Biological control of blue mould on apple by a strain of Candida sake under several controlled atmosphere conditions

Abstract

The biocontrol potential of the yeast Candida sake (CPA-1) against Penicillium expansum decay of apples under several controlled atmosphere conditions was investigated. In a laboratory trial under different commercial cold storage conditions, increasing concentrations of C. sake improved decay control. A maximum reduction of decay was achieved at 3% O 2–3% CO 2 atmosphere. It amounted to a 97% lesion reduction after treatment with a suspension containing 2.4×10 6 CFU/ml of C. sake (CPA-1). In a semi-commercial trial at 1°C with wounded fruits, the reduction in decay diameter caused by C. sake exceeded 80% after 60 days at 21% O 2 and 60% after 120 days of storage under controlled atmosphere conditions. For seven controlled atmosphere conditions studied, a significant influence by C. sake on the P. expansum decay was observed, and the lesion size was reduced more than 70% by C. sake at 10 7 CFU/ml. The populations of C. sake (CPA-1) on the apple surface followed the same pattern under all controlled atmosphere conditions studied. They decreased 4–10-fold during the first 2 weeks, followed by an increase to the initial level after 45 days, and thereafter the count remained constant for the period of 90 days examined. This indicated the capacity of C. sake (CPA-1) to colonize the surface of apples under various storage conditions. The ability to colonize was even higher in apple wounds.