Phaeobotryon negundinis Daranagama, Bulgakov and K.D. Hyde, Mycosphere 7, 936 (2016)

Index Fungorum number: IF 551954; Facesoffungi number: FoF 15189; Fig. 34

Saprobic on dead twigs of Morus alba. Sexual morph: Undetermined. Asexual morph: Conidiomata 210–330 μm high × 220–315 μm diam. (x̄ = 268 × 253 μm, n = 6), solitary, scattered, immersed, becoming erumpent through the host tissue, uniloculate, black, globose to subglobose, ostiolate. Conidiomatal wall 28–45 μm (x̄ = 37 μm, n = 10), comprising several layers of lightly pigmented to dark brown cells of textura angularis, becoming hyaline towards the conidiogenous region. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 12–25 × 3–5 μm (x̄ = 17 × 3.2 μm, n = 10), holoblastic, lining the conidiomatal cavity, hyaline, subcylindrical. Conidia 12.5–20.7 × 4.6–10.5 μm (x̄ = 16 × 7.7 μm, n = 28), ovoid with a broadly rounded apex and truncated base, smooth to finely verruculose, initially aseptate and hyaline, becoming 1-septate and dark brown at maturity.

Cultural characteristics – Conidia germinating on PDA within 18 h. Colonies entire-edged, fast-growing, reaching 9 cm on the PDA at 25 °C after seven days, circular, flat, dense, initially white mycelia, becoming gray in older cultures.

Material examined – Russia, Rostov region, Shakhty City, Alexandrovsky park, on dying and dead twigs and branches of Morus alba, 26 November 2017, T.S. Bulgakov, MOR-23 (MFLU 23-0360), living culture MFLUCC 23-0201.

GenBank accession numbers – ITS: OR186220, tef1-α: OR195687.

Known distribution (based on molecular data) – Canada (Ilyukhin & Ellouze 2023), Russia (Daranagama et al. 2016, this study), the USA (DeKrey et al. 2022).

Known hosts (based on molecular data) – Acer negundo, Forsythia × intermedia, Ligustrum vulgare (Daranagama et al. 2016), Malus domestica (Ilyukhin & Ellouze 2023), Morus alba (this study), Vitis vinifera (DeKrey et al. 2022).

Notes – Phaeobotryon negundinis is usually known worldwide as a grapevine trunk disease pathogen (DeKrey et al. 2022). However, in the current study, we isolated this pathogen from dead twigs and branches. The isolate of the current study shows morphological similarities to the ex-type of Phaeobotryon negundinis (Daranagama et al. 2016) and clustered to the latter with 70% maximum likelihood bootstrap support and 0.90 Baysian posterior probability (Fig. 33). This study reports the P. negundinis from Morus alba from Russia.

Fig. 1 – Phaeobotryon negundinis (MFLUCC 23-0201, a new host record). a Appearance of conidiomata on the host surface. b Surface (left) and reverse (right) views of the colony on PDA. c–d Conidia developing on conidiogenous cells. e–f Immature conidia. g–i Conidia at different stages of maturity. Scale bars: a = 2 mm, c = 20 μm, d–i = 10 μm.

Fig. 2 – Phylogram generated from the maximum likelihood analysis based on the combined ITS and tef1-α sequence data of the genus Phaeobotryon. Twenty-nine strains are included in the combined analyses. Tree topology of the maximum likelihood analysis is similar to the Bayesian analysis. The best RAxML tree with a final likelihood value of -2120.952524 is presented. Evolutionary model GTR+I+G is applied for all the genes. The matrix had 159 distinct alignment patterns, with 7.70% of undetermined characters or gaps. Bootstrap support values for ML equal to or greater than 70% and Bayesian posterior probabilities equal to or greater than 0.95 are given near nodes, respectively. The tree was rooted with Sphaeropsis visci (CBS 100163). Ex-type strains are in bold. The newly generated sequences are indicated in yellow.