Do “toxins” affect pathogenesis by Endothia parasitica?

A sensitive and semi-quantitative method for assaying the toxicity of metabolites from Endothia parasitica was developed using American and Chinese chestnut inner bark. Skyrin and rugulosin showed detectable toxic effects in high concentrations. However, diaporthin and other metabolites extractable in organic solvents showed no toxic affect on chestnut tissue. Skyrin, rugulosin and diaporthin were not detectable in samples taken from the advancing mycelium at the periphery of cankers. These compounds were found only in areas associated with well developed necrosis and active sporulation. Results presented here do not support the concept that skyrin, rugulosin, diaporthin or other extractable aromatic or heterocyclic compounds effect the advance of E. parasitica mycelium into chestnut inner bark.