Phragmidium rosae-roxburghii J.E. Sun & Yong Wang bis, 2022

Sun, Jing-E, Zhang, Qian, Luo, Wen-Mei, Yang, Yuan-Qiao, An, Hua-Ming & Wang, Yong, 2022, Four new Phragmidium (Phragmidiaceae, Pucciniomycetes) species from Rosaceae plants in Guizhou Province of China, MycoKeys 93, pp. 193-213 : 193

Phragmidium rosae-roxburghii J.E. Sun & Yong Wang bis sp. nov.

Figs 2 , 3

Diagnosis.

Phragmidium rosae-roxburghii easily to be distinguished by its unique square to diamond-shaped urediniospores.

Holotype.

China. Guizhou Province, Panzhou city, 25°89'61"N, 104°56'07"W, 750 m, 21 Mar 2021, on Rosa roxburghii , coll. J.E. Sun & Y.Q. Yang, HGUP21025, ITS: OL684818, LSU: OL684831.

Etymology.

Referring to the host, Rosa roxburghii , on which the fungus was first found.

Description.

Spermogonia: unknown. Aecia formed on gold distinct, circular lesions on both sides of the stems, petioles and leaves, rarely produced on the abaxial leaf surface, scattered, flat oval to subglobose, powdery, 1.0-5.0 mm diam. Aeciospores formed in basipetal succession, oval o subglobose, 22-30 × 14-22 µm (mean 26 × 18 µm, n = 30), inclusions golden, to bright-yellow; wall 1.8-3.1 µm thick, colorless, mostly with irregularly elongated verrucae on the surface. Uredinia produced on the abaxial leaf surface, scattered to gregarious, hypophyllous, orange-colored or white, powdery, oval to rounded, 0.1-1.0 mm diam, paraphysis in the periphery of the uredinia, curved, 30-55 × 9-20 µm, colorless thin-walled. Urediniospores generally angular, square to diamond-shaped, yellowish to orange-colored, 20-30 × 16-21 µm (mean: 25 × 19 µm, n = 30), thick-walled, 0.5-2.0 µm thick, colorless, regularly echinulate with stout spines.

Rust diseases symptoms: In the early stage (March) of rust disease yellowish-orange powdery aecia formed on the stems and petioles on Rosa roxburghii and Rosa sp., the aecia were scattered, flat oval or nearly round and bordered (Fig. 2 ). In middle of June (Fig. 3 ), the upper surface of the lower leaves was turning yellow and orange spots gradually appeared on the under surface caused by uredinia, which are powdery, aggregated but without obvious boundaries.

Habitat.

Rosa roxburghii , Rosa sp.

Known distribution.

China, Guizhou Province.

Additional material examined.

China. Guizhou Province: Duyun city, 26°45'88"N, 106°98'42"W, 820 m, 22 Jun 2021, on Rosa roxburghii , coll. J.E. Sun, HGUP21026; Tongren city, 28°14'09"N, 108°34'03"W, 810 m, 04 Sep 2021, on Rosa roxburghii , coll. J.E. Sun, HGUP21027; Guiyang city, 26°44'74"N, 106°58'67"W, 960 m, 27 Mar, 2021, on Rosa sp., coll. J.E. Sun, HGUP21028 .

Notes.

Phragmidium rosae-roxburghii was the first species of Phragmidium described on Rosa roxburghii . It is easily to distinguish species by its unique square to diamond-shaped urediniospores, since in other Phragmidium species the urediniosporas are oval to nearly spherical ( Yun et al. 2011; Ono 2012; Zhuang et al. 2012; Yang et al. 2015; Liu et al. 2018, 2019, 2020; Ono and Wahyuno 2019). In phylogeny, this species only kept a close relationship to Ph. warburgiana (Fig. 1 ) but its urediniospores are yellowish to orange-colored different to Ph. warburgiana with colorless urediniospores ( Ono 2012). We proposed Ph. rosae-roxburghii as a new taxon.

Figures

Figure 1. The maximum parsimony tree of 42 Phragmidium taxa based on ITS and LS U genes; host plants are also given.

Figure 2. Phragmidium rosae-roxburghii sp. nov. (HGUP 21025, holotype) on Rosa roxburghii a-c aecia on stem and leaf pieces. d longitudinal section of aecium e-h aeciospores. Scale bars: 2 mm (b-c); 50 µm (d); 10 µm (e-h).

Figure 3. Phragmidium rosae-roxburghii sp. nov. (HGUP 21026) on Rosa roxburghii a appearance of infected plants b uredinia on a leaf c longitudinal section of uredinium d paraphyses e-i urediniospores. Scale bars: 5 mm (b); 50 µm (c); 25 µm (d); 12.5 µm (e-i).