Phaeobotryon fraxini Y. Y. Wu & C. M. Tian, 2024

Wu, Yingying, Peng, Cheng, Yuan, Rong, Zhang, Mingwei, Hu, Yang & Tian, Chengming, 2024, New species and records of Botryosphaeriales (Dothideomycetes) associated with tree dieback in Beijing, China, MycoKeys 106, pp. 225-250 : 225-250

Phaeobotryon fraxini Y. Y. Wu & C. M. Tian sp. nov.

Fig. 6

Etymology.

Named after the host, Fraxinus chinensis .

Holotype.

China, Beijing City, Tongzhou District, Central Green Forest Park , 39 ° 52 ' 16 " N, 116 ° 42 ' 04 " E, on the dead branches of Fraxinus chinensis , 19 April 2023, C. M. Tian, C. Peng, R. Yuan, M. W. Zhang & Y. Y. Wu (holotype BJFC - S 1953 , ex-type cultures CFCC 70762 ).

Description.

Sexual morph: Not observed. Asexual morph: Conidiomata pycnidial, scattered, occasionally aggregated, superficial or immersed, globose, dark brown to black, unilocular, 200–360 μm diam. Disc inconspicuous. Ostioles single, brown or black, circular, central, papillate, 40–85 μm diam. Locules single, globose, 100–170 μm, Conidiophores reduced to conidiogenous cells. Conidiogenous cells hyaline, smooth, thin-walled, holoblastic, cylindrical, formed from the cells lining the inner walls of the locules, 7.0–14.0 × 1.0–5.0 μm (av. ± S. D. = 10.6 ± 2.0 × 3.1 ± 0.8 µm). Conidia initially hyaline, smooth, thin-walled, then gradually producing light yellow pigment, becoming yellow or light brown, occasionally with bubbles, mature with 1 - septate, brownish yellow to dark brown, oblong, obtuse, rounded at both ends, 13.0–20.0 × 7.0–10.0 μm (av. ± S. D. = 17.6 ± 1.3 × 8.7 ± 0.7 µm).

Culture characters.

Colonies on PDA with aerial gray-white mycelium, thick and dark black at the edge, thin and paler in color in the center, fluffly, entire margin, reverse with black pigment accumulation, reaching 60 mm diam in 7 days at 25 ° C.

Other material examined.

China, Beijing City, Tongzhou District, Central Green Forest Park , 39 ° 52 ' 16 " N, 116 ° 42 ' 04 " E, on the dead branches of Fraxinus chinensis , 19 April 2023, C. M. Tian, C. Peng, R. Yuan, M. W. Zhang & Y. Y. Wu, BJFC - S 2368 , living culture CFCC 70763 .

Notes.

Based on multi-locus phylogenetic analysis, the two isolates cluster separately in a high-supported clade with 100 % MP, 100 % ML, and 1.00 BYPP value (Fig. 4 ). In the phylogenetic analysis, Phaeobotryon fraxini showed a close relationship to P. mali and P. rhois . These three species could be distinguished based on ITS, tef 1 - α, and LSU loci from P. mali by nineteen bp (6 / 465 in ITS; 10 / 184 in tef 1 - α; 3 / 559 in LSU) and P. rhois by twenty-two bp (7 / 465 in ITS; 12 / 184 in tef 1 - α; 3 / 559 in LSU). Moreover, P. fraxini differs from P. mali and P. rhois in having smaller conidia (13.0–20.0 × 7.0–10.0 µm vs. 22.0–31.5 × 12–16.5 µm for P. mali and 20–25 × 10–12 µm for P. rhois ) ( Fan et al. 2015 b; Jia et al. 2023) (Table 3 ). Therefore, P. fraxini is introduced as a novel species.

Figures

Figure 4. Phylogram generated from RAxML analysis based on ITS, LSU, and tef 1 - α sequence data of Phaeobotryon isolates. The tree was rooted in Alanphillipsia aloeicola (CBS 138896). The MP, ML (≥ 50 %), and BI (≥ 0.9) bootstrap supports are given near the nodes, respectively. Isolates from this study are marked in blue, and ex-type strains are marked in bold.

Figure 6. Phaeobotryon fraxini (BJFC - S 1953) A habit of conidiomata on branch B transverse section of conidioma C longitudinal section through conidioma D, E conidiogenous cells and conidia F top (left) and bottom (right) sides of colonies on potato dextrose agar (PDA) G - L conidia. Scale bars: 500 μm (A); 200 μm (B, C); 10 μm (D, E, G – L).