Mirohelminthosporium K. Zhang, D.W. Li & R.F. Castañeda, in Zhang et al., Mycotaxon 135(4): 778 (2020).
Index Fungorum number: IF 833028; Facesoffungi number: FoF 11598, 1 morphological species (Species Fungorum 2022), no molecular data available.
Colonies on CMA medium hairy, brown to dark brown. Asexual morph: Conidiophores macronematous, mononematous, unbranched, erect, straight, cylindrical, septate, smooth, brown to dark brown. Conidiogenous cells biontogenous, sometimes on the same cell: i) polytretic, integrated, mostly intercalary, cylindrical, sometimes terminal with subapical tretic loci and apical blastic loci; ii) monoblastic, integrated, terminal, sometimes with several tretic loci near below the blastic locus on the same cell. Conidia solitary, dimorphic: i) acropleurogenous, mostly pleurogenous, cylindrical, oblong, straight or curved, rounded at the ends, melanized or obscure at the base, distoseptate, smooth, brown to dark brown or black, dry, borne on tretic conidiogenous loci; ii) acrogenous, solitary, cylindrical, clavate to subclavate, attenuate, rounded or obtuse at the apex, truncate at the base, euseptate, smooth, brown to dark brown or black, dry, borne on the apical blastic conidiogenous loci. Sexual morph: Unknown (adapted from Zhang et al. 2020).
Type species: Mirohelminthosporium bigenum (Matsush.) K. Zhang, D.W. Li & R.F. Castañeda
Notes: Mirohelminthosporium is characterised by macronematous, mononematous, unbranched conidiophores, biontogenous conidiogenous cells, and solitary, dimorphic conidia. Mirohelminthosporium bigenum was previously known as Helminthosporium bigenum but was not congeneric with the type species of Helminthosporium, H. velutinum due to its atypical combination of holoblastic euseptate conidia produced from apical conidiogenous cells and tretic (enteroblastic) distoseptate conidia from intercalary conidiogenous cells (Matsushima 1993). Zhang et al. (2020) considered the conidial characters and conidiogenous events as significant morphological characters to delineate species of Mirohelminthosporium. Mirohelminthosporium is morphologically a distinct genus in Massarinaceae but lacks molecular data. Fresh collections with DNA sequence data are needed to confirm the taxonomic placement of the genus.
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