Cytospora salicicola C. Norphanphoun, Bulgakov & K.D. Hyde, sp. nov
Index Fungorum number: IF 551803, Facesoffungi number: FoF 01768, Fig. 3
Etymology – Named after the host genus on which the fungus occurs.
Holotype – MFLU 14–0785

Pathogen causing dieback of twigs and branches of Salix alba L. Conidiomata 500 – 300 μm diam. (x̄ = 400 × 350 μm, n = 10), pycnidial, solitary, immersed in host tissue, unilocular, dark brown, ostiolate. Ostiole 150 – 40 μm diam. (x̄ = 145 × 40 μm, n = 10), at the same level as the disc surface. Peridium comprising a few to several layers of cell of texture angularis, with inner most layer thin, hyaline, outer layer brown to dark brown. Conidiophores reduced to conidiogenous cells. Conidiogenous cells blastic, enteroblastic phialidic, formed from the inner most layer of pycnidial wall, hyaline, smooth. Conidia (3.4–) 4.3 – 5.3 × 0.7 – 0.8 (–1) μm (x̄ = 4.3 × 0.8 μm, n = 30), unicellular, allantoid to subcylindrical, hyaline, smooth-walled. Sexual morph Undetermined.

Culture characteristics – Colonies on PDA, reaching 3.5 cm diam. after 10 days at 25 °C, producing dense mycelium, circular, rough margin white, after 5 days, flat or effuse on the surface, without aerial mycelium.

Material examined – RUSSIA, Rostov Region, Krasnosulinsky District, Donskoye forestry, riparian forest, on dead twigs and branches of Salix alba L. (Salicaceae), 21 May 2014, T.S. Bulgakov (MFLU 14–0785, holotype; PDD, isotype); ex-type-living cultures, MFLUCC 14–1052, ICMP.

Notes – Cytospora salicicola belongs in Valsaceae based on morphology and phylogeny. The new species has immersed, uniloculate conidiomata, with a single ostiole and shares common walls with the host tissue. Cytospora salicicola is most similar to C. schulzeri Sacc. & P. Syd. in conidia size [4.5– 8(6.3)×0.9–1.3(1.1) μm]. It however, differs in having a single locule, while C. schulzeri hasmultiple locules with 2-11 ostioles per disc (Mehrabi et al. 2011). Phylogenetic analyses, using ITS sequence data (Fig. 1) indicate that C. salicicola can be distinguished from other species within the genus Cytospora. The tree using ACT, ITS and LSU sequence data (Fig.1) demonstrate that C. salicicola separates from other sequenced species in Cytospora, and should be introduced as a new species.

Fig. 1 Maximum Parsimony (MP) majority rule consensus tree for the analyzed Cytospora isolates based on a combined dataset of ACT, ITS and LSU sequence data.MP bootstrap support values higher than 50 % and Bayesian posterior probabilities (PP) above 95 % (MP/PP). The tree is rooted with Diaporthe vaccinii (CBS 160.32). The strain numbers are mentioned after the species names. The species obtained in this study is in blue bold and extype strains in black bold.

Fig. 2 Phylogenetic tree based on an alignment of the sequences of the ITS sequence data for Cytospora, Leucostoma, and Valsa species, which was generated using the MP and Bayesian posterior probabilities (PP) in PAUP. Numbers separated by a slash represent MP bootstrap values >50 % and Bayesian posterior probabilities (PP) above 95 % are given at the nodes (MP/PP). The tree is rooted in outgroup taxon Diaporthe vaccinii (CBS 160.32). New strains are in blue bold and ex-type strains are in black bold.

Fig. 3 Cytospora salicicola (holotype) a Appearance of fruiting bodies in wood b Fruiting bodies on substrate c Surface of fruiting bodies d Cross section of the conidioma e Peridium f Ostiole of conidioma g Conidia h – g Colonies on PDA (P from below). Scale bars: a = 2 mm, b – c = 1 mm, d = 100 μm, e=10 μm, f=50 μm, and g = 20 μm.