Pleosporales » Cucurbitariaceae

Cucurbitaria

Cucurbitaria Gray, Nat. Arr. Brit. Pl. (London) 1: 508, 519 (1821).

Index Fungorum number: IF 1348; Facesoffungi number: FoF 08180, 95 morphological species (Species Fungorum 2022), 7 species with molecular data.

Saprobic or pathogenic on host. Sexual morph: Ascomata erumpent from bark, scattered or aggregated in clusters on a subiculum, globose to turbinate, brown to black; apex obtuse, surface usually coarsely warted. Ostiolar openings inconspicuous, central, sunken, sometimes visible as a minute, light-colored areas. Peridium firm and thick, pseudoparenchymatous, brown to black outside, lighter-coloured to the inside, typically thickened and often distinctly elongated basally. Hamathecium of branched paraphyses. Asci cylindrical, bitunicate, fissitunicate, with a short stipe, a simple or knob-like base, and a distinct ocular chamber; containing 8 ascospores in uniseriate arrangement. Ascospores ellipsoid, straight, muriform, slightly constricted at the median primary septum, golden-, reddish- to dark brown, smooth. Asexual morph: pyrenochaeta-like. Pycnidia on natural hosts and in artificial culture with apical setae, superficial (or immersed in agar), more or less globose, dark brown to black. Peridium thin, pseudoparenchymatous, brown. Conidiogenous cells phialidic, cylindrical to lageniform, formed on simple or basally branched conidiophores and on basal hyaline cells in nature and in artificial culture. Conidia produced acropleurogenously, i.e. at one side of the conidiophore on phialides or pegs, and terminally. Conidia 1-celled, oblong, cylindrical or ellipsoid, straight or curved, hyaline to pale brownish, guttulate (adapted from Jaklitsch et al. 2018).

 Type species: Cucurbitaria berberidis (Pers.) Gray

Notes: Cucurbitaria is characterised by erumpent globose to turbinate, brown to black ascomata with an obtuse apex, cylindrical, bitunicate, fissitunicate asci, and ellipsoid, straight, muriform ascospores. The asexual morph is characterised by pyrenochaeta-like, dark brown to black pycnidia, pseudoparenchymatous, brown peridium, phialidic, cylindrical to lageniform conidiogenous cells, and acropleurogenously produced 1-celled, oblong, cylindrical or ellipsoid conidia. Welch (1926) re-examined materials from American herbaria and accepted only five species in Cucurbitaria namely C. arizonica, C. berberidis, C. caraganae, C. elongata and C. laburni. Mirza (1968) provided the first monograph of Cucurbitaria in the pre-molecular era and reported a camarosporium-like asexual morph for several Cucurbitaria taxa. Sivanesan (1984) reported a similar observation. Barr (1990) accepted 11 species of Cucurbitaria from North America. Some phoma-like genera such as Pleurostromella, Pleurophoma, Pleurophomella, and Pyrenochaeta are reported as morphological variants for the same asexual morphs that have been associated with Cucurbitariaceae (de Gruyter et al. 2013, Jaklitsch and Voglmayr 2017). Checa et al. (2015) identified several Cucurbitaria species as belonging to different genera, for example, they reported Cucurbitaria bicolor as a synonym of Thyronectria rhodochlora, the type species of Thyronectria and retained only a few taxa in Cucurbitariaceae sensu stricto. Wanasinghe et al. (2018) accommodated several Cucurbitaria species that occurred on fabaceous hosts, for example, Cucurbitaria caraganae, C. elongata and C. laburni in the new genus Camarosporidiella (Camarosporidiellaceae). Several authors reported that the type species of Cucurbitaria (C. berberidis) is linked to Pyrenochaeta berberidis (Sacc.) Brunaud hence, Hyde et al. (2013) accepted that Cucurbitaria has “Pyrenochaeta”- like asexual morph. However, Doilom et al. (2013) reported that Pyrenochaeta nobilis, the type species of Pyrenochaeta, is distantly related to Cucurbitaria berberidis, hence, Hyde et al. (2013) did not synonymize Pyrenochaeta under Cucurbitaria (Doilom et al. 2013). Recently, Appadoo et al. (2021) added a new species Cucurbitaria berberidicola. Cucurbitaria is a distinct and well-supported type genus of Cucurbitariaceae but several synonyms of Cucurbitaria listed in Index Fungorum (2022) and by Doilom et al. (2013) seems to be different taxa and hence, the genus needs revision. Molecular markers available for Cucurbitaria are ITS, LSU, SSU, Actin and RPB2.

 

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