Phyllachora Nitschke ex Fuckel, Jb. nassau. Ver. Naturk. 23-24: 216 (1870) [1869-70]
Sordariomycetidae, Phyllachorales, Phyllachoraceae, Phyllachora
Parasitic on plants. Sexual morph: Leaf spots on host black, abundant, scattered, raised, typically oblong to rounded or elongated, sometimes parallel with leaf venation, enclosed by light brown necrotic region. Ascomata flattened, globose, with thin walls, lying in leaf tissues or in a stroma and maturing in living leaves, ostiolate and sometimes with a clypeus formed by the lateral proliferation of ostiolar hyphae. Peridium clypeate, thickest adjacent to ostiolar canal, formed from a deeply melanized, brown-black, amorphous layer of host cuticle and epidermal cells, often merging with a lighter pigmented region of brownish, distorted parenchyma cells penetrated with fungal hyphae, beneath the clypeus; lower and lateral peridium formed from two layers, an outer region encompassing numerous layers of dark brown, flattened, thin-walled fungal cells, which merge inwardly with several layers of hyaline, flattened, thin-walled fungal cells; lateral peridium fuses outwardly with an irregular, tapered region of distorted host parenchyma infiltrated by fungal cells; the basal peridium merges outwardly with either a narrow zone of infiltrated and distorted host parenchyma and occasionally lower epidermal cells, or integrates directly with a lower clypeus, similar in construction to that of basal peridium. Paraphyses numerous, persistent, filiform, branched, slightly longer than asci. Asci 8-spored, persistent, cylindrical to fusiform, short pedicellate, with walls fairly uniform in thickness, not specially thickened at apex, apical ring often present, J-, or J+. Ascospores hyaline, 1–3-seriate, fusiform to barely oval, with or without attenuated base, sometimes with pad like appendages. Asexual morph: Coelomycetous, with conidia in locules within a stroma. Conidiomata similar to ascomata, immersed, subcuticular, strongly raising the host surface, occasionally pycnidial, occupying the region between the cuticle and epidermis, ostiolate. Conidiophores cylindrical, hyaline, thin-walled, directly composed of the strongly contorted cells of the lower wall. Conidiogenous cells arising from the basal and lateral walls, cylindrical, phialidic, aseptate, hyaline, forming conidia singly at the apex. Conidia hyaline, clavate, aseptate (adapted from Maharachchikumbura et al. 2016).
Type species: Phyllachora graminis (Pers.) Fuckel, Jb. nassau. Ver. Naturk. 23-24: 216 (1870) [1869-70]
Notes: Phyllachora, which is typified by P. graminis and is the type genus of Phyllachoraceae with around 1513 species currently recognized (Maharachchikumbura et al. 2016, Dayarathne et al. 2017, Species Fungorum 2020). Most species are named based on their host association and this may not reflect the actual number of species (Cannon 1988). Phyllachora comprises species that grow immersed in a clypeate pseudostroma in leaf tissues, varying from a subcuticular or intra epidermal, to a generalized infection of the entire section of the mesophyll, inducing characteristic black shiny superficial symptoms, commonly known as tar spots (Santos et al. 2016). However, differences in depth of ascomata can be influenced by the consistency of the host tissue (Cannon 1991); therefore, this is not a valid character to distinguish genera.
Species illustrated in this entry:
Phyllachora nigeriensis Sivan. & Okpala
Cannon PF. 1988 – Proposal to merge the Phyllachorales with the Diaporthales, with a new family structure. System Ascom 7, 23–43
Cannon PF. 1991 – A revision of Phyllachora and some similar genera on the host family Leguminosae. Mycological Papers 163, 1–302
Dayarathne MC, Maharachchikumbura SSN, Jones EBG, Goonasekara ID et al. 2017 – Neophyllachora gen nov. (Phyllachorales), three new species of Phyllachora from Poaceae and resurrection of Polystigmataceae (Xylariales). Mycosphere 8, 1598–1625
Maharachchikumbura SSN, Hyde KD, Jones EBG, McKenzie EHC et al. 2016 – Families of Sordariomycetes. Fungal Diversity 79, 1–317
Santos MD, Fonseca-Boiteux ME, Boiteux LS, Câmara PE et al. 2016 – ITS-phylogeny and taxonomy of Phyllachora species on native Myrtacae from the Brazilian Cerrado. Mycologia 108, 1141–1164
Species Fungorum. 2020 – http://www.speciesfungorum.org/Names/Names.asp.