Erysiphe ulmi Castagne, Cat. Pl. Mars.

Kirschner, Roland, Lotz-Winter, Hermine & Piepenbring, Meike, 2020, A new species of the elm powdery mildew species complex (Erysiphaceae) on Chinese elm (Ulmus parvifolia) in East Asia segregated from Erysiphe ulmi, Phytotaxa 447 (4), pp. 276-282 : 279-280

Erysiphe ulmi Castagne, Cat. Pl. Mars. : 192 (1845) ( Fig. 4 )

Description (based on R. Kirschner 4674, if not stated otherwise): Colonies amphigenous, white on mature green leaves, thin. Hyphae smooth or verruculose, 3–6 μm wide. Hyphal appressoria solitary when nipple-shaped or predominantly in opposite pairs when slightly to strongly lobed. Conidiophore stipes arising from the upper or lateral side at approximately the middle of the supporting hyphal cell, usually curved at the base, with basal septum not conspicuously raised, composed of a foot cell, (55–)60–78(–80) × 8–10 μm [n=20; R. Kirschner & H. Lotz-Winter 4795: (40–)53–74(–85) × 9–11(–12) μm, n=30)], and 1–3 shorter cells, smooth, conidiophore (75–)95–122(–140) × (9–)10(–11) μm [n=20; R. Kirschner & H. Lotz-Winter 4795: (75–)95–131(–151) μm long, n=30]. Conidia solitary, oblong-cylindrical, with fine longitudinal striation on surface, (33–)34–42(–45) × (13–)14–15.5(–17) μm (n=30), germinating at one or both ends with hyphae (shorter than conidia) with strongly lobed appressoria. Ascomata 88–123 μm diam., peridial cells 6–22 μm long. Ascomatal appendages 10–17 per ascoma, hyaline, smooth (when fresh) to verrucose below the smooth coiled apex (when dried), aseptate, at the end loosely or tightly uncinated in one plane, thin-walled and up to 7 μm wide, proximal to these ends 4–6 μm wide and thick-walled (1 μm, when fresh, thicker when dried), (41–)60–99(–123) μm long (n=30). Asci 3–5 per ascoma, ca. 2-spored, 47 × 34. Ascospores broadly oblong or ovoid, 26–30 × 14–16 μm.

Material examined:— (all deposited in FR) GERMANY. Hessen, Darmstadt-Eberstadt , railway train station, on Ulmus sp. , 20 August 2018, R. Kirschner 4674 ; ITS sequence GenBank MT218387 . Taunus, Hofheim am Taunus ,

Königsteiner Weg zwischen Gundelhard und Meisterturm, 50.109 250, 8.437 803, on U. cf. laevis , 21 October 2018, M. Piepenbring & M. U. Schmidt MP5423 ; ITS sequence GenBank MT218391 . Frankfurt-Schwanheim, Rheinlandstrasse 5, terminal station of tram line 12, hedgerow, 50.082 482, 8.581 571, on U. cf. minor , 6 November 2018, leg. & det. H. Lotz-Winter, R. Kirschner 4693 ; ITS sequence GenBank MT218388 . Ibid., 21 August 2019, R. Kirschner & H. Lotz-Winter 4796 ; ITS sequence GenBank MT218390 . Kelsterbach , Leinepfad near T junction of Schindkaute, 50.063 678, 8.526 302, on Ulmus sp. , 21 August 2019, R. Kirschner & H. Lotz-Winter 4795 ; ITS sequence GenBank MT218389 . Known distribution:— Europe .

Figures

FIGURE 4. Erysiphe ulmi from Ulmus sp., Germany (R. Kirschner 4674). a Hyphae and appressoria. b Conidiophores. c Conidia, surface ornamentation indicated in the left conidium. d Germinating conidia. e, f Appendages of ascoma. g Ascus. h Ascospores. Scale bars: a, f = 10 μm, others = 20 μm.