Pseudophaeocytostroma Monkai & Phookamsak, gen. nov.
MycoBank number: MB 559820; Index Fungorum number: IF 559820; Facesoffungi number: FoF 12716;
Description
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 smooth-walled.
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). Pseudophaeocytostroma is similar to Massariothea in having uni- to multilocular conidiomata, ostiolate and filiform paraphyses (Thambugala & Hyde 2018). But, Massariothea has distoseptate conidia (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). Pustulomyces can be distinguished from Pseudophaeocytostroma by pustule-like conidiomata and aseptate, fusiform or sigmoid conidia (Dai et al. 2014).
Phylogenetic results showed that Pseudophaeocytostroma clustered with Pustulomyces with low support (50% ML) 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). Pustulomyces also formed a separate branch basal to Phaeocytostroma with no support in BI analysis indicating its phylogenetic placement is not stable. 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, Stenocarpella), although the morphological characters of Pseudophaeocytostroma and Phaeocytostroma are not significantly different.