Cytospora leucostoma (Pers.) Sacc., Michelia 2: 264 (1881) Figs 4, 5

Sphaeria leucostoma Pers., Ann. Bot. 11: 23 (1794)

Valsa leucostoma (Pers.) Fr., Summa Veg. Scand., Section Post. (Stockholm): 411 (1849)

Valsa persoonii Nitschke, Pyrenomyc. Germ. 2: 222 (1870)

Leucostoma persoonii (Nitschke) Höhn ., Mitt. Bot. Inst. Tech. Hochsch. Wien 5: 78 (1928)[Additional synonyms in Species Fungorum.]

Description.

Necrotrophic on branches of Betulaceae, Juglandaceae and Rosaceae . Sexual morph: Ascostromata immersed in the bark, erumpent through the surface of bark, scattered, 950-2550 µm in diam., with 8-10 perithecia arranged circularly to irregularly. Conceptacle absent. Ectostromatic disc pale grey, fusoid, 600-2150 µm in diam., with 8-10 ostioles arranged irregularly per disc. Ostioles numerous, dark grey to black, at the same or above the level as the disc, concentrated, arranged irregularly in a disc, 60-120 µm in diam. Perithecia beige with a little black when mature, flask-shaped to spherical, arranged circularly to irregularly, 270-560 µm in diam. Paraphyses large, broad and cylindrical with 1-4 septa, 39-78 × 5.8-8.7 (av. = 50.6 ± 13.7 × 7 ± 0.8, n = 10) μm . Asci free, clavate to elongate obovoid, 35-45 × 6-8 (av. = 40.4 ± 3.3 × 6.9 ± 0.5, n = 10) μm, 8-spored. Ascospores uniseriate to biseriate, elongate-allantoid, thin-walled, hyaline, aseptate, 7-10 × 2-3 (av. = 8.3 ± 0.9 × 2.6 ± 0.2, n = 30) μm . Asexual morph: Conidiomata pycnidial, immersed in the bark, scattered, erumpent through the surface of bark, with multiple locules and a conspicuous central column. Central column beneath the disc more or less conical, brown. Conceptacle absent. Ectostromatic disc buff, discoid, circular to ovoid, 190-310 µm in diam., with 1-2 ostioles per disc. Ostioles grey to black, at the same or above the level as the disc surface, 60-65 μm in diam. Locules numerous, subdivided frequently by invaginations with common walls, circular to ovoid, 700-1000 µm in diam. Conidiophores hyaline, branched at the base or unbranched, approximately cylindrical, 8-14 × 1-2 (av. = 11.5 ± 1.8 × 1.4 ± 0.2, n = 10) µm, sometimes reduced to conidiogenous cells. Conidiogenous cells enteroblastic phialidic, sub-cylindrical to cylindrical, 7-11 × 1-2 (av. = 9 ± 1.4 × 1.5 ± 0.3, n = 10) μm . Conidia hyaline, elongate-allantoid, smooth, aseptate, 4.5-6 × 1-2 (av. = 5.4 ± 0.3 × 1.5 ± 0.2, n = 30) μm .

Culture characteristics.

Cultures initially are white, growing fast up to 8 cm in diam. after 3 days and entirely covering the 9 cm Petri dish after 4 days, becoming greenish-olivaceous after 7-10 days and grey olivaceous after 30 days. In reverse, the cultures are the same as the upper colour after 7 days, becoming olivaceous grey to iron grey after 30 days. Colonies are flat with a uniform texture; sterile.

Habitat and distribution.

Known from several species of Betulaceae, Juglandaceae and Rosaceae around the world.

Materials examined.

China, Beijing City, Mentougou District, Mount Dongling, Xiaolongmen Forestry Centre (115°26'47.36"E, 39°56'06.45"N), from branches of Prunus sibirica, 17 Aug 2017, H.Y. Zhu & X.L. Fan, CF 2019814, living culture CFCC 53140; ibid. CF 2019815, living culture CFCC 53141. China, Beijing City, Mentougou District, Mount Dongling, Xiaolongmen Forestry Centre (115°29'20.52"E, 39°57'47.49"N), from branches of Juglans mandshurica, 17 Aug 2017, H.Y. Zhu & X.L. Fan, CF 2019809, living culture CFCC 53156.

Notes.

Cytospora leucostoma is commonly associated with canker disease of Prunoideae of Rosaceae in China (Fan et al. 2020). Morphologically, our taxa are similar to previous descriptions of C. leucostoma in having multi-loculate pycnidial stromata with a conspicuous black conceptacle, producing elongate-allantoid, large conidia (4.5-6 × 1-2 μm) (Teng 1963, Zhuang 2005, Fan et al. 2020). The greenish-yellow of the cultures on PDA medium from Juglans mandshurica is similar to descriptions of those collected from Prunoideae (Fan et al. 2020). Multigene phylogenetic analyses supported the morphological results with high support values (ML/MP/BI = 100/100/1, Fig. 2). By combining morphology and the DNA data, our isolates collected from dead branches of Prunus sibirica and Juglans mandshurica belong to this species. The current study represents a new host record of Juglans mandshurica .