Cosmospora diatrypicola Lechat & Gardiennet, sp. nov.
Mycobank : 
Anamorph : Fusarium sp.
Etymology : The epithet diatrypicola refers to the substratum Diatrype bullata (Hoffm. : Fr.) Fr.

Latin diagnosis: Ascomata superficialia, haud stromatica, super stromata Diatrype bullatae (Hoffm. : Fr.) Fr. fixa, large piriformia, 250-280 µm in diametro, 280-320 µm in longitudine, vive rubra, violacea facta in KOH (3%), laterali pariete 30-35 µm spissa. Asci a cylindricis ad stricte clavatos, 75-90 x 6,5-8 µm, cum octo ascosporis uniseriatis ellipsoideis, 13-14 x 6-7,2 µm, pallide  brunneoflavis in maturitate, una pariete, leviter verrucosis. Status asexualis Fusarii cf. merismoidis similis.

Description: Ascomata superficial, nonstromatic, gregarious or in group of 2-10, seated on stroma of Diatrype bullata (Hoffm. : Fr.) Fr.,  widely pyriform, 280-320µm high, 250-280 µm diam., finely roughened, bright red , turning purple in 3%KOH, yellow in lactic acid, with a darker discoid apex 40-50 µm high x 120-140 µm diam., collapsing laterally or vertically when dry.
Ascomatal wall 30-35 µm thick, made of two regions: outer region 20-25 µm thick, composed of thick-walled globose to ellipsoid  cells 5-6 x 5-8 µm with wall 1.5-2,5 µm thick;  inner region 5-10 µm thick, composed of thin-walled, hyaline, flattened cells 5-7 x 8-12 µm; apex made of thick-walled cylindrical to clavate cells, cells at surface of ascomata forming textura epidermoidea.
Asci unitunicate, cylindrical, short-stipitate, 75-90 x 6.5-8 µm, 8-spored, apically rounded with a faint refracting ring, ascospores uniseriate, moniliform paraphyses inserted between the asci, up to 10µm wide towards base.
Ascospores 13-14 x 6-7,2 µm, ellipsoid, equally two-celled with one large drop in each cell, slightly constricted at the septum, pale brownish-yellow when mature, finely verrucose. Fusarium anamorph on 2% potato-dextrose-agar (PDA): colonies 4-5 cm after 12 days, slimy, salmon. Microconidia 5-8 (-10) x 2-3 µm, non-septate,  oval to obclavate, macroconidia slightly curved with pedicellate foot-cell most often 1-3-septate 14-35 x 3-4 µm, when 5-septate 38-45 x 4-4,5 µm, chlamydospores not observed. Perithecia formed after 35 days.

 

Typus : France, Is-sur-Tille, Côte d’Or,  near the river Tille, close to « ferme du Fossé », on Diatrype bullata on Salix, 05 Nov 2008, collected by A. Gardiennet, deposited at Faculté de Pharmacie de Lille, France (LIP) AG08NE4, holotypus, culture ex-type CBS 124395.

Additional specimens : France, Is-sur-Tille, Côte d’Or, near the river Tille, close to athletic stadium, on Diatrype bullata on Salix, 08 Nov 2008, collected by A. Gardiennet, AG08NE12 ; Luxembourg, Kockelscheuer, Weier, 02.nov.2008, collected by G. Marson on Diatrype bullata, on still attached Salix cinerea branch, HB 8960b.

Notes: The following features : fungicolous habitat, ascomatal wall thickness, Fusarium anamorph and 3%KHO+ place this species in the genus Cosmospora as defined by Rossman et al.¹. Cosmospora diatrypicola remaining to the “episphaeria group” as defined by C. Booth²  and is closely related to Cosmospora purtonii (Grev.) Rossman & Samuels but deviates from it for its larger ascospores (13-14 x 6-7,2 µm vs 8-11 x 3,5-4,5 µm), and septa of conidia of Fusarium anamorph (1-5-septate vs 1-septate) . This species was collected abundantly and simultaneously in France and Germany on stroma of Diatrype bullata (Hoffm. : Fr.) Fr. on Salix, simultaneity of these two collections is amazing to notice.

Colour illustrations : Edge of the river Tille (A. Gardiennet); ascomata on host substratum, vertical section through ascomatal wall, asci and ascospores (C. Lechat)

References: ¹Rossman, A. Y., G. J. Samuels, C. T. Rogerson, & R. Lowen (1999). Genera of Bionectriaceae, Hypocreaceae, Nectriaceae (Hypocreales, Ascomycetes). Studies in Mycology 42: 1-248. ²C. Booth (1959). Studies in pyrenomycetes. IV. Nectria (part 1) Mycol. Pap. 73: 1-115.