Ability of Pythium oligandrum strains to protect Vitis vinifera L., by inducing plant resistance against Phaeomoniella chlamydospora, a pathogen involved in Esca, a grapevine trunk disease

• P. oligandrum inocula colonized the rhizosphere throughout the experimental period.
• Plant root system colonization by P. oligandrum reduced P. chlamydospora necroses.
• Plant molecular responses differed according to treatments.
• P. oligandrum enhanced certain gene expression in P. chlamydospora infected plants.

Biological control of Phaeomoniella chlamydospora, a pathogen involved in Esca, a grapevine trunk wood disease, was performed using the oomycete, Pythium oligandrum. Three 4-month greenhouse assays showed that necrosis of Vitis vinifera L. cv. Cabernet Sauvignon cuttings caused by P. chlamydospora was significantly reduced (40–50%) when P. oligandrum colonized the plant root systems. The expression of a set of 22 grapevine defense genes was then quantified by real-time polymerase chain reaction to determine plant responses in the interaction between P. oligandrum/V. vinifera L./P. chlamydospora. In the trunk, specific grapevine responses to the different treatments (control, P. oligandrum, P. chlamydospora and P. oligandrum + P. chlamydospora treatments) were significantly differentiated. Expression levels of 6 genes associated with P. chlamydospora infection showed higher induction than when plants were pre-treated with P. oligandrum. These genes are involved in various pathways (PR proteins, phenylpropanoid pathways, oxylipin and oxydo-reduction systems).

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