Dichotomophthora Mehrl. & Fitzp., Mycologia 27(5): 550 (1935).
Index Fungorum number: IF 506175; Facesoffungi number: FoF 08348, 5 morphological species (Species Fungorum, 2022), 4 species with molecular data.
Pathogenic on host. Asexual morph: Conidiophores macronematous, mononematous, unbranched or irregularly branched, sometimes swollen and repeatedly dichotomously or trichotomously branched or lobed at apex, forming a stipe and head; stipe hyaline to brown; branches usually short. Conidiogenous cells mono- or polytretic, integrated, terminal, lobed, cicatrized. Conidia solitary, dry, simple, ellipsoidal to cylindrical, rounded at ends, subhyaline to brown, multi-distoseptate. Microconidia ovoid, 0–2-distoseptate. Sclerotia often formed in culture resembling immature perithecia, semi- or immersed in agar, subglobose, ellipsoidal, ovoid, dark brown or black. Sexual morph: unknown (Adapted from Ellis, 1971 and Marin-Felix et al., 2019).
Type species: Dichotomophthora portulacae Mehrl. & Fitzp. ex M.B. Ellis
Notes: Dichotomophthora was introduced by Mehrlich and Fitzpatrick (1935) with D. portulacae as type species. Dichotomophthora is characterized by macronematous, mononematous, unbranched conidiophores, mono- or polytretic conidiogenous cells, solitary, dry, simple, ellipsoidal to cylindrical conidia and ovoid, 0–2-distoseptate microconidia. There is often production of sclerotia in culture which resembles immature perithecia. Since the original publication lacked a Latin diagnosis, the name ‘Dichotomophthora’ was invalid (Mehrlich & Fitzpatrick, 1935). Rao (1966) provided a Latin diagnosis of D. portulacae and added a new species D. indica but the validation was inappropriate hence both names were unacceptable. Ellis (1971) examined the holotype specimen of D. portulacae (IMI 8742) and formally validated the genus. De Hoog and van Oorschot (1983) revised Dichotomophthora and included D. portulacae and D. lutea. Dichotomophthora portulacae was limited to taxa characterized by dichotomously branched conidiophores, and conidia with 2–3 septa while D. lutea is characterized by unbranched or irregularly branched conidiophores, and conidia with 1–5 septa, 30–115 × 10–20 μm. Marin-Felix et al. (2019) reported that several records of D. portulacae might represent D. lutea because of prior taxonomic confusion, host and distribution data must be re-studied. Marin-Felix et al. (2019) accepted Dichotomophthora in Pleosporaceae based on morphology and phylogenetic analyses of ITS, gapdh and rpb2 sequence data and added two new species D. basellae and D. brunnea. Members of Dichotomophthora are morphologically variable in culture and on natural hosts therefore phylogenetic analyses are needed for precise documentation of new species. Dichotomophthora is morphologically and phylogenetically a distinct genus in Pleosporaceae. Molecular markers available for Dichotomophthora include LSU, ITS, GAPDH and RPB2.