Efficacy of antagonistic bacteria in protection of apples against Botrytis cinerea and Penicillium expansum under CA conditions

Of 300 isolates of epiphytic bacteria originating from leaf and fruit surfaces of apple, three (B90, B194, B224) were selected which showed very high activity in protection of apples against grey mould (B. cinerea) and blue mould (P. expansum). The bacterial suspension of each isolate was placed on wounds of apples cv. Jonagold followed by inoculation with a conidial suspension of the particular pathogen. Apples were then stored in normal storage at 2-3 degrees C or in controlled atmospheres (CA) containing 1.5% CO2+1.5%O-2 or 5%CO2+3%O-2. After 40 days, the diameter of the rot spot developed around each wound was measured and the number of bacteria determined. The tested bacterial isolates totally protected apples against blue mould in all storage conditions. However, they showed differential activity against grey mould. In one experiment, total protection by all isolates was obtained only in CA. In a second experiment, only the isolate B90 was more effective in CA than in normal storage. No significant differences in protective activity of bacteria between the CA treatments were found. The number of bacteria of all isolates significantly decreased in wounds in CA, and in normal storage they decreased only in case of isolate B90 and B224. The tendency of highest reduction in bacterial population was observed in the atmosphere containing 1.5% CO2 and 1.5% O-2.