Survey of Phaeomoniella chlamydospora in vineyard weeds

Petri disease is serious, complex and difficult to control in vines worldwide. The main causal agent of this disease is the fungus Phaeomoniella chlamydospora. This fungus also occurs in the vineyard weed Convolvulus arvensis. In Brazil, this fungus was found only in grapevines. Thus, the aim of the present study was to carry out a phytosociological survey of weeds in an area with different vine rootstocks, as well as in a field of seedlings production, in an experimental area with vines and in different areas with commercial vineyards, besides verifying which weed species could be hosting the fungus P. chlamydospora. For the phytosociological survey of weeds, a square was randomly cast ten times at the site, followed by counting, identification and sampling of all species. To verify host species of the fungus, vascular tissue of plants was isolated in culture media and DNA extraction from the same plant tissue was carried out followed by PCR with specific primers of the fungus for the elongation factor gene (Pchlamy-EF-F 5’-CTCATTATCACATTTTGCTGC-3’ and Pchlamy-EF-R 5’-GAGAACAGTCAGTGATGAGC-3’). Considering all surveyed fields, 46 weed species were detected in 17 families, especially Asteraceae and Poaceae, which had the largest number of species. Using conventional or molecular methods, the fungus P. chlamydospora was not detected infecting weeds, which highlights that Petri disease occurs only in grapevines.