Pleosporales » Torulaceae

Torula

Torula Pers., Ann. Bot. (Usteri) 15: 25 (1795).

Index Fungorum number: IF 10248; Facesoffungi number: FoF 01740, 49 morphological species (Species Fungorum 2022), 17 species with molecular data.

Saprobic on host. Sexual morph: Unknown. Asexual morph: Colonies discrete, dark brown to black, effuse, dry, velvety. Mycelium mostly immersed. Conidiophores reduced to conidiogenous cells, or with one brown supporting cell. Conidiogenous cells solitary on mycelium, erect, doliiform to ellipsoid or clavate, brown, smooth to verruculose, mono to polyblastic. Conidia phragmosporous, in branched chains, acrogenous, brown, apex pale brown, dry, constricted at septa, smooth to verrucose, fragmenting into segments, conidiogenous cell and fertile cell in conidial chain (where branching occurs) darker brown than other cells; cells subglobose, conidia strongly constricted at the septa (adapted from Crous et al. 2015).

            Type species: Torula herbarum (Pers.) Link

Notes: Torula is characterised by discrete, dark brown to black velvety mycelium, doliiform to ellipsoid or clavate conidiogenous cells and phragmosporous conidia. Mason (1941), Hughes (1953), Subramanian (1971) and Ellis (1971, 1976) used morphological characters namely the melanized, verrucose, phragmoconidia that are produced acropetally in simple or branched chains to delineate species in Torula. Hashmi et al. (1973) studied the ontogeny of conidia in Torula herbarum by time-lapse photomicrography and reported that the fungus produces conidia holoblastically in acropetal chains. Crane and Schoknecht (1977) provided an argument regarding the conidiogenesis in Torula based on light and transmission electron microscopy. Crous et al. (2015) added three new species, Torula ficus, T. hollandica and T. masonii based on the number of septa per conidium and provided an updated phylogeny of the genus based on LSU sequence data. Crous et al. (2015) also designated a neotype for T. herbarum and confirmed the placement of Torula in Pleosporales. Crous et al. (2015) proposed that Deightoniella indica, the type of Bahusaganda, belongs in Torula s. str. Crane and Miller (2016) re-examined several Torula species and transferred some of them to other genera as they were not congeneric with T. herbarum. Crane and Miller (2016) transferred T. rhombica and T. terrestris to Bahusandhika. Torula resembles Bahusaganda in having conidiogenous cells which are corona cells but differs in that Torula has catenate conidia while Bahusaganda has solitary conidia. Su et al. (2016) provided a description of Torula and introduced a new genus Neotorula based on phylogenetic analysis of ITS, LSU and SSU sequence data. Torula resembles Neotorula in having clavate to subcylindrical, brown conidia, with rounded ends that are produced in branched chains but differs in that Neotorula has distinct conidiophores consisting of a few cells and polytretic conidiogenesis, while in Torula the conidiophores comprise a single or few cells and has polyblastic conidiogenesis (Su et al. 2016). Su et al. (2016) reported that the conidiogenous cells of Torula are cupulate at maturity as previously observed by Ellis (1971). Su et al. (2018) added one new species T. aquatica and re-studied the phylogenetic relationship of the genus based on ITS, LSU, RPB2 and TEF1 sequence data. Torula is morphologically and phylogenetically a distinct genus in Torulaceae but several species which lack molecular data might belong to other genera. Hence, this genus needs revision to attain a stable taxonomy. Molecular markers available for Torula include ITS, LSU, SSU, RPB2 and TEF1.

 

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