COMPETITION BETWEEN NATIVE ANTAGONIST YEASTS AND PENICILLIUM EXPANSUM, TABLE GRAPES PATHOGEN UNDER POSTHARVEST CONDITIONS

PEDROZO P. ; RODRÍGUEZ L. ; PESCE V.M. ; TORO M.E. ; MATURANO Y.P.; NALLY M.C. ; VAZQUEZ F.

San Carlos de Bariloche

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

Table grapes are preserved in cold storage chambers for its subsequentcommercialization, but this environment is favorable for the development of pathogenic fungi such as Penicillium expansum. As an alternative to the use of synthetic fungicides that affect the quality of the grape, the environment and human health, biological antifungal agents are proposed for the control of P. expansum. Through the study of the mechanisms of competition for nutrients between pathogens and antagonists, it is possible to determine the coexistence or competitive exclusion among them, depending on the level of partition or overlap of nutritional resources. In the same way, the competence can be evaluated by measuring the ability of yeasts to produce micronutrient chelating compounds such as iron. With the objective to evaluate the competition for nutrients between antagonistic and pathogenic microorganisms, the following were determined: Niche superposition index (NOI), niche size (NS) and siderophore production at 0±1°C. We used 15 yeasts isolated from fermenting musts and grapes stored in cold storage, all of them biosuppressors of P. expansum PSS6:Rhodotorula glutinis (Rg 4, 14, 19, 56), Cryptococcus magnus (Cm 16, 23),Aureobasidium pullulans (Ap 13, 77, 88) and Metschnikowia pulcherrima (Mp 22, 36.43, 45, 46, 53). Results suggest that there would be competitive exclusion between Rg4, Rg14, Rg19, Cm23, Rg56, Ap77 and PSS6. These yeasts could affect the development of the pathogenic fungus by decreasing the availability of nutritive resources. A. pullulans Ap13 could be proposed as an effective antagonist against PSS6, being the only yeast capable to compete for carbon and nitrogen nutrients and to produce siderophores under refrigerated chamber conditions. The study of mechanisms of action of yeasts based on the microbial interactions of competition for substrate is a relevant contribution, since there are no reports on this specific pathosystem in low temperaturepostharvest conditions.