Semi-commercial testing of regional yeasts selected from North Patagonia Argentina for the biocontrol of pear postharvest decays

The efficacy of two regional yeasts, Pichia membranifaciens NPCC 1250 and Vishniacozyma victoriae NPCC 1263, for controlling pear postharvest decay was evaluated at large scale (semi-commercial conditions) in two different packing houses. The human safety of the two yeast strains was initially assayed by assessing growth at body temperature, pseudohyphal growth, phospholipases production, and growth in simulated gastric juice. Subsequently, yeasts biomass was produced in a bioreactor (22 L) containing 18 L of culture medium based on sugarcane molasses plus urea. The produced biomass, with/without CaCl2 (2% w/v) addition, was used in biocontrol experiments carried out at semi-commercial scale on Beurre d'Anjou and Packham's Triumph pears. Vishniacozyma victoriae NPCC 1263 plus CaCl2 showed high performance on controlling decay caused by Penicillium expansum and Botrytis cinerea. On Beurre d'Anjou cv, P. expansum and B. cinerea incidence was reduced by 70% and 100%, respectively, after 90 days of commercial storage. On Packham's Triumph the incidence of the two decay forms was 63% after 150 days. The two antagonistic yeasts were able to establish and colonize the surface of the fruits, with an estimated increase in the population density of approximately three orders of magnitude during the postharvest period. This work is the first to evaluate and demonstrate the efficacy of local biocontrol experiments with regional yeasts under semi-commercial conditions.