New Potential Biological Limiters of the Main Esca-Associated Fungi in Grapevine

The strains Trichoderma harzianum TH07.1-NC (TH), Aphanocladium album MX95 (AA), Pleurotus eryngii AL142PE (PE) and Pleurotus ostreatus ALPO (PO) were tested as biological limiters against Fomitiporia mediterranea Fme22.12 (FM), Phaeoacremonium minimum Pm22.53 (PM) and Phaeomoniella chlamydospora Pc22.65 (PC). Pathogens were obtained from naturally Esca-affected 'Nero di Troia' vines cropped in Grumo Appula (Puglia region, Southern Italy). The antagonistic activity of each challenge organism was verified in a dual culture. TH and PO completely overgrew the three pathogens. Partial replacement characterized PE-FM, PE-PM, PE-PC and AA-PC interactions. Deadlock at mycelial contact was observed in AA-FM and AA-PM cultures. The calculated antagonism index (AI) indicated TH and PE as moderately active antagonists (10 < AI < 15), while AA and PO were weakly active (AI < 10). The maximum value of the re-isolation index (s) was associated with deadlock among AA-PM, AA-PC and PE-FM dual cultures. The tested biological limiters were always re-isolated when PO and TH completely replaced the three tested pathogens. TH and AA confirmed their efficiencies as biological limiters when inoculated on detached canes of 'Nero di Troia' in dual combination with FM, PC and PM. Nevertheless, additional experiments should be performed for a solid conclusion, along with validation experiments in the field.