Cytospora sibiraeae C.M. Tian, X.L. Fan & K.D.Hyde.
MycoBank MB811222, Facesoffungi number: FOF00490, Fig. 1
Etymology: sibiraeae (Lat.), referring to Sibiraea angustata, on which the fungus was collected.
Pathogen on twigs and branches of Sibiraea angustata. Sexual morph Stromata immersed in bark. Ascostromata erumpent through the surface of bark, circular to ovoid, extending to a large circular area, (0.98–)1.15–1.53(–1.71) mm (x=1.32 mm, n=20) diam., 4–10 locules arranged at one depth in the bark, conceptacles dark. Disc deep grey to black, nearly flat, circular to ovoid, (0.28–)0.32–0.38(–0.41) mm (x=0.35 mm, n=20) diam. Ostioles numerous, dark brown to black, at the same level as the disc, occasionally area below disc a lighter entostroma, (67.2–)71.3–107.1(–126.3)μm (x=88.2μm, n=20) diam. Locules dark brown, arranged circularly, flask-shaped to sphaerical, (0.22–)0.28–0.35(–0.39) mm (x=0.34 mm, n=20) diam. Asci (36.3–) 41.5–49.9 (–50.1)×(5.2–)6.4–7.8(–9.7)μm (x in 45.7×7.4μm, n=20), 8-spored, free, clavate to elongate-obovoid. Ascospores (7.8–)8.1–13.3 (–13.6)×(1.9–)2.1–2.5(–3.1)μm (x in 11.7×2.3μm, n=50), biseriate, elongateallantoid, thin-walled, hyaline, lacking guttules, aseptate. Asexual morph Undetermined.
Culture characters: Colony white, flat, felty, texture uniform, conidiomata sparse, irregularly distributed.
Material examined: CHINA, Gansu Province, Gannan, Lintan, 34°31′50.10″ N, 103°08′32.47″ E, 2750 m asl., on twigs and branches of Sibiraea angustata (Rehder) Hand.-Mazz. (Rosaceae), 8 August 2012, X.L. Fan (BJFC-S783, holotype); ex-type living culture, CFCC 50045. GenBank ITS: KP340987; LSU: KP340991; RPB2: KP340995; ibid., living culture, CFCC 50046. GenBank ITS: KP340988; LSU: KP340992; RPB2: KP340996.
Notes: Cytospora species with black conceptacles were previously placed in the genus Leucostoma. Adams et al. (2005) redefined Cytospora using ITS phylogeny and combined Leucostoma and other sexual morphs (Valsa, Valsella and Valseutypella) under Valsa, as subgenera or species with no additional infrageneric rank. Cytospora sibiraeae possesses obviously black conceptacles, which are similar to those of C. nivea and C. atrocirrhata. However the taxon clusters in an individual clade in ITS and multi-gene phylograms (Figs. 1 and 2). Few pathogenic fungi have been reported from Sibiraea angustata. This novel species represents the first record of a Cytospora isolated from Sibiraea angustata.
Fig. 1 Cytospora sibiraeae (holotype) a Habit of ascomata on a twig b Multi-ostioles on disc c Transverse sections through ascomata d Longitudinal sections through ascomata e ascus f ascospores. Scale bars: a–d=1 mm; e–f=10μm.
Fig. 2 Phylogram generated from Maximum likelihood (RAxML) analysis based on combined ITS, LSU, RPB2 and β-tubulin sequenced data of Xylariaceae. Maximum Likelihood bootstrap support values greater than 50 % are indicated above or below the nodes. The ex-types (ex-epitypes) are in bold. New sequences are in blue. The tree is rooted with Sordaria fimicola CBS 723.96.