Significant hybridization between the invasive North American fungal plant pathogen Heterobasidion irregulare and its Eurasian sister species H. annosum is ongoing in Italy. Whole genomes of nine natural hybrids were sequenced, assembled and compared with those of three genotypes each of the two parental species. Genetic relationships among hybrids and their level of admixture were determined. A multi-approach pipeline was used to assign introgressed genomic blocks to each of the two species. Alleles that introgressed from H. irregulare to H. annosum were associated with pathways putatively related to saprobic processes, while alleles that introgressed from the native to the invasive species were mainly linked to gene regulation. There was no overlap of allele categories introgressed in the two directions. Phenotypic experiments documented a fitness increase in H. annosum genotypes characterized by introgression of alleles from the invasive species, supporting the hypothesis that hybridization results in putatively adaptive introgression. Conversely, introgression from the native into the exotic species appeared to be driven by selection on genes favoring genome stability. Since the introgression of specific alleles from the exotic H. irregulare into the native H. annosum increased the invasiveness of the latter species, we propose that two invasions may be co-occurring: the first one by genotypes of the exotic species, and the second one by alleles belonging to the exotic species. Given that H. irregulare represents a threat to European forests, monitoring programs need to track not only exotic genotypes in native forest stands, but also exotic alleles introgressed in native genotypes.

中文翻译：

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来自侵入性外来真菌森林病原体的基因渗入增加了同胞本地病原体的建立潜力

在意大利，正在进行入侵的北美真菌植物病原体异源杂种异虫与其欧亚姐妹种H. annosum之间的显着杂交。对九个天然杂种的整个基因组进行测序，组装，并与两个亲本物种各自的三个基因型的基因组进行比较。确定了杂种之间的遗传关系及其混合水平。使用多方法管道将渗入的基因组块分配给两个物种中的每一个。从不规则H.nonosum渗入到H. annosum的等位基因可能与腐菌过程有关，而从天然到入侵物种渗入的等位基因则主要与基因调控有关。在两个方向渗入的等位基因类别没有重叠。表型实验记录了以来自入侵物种的等位基因渗入为特征的番荔枝基因型的适应性增加，支持杂交导致假定的适应性渗入的假设。相反，从本地物种渗入外来物种似乎是由对有利于基因组稳定性的基因的选择驱动的。由于特定等位基因从外来物种的基因型渗入到本地的虎耳草增加了后者物种的侵袭性，我们提出两种入侵可能同时发生：第一个是外来物种的基因型，第二个是由外来物种的基因型引起的。一个是属于外来物种的等位基因。考虑到不规则H.对欧洲森林构成威胁，监测计划不仅需要追踪原生林分中的外来基因型，