Species diversity of Pseudoplagiostoma and Pyrispora (Diaporthales) from Fagaceae hosts in China

<i>Diaporthales</i> is an important fungal order comprising plant-associated pathogens, endophytes, and saprobes in commercial crops and forest trees. Over the past decades, utilizing multiple gene phylogeny has substantially advanced our understanding of taxonomic relationships within this order, leading to the recognition of 35 morphologically and molecularly well-supported families. Among these, Pseudoplagiostoma (Pseudoplagiostomataceae) and Pyrispora (Pyrisporaceae) form two phylogenetically closely related lineages that exhibit distinct morphological characteristics. In this study, we conducted comprehensive morphological and phylogenetic analyses of fungal specimens associated with <i>Fagaceae</i> hosts and proposed four new species and two new combinations: <i>Ps.fagaceaearum</i> <b>sp. nov.</b>, <i>Ps.neocastanopsidis</i> <b>sp. nov.</b>, <i>Ps.quercus</i> <b>sp. nov.</b>, <i>Py.humilis</i> <b>comb. nov.</b>, <i>Py.myracrodruonis</i> <b>comb. nov.</b>, and <i>Py.quercicola</i> <b>sp. nov.</b> Furthermore, based on detailed morphological comparisons and molecular evidence, we synonymized <i>Neoplagiostoma</i> with <i>Pyrispora</i>, <i>Ps.castaneae</i> and <i>N.castaneae</i> with <i>Py.castaneae</i>, <i>Ps.ilicis</i> with <i>Ps.wuyishanense</i> and <i>Ps.diaoluoshanense</i> with <i>Ps.mangiferae</i>. This study provides substantial morphological and molecular data that significantly contribute to our understanding of <i>Pseudoplagiostomataceae</i> and <i>Pyrisporaceae</i>, thereby establishing a robust foundation for future taxonomic revisions and systematic investigations within <i>Diaporthales</i>. The findings not only expand our knowledge of fungal diversity associated with <i>Fagaceae</i> but also enhance our comprehension of evolutionary relationships within these important fungal families.