Cold-adapted yeast as biocontrol agents of postharvest pathogens in cherries of Patagonia Sur, Argentina

LOPEZ, SOFIA; SANGORRIN, M.P.; PILDAIN, MARIA BELEN

Recife

Jornada; V Jornadas Sudamericanas de Biología y Biotecnología de Levaduras; 2015

Cherries are marketed fresh and cold-stored to extend its useful life. One problem of thiscommodity is the postharvest decay caused by moulds. In our country there are nofungicides registered for post-harvest stage in cherries. Among different biologicalapproaches suggested in the literature, the use of biocontrol agents (BCAs) show greatpotential as an alternative method of postharvest disease control. The objectives of thiswork was to select antagonistic indigenous yeasts to be used in the biocontrol ofpostharvest pathogens. For that purpose we evaluated: a) the ability of growing at 0°C ofthe isolated yeasts; b) biocontrol efficacy against virulent postharvest pathogens(Penicillium crustosum and Mucor piriformis), in storage fruit (30 days at 0°C and 3 daysat 22°C) and marketing conditions (7 days at 22°C); and c) putative mechanisms involvedin the biocontrol capacity of yeasts: production of antifungal compounds (diffusible andvolatile), inhibition of conidia germination, biofilms formation, killer toxin secretion andsecretion of hydrolytic enzymes. Growth capacity at 0°C was evaluated in 660 native yeastisolates, of which 54 were selected for testing their growth rate under these conditions.Cryptococcus adeliensis 441, Cryptococcus stepposus 614, Aureobasidium pullulans 1141isolates reduced the incidence and severity of P. crustosum. While Cryptococcus victoriae30, C. adeliensis 154, Meyerozyma guillermondii 199 and Gueomyces pullulans 899reduced incidence and severity of M. piriformis. A. pullulans 631, C. victoriae 771 andCystofilobasidium capitatum 1204 reduced the incidence and severity of both fungi. Thoseisolates were selected for evaluation of the mechanisms of action in vitro. A. pullulans 1141and C. capitatum 1204 produces hydrolytic enzymes, inhibition of conidia germination andproduction of antifungal compounds. C. stepposus 614 and C. victoriae 30 shows thecapacity to form biofilms and killer toxin secretion respectively. A. pullulans 1141 and C.capitatum 1204 were the most effective and promising of the antagonists. Our studyindicates that multiple modes of action may explain why selected yeast provided excellentcontrol of postharvest cherries disease.