Abstract
Two osmotolerant strains (87 and 101) of the yeast, Candida sp., were tested for ability to reduce lesion development in Golden Delicious apple after challenge with 105 or 104 conidia per milliliter of the postharvest pathogens Botryis cinerea and Penicillium expansum. Lesion size and frequency of Botrytis rot were significantly less in fruit pretreated with aqueous suspensions of strains 87 ad 101 (107 and 108 colony-forming units [cfu]/ml) as compared with controls pretreated with water. Significant, but marginal, reduction of Penicillium rot was observed in treatments with these yeasts at 108 cfu/ml. Biological control of Biological control of Botrytis rot was enhanced when wounds were treated with strain 87 at 107 cfu/ml in 2% (w/v) aqueous solutions of CaCl2, CKl,and CaCO3, as compared with aqueous suspensions of the strain alone. Salt solutions applied to wounds without yeast cells did not reduce rot. The ability of the salt solutions to enhance control with yeasts was not related to the osmotic potential of the solutions. Calcium chloride was the most effective salt. Yeast strains differed slightly in their response to calcium chloride; a 1% concentration enhanced biocontrol with strain 87, whereas a 2% concentration was necessary to enhance control withs train 101. Calcium chloride facilitated control of Botrytis rot with yeast populations as low as 106 cfu/ml. Decay due to Penicillium expansum also was significantly reduced when fruit were treated with strains 87 and 101 in the presence of calcium chloride.