Geographic variation of Chondrostereum purpureum detected by polymorphisms in the ribosomal DNA

Variation in the ribosomal (rDNA) repeat was analyzed for 107 isolates of the pathogenic fungus Chondrostereum purpureum, collected from Europe, New Zealand, and North America. The rDNA repeat of a representative Canadian isolate of C. purpureum was cloned into the lambda vector EMBL-3, and a detailed restriction map was constructed. Variation in the large non-transcribed spacer region of the rDNA was determined for the entire collection of isolates following amplification by the polymerase chain reaction (PCR) and analysis of restriction fragment length polymorphisms (RFLPs). Three distinct nuclear type patterns were identified using the restriction endonuclease HaeIII. Nuclear type I was found in North American, European, and New Zealand isolates. Nuclear type II was only detected in isolates collected from North America, and nuclear type III was observed in isolates collected from both Europe and New Zealand. Nuclear type I was the predominant nuclear type in eastern North America as indicated by a frequency of 0.78, and nuclear type II occurred with a frequency of 0.89 in western North America. Gene flow across the continent was indicated by nearly equal nuclear type distributions (nuclear type I, 0.41; nuclear type II, 0.59) in central North America, but geographic separation has led to unequal nuclear-type distributions across North America.