Approach to the study of induction of resistance in Pyrus communis to E. amylovora: development of bioassays and cloning of fragments of NPR1-like genes.

摘要

A study was undertaken on Pyrus communis to assess the potential of wounding and chemical inducers to induce resistance to Erwinia amylovora, the agent of fire blight. To determine any direct effect of chemicals on bacterial growth, inducers were supplemented at different concentrations to a liquid medium and the bacterial concentration was determined at 24 h. Bioassays based on the inoculation of immature pear slices and of in vitro plantlets (cv. William), were used for induction of resistance. Inducing treatment with gentisic acid (GA), a known pathogen inducible signal, caused a mild decrease of ooze production on fruit slices and of disease severity on in vitro plantlets. Wounding strongly reduced ooze production on fruit slices. Degenerate primers-based PCR amplifications were used to clone cDNA fragments with evident homology to known NPR1 or NPR1-like genes of other plant species. The possibility that a genuine induction of resistance could be triggered in the assays and the importance of characterizing genes involved in signal transduction of inducers are discussed..