Podosphaera rosae (Jacz.) D. - N. Jin & S. - Y. Liu comb. nov.

Fig. 8

≡ Sphaerotheca rosae (Jacz.) Z. - Y. Zhao, Acta Microbiol. Sin. 4: 439, 1981.

Basionym.

Sphaerotheca macularis f. rosae Jacz., Karmannyi opredelitel’ gribov II. Muchnistorosyanye griby: 76. 1927.

Type.

Lectotype (designated here, MBT 10029826), • original illustration in Jaczewski (1927: 77, fig. 19). Epitype (designated here, MBT 10030086): China • Shaanxi, Yulin, on Rosa davurica, 18 Oct. 2023, L. Liu & Z. - Y. Zhang (HMJAU -PM 92763). Ex-epitype sequences: PX 239405 (ITS), PX 239284 (28 S), PX 239896 (IGS).

Mycelium on stems and both sides of leaves, more abundant on the lower surfaces of the leaves, infected shoots often curled and distorted, forming irregular patches or effuse, persistent; primary hyphae hyaline, thin-walled, 3.0–4.5 μm wide, secondary hyphae hyaline, thick-walled, 3.5–6 μm wide, sparsely branched, often intertwined with each other on the lower surface of the leaves; hyphal appressoria indistinct to nipple-shaped, solitary or side by side; conidiophores arising from the upper surface of mother cells, erect, very long, 65–240 (– 342) × 7–10.5 μm, foot cells straight, cylindrical, long, 31–195 (– 302) × 7–10.5 μm, followed by 2–3 shorter cells, forming catenescent conidia; conidia doliiform to ellipsoid, 22–29 (– 31) × 11.5–15.5 (– 16.5) μm, length / width ratio 1.5–2.3; germ tubes almost terminal or terminal, short or long. Chasmothecia scattered, subglobose to globose, amphigenous, mostly on the lower surface of leaves, (74 –) 77–101 (– 106) μm diam.; peridium cells round to irregularly polygonal, 6.5–17.5 μm diam.; appendages mycelioid, some of them slightly spirally twisted at the base, arising from the equator of the chasmothecia, sometimes curved, wall thick and smooth, light brown below, paler towards the apex, numerous, various in length, (59 –) 80–405 (– 483) μm, 4–6 μm in width, septate; ascus ovoid to broad fusiform, colorless, thick-walled, sessile, 84–116 (– 121) × 56–79 μm, length / width ratio 1.3–1.6, terminal oculus obvious, large, 17–27 μm diam., 8 - spored; ascospores ellipsoid – ovoid, colorless, 20–26 × 10–15 μm, length / width ratio 1.5–2.2.

Additional specimens examined.

• A total of 33 specimens were examined, including 27 specimens with voucher numbers HMJAU -PM 92759 to HMJAU -PM 92785 and six specimens from Herbarium Mycologicum Academiae Sinicae, HMAS 01630, HMAS 14132, HMAS 39017, HMAS 39018, HMAS 39019, and HMAS 39020. Detailed specimen information is presented in Suppl. material 1.

Host range and distribution.

On Rosa (davurica, koreana, multiflora, rugosa, sp.), Rosaceae; Asia (China, Korea).

Notes.

This species was once proposed as Sphaerotheca rosae by Zhao (1981) and accepted by Zheng and Yu (1987), whereas most other authors considered this name a synonym of P. pannosa (Braun 1987, 1995; Shin 2000; Liu 2010; Braun and Cook 2012). After our detailed examinations, including the results of sequence analyses, Zhao’s (1981) taxonomic treatment can be confirmed, i. e., S. rosae can be confirmed as a species. P. rosae is different from P. pannosa in (1) forming chasmothecia mostly on the lower surfaces of the leaves; (2) having longer conidiophores and foot cells; (3) smaller chasmothecia and asci with larger terminal oculi; and (4) longer chasmothecial appendages. Sequences of S. rosae, including ex-type sequences (PX 239400 and PX 239279 from HMAS 39018; PX 239428 and PX 239307 from HMAS 39020), grouped together in a monophyletic, highly supported clade separate from the P. pannosa clade. As a result, S. rosae should be reinstated as the new combination Podosphaera rosae. P. pannosa reported by Lee et al. (2011) on Rosa rugosa in Korea is morphologically and phylogenetically consistent with P. rosae.