Population Dynamics ofCryphonectria parasiticain a Mixed-Hardwood Forest in Connecticut

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Abstract
A natural population of the chestnut blight fungus, Cryphonectria parasitica, was found early in a cycle of the blight epidemic, and the vegetative compatibility profile of the population was censused from summer 1982 through fall 1985. All of the American chestnut sprouts in a 60- .times. 60-m area in this mixed-hardwood forest were examined regularly, and new cankers on living trees at least 2.5 cm diameter at breast height (dbh) were sampled. C. parasitica was isolated, and the vegetative compatibility (v-c) types of the isolates were determined. The typed isolates were then referred to as strains. The strains were paired in the laboratory with strains of C. parasitica containing European hypovirulence (H) determinants to convert them to H strains by cytoplasmic transfer across anastomosis bridges. Each new H strain was inoculated around the margin of the canker from which its progenitor had come to halt canker expansion. In 1982 we found six v-c types in 12 cankers on four (living) trees. By November 1985 we had found 48 v-c types in 272 cankers on 42 trees. By the end of 1985, 25 cankers that had not been treated had yielded isolates with the phenotype of European hypovirulent strains.