The Biocontrol Root-Oomycete,Pythium Oligandrum, Triggers Grapevine Resistance and Shifts in the Transcriptome of the Trunk Pathogenic Fungus,Phaeomoniella Chlamydospora

The worldwide increase in grapevine trunk diseases, mainly esca, represents a major threat for vineyard sustainability. Biocontrol of a pioneer fungus of esca,Phaeomoniella chlamydospora, was investigated here by deciphering the tripartite interaction between this trunk-esca pathogen, grapevine and the biocontrol-oomycete,Pythium oligandrum. WhenP. oligandrumcolonizes grapevine roots, it was observed that the wood necroses caused byP. chlamydosporawere significantly reduced. Transcriptomic analyses of plant and fungus responses were performed to determine the molecular events occurring, with the aim to relateP.chlamydosporadegradation of wood to gene expression modulation. FollowingP. oligandrum-root colonization, major transcriptomic changes occurred both, in the grapevine-defense system and in theP. chlamydospore-virulence factors. Grapevine-defense was enhanced in response toP. chlamydosporaattacks, withP. oligandrumacting as a plant-systemic resistance inducer, promoting jasmonic/ethylene signaling pathways and grapevine priming.P. chlamydosporapathogenicity genes, such as those related to secondary metabolite biosynthesis, carbohydrate-active enzymes and transcription regulators, were also affected in their expression. Shifts in grapevine responses and key-fungal functions were associated with the reduction ofP. chlamydosporawood necroses. This study provides evidence of wood fungal pathogen transcriptional changes induced by a root biocontrol agent,P. oligandrum, in which there is no contact between the two microorganisms.