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

PEDROZO PAULA; RODRIGUEZ LETICIA; PESCE VIRGINIA MERCEDES; TORO MARIA EUGENIA; MATURANO PAOLA; NALLY CRISTINA; VAZQUEZ FABIO

BARILOCHE

Simposio; INTERNATIONAL SPECIALIZED SYMPOSIUM OF YEAST; 2018

Table grapes are preserved in cold storage chambers for its subsequentcommercialization, but this environment is favorable for the development of pathogenicfungi such as Penicillium expansum. As an alternative to the use of synthetic fungicidesthat affect the quality of the grape, the environment and human health, biologicalantifungal agents are proposed for the control of P. expansum. Through the study of themechanisms of competition for nutrients between pathogens and antagonists, it ispossible to determine the coexistence or competitive exclusion among them, dependingon the level of partition or overlap of nutritional resources. In the same way, thecompetence can be evaluated by measuring the ability of yeasts to producemicronutrient chelating compounds such as iron. With the objective to evaluate thecompetition for nutrients between antagonistic and pathogenic microorganisms, thefollowing were determined: Niche superposition index (NOI), niche size (NS) andsiderophore production at 0±1°C. We used 15 yeasts isolated from fermenting mustsand 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 developmentof the pathogenic fungus by decreasing the availability of nutritive resources. A.pullulans Ap13 could be proposed as an effective antagonist against PSS6, being theonly yeast capable to compete for carbon and nitrogen nutrients and to producesiderophores under refrigerated chamber conditions. The study of mechanisms of actionof yeasts based on the microbial interactions of competition for substrate is a relevantcontribution, since there are no reports on this specific pathosystem in low temperaturepostharvest conditions.