Pythium oligandrum induces grapevine defence mechanisms against the trunk pathogen Neofusicoccum parvum

Abstract

Grapevine trunk diseases (GTDs) are increasing in vineyards in many grape production regions. Among the pathogens causing these diseases, Neofusicoccum parvum, is one of the most frequent and virulent. To control GTDs, biocontrol is being developed using plant beneficial microorganisms. Strains of the oomycete Pythium oligandrum have been shown to naturally colonize grapevine roots in vineyards in several countries in Europe. This study examined the ability of the root-coloniser P. oligandrum to induce grapevine resistance against N. parvum, by deciphering the gene expression changes in a set of 62 genes involved in different grapevine defence pathways. Two greenhouse assays showed that the wood necrosis of vine cuttings caused by N. parvum was reduced by 65% when P. oligandrum colonized root systems of the plants. The relative expression levels of selected genes in the host trunks were studied by real-time PCR. Plant responses were assessed after inoculation by P. oligandrum and/or N. parvum, at three different sampling time points (0, 14 and 150 d after N. parvum inoculation). Sampling time influenced gene expressions for the different inoculation treatments. At each sampling time, specific host responses to the different treatments were also detected, for controls, and for inoculations with P. oligandrum, N. parvum or P. oligandrum + N. parvum. When P. oligandrum colonized grapevine root systems, inoculation with the pathogen was associated with increased up-regulation and over-expression of particular genes, including those regulating Pathogen-Related proteins, cell wall reinforcement proteins and hormone signalling pathways. A priming effect of the grapevine defence system was induced in roots colonized by P. oligandrum.

Keywords

• Biocontrol
• induced resistance
• gene expression