Large-spored <i>Drechslera gigantea</i> is a <i>Bipolaris</i> species causing disease on the invasive grass <i>Microstegium vimineum</i>

Environmentally damaging invasive plants can also serve as reservoir hosts for agricultural pathogens. <i>Microstegium vimineum</i> is an invasive C4 annual grass that is present throughout the midwestern and eastern United States. It can reach high densities in disturbed areas such as crop-forest interfaces, which creates the potential for pathogen spillover from <i>M. vimineum</i> to agricultural crops and native plants. A previous study that surveyed disease on <i>M. vimineum</i> found a large-spored <i>Bipolaris</i> species that was widespread on <i>M. vimineum</i> and also isolated from co-occurring native grasses. Here, we report that the large-spored fungus isolated from <i>M. vimineum</i> and the native grass <i>Elymus virginicus</i> is <i>Drechslera gigantea</i>, based on comparison with published descriptions of morphological traits, and establish that <i>D. gigantea</i> is a pathogen of <i>M. vimineum</i> and <i>E. virginicus</i>. We review the phylogenetic placement and taxonomic history of <i>D. gigantea</i> and propose that it be reassigned to the genus <i>Bipolaris</i> as <i>Bipolaris gigantea.</i>

对环境具有破坏性的外来入侵植物，亦可作为农业病原物的储存宿主。柔枝莠竹（Microstegium vimineum）是一种入侵性C4一年生草本，广泛分布于美国中西部及东部地区。该草可在林农交错带等受干扰生境中形成高密度种群，这使得病原物存在从柔枝莠竹向农作物及本土植物扩散的潜在风险。此前一项针对柔枝莠竹病害的调查研究，发现了一种在该草上广泛分布的大孢子平脐蠕孢属（Bipolaris）物种，且该物种亦可从伴生的本土草本中分离得到。本研究通过与已发表的形态性状描述进行比对，确认从柔枝莠竹及本土草本弗吉尼亚披碱草（Elymus virginicus）中分离得到的大孢子真菌为巨形德氏霉（Drechslera gigantea），并证实该真菌是柔枝莠竹与弗吉尼亚披碱草的病原菌。本研究梳理了巨形德氏霉的系统发育地位与分类学历史，并提议将其重新划归平脐蠕孢属（Bipolaris），更名为巨形平脐蠕孢（Bipolaris gigantea）。