Erysiphe jiangxiensis F.G. Luan D. Li & H.Y. Zhang, 2025

Zhang, Haiyan, Xie, Feng, Shu, Qiwen, Luan, Zhiyuan, Li, Dong & Luan, Fenggang, 2025, Erysiphe jiangxiensis sp. nov. associated with powdery mildew on Castanopsis sclerophylla in Jiangxi, China, Phytotaxa 702 (1), pp. 102-108 : 105-107

Erysiphe jiangxiensis F.G. Luan D. Li & H.Y. Zhang sp. nov.

Fig. 1

MycoBank 855497.

Differs from Erysiphe kissiana by having smaller chasmothecia, fewer asci and ascospores, and occurring on Castanopsis sclerophylla .

Etymology:— jiangxiensis , a fungus found in Jiangxi Province, China.

Type:— CHINA. Jiangxi Province: Nanchang, Jiangxi Agricultural University , on Castanopsis sclerophylla (Lindl.) Schott. ( Fagaceae ), October 8, 2020, F.G. Luan, D. Li & C.H. Wei ( JXAU20201008 ); ex-type rDNA sequences, OL782609 (ITS) .

Colonies epiphyllous, initially circular with radial margins in the early stage, then merging. Chasmothecial appendages 7–22.5 µm long (mean 12.25 µm, n = 20), hyaline, radiating, stiff, straight to curved. Chasmothecia scattered, 45–67.5 µm (mean 55.5 µm, n = 26) in diameter, dark brown, mostly globose ( Fig. 1D,E ) with 2–4 asci. Asci ellipsoid to spherical, 45–65 × 32.5–50 µm with 4–7 ascospores per ascus. Ascospores subcylindrical, 17.5–27.5 × 10–13.5 µm (mean 22.1 × 11.8 μm, n = 33) ( Fig. 1F ). Conidia hyaline, cylindrical, rarely ovoid, solitary, occasionally 3 to 5 remaining in a short false chain, 5.0–12.5 × 3.75–7.5 μm, length/width ratio 1.0–2.5, averaging 1.4 ( Fig. 1G ).

Distribution:— on C. sclerophylla , China.

Phylogenetic analysis

The internal transcribed spacer (ITS) region sequence, measuring 639 bp, was obtained and deposited in GenBank under accession number OL782609 . BLASTn analysis revealed this sequence to be 99.19% similar to the ex-types of E. kissiana . The dataset of 28 taxa sequences after alignment provided 1559 characters where 518 were constant and 246 were parsimony-informative. The sequence of Bulbomicroidium bauhiniicola MUMH 6844 was used as the outgroup. In Figure 2 , bootstrap support values (≥50%) are shown on the respective branches for the maximum likelihood analysis, followed by posterior probabilities greater than 0.5 for the Bayesian analysis. The phylogenetic analysis showed that the ITS sequence of JXAU20201008, obtained from powdery mildew on C. sclerophylla in China, did not have a good clustering relationship with the E. kissiana clade, with relative low reliability (ML = 66%, BI = 0.53).

Field inoculation and pathogenicity assay

In the field inoculation studies, visual powdery mildew symptoms started to appear on all inoculated leaves after 5 days ( Fig. 1C ), progressing to cover almost all the leaves within a 10-day period after inoculation. Non-inoculated control plants remained symptomless. The same results were obtained in the repeated experiment. The ITS region of powdery mildew from mycelium after inoculation was successfully amplified with PCR and sequenced. This ITS sequence was identical to the sequence of JXAU20201008.

Figures

FIGURE 1. Erysiphe jiangxiensis. A, B. Epiphyllous, circular white colonies. C. Colonies on leaves 7 days after inoculation. D. Chasmothecia with appendages. E, F. Chasmothecia with multiple asci. G. Conidia.

FIGURE 2. Phylogenetic analysis based on ITS region for 27 sequences from the genus Erysiphe. Bootstrap values over 50% and significant Bayesian posterior probabilities (≥ 0.5) are indicated on the branches. Bulbomicroidium bauhiniicola was used as the outgroup. The scale bar represents 0.03 substitutions per site.