Biodiversity of pathogenic wood fungi isolated from Xylotrechus arvicola (olivier) galleries in vine shoots

Aim: Grapevine decline caused by wood fungi seriously threatens viticulture worldwide. In Spain, the polyphagous borer Xylotrechus arvicola (Coleoptera, Cerambycidae) is becoming a serious pest in different Qualified Designation of Origin (DOC) wine regions The aim of the present work was to identify the fungal species growing in the galleries excavated by X. arvicola larvae inside the vine branches and investigate the possible relationship between wood pathogenic fungi and this borer. Methods and results: Wood samples from branches of Tempranillo vines and Prunus pisardi trees affected by the borer X. arvicola were collected in La Rioja DOC vineyards (Northern Spain) and analyzed for the presence of fungi using both morphological techniques and genetic tools based on Internal Transcribed Spacer 2 (ITS2) sequence. Among the 20 different fungal species/isolates identified, 7 belonged to fungi associated with grapevine decline (esca, Petri disease, and Eutypa dieback), 6 were plant pathogens, 6 were saprophytic and one was entomopathogenic (Beauveria bassiana). Conclusion: The fact that 65% of the fungi detected inside X. arvicola galleries belong to species recognized as plant pathogens suggests that this borer, in addition to causing a progressive decay of the branches, could facilitate the transmission of plant diseases, further threatening the vineyards by spreading grapevine decline pathogens. Significance and impact of the study: The present work represents a first step in recognizing the association between the fungal pathogens associated with grapevine decline and the borer X. arvicola, suggesting a possible role of this insect as a vector in the transmission of these fungi.