Biological Control of Apples Blue Mold by Isolates of Saccharomyces Cerevisiae

Yeasts (52, 51, 69, and 04) were received from Biotechnology Center of Karaj and Penicillium expansum isolates P11 and P12 isolated from Golden Delicious. Isolates were evaluated as a potential biological control agents of apple blue mold caused by P. expansum. Dual culture, cell free metabolites and volatile test were used in vitro assay. All tested of yeast isolates inhibited growth of P. expansum. The inhibition varied among isolates of yeasts and ranged from 19.81% to 40.73%, in dual culture, from 43.16% to 66.44% in volatile metabolite and from 22.16% to 50.23% in cell free metabolite test. Apple fruit wounds were inoculated with 40 μl of yeast cell suspension (107cell/ml) followed 48 h later by P. expansum (105 conidia/ ml). The apples were then incubated at 25°C. Four isolates of Saccharomyces cerevisiae reduced, the decay area from 13.46 to 24.92 cm2 compared to 32.18 cm2 in control after incubation for 14 days at 25°C. At 5°C, the lesion size ranged from 13.58 to 24.68 cm2 for the antagonist treatments compared to 22 cm2 for the control treatments after 32 days. The isolate 69 of S. cervisiae was the most effective isolate at both tempetures in this assay and could be one of important new biological control agents for apple blue mold.