ELICITATION OF RESISTANCE TO FIRE BLIGHT BY A MICROBIAL CONSORTIUM: SEARCH FOR AN EVIDENCE THROUGH A TRANSCRIPTOMIC APPROACH

Fire blight is the most destructive bacterial disease of pome
fruits: it is caused by Erwinia amylovora and its management remains
cumbersome. Nowadays, treatments with several beneficial
microorganisms can lead to an affective integrated pest management
(IPM): nevertheless, their specific activity in enhancing plant
defence mechanisms is only partially understood. An extensive
3-years study in a commercial pear orchard was carried out, to
verify the efficacy of a commercial microbial consortium (Micosat
F®, CCS Aosta srl, Italy) to control a fire blight outbreak. In
parallel, we have used a dHPLC (denaturing High Performance
Liquid Chromatography) and automated DNA fragment collection
using the WAVE System to analyse and recover cDNA-AFLP fragments.
This transcriptomic approach was applied to understand
which complex transcriptional changes these microorganisms may
have elicited in the plant-pathogen interaction. In the commercial
orchard, the beneficial effects of microbial consortium were confirmed
by a significant disease reduction starting from the first year
of application, as compared with other treatments commonly used
by orchardists in IPM strategies. Among the eighty-five transcriptderived
fragments (TDFs) collected and identified through the
cDNA-AFLP-dHPLC approach, fourteen were found involved
in systemic acquired resistance (SAR) according to the available
literature. The transcriptomic approach developed in this study
has been a robust and user-friendly mRNA fingerprinting method
for the identification of differentially expressed genes, where prior
knowledge of specific gene sequences is not a prerequisite. Finally,
we confirmed the activity of such the microbial consortium as resistance
inducer.