Effectiveness of a Peptide-rich Fraction from <i>Xenorhabdus budapestensis</i> Culture against Fire Blight Disease on Apple Blossoms

Abstract

Erwinia amylovora is one of the most frequently occurred plant pathogenic bacterium. It causes necrosis and blight symptoms on host plantsand it lead to considerable yield losses throughout the world on apple trees. There is no effective chemical treatment is currently available against fire blight. The purpose of the present study was to search a new, alternative control method. The evaluation of the plant protection potential of an enriched fraction of Xenorhabdus budapestensis cell-free conditioned media was investigated. Purified samples were tested in vitro and in plantaagainst the phytopathogenic bacterium. A reproducible method for isolation of a peptide-rich fraction from Xenorhabdus cell-free conditionedmedia was established. The process resulted in 400 mg of dry sample prepared from three litres of Xenorhabdus cell culture. Significant correlation was found between the concentration of the purified preparation and the induced inactivation zones against Erwinia amylovora Ea1 in agardiffusion test method. The minimum inhibitory concentration and minimum bactericidal concentration of the purified fraction against Ea1strain were 8 ;g/mL and 16 ;g/mL, respectively. In planta experiments were tested on an apple cultivar (‘Watson Jonathan’) susceptible to fireblight. The effective range of concentration was 62-200 μg/mL, while treatment with 300 μg/mL and larger amounts caused necrotic symptomson the petals of flowers. Current study pointed to the effectiveness of the compounds produced by X. budapestensis against fire blight. Thedevelopment of a commercially applicable formulation of these compounds would allow growers to effectively control fire blight in apple and pearorchards.