A national research program was established to test the field efficacy of the native fungal pathogen Chondrostereum purpureum (Pers. ex Fr.) Pouzar) for control of hardwood vegetation. During 1995, two fungal isolates were applied as a biocontrol agent to the cut stumps of Populus tremuloides Michx. (trembling aspen) and Alnus viridis ssp. sinuata (Regel) Á. Löve & D. Löve (Sitka alder). Treatments consisted of two formulations (BC, ON) in combination with two fungal isolates (2139, JAM6), blank formulations, cutting only, triclopyr herbicide application, and an uncut control. Analysis of Sitka alder clump mortality indicated isolates JAM6 and 2139 in combination with the BC formulation caused clump mortality of 90 and 88%, respectively. The blank formulation treatments caused the lowest clump mortality and appeared to promote sprouting and growth of Sitka alder when compared with cutting alone. At the aspen installation, the BC formulation with isolate 2139 was found to be the most effective fungal treatment resulting in 84% aspen stem mortality. The results from both installations suggest that C. purpureum efficacy appears to be dependent on the virulence of the isolate and the formulation.
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 λ 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. Keywords: Chondrostereum purpureum, biological control, genetic variation, ribosomal DNA.
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