Pseudophaeocytostroma Monkai & Phookamsak, 2022

Monkai, Jutamart, Phookamsak, Rungtiwa, Xu, Sheng, Xu, Jianchu, Mortimer, Peter E., Karunarathna, Samantha C., Suwannarach, Nakarin & Lumyong, Saisamorn, 2022, Pseudophaeocytostroma bambusicola gen. et sp. nov. (Diaporthaceae) from bamboo in Yunnan, P. R. China, Phytotaxa 571 (1), pp. 39-51 : 44-45

Pseudophaeocytostroma Monkai & Phookamsak , gen. nov.

Index Fungorum number: IF559820; Facesoffungi number: FoF 12716

Etymology: “ Pseudophaeocytostroma ” refers to the morphological similarity to the genus Phaeocytostroma .

Saprobic on dead bamboo culms. Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata pycnidial, immersed in the clypeus, becoming raised, erumpent, penetrating on host surface, with small black dots of conidial masses, hemispherical to subconical or lenticularis, uni- to bi-loculate, with an ostiole at the center, occasionally produced 2 ostioles in a locule, glabrous. Ostioles minutely papillate, immersed in host epidermis, circular. Conidiomatal wall consist of several layers of pseudoparenchymatous cells, arranged in a textura angularis, with dark brown outer layers and hyaline to pale brown towards the inner layers. Paraphyses intermingled between conidiophores, broadly filiform, septate, hyaline, unbranched, obtuse at the apex, with small granules. Conidiophores tightly aggregated, subcylindrical to ampulliform, or irregular in shape, septate, hyaline to pale brown, branched only at the base. Conidiogenous cells enteroblastic, phialidic, determinate, integrated, subcylindrical, tapering towards the apex, hyaline, smooth-walled. Conidia oblong to ellipsoid, obtuse at both ends, aseptate, brown, thick and smoothwalled, guttules.

Type species:— Pseudophaeocytostroma bambusicola Monkai & Phookamsak

Notes:— Pseudophaeocytostroma resembles the generic description of Phaeocytostroma including immersed, uni- to multilocular conidiomata, filiform paraphyses and aseptate conidia ( Sutton 1980). However, their conidial shapes are different as Pseudophaeocytostroma has oblong to ellipsoid conidia, while Phaeocytostroma has ellipsoid to fusiform or pyriform conidia ( Sutton 1980). Pustulomyces also has aseptate conidia, but can be distinguished from Pseudophaeocytostroma by pustule-like conidiomata and fusiform or sigmoid conidia ( Dai et al. 2014). Pseudophaeocytostroma is different from Massariothea which produces distoseptate conidia, but they are similar in having uni- to multilocular conidiomata, ostiolate and filiform paraphyses ( Thambugala & Hyde 2018). Stenocarpella differs from Pseudophaeocytostroma in having unilocular, elongated conidiomata, lacking paraphyses and 0–3 septate conidia ( Sutton 1980, Lamprecht et al. 2011).

Phylogenetic analyses results showed that Pseudophaeocytostroma clustered with Pustulomyces with 50% ML support and both genera formed a well-resolved clade basal to Phaeocytostroma sensu stricto, Massariothea and Stenocarpella with 78% ML and 76% MP support ( FIGURE 1 ). The weak support in Pustulomyces is probably caused by the single strain. Pustulomyces also formed a separate branch basal to Pseudophaeocytostroma with no support in BI analysis, thus more sequence data from fresh collections are essential to resolve its phylogenetic placement. Therefore, we introduce Pseudophaeocytostroma as a new genus in Diaporthaceae based on a strong support in phylogenetic incongruence to other related genera (viz. Phaeocytostroma , Pustulomyces , Massariothea and Stenocarpella ), although the morphological characteristics of Pseudophaeocytostroma and Phaeocytostroma are not significantly different.

Figures

FIGURE 1. Phylogenetic tree obtained from RAxML analysis of a combined ITS, LSU and TEF1-α sequence data. Bootstrap support values for ML equal to or greater than 50%, MP equal to or greater than 60% and Bayesian posterior probabilities equal to or greater than 0.90 PP are indicated at the nodes as ML/MP/PP. The ex-type and ex-epitype strains are in black bold and the new isolates obtained in this study are in red. The tree is rooted to Cytospora elaeagni (CFCC 89633) and C. gigaspora (CFCC 89634).