Population genetic analyses provide insights on the introduction pathway and spread patterns of the North American forest pathogen Heterobasidion irregulare in Italy

A population genetics approach is used to identify the most likely introduction site and introduction pathway for the North American forest pathogen Heterobasidion irregulare using 101 isolates from six sites in Italy and 34 isolates from five sites in North America. Diversity indices based on sequences from ten loci indicate the highest diversity in Italy is found in Castelfusano/Castelporziano and that diversity progressively decreases with increasing distance from that site. AMOVA, Bayesian clustering and principal coordinates analyses based on 12 SSR loci indicate high levels of gene flow among sites, high frequency of admixing, and fail to identify groups of genotypes exclusive to single locations. Cumulatively, these analyses suggest the current infestation is the result of multiple genotypes expanding their range from a single site. Based on two sequenced loci, a single source site in North America could provide enough variability to explain the variability observed in Italy. The...本研究采用种群遗传学方法，利用采自意大利6个样地的101个分离株与北美5个样地的34个分离株，对北美森林病原菌不规则异担子菌（Heterobasidion irregulare）的最可能入侵引入位点及引入路径开展鉴定。基于10个基因位点序列计算的多样性指数显示，意大利种群的最高遗传多样性集中于卡斯泰尔富萨诺/卡斯泰尔波尔齐亚诺样地，且多样性随与该样地距离的增加呈逐步降低趋势。基于12个简单序列重复（Simple Sequence Repeat, SSR）位点的分子方差分析（Analysis of Molecular Variance, AMOVA）、贝叶斯聚类及主坐标分析结果表明，各样地间存在高水平基因流，遗传混合频率较高，且未发现仅局限于单一样地的基因型类群。综合上述分析结果，本研究认为当前的侵染定殖事件系由单个源地的多种基因型逐步扩散所致。基于2个测序基因位点的分析结果显示，北美单个源地种群所具备的遗传变异足以解释意大利种群中观测到的遗传变异水平。The...