Erysiphe clematidis Zhao Y. Zhang & S. Y. Liu, 2025

Zhang, Zhao-Yang, Wu, Xue-Lian, Lv, Xiao-Xue, Liu, Tie-Zhi, Jin, Dan-Ni, Liu, Li, Wang, Shuang-Bao, Feng, Jing, Hsiang, Tom, Li, Yu & Liu, Shu-Yan, 2025, Discover hidden taxa of Erysiphe section Erysiphe fungi (Ascomycota, Erysiphaceae) based on morphology and multilocus phylogeny in China, MycoKeys 118, pp. 119-146 : 119-146

Erysiphe clematidis Zhao Y. Zhang & S. Y. Liu sp. nov.

Fig. 3

Etymology.

Epithet derived from the name of the host genus, Clematis .

Diagnosis.

Morphologically resembling E. aquilegiae var. ranunculi , but distinguished by chasmothecial appendages that are colorless or only pigmented at the base, only with 0–2 septa. Differs from var. aquilegiae in having much shorter appendages, 0.7–3.5 times as long as the chasmothecial diam., mycelioid, geniculate-sinuous, and colorless or only pigmented at the base. Furthermore, forming a highly supported species clade in all phylogenetic analyses, in sister position to the E. aquilegiae cluster.

Description.

Mycelium on leaves and stems, amphigenous, effuse or in patches, on stems colonies usually thick, ± persistent. Sexual morph: Chasmothecia mostly scattered, dark brown, mainly on leaf abaxial surface of leaves and stems, more abundant on the upper side of the leaf blade, (66 –) 74–122 (– 129) µm; peridium cells irregularly polygonal, 5–13 µm; appendages unequal in number, mycelioid, continuously curved, with small irregular branchlets, some bifurcate branches present, 0–2 - septate, hyaline, sometimes yellowish brown near the base, or light brown, paler or colorless towards the apex, uneven in thickness, length about 0.7–8.6 times as long as the chasmothecial diam., sometimes up to 338 μm; asci 4–10, (32 –) 46–73 × 27–50 µm, ellipsoid-obovoid, short-stalked to sessile; ascospores (1 –) 2–4, 16–28 × 13–19 µm, subglobose, ovoid, irregularly ovoid, ellipsoid, reniform, colorless.

Holotype.

China, Qinghai Prov. • 1; Xining City ; 36°38'2"n, 101°45'36"e; ca. alt. 2260 m a. s. l.; 15 Oct. 2023; Zhao-Yang Zhang & Li Liu leg.; on Clematis macropetala ; HMJAU -PM 92226 . Isotype: same data as for holotype; HMAS 353407 .

Distribution.

Asia ( China).

Host.

Clematis spp. ( Ranunculaceae ).

Additional material examined.

China, Gansu Prov. • 1; Dingxi City ; 36°36'33"n, 104°35'5"e; ca. 1860 m a. s. l.; 17 Oct. 2023; Zhao-Yang Zhang & Li Liu leg.; on Clematis glauca ; HMJAU -PM 92227 . • 1; Zhangye City ; 38°55'56"n, 100°23'45"e; ca. 1456 m a. s. l.; 23 Oct. 2023; Dan-Ni Jin & Xue-Lian Wu; on Cl. intricata ; HMJAU -PM 92224 . – Qinghai Prov. • 1; Xining City ; 36°37'17"n, 101°47'7"e; ca. 2278 m a. s. l.; 12 Oct. 2023; Zhao-Yang Zhang & Li Liu leg.; on Cl. glauca ; HMJAU -PM 92225 . • 1; Xining City ; 36°37'17"n, 101°47'7"e; ca. 2280 m a. s. l.; 12 Oct. 2023; Zhao-Yang Zhang & Li Liu leg.; on Cl. intricata ; HMJAU -PM 92223 . – Shaanxi Prov. • 1; Yulin City ; 38°15'14"n, 109°44'51"e; ca. 1040 m a. s. l.; 18 Oct. 2023; Zhao-Yang Zhang & Li Liu leg.; on Cl. intricata ; HMJAU -PM 92222 .

Notes.

Based on the applied morphological concept of Erysiphe aquilegiae s. lat., Braun and Cook (2012) listed Clematis spp. as hosts of var. aquilegiae as well as var. ranunculi . In this study, we assigned the new species Erysiphe clematidis for our collections on genus Clematis based on the obvious morphological differences. The appendages of E. clematidis are significantly shorter than those of E. aquilegiae var. aquilegiae [0.7–8 vs. (1 –) 3–12 times as long as the chasmothecial diam.], and the color of their appendages also differs: the appendages of E. clematidis have basal pigmentation (colorless to faintly pigmented), whereas those of E. aquilegiae var. ranunculi are brown throughout or paler towards the apex. Unexpectedly, two types of ascospore morphologies were observed on the specimen of C. glauca ( HMJAU -PM 92227 ): macro-ascospores [14–31 × (6 –) 10–18 µm] and micro-ascospores [4–17 × 4–14 µm] (Fig. 4 ). Furthermore, some germinating ascospores were also observed, which is very unusual in powdery mildews. More specimens need to be collected to determine whether this phenomenon is common.

Figures

Figure 3. Symptoms and sexual morph of Erysiphe clematidis sp. nov. on Clematis macropetala (holotype: HMJAU - PM 92226) A, B powdery layer and chasmothecia on leaves C chasmothecium D peridium cells E appendages F, G asci H – K ascospores Scale bars: 10 µm (D, H – K); 50 µm (C, E); 20 µm (F, G).

Figure 4. Symptoms and sexual morph of Erysiphe clematidis sp. nov. on Clematis glauca (HMJAU - PM 92227) A, B powdery layer and chasmothecia on leaves C chasmothecium D peridium cells E appendages F asci G – K two types of ascospores L, M germinating ascospores Scale bars: 50 µm (C); 20 µm (D – F); 10 µm (G – M).