Cronartium castaneae P. Zhao & L. Cai.
MycoBank number: MB 842416; Index Fungorum number: IF 842416; Facesoffungi number: FoF 00010;
Spermogonia not found. Aecia caulicolous, not forming definite swellings, mostly embedded in host tissue, peridia not found, aeciospores 25–33 × 14–22 µm, wall 2.0–3.5 µm, wall coarsely verrucose, warts annulate, 4–6 annuli. Uredinia not found. Telia with cornute columns, 0.5–1.5 mm long, straight, bright yellow, cross-section of telia with 6–9 teliospores, teliospores oblong, 33–56 × 14–22 µm, catenulate, wall brownish, 0.6–1.0 µm thick, without surface ornamentation. Basidia external.
Material examined: China, Nanjing, III on Castanea sp., 24 Jul 1922, B.N. Jiang & R.Y. Zheng, HMAS18841 (holotype). China, Nanjing, III on Castanea mollissima, 8 Jun 1929, S.C. Teng, HMAS769; China, Nanjing, III on Castanea sp., 1 Dec 1954, B.N. Jiang & R.Y. Zheng, HMAS94221; China, Nanjing, III on Castanea sp., 1 Dec 1954, B.N. Jiang & R.Y. Zheng, HMAS94222; China, Nanjing, III on Castanea sp., 1 Dec 1954, B.N. Jiang & R.Y. Zheng, HMAS94223; USA, California, 0, I on P. ponderosa, 14 May 1923, E. Bethel, HMAS8970
Distribution: China; USA
Sequence data: SSU: OM745917; ITS: OM746356; LSU: OM746524; CO3: OM721342 (holotype).
Notes: Cronartium castaneae is phylogenetically close to C. keteleeriae and C. fusiforme (Fig. 1D). Morphologically, it differs from C. keteleeriae in the size of aeciospores (25–33 × 14–22 µm vs 40–65 × 31–47 µm), the ornamentation of aeciospores, and the dimension of teliospores (33–56 × 14–22 µm vs 25–39 × 11–17 µm); from C. fusiforme in its aecia without peridia, and the dimension of aeciospores (25–33 × 14–22 µm vs 17–45 × 15–27 µm) . Cronartium orientale and C. quercuum had previously been reported on Castanea species, but C. castaneae is phylogenetically distinct from these two species. Cronartium castaneae differs from C. orientale in aecia without peridia, dimension of aeciospores (25–33 × 14–22 µm vs 18–25 × 13–22 µm) and length of telia; from C. quercuum in its aecia without peridia, morphologies of uredinia. The telial hosts of two species are different.
Fig. 1. Morphology of Cronartium castaneae. a-b. Hair-like, hypophyllous telia on Castaneae species; c. Columnar telia observed by SEM; d. Section of a telium observed by LM. Scale bars: c = 300 µm; d = 30 µm.