Phytotoxic extracellular polysaccharide fractions from Cryphonectria parasitica (Murr.) Barr strains

Two hypovirulent and one virulent strains of Cryphonectria parasitica, the causal pathogen of chestnut blight, produced a large amount of pullulan and a minor polysaccharide fraction containing galactose, mannose and, in one case, also rhamnose. The minor fractions of all strains elicited higher phytotoxicity on chestnut (Castanea sativa L.) leaves, twigs and seedlings or on tomato cuttings (Lycopersicon esculentum L.) than that given both by pullulan and native extracellular polysaccharide fractions. One of the components of the minor fraction was identified to be a galactan whose structure, on the basis of chemical and spectroscopic methods consisted of the repeat unit: [--> 6)-beta-D-Galf-(1-->5)-beta-D-Galf-(1-->](n). This is the first report on the production of polysaccharides by C. parasitica and their phytotoxic activity. (C) 1998 Elsevier Science Ltd. All rights reserved.