Biological control of apple scab and fire blight by the application of the non-pathogenic bacterium Pseudomonas fluorescens Bk3 to the leaf surface

摘要

The biological control of plant diseases by application of antagonistic microorganisms toudthe plant phyllosphere is an alternative strategy to prevent the frequent treatment of plantsudby pesticides. Microbiological antagonists can firstly interact directly against the pathogenudby releasing antimicrobial compounds and/or secondly induce the plant resistance of theudhost plant by expression of pathogenesis-related proteins (PR proteins). The focus of ourudstudy is on the interaction of the non-pathogenic bacterium Pseudomonas fluorescens Bk3udto the plant phyllosphere of Malus domestica cv. Holsteiner Cox. After application of P.udfluorescens Bk3 to the phyllosphere of M. domestica cv. Holsteiner Cox we observeduddramatic changes in the protein composition of the apoplast of the host plant. Sequencingudof the induced proteins by ESI-Q-ToF mass spectrometry and homology search identifiedudthese additional proteins as pathogenesis related proteins (PR) like ß-1,3- glucanase,udthaumatin-like protein, chitinase and hevein-like protein. To confirm these findings, audsuppressive subtractive hybridization with total RNA from leaves before and afterudinoculation of P. fluorescens Bk3 to the leaves of the host plant was performed. It revealedudan increased expression level of many PR and stress related genes.udThe induction of PR proteins and plant defence genes in host plants after application ofudnon-pathogenic bacterial antagonists to the plant phylloshere can presumably prevent orudreduce successful infections by plant pathogens.