Yeast as potential biocontrol agents for Aspergillus carbonarius

PONSONE, M.L; CHIOTTA, M.L ; COMBINA, M; DALCERO, A.M; CHULZE, S.N

Mendoza

Congreso; Strategies to reduce the impact of mycotoxins in LatinAmerica in a global context; 2011

UNRC, ISM, Mycored

Aspergillus species, section Nigri have been reported as agents of black grape rot. The significance of this disease increase when black Aspergilli, particularly A. carbonarius, were recognized as potential sources of ochratoxin A (OTA) in grapes and wine. Biological control has been proposed as a strategy to reduce the impact of ochratoxigenic species in the vineyards. This control needs to be used during grape development as a preventive strategy to avoid the grape colonization by ochratoxigenic species and, consequently, OTA accumulation. Among the microorganisms considered as potential biological control agents, yeasts are particularly promising, due to their capacity of colonizing plant surfaces or wounds for long periods under dry conditions. The efficacy of two strains of Kluyveromyces thermotolerans (RCKT4 and RCKT5) in preventing the growth and ochratoxin A (OTA) accumulation of ochratoxigenic fungi under greenhouse conditions was evaluated. The biocontrol agents were used as cell suspension in distilled water containing adjuvant (0.01%). Inocula were adjusted to 1 x 104 and 1 x 106 cells/ml. The experiment was done in a complete randomized block design with 4 replicates. The yeasts were sprayed on the grape bunches  at veraison and one month after veraison, while the A. carbonarius strain was applied one month after veraison on damaged and undamaged grapes. Untreated grapes were sampled at the beginning of the experiment, second and third sampling dates of treated and untreated vine plants were done at one month after veraison and at harvest (during 2010/2011 vintage). From  each plant  at each sampling stage fifty berries, randomly selected from the ten different bunches, were surface disinfected and plated onto a Dichloran 18% Glycerol Agar (DG18) and Dichloran Rose Bengal Chloramphenicol Agar (DRBC) media, for A carbonarius and yeasts quantitation. Data from this study showed that both yeast strains were able to control Aspergillus carbonarius growth. Also was observed that the yeast population was successfully established after the first application until the harvest stage in the inoculated grapes. Ochratoxin A accumulation was determined at harvest stage and it was observed that K. thermotolerans RCKT5 was able to control OTA production by A. carbonarious RC13I at an inoculum level of 1 x 104 cells/mL  These results are promising for future development of a biopesticide based on grape native yeasts.