New Helminthosporium (Massarinaceae, Dothideomycetes) and Nigrospora (Incertae sedis, Sordariomycetes) species associated with walnut (Juglans regia L.) in China

Six collections of ascomycetes were obtained from samples collected from dead branches and leaves of <i>Juglansregia</i> in Guizhou and Yunnan provinces, China. By incorporating multigene phylogenetic analysis (ITS, LSU, <i>rpb2</i>, SSU, <i>tef1-α</i>, <i>tub2</i>) supplemented by morphological data, we establish two novel species, namely <i>Helminthosporiumguizhouense</i> and <i>Nigrosporayunnanensis</i>. In morphology, <i>H.guizhouense</i> can be distinguished from <i>H.caespitosum</i> by its narrower conidia (13-16 µm vs. 27.3-35.5 µm), and <i>N.yunnanensis</i> is characterized by black, globose conidia (16.2 × 14.4 µm). The phylogenetic results further substantiated them as novel taxa. The present study contributes to our comprehension of the range of fungi found in <i>Juglansregia</i>, thereby expanding our knowledge of the diversity of fungi within this host.