Data from: 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. These results support the notion that H. irregulare was introduced originally in Castelporziano: because Castelporziano has been sealed off from the rest of the world for centuries except for a camp set up by the US military in 1944, we conclude the fungus may have been transported in infected wood used by the military. Finally, spatial autocorrelation analyses using SSR data indicate a significant under-dispersion of alleles up to 0.5–10 km, while a significant overdispersion of alleles was detected at distances over 80 km: these ranges can be used to make predictions on the likely dispersal potential of the invasive pathogen.本研究采用种群遗传学方法，对北美森林病原菌不规则异担子菌（Heterobasidion irregulare）的最可能入侵来源地与入侵路径展开鉴定；实验共采集意大利6个采样位点的101个菌株分离株，以及北美5个采样位点的34个菌株分离株。基于10个基因座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出现在卡斯泰尔富萨诺/卡斯泰尔波尔齐亚诺（Castelfusano/Castelporziano）位点，且种群多样性随距该位点距离的增加呈逐步下降趋势。基于12个简单序列重复（SSR, Simple Sequence Repeat）基因座的分子方差分析（AMOVA, Analysis of Molecular Variance）、贝叶斯聚类分析与主坐标分析结果表明，不同采样位点间存在高水平的基因流，基因型混合频率较高，且未发现仅局限于单一地点的专属基因型类群。综合上述分析结果，当前的入侵种群是由单一来源地的多种基因型逐步扩散形成的。基于2个测序基因座的分析显示，北美单个来源位点的遗传变异水平足以解释意大利种群中观测到的遗传多样性。上述结果支持不规则异担子菌（H. irregulare）最初于卡斯泰尔波尔齐亚诺完成入侵的结论：由于卡斯泰尔波尔齐亚诺数百年来与外界隔绝，仅1944年美军在此设立过临时营地，因此推测该病原菌可能通过美军使用的受感染木材传入。最后，基于SSR数据开展的空间自相关分析显示，在0.5–10 km范围内，等位基因呈现显著的聚集分布，而在80 km以上的距离区间则检测到等位基因的显著离散分布；该结果可用于预测该入侵病原菌的潜在扩散能力。