Toxicity of Ophiostoma Quercus Metabolites for Pedunculate Oak Leaves : Disease/Environment Interactions in Forest Decline. Proceedings of a Workshop of the Working Party Disease/Environment Interactions in Forest Decline IUFRO 7.02.06, Vienna, Austria, March 16-21, 1998
Ophiostoma quercus strains were isolated from tissues of adult oaks of Quercus robur, Quercus rubra which showed symptoms of crown decline. The strains were cultivated first on solid malt agar medium then in liquid cultures on an oat and malt medium for 29 days. The liquid remaining after sterile filtration was used for phytotoxicity tests. The influence of the fungal metabolites on 30 100-day-old leaves, taken from 3-6 months old greenhouse cultivated oak seedlings was evaluated according to a 4 degree class of damage. The results showed that the damage of leaves increased with the concentration of the filtrate and occurred mainly on the leaf edges in the form of dark-brown spots. The strain originating from Quercus robur showed more extensive leaf damage than those from the other two species. Generally, the damage of leaves observed during the tests was very limitited and did not have a significant influence on the health of the plants tested. Therefore the hypothesis that Quercus quercus can cause similar foliage symptoms like fungi responsible for vascular diseases was not proved in the in vitro experiment conditions.
