Post-harvest control of Penicillium expansum on pome fruits by the bacterium Pantoea ananatis CPA-3

Antagonistic bacteria and yeasts were isolated from the epiphytic flora of different cultivars of apples, stored in different packing-houses, and evaluated for their ability to control Penicillium expansum on pome fruits. Most microorganisms isolated from apples stored in packing-houses were bacteria (96% of strains), and only 4% were yeasts. A bacterial strain, identified as Pantoea ananatis (CPA-3), was particularly effective in post-harvest control of blue mould in different cultivars of pome fruits. This strain provided excellent control of the blue mould pathogen during short-term storage at 20degreesC, at concentrations close to 10(8) cfu ml(-1), for 'Golden Delicious' and 'Starking Delicious' apples, and for 'Blanquilla' and 'Devoe' pears. Moreover, this bacterium provided good control of blue mould on 'Golden Delicious' apples under cold storage conditions for 2 months, but was better in a low oxygen atmosphere than in air. The rapid growth of P ananatis in fruit wounds under different storage temperatures demonstrates that this bacterium can be considered as a biocontrol agent for pome fruits. Moreover, in vitro studies showed that this bacterium could not grow at pH values close to that of gastric juice, or at 37degreesC.