Heterohelminthosporium Khuna, Hongsanan & Xie N., gen. nov.
Index Fungorum number: IF903729; Facesoffungi number: FoF17751
Etymology – Refers to the new genus's similarity to Helminthosporium.
Type species – Heterohelminthosporium hydei Khuna, Hongsanan & Xie N
Endophytic in leaves of Pandanus tectorius (Pandanaceae). Mycelia superficial and immersed, composed of septate, branched, hyaline, with smooth and thick-walled hyphae. Sexual morph: Ascomata brown to black, semi-immersed to superficial, covered with mycelia, globose to subglobose, irregular, solitary or aggregated. Peridium thin-walled, 6–7-layered, composed of light brown compressed cells of textura angularis, cells towards inside lighter and somewhat flattened, at the outside, darker, fusing and indistinguishable from the host tissues. Asci 8-spored bitunicate, fissitunicate, cylindrical-clavate, apically rounded, slightly curved, sessile. Ascospores uniseriate or biseriate, hyaline when immature, pale brown to brown when mature, fusoid with rounded ends, tapering towards both ends, asymmetrical, straight or slightly curved, with 1 eccentric primary septum and often with 2-eusepta, constricted at the primary septum, slightly constricted at eusepta, smooth-walled with guttules, without mucilaginous sheath or appendages. Asexual morph: Undetermined.
Notes – The phylogenetic analysis based on a multi-locus dataset (SSU, LSU, ITS, tef1-α, and rpb2, Fig. 17) indicated that our collections (MBSZU 25–015 and MBSZU 25–016) formed an independent lineage within Massarinaceae sister to the genus Massarina (M. tangneyae and M. pandanicola) with high statistical support (Fig. 17). Morphologically, our collection can be distinguished from Massarina species in having pale brown to brown, fusoid, 1-sepate ascospores without mucilaginous sheath whereas Massarina has hyaline, broadly fusiform, multi-septate ascospores with mucilaginous sheath or appendages (Aptroot 1998, Hyde & Aptroot 1998, Tanaka & Harada 2003, Zhang et al. 2009, Hongsanan et al. 2020a). In addition, our collection shares similarities with Helminthosporium by pale brown, asymmetrical ascospores (Voglmayr & Jaklitsch 2017). However, Helminthosporium differs from our collection in having few to numerous ring-like thickenings of the inner wall, which gives the inner wall an irregularly wavy outline (Voglmayr & Jaklitsch 2017). Therefore, we identify our collection as a novel genus within Massarinaceae, based on both morphological and phylogenetic evidence. However, additional taxon sampling is essentially required to resolve the phylogenetic affinities of Massarina, Helminthosporium, and Heterohelminthosporium.
Species