Abiomyces Lan Zhuo & C. L. Hou, 2025

Zhuo, Lan, Wang, Hai-Qi, Zhang, Peng, Sui, Xiao-Nan, Guo, Mei-Jun, Wang, Shi-Juan & Hou, Cheng-Lin, 2025, New genera and species of coniferous twig-inhabiting Rhytismatales from China, IMA Fungus 16, pp. e 138790-e 138790 : e138790-

Abiomyces Lan Zhuo & C. L. Hou gen. nov.

Etymology.

Referring to the type that growing on twigs of Abies .

Diagnosis.

This new genus is similar to Coccomyces De Not. on coniferous twigs and barks, but differs from Coccomyces by truncate acsi. Abiomyces is also similar to Therrya Sacc. , but differs in having simple paraphyses, which do not form an epithecium, and aseptate ascospores.

Type species.

Abiomyces laojunshanensis Lan Zhuo & C. L. Hou , described below.

Sexual morph.

Ascomata on twigs of Abies , scattered, round or slightly irregular, black (# 000000), opening by radial or irregular splits to expose a yellow (# ffd 400) to pale orange (# ffa 500) hymenium. In median vertical section, ascomata intracortical. Lips absent. Covering stroma well developed. Basal Covering stroma poorly developed. Internal matrix of Covering stroma present, consisting of hyaline, thin-walled, angular cells with some irregular crystalloids and short hyphae. Subhymenium consisting of small, hyaline cells. Paraphyses filiform, simple. Asci clavate, thin-walled, J –, 8 - spored. Ascospores aseptate, filiform, hyaline, without a gelatinous sheath.

Asexual morph.

Conidiomata and zone lines not seen.

Notes.

Phylogenetically, the molecular sequences of species belonging to this new genus form a distinct lineage (Clade 3, Fig. 1 ) with high support (MLB = 100 %, MPB = 97 %, PP = 1.00). In the phylogenetic tree, the sequences of species of Abiomyces are clustered with sequences of species of Cudoniaceae , a group of fungi that live in the soil and leaf litter. Some species of Cudoniaceae are associated with conifer, so that the species of Abiomyces and Cudoniaceae may have evolved together in the same habitat.

Morphologically, the ascomatal shape of A. laojunshanensis is similar to those of Coccomyces and Therrya that develop on twigs of conifers. Until now, 16 species of Coccomyces have been reported growing on coniferous twigs and bark (https://www.ars.usda.gov/). However, except for Co. mertensianae , other species in Coccomyces lacks apically truncate asci. Species of Therrya differ from A. laojunshanensis by apically inflated paraphyses embedded in gelatinous sheaths forming an epithecium and multi-septate ascospores ( Reid and Cain 1961; Sherwood 1980). Based on the separate phylogenetic positions and morphological characteristics, we propose Abiomyces as a separate genus.

Figures

Figure 1. Phylogenetic tree derived from maximum likelihood analysis of combined ITS, nrLSU, and mtSSU rDNA sequences of Rhytismatales, using Cudoniella clavus (AFTOL-ID 166) and Pezicula carpinea (KUS-F 51029) as outgroups. Bootstrap support values for ML analysis (MLB) and MP analysis (MPB) greater than 70 % and Bayesian posterior probabilities (PP) greater than 0.95 are given above the nodes. Names of new species and a new combination are written in bold. Species name T – Type species; Species name H – Holotype.