Data from: Phylogenetic and population genetic analyses of Phaeosphaeria nodorum and its close relatives indicate cryptic species and an origin in the Fertile Crescent

The origin of the fungal wheat pathogen Phaeosphaeria nodorum remains unclear despite earlier intensive global population genetic and phylogeographical studies. We sequenced 1,683 bp distributed across three loci in 355 globally distributed Phaeosphaeria isolates, including 74 collected in Iran near the center of origin of wheat. We identified nine phylogenetically distinct clades, including two previously unknown species tentatively named P1 and P2 collected in Iran. Coalescent analysis indicates that P1 and P2 are sister species of P. nodorum and the other Phaeosphaeria species identified in our analysis. Two species, P. nodorum and P. avenaria f. sp. tritici 1 (Pat1), comprised ∼85% of the sampled isolates, making them the dominant wheat-infecting pathogens within the species complex. We designed a PCR-RFLP assay to distinguish P. nodorum from Pat1. Approximately 4% of P. nodorum and Pat1 isolates showed evidence of hybridization. Measures of private allelic richness at SSR and sequence loci suggest that the center of origin of P. nodorum coincides with its host in the Fertile Crescent. We hypothesize that the origin of this species complex is also in the Fertile Crescent, with four species out of nine found exclusively in the Iranian collections.

尽管此前已开展过大量全球范围的种群遗传学与系统地理学研究，小麦致病真菌小麦壳针孢（Phaeosphaeria nodorum）的起源仍未明晰。本研究对全球分布的355株壳针孢属（Phaeosphaeria）分离株进行了3个基因位点共1683个碱基对（bp）的测序，其中包含74株采自伊朗、靠近小麦起源中心的菌株。本研究共鉴定出9个系统发育上独立的演化支，其中包含2个此前未被发现的物种，暂命名为P1和P2，采自伊朗地区。溯祖分析（coalescent analysis）结果显示，P1和P2与小麦壳针孢及本研究中鉴定出的其他壳针孢属物种互为姊妹种。在采样分离株中，小麦壳针孢（P. nodorum）与燕麦壳针孢小麦专化型1（P. avenaria f. sp. tritici 1，缩写为Pat1）两个物种占比约85%，为该物种复合群中主要的小麦致病病原菌。本研究设计了聚合酶链式反应-限制性片段长度多态性（PCR-RFLP）检测方法，用以区分小麦壳针孢与Pat1。约有4%的小麦壳针孢与Pat1分离株表现出杂交迹象。对简单序列重复（Simple Sequence Repeat，缩写为SSR）位点与序列位点的私有等位基因丰富度的分析结果表明，小麦壳针孢的起源中心与其寄主在新月沃地的分布重合。本研究推测，该物种复合群的起源地同样位于新月沃地，9个物种中有4个仅在伊朗的采集样本中被发现。