Sesquicillium W. Gams

Sesquicillium W. Gams, Acta bot. neerl. 17 (6): 455 (1968) Classification. Bionectriaceae, Hypocreales, Sordariomycetes Morphological characteristics. Sexual morph: Ascomycetous. Perithecia solitary, gregarious or loosely aggregated, globose to subglobose, 200–400 μm diam, pale yellow or pale to light orange, not papillate, Perithecial wall either consisting of two or one major wall regions. Asci clavate, 8 - spored, with flat or rounded apex. Ascospores aseptate or 1 - septate, hyaline, spinulose, warted, with short striae, ellipsoidal to fusiform. Asexual morph. Hyphomycetous. Conidiophores macronematous, mononematous, monomorphic or dimorphic, penicillate, verticillate; branches at apex. Phialides one or two successive intercalary phialides, terminal, terminal whorls consisting of narrowly flask-shaped, hyaline. Conidia obovoid, ellipsoid, or fusoid, slightly curved or straight, hyaline, aseptate, smooth-walled, thin-walled. Type species. Sesquicillium buxi (J. C. Schmidt ex Link) W. Gams, Acta bot. neerl. 17 (6): 455 (1968) Notes. Sesquicillium was established by Gams (1968). Morphologically, Sesquicillium shares similar characteristics with Clonostachys in that the conidiophores are macronematous, monomorphic or dimorphic, penicillate, verticillate-like, branched, flask-shaped conidiogenous cells (Preedanon et al. 2023; Zhao et al. 2023). Zhao et al. (2023) revealed the close relationship between Clonostachys and Sesquicillium and reclassified eight species of Clonostachys to Sesquicillium. The difference between Sesquicillium and Clonostachys lies in the development of their conidiophores. In Sesquicillium, the conidiophore will form a lateral conidia process after bifurcation, leading to the production of conidia. In Clonostachys, the conidiophore will not form lateral conidia protrusions after bifurcation. It continues to differentiate into terminal phialides (Gams 1968; Schroers 2001). Based on the research of Chen et al. (2023), and Zhao et al. (2023), we used ITS, 28 S, tef 1, tub 2, and rpb 2 to reconstruct a phylogenetic tree to investigate the relationship of Clonostachys species. The results show that Clonostachys aquatica and C. shanghaiensis are far from Clonostachys and more closely related to Sesquicillium. Therefore, based on morphological and phylogenetic analysis, we propose C. aquatica and C. shanghaiensis are synonyms of S. aquaticum and S. shanghaiense.