Ophiobolus Riess, Hedwigia 1(6): 27 (1854)
Saprobic or hemibiotrophic on various hosts. Ascomata solitary to gregarious, scattered, semi-immersed to erumpent though host tissue with short to long beak, uniloculate, subglobose or ovoid or ampulliform, glabrous or covered by hyphae, dark brown to black, ostiolate, papillate. Peridium thick-walled, composed of dark brown to black, scleroplectenchymatous cells, arrange in textura angularis to textura globulosa. Hamathecium composed of numerous, filiform, cellular pseudoparaphyses, with distinct septa, anastomosing at the apex. Asci 8-spored, bitunicate, cylindrical to cylindric-clavate, short pedicellate, apically rounded with indistinct ocular chamber. Ascospores fasciculate, 3–4-seriate, scolecosporous, filiform or filamentous, with enlarged central cells, yellowish-brown to brown, multi-septate, non-constricted at the septa, separating into two part spores, smooth-walled, with or without appendages.
Type species: Ophiobolus disseminans
Phylogenetic study: Dong et al. 1998, Ariyawansa et al. (2014c)
Notes: Ophiobolus was introduced by Riess (1854) and typified by O. disseminans. Ascomata were described as discrete with distinct ostioles and ascospores as filiform and multi-septate (Zhang et al. 2012). Ophiobolus has been found on a wide range of hosts, mostly reported from Europe and North America (Farr and Rossman 2014). Holm (1948) and Müller (1952) used a broad concept of the genus Ophiobolus; however, Holm (1957) treated Ophiobolus in a much narrower sense, based on European collections (Shoemaker 1976). Three species were accepted by Holm (1957) and most Ophiobolus species were transferred to Nodulosphaeria and Leptospora (Holm 1957; Shoemaker 1976; Zhang et al. 2012). Shoemaker (1976) re-circumscribed species of Ophiobolus from Canada and some North America collections and accepted 31 species with two new species and five new combinations. Walker (1980) provided various illustrations of scolecosporous taxa from type material which had previously been accommodated in Ophiobolus (Saccardo 1883; Zhang et al. 2012). Ophiobolus species were also transferred to Acanthophiobolus, Entodesmium, Gaeumannomyces, Leptosphaeria and Leptospora (Shoemaker 1976; Walker 1980; Zhang et al. 2012). Barr (1979) initially accommodated Ophiobolus in Phaeosphaeriaceae and later transferred it to Leptosphaeriaceae (Barr 1987b). However, Zhang et al. (2012) reinstated the genus in Phaeosphaeriaceae based on morphological characters which are similar to Nodulosphaeria and Ophiosphaerella. There are 357 epithets listed in Ophiobolus in Index Fungorum (2014).
There is very little sequence data for Ophiobolus available in GenBank with two sequences of O. fulgidus. Zhang et al. (2012) mentioned that the genus should be placed in Phaeosphaeriaceae based on morphology and the phylogenetic investigation of Dong et al. (1998). However, Dong et al. (1998) could not resolve the placement of Ophiobolus as too few strains were used in their molecular analysis. Thus the genus needs to re-circumscribed using fresh collections (Zhang et al. 2012).
The asexual state of Ophiobolus has been reported in several genera such as coniothyrium-like, Rhabdospora, phoma-like and Scolecosporiella (Shoemaker 1976; Sivanesan 1984; Hyde et al. 2011; Wijayawardene et al. 2012; Zhang et al. 2012). However, these need confirmation as Ophiobolus is probably polyphyletic.
In this study, two species of Ophiobolus are included in the phylogenetic analysis. The detailed descriptions are provided in Ariyawansa et al. (2014c) and a description of the generic type is provided below. Based on multigene phylogenetic analysis, Ophiobolus clusters in Phaeosphaeriaceae. However, there are limited sequences in GenBank and the type species lacks molecular data to confirm its natural placement. Thus Ophiobolus is tentatively placed in Phaeosphariaceae until the generic type strain is sequenced to confirm the natural placement (Table 1).
Table 1. Synopsis of Ophiobolus species discussed in this study