STUDIES ON ANTAGONISTIC YEAST SPECIES AGAINST ERWINIA AMYLOVORA IN CO-CULTURE AND ON APPLE BLOSSOMS

Epiphytic yeast strains have antagonistic activity against Erwinia amylovora on detached apple blossoms in growth chamber and field experiments. A total of sixteen yeast-like fungi and yeast strains were investigated. Among them were the strains Aureobasidium pullulans CF10 and CF40 and Metschnikowia pulcherrima MSK1. In addition, five isolates from the apple phyllosphere, and seven yeast strains selected for postharvest disease control and obtained from the German collection of microorganisms (DSMZ), were investigated in co-culture and on detached apple blossoms. Based on these experiments Aureobasidium pullulans CF10, Candida sake and Metschnikowia pulcherrima strain 4 were selected for further experiments in growth chamber and orchard experiments. Fruit russeting resulted from some treatments on certain apple cultivars. The pH of the medium decreased to pH 5 or lower 48 h after co-culture with E. amylovora. A low pH of the medium alone did not result in strong growth inhibition.