibitory effects on the above fungal species and assayed by an in vitro nutritional competition test for their antagonistic capacity towards three selected ochratogenic strains. Six yeast isolates belonging to five species, namely 2 isolates of Issatchenkia orientalis and one each of Metschnikowia pulcherrima, Kluyveromyces thermotolerans, Issatchenkia terricola and Candida incommunis species, were finally selected and screened on wounded grape berries for their ability to inhibit the contemporary infection by ochratoxigenic molds and reduce the formation of ochratoxin A. With the exception of the K. thermotolerans isolate, when inoculated at 109 CFU/wound, the other five challenger yeasts reduced the A. carbonarius and A. niger colonization on grape berry (P < 0.05). In particular, the best antagonistic activity was shown by the two I. orientalis isolates. Results suggest that antagonist yeasts with the potential to control of A. carbonarius and A. niger on grape can be found among the microflora associated with the berries.