Boxwood blight is a disease threat to natural and managed landscapes worldwide. To determine mating potential of the fungi responsible for the disease, Calonectria pseudonaviculata and C. henricotiae, we characterized their mating-type (MAT) loci. Genomes of C. henricotiae, C. pseudonaviculata and two other Calonectria species (C. leucothoes, C. naviculata) were sequenced and used to design PCR tests for mating-type from 268 isolates collected from four continents. All four Calonectria species have a MAT locus that is structurally consistent with the organization found in heterothallic ascomycetes, with just one idiomorph per individual isolate. Mating type was subdivided by species: all C. henricotiae isolates possessed the MAT1-1 idiomorph, whereas all C. pseudonaviculata isolates possessed the MAT1-2 idiomorph. To determine the potential for divergence at the MAT1 locus to present a barrier to interspecific hybridization, evolutionary analysis was conducted. Phylogenomic estimates showed that C. henricotiae and C. pseudonaviculata diverged approximately 2.1 Mya. However, syntenic comparisons, phylogenetic analyses, and estimates of nucleotide divergence across the MAT1 locus and proximal genes identified minimal divergence in this region of the genome. These results show that in North America and parts of Europe, where only C. pseudonaviculata resides, mating is constrained by the absence of MAT1-1. In regions of Europe where C. henricotiae and C. pseudonaviculata currently share the same host and geographic range, it remains to be determined whether or not these two recently diverged species are able to overcome species barriers to mate.

黄杨木枯病是对全球自然景观和受管理景观的一种疾病威胁。为了确定造成该病的真菌假单胞菌和拟南芥C. henricotiae的交配潜力，我们对它们的交配型（MAT）基因座进行了表征。的基因组C. henricotiae，C. pseudonaviculata和另外两个Calonectria物种（C. leucothoes，C. naviculata）进行测序并用于设计PCR试验从四个大洲收集268个菌株交配型。所有四种Calonectria物种均具有MAT与异源杂种囊虫中发现的组织在结构上一致的基因座，每个单独的分离物只有一个独特的形态。交配类型按物种细分：所有C. henricotiae分离株均具有MAT1-1独特型，而所有C. pseudonaviculata分离物均具有MAT1-2独特型。为了确定在MAT1基因座处发散的可能性，以提出种间杂交的障碍，进行了进化分析。系统生物学估计表明，C。henricotiae和C. pseudonaviculata发散约2.1妙。但是，通过MAT1基因座和近端基因的同义比较，系统发育分析和核苷酸差异估计，在该基因组区域中的差异最小。这些结果表明，在北美和欧洲仅存假拟南芥（C. pseudonaviculata）的部分地区，由于缺少MAT1-1而限制了交配。在欧洲地区的C. henricotiae和C. pseudonaviculata当前拥有相同的寄主和地理范围的地区，这两个最近分化的物种是否能够克服物种交配的障碍尚待确定。