POSSIBLE ANTIFUNGAL ACTION MECHANISMS OF VITICULTURE YEASTS AGAINST BOTRYTIS CINEREA ISOLATED FROM LETTUCE. SAN JUAN. ARGENTINA

NALLY M.C; LENCINAS M. ; PESCE V.M. ; FLORES B. ; PEDROZO P.; TORO M. E. ; CHULZE S. ; VAZQUEZ F.

San Carlos de Bariloche

Simposio; International Specialized Symposium of Yeasts (ISSY 34); 2018

The use of naturally occurring yeasts as biocontrol agents has attracted special interest because of their special attributes, nevertheless it has been recognized that the efficacy and consistent performance of such agents are affected by different factors. Elucidation of the action mechanisms could be useful for formulation and optimization of a biocontrol inoculum. In order to select a biocontrol agent for controlling gray mold in lettuce, 16 indigenous viticulture yeasts (15 S. cerevisiae y 1 S. pombe) were tested accordingly to inhibitory activity on the mycelial growth of Botrytis cinerea B1 (from Lettuce) in vitro for detecting the potential production of diffusible metabolites. Weevaluated the capacity competition for nutrients (Niche Overlap Index) between yeasts and B11. Materials and Methods: 1-In vitro yeastހpathogen direct interaction: The potential biocontrol yeasts were co-cultured with the pathogen on Petri dishes containing Czapeck-Yeast extract-Agar, to test antagonistic activity, pH4.6. Niche Overlap Index (NOI): Fungal mycelium discs (9mm) and yeast aliquots (20 μL, 106 cells/mL) were inoculated on separate plates. Each plate contained one carbon source (10 mM), YNB with 20 g/L Agar, pH 5.5. The assayed carbon sources (14) are present in lettuce and represent the size of the niche. Results showed that all the evaluated yeasts significantly reduced the growth from 22 to 52%, in comparison with the untreated control (100%). Nine Saccharomyces-fungus interactions showed NOI values between 0.92 and 1. These yeasts also inhibited B. cinerea in vitro. These results suggest that the yeasts assayed were able to inhibit B. cinerea and successfully assimilate a wide variety of carbon sources, making these nutrients unavailable to fungi and allowing rapidly proliferation of yeasts (competitive exclusion). Furtherexperiments should be conducted to determine the efficacy of these yeasts undercommercial lettuce production.