Germain H, Bergeron M-J, Bernier L, Laflamme G, Hamelin R C
Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Stn. Sainte-Foy, Quebec, QC, Canada G1V 4C7.
Mol Ecol. 2009 Nov;18(21):4422-33. doi: 10.1111/j.1365-294X.2009.04370.x. Epub 2009 Oct 5.
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.
担子菌纲真菌绒毛奥氏菌是北美分布最广的根腐病病原体之一。尽管该病在云杉和松树上更为严重，但这种病原体可感染多种针叶树种。为了研究绒毛奥氏菌的种群结构，我们于1997年秋季在魁北克西部一个45年树龄的白云杉人工林中采集了180个担子果，并直接从单个担子果中提取DNA。基于两个线粒体和三个核基因座的分析，结合空间坐标和分子数据，我们测量了平均基因大小和分子多样性，并评估了担孢子和营养生长对林分定殖的相对贡献。在空间上聚集的大多数采样担子果属于同一个基因。共获得37个离散的多位点基因，平均大小为3.42米。基因大小分布偏向于较小的基因（<3米），这些较小的基因比大基因（>3米）表现出更高的多样性。在较大的基因中，核基因座处于哈迪-温伯格平衡，但在较小的基因中则不然，较小的基因表现出杂合子不足。这表明存在瓦伦德效应，即不同的定殖事件导致预期杂合度高于观察到的杂合度。利用对该真菌生长速率的估计，只有少数最大的基因大约与人工林的年龄相同。这些观察结果与整地和植树后担孢子定殖，随后是二次定殖事件和营养体传播相一致。
