Labivalidus 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-

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

Etymology.

Labium (Latin) = lip, validus (Latin) = strong, referring to the well-developed lips of ascomata.

Diagnosis.

This new genus is similar to Hypoderma , but differs from Hypoderma by broadly elliptical ascomata and filiform ascospores.

Type.

Labivalidus cunninghamiae Lan Zhuo & C. L. Hou , described below.

Sexual morph.

Ascomata often scattered, elliptical to broadly elliptical, black (# 000000), opening by a single longitudinal split. Lips well-developed, creamy white (# fffeea). Ascomata intraepidermal. Covering stroma consisting of carbonized, thick-walled, angular to globose cells. Basal Covering stroma moderately to well developed, consisting of carbonized, thick-walled, angular to globose cells. Internal matrix of Covering stroma absent. Paraphyses filiform, not branched, not swollen or swollen at tips. Asci ripening sequentially, cylindrical, rostrate at apex at maturity, thin-walled, J –, 8 - spored. Ascospores aseptate, filiform, hyaline, covered by a gelatinous sheath.

Asexual morph.

Conidiomata and zone lines not seen.

Notes.

In the context of the present study, molecular data for the species described as Lophodermium jianchuanense have been obtained. Phylogenetic analyses shows that the molecular sequences of Lo. jianchuanense and the new species Labivalidus cunninghamiae (described below) form a distinct clade (Clade 10, Fig. 1 ). Both species are distantly related to the type species of the genus Lophodermium , Lo. arundinaceum (Schrad.) Chevall. , as well as the species of Lophodermium on needles of conifers, indicating that La. cunninghamiae and Lo. jianchuanense should not be classified in the genus Lophodermium .

Morphologically, the ascomata of both Lo. jianchuanense and La. cunninghamiae have conspicuous, creamy-colored lips, which are similar to some species of the genus Hypoderma . However, species in the genus Hypoderma s. str. are usually saprotrophic, with a wide host range, their ascomata are often elliptical to elongate in shape, and ascospores elliptical to cylindrical ( De Notaris 1847; Powell 1974; Cannon and Minter 1986; Johnston 1990 a), whereas Lo. jianchuanense and La. cunninghamiae have a narrow host range, known only from Cupressaceae , have broadly elliptical ascomata and filiform ascospores. Furthermore, Lo. jianchuanense and La. cunninghamiae are also distant from the type of Hypoderma in the phylogenetic tree, suggesting that they should not be classified in Hypoderma .

Considering the phylogenetic and morphological evidence, it is necessary to establish a new genus to accommodate Lo. jianchuanense and La. cunninghamiae . Lophodermium jianchuanense is transferred to Labivalidus as a new combination, La. jianchuanensis .

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.