Coniochaeta caraganae D. Pem, Bulgakov & K.D. Hyde, sp. nov.
Index Fungorum number: IF559528; MycoBank number: MB 559528; Facesoffungi number: FoF 08686; Fig. 1
Etymology – ″caraganae″ refers to the host plant from which the fungus was isolated.
Holotype – MFLU 17-2500
Saprobic on dead branch of Caragana frutex. Sexual morph: Not observed. Asexual morph: Coelomycetous. Conidiomata 106–114 μm diam., 4–7 μm high (x̄= 110.7 × 6.2 μm, n = 20), small, pycnidial, solitary, scattered, immersed, uniloculate, globose to subglobose, thin-walled. Peridium 26–32 μm composed of two layers. Inner layer consisting cells of textura prismatica, hyaline to subhyaline, strongly compressed. Outer layer consisting of densely packed, moderately thick-walled, brown cells of textura angularis, tending to be darker and more isodiametric towards the outside. Conidiophores 7–10×2–3 μm (x̄=6.5 × 2.3 μm, n=20), hyaline, straight or irregularly bent, reduced to conidiogeneous cells. Conidiogenous cells 2–3×4–6 μm (x̄=3.1×5.1 μm, n=20), holoblastic, annellidic, simple, determinate, hyaline, doliiform to cylindrical, smooth-walled. Conidia 3–4 × 5–6 μm (x̄=4.1 × 5.8 μm, n= 20) oblong to ovoid, straight, rounded at both ends, sometimes truncate at base, cylindrical, aseptate, smooth and thick-walled, eguttulate.
Culture characteristics – colonies on MEA, reaching 25–35 mm diam. after 4 weeks at 25 °C, grey whitish, dense, effuse, with white hyphal stands towards the edge, rough surface towards centre, diffuse margin; reverse dark grey with whitish edges, grayish orange at the center, radiating, effuse and zonate.
Material examined – Russia, Donetsk People’s Republic, Shakhtersk district, regional landscape park «Donetsk ridge» (Rus. «Donetsky kryazh»), steppe near Leontievsky forest, on dead twigs of Caragana frutex (L.) K. Koch (Fabaceae), 19 May 2017, Timur S. Bulgakov (MFLU 17-2500, holotype); ex-type living culture MFLUCC 18-0780.
GenBank numbers – MT573224 (ITS), MT573223 (LSU).
Notes – Based on phylogenetic analyses, the new asexual species Coniochaeta caraganae is closely related with C. coluteae (Samarakoon et al. 2018; Fig. 2). The asexual morph of C. coluteae is hyphomycetous and has been obtained from culture. It is characterized by hyaline vegetative hyphae, hyphoide conidiophores, phialidic conidiogenous cells and one celled hyaline conidia. Our new species C. caraganae has been obtained from dead branch of Caragana frutex and is characterized by pycnidial conidiomata, hyaline conidiophores and oblong to ovoid conidia. In a comparison of the 565 ITS (+5.8S) nucleotides of these two strains C. coluteae MFLUCC 17-2299 to that of C. caraganae reveals 11 (1.9%) nucleotide differences which justifies these two isolates as two distinct taxa (Jeewon and Hyde 2016). Therefore, C. caraganae is introduced herein as a new species.
Figure 1 – Coniochaeta caraganae (MFLU 17–2500, holotype). a, b. Appearance of conidiomata on host surface. c. Vertical section through the conidioma. d. Peridium. e, f. Conidiogenesis. g–k. Conidia. Scale bars: a, b=500 µm, c, d=30 µm, e–k=10 µm
Figure 2 – Phylogenetic tree generated from Maximum likelihood analysis (RAxML) based on combined ITS and LSU sequence data of Coniochaetaceae in the order Coniochaetales. Maximum likelihood bootstrap support values≥70% (in blue) and Bayesian posterior probabilities≥0.95 (in green) are indicated on the branches. The new isolate is in blue. The tree is rooted with Chaetosphaeria jonesii (MFLUCC 15–1015) and Chaetosphaeria garethjonesii (MFLUCC 15–1012)