Degradation of stilbene‐type phytoalexins in relation to the pathogenicity of Botrytis cinerea to grapevines

The ability of eight isolates of Botrytis cinerea to degrade the stilbene phytoalexins, resveratrol and pterostilbene, was compared with their pathogenicity to grapevines. All strains which degraded resveratrol and pterostilbene were highly or moderately pathogenic to in vitro cultures of grapevines (Vitis rupestris) after inoculation with agar disks containing mycelium, while those which were unable to degrade phytoalexins were non‐pathogenic. In all cases, the hydroxystilbene‐degrading activity was related to the presence of laccase activity in the culture filtrates, as shown by using syringaldazine as substrate. The role of laccase‐mediated degradation of phytoalexins in relation to pathogenicity of B. cinerea to grapevines in discussed.