Phyllosticta cangshanensis Z.Y. Huang, H.W. Shen & Z.L. Luo, 2024

Huang, Zi-Yang, Shen, Hong-Wei, Su, Xi-Jun & Luo, Zong-Long, 2024, Phyllosticta cangshanensis sp. nov., an endophytic fungus from Rhododendron decorum in Cangshan Mountain, Yunnan Province, China, Phytotaxa 678 (3), pp. 146-166 : 150-153

Phyllosticta cangshanensis Z.Y. Huang, H.W. Shen & Z.L. Luo , sp. nov. ( Fig. 2 )

Fungal Names number: FN 572055.

Holotype:— KUN-HKAS 136942

Etymology:— “cangshanensis ” refers to the Cangshan Mountain, where the holotype was collected.

Endophytic in healthy Rhododendron decorum leaves. Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata on PDA, pycnidial, gregarious, globose to pyriform, black, erumpent, exuding grey to black conidial masses. Pycnidial walls 56–77 μm wide (x = 66.5 μm, n = 25), comprising several layers of textura angularis cells, outer layers dark brown to black, inner layers pale brown to hyaline. Ostiole single, central, 5–8 μm wide (x = 6.5 μm, n = 30). Conidiophores cylindrical to ampulliform, often reduced to conidiogenous cells. Conidiogenous cells 15–17 × 4–12 μm (x = 16 × 8 μm, n = 30), terminal, arising from the inner layer of the pycnidial wall, subcylindrical or ampulliform, hyaline. Conidia 10–12 × 6–8 µm (x = 11 × 7 μm, n = 30), solitary, ellipsoidal to obovoid, hyaline, aseptate, guttulate, with a large central guttule when immature, smooth walled, truncate at the base, consisting of an apical appendage. Appendages 7.4–8.2 × 1.3–1.5 μm (x = 7.8 × 1.4 μm, n = 30), flexuous, unbranched, straight or curved, tapering towards a rounded tip.

Culture characteristics:— Colonies growing on PDA were incubated in darkness at 25 ℃ for 14 days, during which they grew about 30–50 mm, with a growth rate of 2.1–3.6 mm /day. The surface and reverse of colonies are grayish to black, with an irregular edge. Gray to black conidiomata are formed after 14 days on PDA.

Material examined:— China, Yunnan Province, Dali City, Cangshan Mountain , 25°50′44″ N, 100°4′22″ E (2753 m), isolated from healthy leaves of R. decorum , March 2024, X. J. Su, B-44 ( KUN-HKAS 136942 , holotype), extype living culture, CGMCC 3.27856 = KUNCC 24-18304 ; Cangshan Mountain , 25°50′44″ N, 100°4′22″ E (2753 m), isolated from healthy leaves of R. decorum , March 2024, X. J. Su, B-48 ( KUN-HKAS 136943 ), living culture, CGMCC 3.27857 = KUNCC 24-18306 .

Notes:— Our two strains, CGMCC 3.27856 and CGMCC 3.27857, grouped and formed a sister clade to P. rhodorae ( CBS 901.69), and are located within the P. rhodorae species complex with strong support (100% ML /1.00 PP, Fig. 1 ). There are 88 nucleotides base differences between CGMCC 3.27856 and P. rhodorae (28/516 bp in ITS, 3/763 bp in LSU, 21/215 bp in tef 1-α, 13/202 bp in act, and 23/623 bp in gpdh). From a morphological perspective, CGMCC 3.27856 differs from P. rhodorae by its smaller conidia (10–12 × 6–8 μm vs. 11.5–17.5 ×7.5–9.5 μm). In addition, our species has apical appendages, but this feature was not observed in P. rhodorae ( Davis 1946) . Notably, our species and P. rhodorae were isolated from the leaves of Rhododendron species. Based on phylogenetic analyses and morphological characteristics, we establish a new species, P. cangshanensis .

Figures

FIGURE 1. Maximum likelihood tree based on the analysis of combined ITS, LSU, tef1-α, act, and gpdh dataset. Bootstrap support values (ML) equal to or greater than 75% and BI posterior probabilities (PP) equal to or higher than 0.95 are given near the nodes as ML/PP. A hyphen represents bootstrap values below 75% for ML and below 0.95 for PP.The tree is rooted with Botryosphaeria obtusa (CMW 8232) and B. stevensii (CBS 112553). Ex-type strains are in bold. Strains from the present study are marked in red.

FIGURE 2. Phyllosticta cangshanensis (KUN-HKAS 136942, holotype) a. Leaves of Rhododendron decorum. b, c. Colonies on PDA (front and reverse view). d. Conidiomata on PDA. e. Section through a conidioma. f–h. Conidiogenous cells and developing conidia. i–m. Conidia. Scale bars: e = 50 μm, f, h = 10 μm, g = 20 μm, i–m = 5 μm.