Mycosphaerellales » Mycosphaerellaceae


Isariopsella Höhn., in Weese, Mitt. bot. Inst. tech. Hochsch. Wien 6(2): 68 (1929).

Index Fungorum number: IF 8638; Facesoffungi number: FoF 08618, 3 morphological species (Species Fungorum 2022), no molecular data available.

Leaf spots amphigenous, fairly indistinct, diffuse or distinct spots of variable shape and size, usually angular-irregular, vein-limited, often confluent, forming large patches, sometimes almost entire leaves discolored, necrotic at first pale greenish, yellowish-ochraceous, later greyish brown, margin usually indefinite. Sexual morph: Unknown. Asexual morph: Conidiomata hypophyllous, synnematous, scattered to loosely grouped, at first greyish white, later pink, often associated with Puccinia cirsii. Mycelium internal, hyphae hyaline or pale, septate, sparsely branched, forming small substomatal stromatic hyphal aggregations, composed of somewhat swollen hyphal cells, colorless or pale. Synemata erect, straight arising from hyphal aggregations, through stomata, composed of numerous closely aggregated conidiophores, septate, smooth at first hyaline, later faintly pigmented, yellowish to pale reddish brown. Conidiogenous cells terminal as well as pleurogenous, splaying out, fertile free ends rather short, subcylindric to geniculate-sinuous, hyaline with somewhat thickened, darkened conidial scars. Conidia solitary to catenate, rarely in branched chains, ellipsoid-ovoid, subcylindric-fusiform, somewhat asymmetric, aseptate, rarely with a single septum, hyaline, almost smooth to verruculose, ends rounded or somewhat attenuated, hila slightly thickened and darkened (adapted from description of Phacellium vossianum in Braun 1998).

 Type species: Isariopsella vossiana (Thüm.) Höhn.

Notes: Isariopsella is characterised by hypophyllous, synnematous conidiomata, erect straight synemata arising from hyphal aggregations, subcylindric to geniculate-sinuous conidiogenous cells and solitary to catenate conidia. Isariopsella is currently a synonym of Phacellium but this has not been confirmed with molecular data. If Phacellium is synonymized with Ramularia, the older name Ramularia vossiana has priority. The placement of Isariopsella in Mycosphaerellaceae is doubtful. Fresh collections with DNA sequence data are needed to confirm the generic placement of the genus.


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