Phyllosticta rhododendri M. Y. Zhang, Z. X. Zhang & X. G. Zhang, 2025

Zhang, Meng-Yuan, Zhang, Zhao-Xue, Li, Du-Hua, Zhang, Xiu-Guo, Xia, Ji-Wen & Li, Zhuang, 2025, Morphological and phylogenetic analysis reveal three new species Phyllosticta (Phyllostictaceae, Botryosphaeriales) in China, MycoKeys 118, pp. 35-54 : 35-54

Phyllosticta rhododendri M. Y. Zhang, Z. X. Zhang & X. G. Zhang sp. nov.

Fig. 4

Etymology.

The specific epithet “ rhododendri ” refers to the host plant Rhododendron × pulchrum Sweet.

Type.

China • Yunnan Province, Hongta District, Yuxi City, Longma Mountain Scenic Area , on diseased leaves of Rhododendron × pulchrum , 13 May 2024, M. Y. Zhang (holotype HSAUP 8342 ), ex-type living culture CGMCC 3.28673 .

Description.

Leaf endogenic and associated with leaves of Rhododendron × pulchrum . Sexual morph: Not observed. Asexual morph: Conidiomata pycnidial, mostly aggregated in clusters, black, erumpent. In PDA culture, exuding white conidial masses within 10 days or longer. Pycnidial wall multi-layered, textura angularis, brown to dark brown. Conidiophores indistinct, often reduced to conidiogenous cells. Conidiogenous cells 7–16 × 1.4–5.2 μm, subcylindrical, ampulliform, hyaline, smooth. Conidia 8.5–11.5 × 6.8–9.4 µm (L / W 1.33 –1.53), ovoid, ampulliform, ellipsoidal to subglobose, hyaline, aseptate, thin and smooth walled, multi-guttulate, or with a single large central guttule, surrounded by a mucilaginous sheath. Sheath 0.8–1.5 μm thick, thicker on both sides, and bearing a hyaline, apical mucoid appendage. Appendages 3–7.5 × 1–1.2 μm, flexible, unbranched, tapering towards an acutely rounded tip. Spermatia 6.3–8.2 × 1–1.5 μm, occurring in conidioma with conidia, hyaline, smooth, guttulate to granular, bacilliform.

Culture characteristics.

Colonies on PDA 19–22 mm in diameter after 14 days at 25 ° C in darkness, with a growth rate of 1.4–1.6 mm / day, greenish black with white edge on obverse and reverse.

Additional specimens examined.

China • Yunnan Province, Hongta District, Yuxi City, Longma Mountain Scenic Area , on diseased leaves of Rhododendron × pulchrum , 13 May 2024, Z. X. Zhang ( HSAUP 8346 ), living culture SAUCC 8346–1 .

Notes.

Phylogenetic analysis showed that Phyllosticta rhododendri formed an independent clade that is sister to a large clade comprising over ten species ( P. anhuiensis , P. aucubae-japonicae , P. citribraziliensis , P. citrichinaensis , P. concentrica , P. cussonia , P. elongata , P. elliptica , P. ericarum , P. fujianensis , P. gardeniicola , P. gwangjuensis , P. hypoglossi , P. iridigena , P. kerriae , P. ophiopogonis , and P. spinarum ) (Fig. 1 ). In morphology, Phyllosticta rhododendri was found to produce spermatia, a structure that is rarely observed within this genus. Therefore, we establish this fungus as Phyllosticta elliptica sp. nov.

Figures

Figure 1. Phylogram of the Phyllosticta, inferred from a concatenated alignment of ITS, LSU, tef 1, ACT, and GPDH sequences. Botryosphaeria obtusa (CMW 8232) and B. stevensii (CBS 112553) were used as outgroup taxa. BI posterior probabilities and ML bootstrap support values above 0.90 and 70 % are shown at the first and second positions, respectively. Ex-type cultures are highlighted in bold, while strains obtained in this study are marked in red. Some branches have been shortened for layout optimization, indicated by double diagonal lines with the corresponding reduction factor. The scale bar at the bottom left represents the number of substitutions per site.

Figure 4. Phyllosticta rhododendri (CGMCC 3.28673) a diseased leaf of Rhododendron × pulchrum b, c colonies (left-above, right-reverse) after 14 days on PDA d conidiomata e, f conidiogenous cells with conidia g, h conidia i spermatia. Scale bars: 10 μm (e – i).