Erysiphe salicicola Hyang B. Lee, P.M. Kirk & T.T.T. Nguyen, sp. nov.

Index Fungorum number: IF 557324; MycoBank number: MB 557324; Facesoffungi number: FoF 09197; Fig. 1

Etymology – Referring to the host plant.

Holotype – CNUFC PWS1

Sexual morph Chasmothecia scattered, 98.5–139.5(–152.5) μm diam., containing 3–13 asci. Each chasmothecium had 26–56 appendages. Appendages hyaline, aseptate, straight to curved, (0.85–)1–1.4 times as long as the cleistothecial diam., 4.5–6.5 µm wide at the base, slightly increasing towards the apex, with single septum at the base, hyaline, sometimes slightly brown at the base, 6–7.5 µm wide at the apex, circinate at the near apex. Asci sessile or short-stalked, 48.5–68.5×27.5–43 μm, obovoid or clavate, with 3–5 ascospores. Ascospores ellipsoidal to obovoid, 15–25(–26.5)×10.5–15 μm. Asexual morph Appressoria developed, nipple-shaped to slightly lobed, solitary or in opposite pairs. Conidiophores arising from the upper part of mother cells, short, cylindrical, 57–95.5×7.5–9.5 μm. Foot cells cylindrical, straight to slightly curved near the base, followed by two shorter cells. Conidia oval, cylindrical, 27–35.5(–38.5)×13.5–18.5(–21) μm.

Material examined – REPUBLIC OF KOREA, Jeonnam Province, garden of the Chonnam National University located in Gwangju (35°10′20.3″ N 126°53′56.9″ E), on Salix gracilistyla var. melanostachys, 17 September 2018, collected by H.B. Lee (CNUFC PWS1, holotype).

GenBank numbers – ITS = MT192530, MT192531, LSU=MT192534, MT192535.

Notes – Erysiphe salicicola belongs to Erysiphe sect. Uncinula and is phylogenetically related to E. adunca. However, E. salicicola differs from E. adunca in having smaller conidia and ascospores. The number of ascospores in the asci (chasmothecium), and appendages are less than E. adunca. Furthermore, phylogenetic analyses indicate that E. salicicola forms a separate branch distinct from E. adunca, confirming it represents a new species. A BLASTn search of the ITS sequences indicated that Erysiphe salicicola was closest to Erysiphe sp. (MH358357) and E. adunca (KY660862) with similarity values of 99.2% and 93.1%, respectively. The species most closely related to E. salicicola, with 97.9% similarity based on LSU sequences was E. adunca (KR048118).

Figure 1 – Erysiphe salicicola (CNUFC PWS1, holotype). a Symptoms of powdery mildew on black pussy willow (Salix gracilistyla var. melanostachys). b Chasmothecia on the leaf-surface. c–g, i Young and mature chasmothecium with appendages. h Appendages. j–p Asci containing ascospores. q–s Conidiophores. t, u Conidia and conidial germ tubes. v, w Appressoria (Fig. b: observed under a stereomicroscope; Figs. c–w: light microscope). Scale bars: c–f, h, j–w=20 µm, g, i=50 µm