Activity of biocontrol agents against the grapevine pathogen Fomitiporia mediterranea

Biological control agents (BCAs) have shown efficacy against several pathogens associated with Esca of grapevines, but their effects on the white rot pathogen Fomitiporia mediterranea (Fmed) have not been extensively studied. An assessment of several potential BCAs evaluated activity against Fmed. This included isolates of Trichoderma simmonsii, T. citrinoviride, T. atroviride, Bacillus subtilis, B. amyloliquefaciens/velezensis and Pseudomonas koreensis, all obtained from grapevines in Austria. Effects of the BCAs on Fmed growth were assessed in dual culture assays and in assays with fresh and autoclaved grapevine wood disks. In the dual culture assays, all the BCAs reduced growth of Fmed compared to experimental controls. In the Trichoderma experiments, Fmed growth only marginally exceeded the size of the initial mycelium plugs, and growth inhibition for all Fmed isolates and strains was 91 to 97%. Growth of Fmed was inhibited by 55 to 66% by B. amyloliquefaciens/velezensis isolates, by 41 to 49% by B. subtilis isolates, and by 55 to 66% by P. koreensis. In the wood disc assays, Fmed colonized fresh and autoclaved wood. All the Trichoderma isolates almost completely suppressed Fmed growth on fresh and autoclaved wood. Less but statistically significant inhibition was recorded for an isolate of B. amyloliquefaciens/velezensis and one of P. koreensis.