ABSTRACT The genus Magnaporthiopsis of Magnaporthaceae (Magnaporthales, Sordariomycetes, Ascomycota) contains species that are predominantly necrotrophic pathogens, often producing simple hyphopodia and dark, ectotrophic runner hyphae on plant roots and stems during colonization. Fungal isolates from turfgrass roots with dark and ectotrophic runner hyphae were examined and identified based on morphological, biological, and phylogenetic analyses. Maximum likelihood and Bayesian methods were implemented to obtain phylogenetic trees for partial sequences of the 18S nuc rDNA, ITS1-5.8S-ITS2 nuc rDNA internal transcribed spacer, and 28S nuc rDNA regions, and of the minichromosome maintenance complex 7 (MCM7), largest subunit of RNA polymerase II (RPB1), and translation elongation factor 1-alpha (TEF1) genes. Our isolates consistently formed a distinct and highly supported clade within Magnaporthiopsis. These findings were reinforced by common and distinctive biological and morphological characters. Additionally, we conducted pathogenicity evaluations and demonstrated the ability of this fungus to colonize roots of ultradwarf bermudagrass, one of its native hosts, via ectotrophic, dark runner hyphae, causing disease symptoms including root discoloration and reduced root and shoot mass. Altogether, our discoveries enabled recognition and description of a new species, Magnaporthiopsis cynodontis, which has widespread distribution in the United States.

中文翻译：

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Magnaporthiopsis cynodontis，一种在美国广泛分布的新型草坪草病原体

摘要 Magnaporthaceae 的 Magnaporthiopsis (Magnaporthales、Sordariomycetes、Ascomycota) 包含的物种主要是坏死性病原体，通常在定植过程中在植物根和茎上产生简单的丝足菌和深色的外营养菌丝。基于形态学、生物学和系统发育分析，检查和鉴定了来自具有深色和外养分生者菌丝的草坪草根的真菌分离物。实施了最大似然和贝叶斯方法以获得 18S nuc rDNA、ITS1-5.8S-ITS2 nuc rDNA 内部转录间隔区和 28S nuc rDNA 区域的部分序列以及最大的微染色体维持复合物 7 (MCM7) 的系统发育树RNA 聚合酶 II (RPB1) 和翻译延伸因子 1-α (TEF1) 基因的亚基。我们的分离株始终在 Magnaporthiopsis 内形成一个独特且高度支持的进化枝。共同和独特的生物学和形态特征加强了这些发现。此外，我们还进行了致病性评估，并证明了这种真菌能够通过外养的暗流道菌丝定殖超矮化狗牙根（其原生宿主之一）的根部，从而导致疾病症状，包括根部变色和根部和芽部质量减少。总而言之，我们的发现使人们能够识别和描述在美国广泛分布的新物种 Magnaporthiopsis cynodontis。我们进行了致病性评估，并证明了这种真菌能够通过外养型暗流道菌丝定植于超矮狗牙根（其原生宿主之一）的根部，从而导致疾病症状，包括根部变色和根部和芽部质量减少。总而言之，我们的发现使人们能够识别和描述在美国广泛分布的新物种 Magnaporthiopsis cynodontis。我们进行了致病性评估，并证明了这种真菌能够通过外养型暗流道菌丝定植于超矮狗牙根（其原生宿主之一）的根部，从而导致疾病症状，包括根部变色和根部和芽部质量减少。总而言之，我们的发现使人们能够识别和描述在美国广泛分布的新物种 Magnaporthiopsis cynodontis。