Ambarignomonia petiolorum (Schwein.: Fr.) Sogonov
≡ Sphaeria petiolorum Schwein.: Fr., Schr. Naturf. Ges. Leipzig 1: 41. 1822: Syst. Mycol. 2: 517 (1823)
≡ Gnomonia petiolorum (Schwein.: Fr.) Cooke, Grevillea 7: 54 (1878)
≡ Gnomoniella amoena var. petiolorum (Schwein.: Fr.) Sacc., Syll. Fung. 1: 414 (1882)
Sexual morph: Ascomata 630–904 ´ 310–340 µm, immersed, scattered, mostly globose or depressed globose, membranous, brown, occurring on petioles near major veins and at the base of the leaf blade. Beak 416–744 ´ 24–40 µm, protruding from the epidermis, with crystalline amorphous material at the base, periphysate, central, with distinct cells of textura porrecta in surface view, with hyaline mass at the tip, 24–31 ´ 32–39 µm, containing hypha-like filaments that are hyaline. Peridium 22–30 µm thick, 4–5 layers wide, composed of two distinct cell layers; outer cell layer pseudoparenchymatic and much broader and less compressed than inner wall layers, 10–16 ´ 6–10 µm; inner cell layers of polygonal, fusoid, compressed, thin walled cells, 12–28 ´ 3–6 µm; cells in surface view pseudoparenchymatic 16–50 ´ 12–24 µm. Paraphyses absent. Asci 30–36 ´ 6–8 µm, broadly clavate, becoming slightly narrower or cylindrical or sometimes truncate at the apex, with tapered fusoid stipe, extremely abundant, loosening from subhymenium and lying freely in the ascomal cavity, unitunicate, provided with a refractive apical apparatus, MLZ-, with 8 ascospores. Ascospores (11–)12– 14 ´ 2–2.5 µm, hyaline, ellipsoid to broadly fusoid, with a single median septum, mostly straight, at times allantoid, mostly in single to occasionally two overlapping fascicles in ascus, with bipolar appendages 4–6 µm long. Asexual morph: Undetermined (Description based on Fallah and Shearer, 2001)
Specimens examined. USA. WISCONSIN: Vilas Co., Trout Lake, UTM Zone 16, 293196mE, 5098921mN, 46°00.838'N, 89°40.283'W, on submerged partially decomposed Acer rubrum leaves, 7 Jan 1996, PMF andJLCP1-46 (ILLS 54016); Big Muskellunge Lake, UTM Zone 16, 297663mE, 5097935mN, 46°00.306'N, 89°36.801 'W, on submerged partially decomposed Acer rubrum leaves, 23 Nov 1996, PMF and JLC P3-58 (ILLS 54015).
Distribution: USA, Wisconsin, Trout lake/Big Muskellunge lake, on submerged partially decomposed Acer rubrum leaves (Fallah and Shearer 2001).
Notes: Lectotype BPI 800519, Epitype BPI 844274, specimens collected from freshwater habitats: ILLS 54015, ILLS 54016. ITS, LSU, RPB2, TEF1a and b-tubulin sequence data are available. Fallah and Shearer (2001) collected two specimens (ILLS 54015 and ILLS 54016) from freshwater habitats and provided descriptions and illustrations and identified the collections as Gnomonia petiolorum. Sogonov et al. (2008) combined this species as Ambarignomonia petiolorum.
Fallah PM, Shearer CA. 2001- Freshwater ascomycetes: new or noteworthy species from north temperate lakes in Wisconsin. Mycologia 93:566–602.
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Sogonov MV, Castlebury LA, Rossman AY, Mejı ´a LC, White JF. 2008 - Leaf-inhabiting genera of the Gnomoniaceae, Diaporthales. Stud Mycol 62:1–79.