These authors contributed equally to the work.
Patterns of colonization and spread in the fungal spruce pathogen Onnia tomentosa
Article first published online: 5 OCT 2009
© 2009 Blackwell Publishing Ltd
Volume 18, Issue 21, pages 4422–4433, November 2009
How to Cite
GERMAIN, H., BERGERON, M.-J., BERNIER, L., LAFLAMME, G. and HAMELIN, R. C. (2009), Patterns of colonization and spread in the fungal spruce pathogen Onnia tomentosa. Molecular Ecology, 18: 4422–4433. doi: 10.1111/j.1365-294X.2009.04370.x
H.G. is a postdoctoral fellow who studies molecular plant-microbe interactions. M.-J.B. is a research biologist with interest in molecular genetics of fungal pathogens. L.B. is a professor in forest pathology and a fungal geneticist. G.L. is a research scientist and a forest pathologist working on the epidemiology and management of forest diseases. R.H. is a research scientist and a professor of forest pathology with research interests in molecular epidemiology and monitoring of forest pathogens.
- Issue published online: 14 OCT 2009
- Article first published online: 5 OCT 2009
- Received 9 April 2009; revision received 4 July 2009, 4 August 2009; accepted 10 August 2009
- Buller phenomenon;
- genetic structure;
- Onnia tomentosa;
- root rot;
- Wahlund effect
The basidiomycetous fungus Onnia tomentosa is one of the most widespread root rot pathogens in North America. Although the disease is more severe on spruce and pine trees, this pathogen can infect several coniferous species. To study the population structure of O. tomentosa, we harvested 180 basidiocarps in a 45-year-old white spruce plantation in western Quebec in autumn 1997 and extracted DNA directly from individual basidiocarps. Using a combination of spatial coordinates and molecular data based on the analysis of two mitochondrial and three nuclear loci, we measured the average genet size and molecular diversity and assessed the relative contribution of basidiospores and vegetative growth to the stand colonization. Most of the sampled basidiocarps that clustered spatially belonged to the same genet. A total of 37 discrete multilocus genets of an average size of 3.42 m were obtained. The genet size distribution was skewed towards smaller genets (<3 m) that displayed higher diversity than the larger genets (>3 m). The nuclear loci were in Hardy–Weinberg equilibrium in the larger genets, but not in the smaller genets, which displayed a deficiency of heterozygotes. This suggests a Wahlund effect, whereby different colonization events resulted in expected heterozygosity higher than observed heterozygosity. Using an estimate of the growth rate of the fungus, only a few of the largest genets were approximately the age of the plantation. These observations are consistent with the colonization by basidiospores subsequent to site preparation and tree planting followed by secondary colonization events and vegetative spread.