Cronartium mongolicum P. Zhao & L. Cai, sp. nov.,
MycoBank number: MB 842419; Index Fungorum number: IF 842419; Facesoffungi number: FoF 12568;
Spermogonia and aecia unknown. Uredinia hypophyllous, scattered, 0.25–0.40 mm, yellow, with intra-uredinial paraphyses, urediniospores obovoid or ellipsoid, 16–25 × 12–19 µm, wall hyaline, 1.0–2.0 µm thick, echinulate. Telia hypophyllous, scattered, forming fusiform columns, straight or slightly curved, 4.0–21.5 mm long, brown, cross-section of telia with 6–9 teliospores, teliospores oblong or ellipsoid, 38–71 × 13–22 µm, wall yellowish brown, smooth, 0.4–1.2 µm. Basidia external.
Material examined: China, Hei Longjiang, Huma, Greater Khingan Range, III on Q. mongolica, 28 Jul 2000, J.Y. Zhuang, HMAS242639 (holotype). China, Hei Longjiang, Huma, Greater Khingan Range, III on Q. mongolica, 28 Jul 2000, J.Y. Zhuang, HMAS82418 & HMAS82417; China, Hei Longjiang, Tahe, Greater Khingan Range, III on Q. mongolica, 2 Sept 2015, P. Zhao, ZP-R7.
Sequence data: SSU: OM745991; ITS: OM746423 (holotype).
Notes: In the phylogenetic analysis Cronartium mongolicum was sister to C. myricae and C. orientale. Morphologically, it differs from C. myricae in the ornamentation of urediniospores and the dimension of teliospores (38–71 × 13–22 µm vs 32–55 × 10–17 µm); from C. orientale in the dimension of urediniospores (16–25 × 12–19 µm vs 22–34 × 11–19 µm), the length of telia (4.0–21.5 mm vs 2–3.8 mm), the dimension of teliospores (38–71 × 13–22 µm vs 39–83 × 10–21 µm), and the number of teliospores in the cross-section of telia (6–9 vs 9–14). This species was found with its telial stage on Q. mongolica in China.
Figures 2 Cronartium mongolicum (holotype). a. Hypophyllous telia on Q. mongolica; b. Hair-like telia on leaf surface; c. Section of a telium observed by LM; d, e. Hair-like telia observed by SEM; f. Capitate paraphyses in uredinium. Scale bars: b = 200 µm; c = 50 µm; d–e = 150 µm; f = 20 µm.