Erysiphe parvifoliae R. Kirschner, 2020

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 : 277-279

Erysiphe parvifoliae R. Kirschner , sp. nov. ( Figs 2‒3 )

Index Fungorum: IF557766

Holotype:— TAIWAN. Taoyuan City, Zhongli District, north of National Central University, Neicuo 3 rd Rd., 24.975 10107, 121.190 31800, ca. 135 m a.s.l., U. parvifolia hedge plantation, 26 December 2017, R. Kirschner 4572 ( TNM F0031688 ).

Etymology:— referring to the host, Ulmus parvifolia

Diagnosis:— Differs from E. ulmi by the foot cell of the conidiophore not exceeding a length of 50 μm.

Description (based on R. Kirschner 4572): Colonies amphigenous, mainly on mature leaves, not causing immediate discoloration of the green tissues ( Fig. 2a ). Hyphae verruculose, 3–6 µm wide. Hyphal appressoria solitary or in opposite pairs, nipple-shaped to strongly lobed. Conidiophores arising from hyphae, above the approximately middle of the mother cell, cylindrico-clavate, total (89–)95–127(–150) × 10–13(–15) µm, foot cell straight or curved at base, with basal septum not conspicuously raised, (12–)26–41(–45) × 8–9 µm (n=30), followed by 2–3 further cells. Conidia solitary, cylindrical, with fine longitudinal-reticulate surface ornament, (37–)39–50(–56) × (12–)13–15.5(–18) µm (n=30), germinating at the base with a short hypha giving rise to a lobed appressorium. Ascomata globose, dark brown, wall composed of epidermoid cells measuring 9–20 × 5–13 µm, 100–140 µm diam., with 13–26 equatorial appendages, straight and tightly coiled at the apex, hyaline, thick-walled and verruculose except for the thin- and smooth-walled coiled apex, (60–)77–107(–115) µm long (n=30), 5–7 µm wide at the base, narrowing to 5–7 µm distally, broadening to 7–9 µm in the coiled part ( Fig. 3 ). Asci 4–5 per ascoma, 50–60 × 37–42 µm. Ascospores 2(–3) per ascus, ellipsoidal, hyaline, smooth, 22–35 × 13–17 µm.

Material examined:— TAIWAN. New Taipei City, Shulin District, Datong Mountain Trail , 24.991 10274, 121.414 21166, ca. 80 m m.s.l., on young planted tree of Ulmus parvifolia , 20 February 2018, R. Kirschner 4614 ( TNM F0031690 ) (anamorphic specimen) ; almost same place and time, R. Kirschner 4612 ( TNM F0031689 ) ; ITS sequence GenBank MH427792 . Taipei City, Songao Road , opposite Taipei City Government , 25.039 375, 121.564 759, on planted U. parvifolia , 22 December 2019, R. Kirschner 4861 (with few ascomata) ; Taoyuan City, Zhongli District, Goat World , 24.982 4276, 121.210 7108, ca. 107 m m.s.l., on ornamentally trimmed U. parvifolia , 25 February 2015, R. Kirschner 4165( TNM F0031687 ) (anamorph and teleomorph) ; same district, north of National Central University, Neicuo 3 rd Rd. , 24.975 10107, 121.190 31800, ca. 135 m m.s.l., U. parvifolia hedge plantation, 26 December 2017, R. Kirschner 4572 ( TNM F0031688 , holotype) (anamorph and teleomorph) ; ITS sequence GenBank MG954111 .

Known distribution:— Korea, Japan, Taiwan.

Figures

FIGURE 2. Erysiphe parvifoliae on Ulmus parvifolia (R. Kirschner 4572). a Powdery mildew symptoms on leaves. b Hyphae and appressoria. c Conidiophores. d Conidia, surface ornamentation indicated in the right conidium. e Germinating conidium. Scale bars: a = 10 µm, others = 20 µm.

FIGURE 3. Teleomorph of Erysiphe parvifoliae on Ulmus parvifolia (R. Kirschner 4572). a Squashed ascoma with appendages. b Two appendages of ascoma. c Four asci exposed from a squashed ascoma. d Ascospores. Scale bars: 50 µm.