First Report of Powdery Mildew Caused by Golovinomyces orontii on Viola delavayi in China

Abstract

HomePlant DiseaseVol. 103, No. 9First Report of Powdery Mildew Caused by Golovinomyces orontii on Viola delavayi in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Powdery Mildew Caused by Golovinomyces orontii on Viola delavayi in ChinaLuchao Bai, Yingtai Cao, Qiang Lin, Jinfeng Zhang, and Guoxin ChenLuchao Baihttp://orcid.org/0000-0003-0641-7184State Key Laboratory of Plateau Ecology and Agriculture, College of Agriculture and Animal Husbandry, Qinghai University, Xining, Qinghai 810016, China, Yingtai CaoThe Technology Bureau of Huzhu County, Haidong, Qinghai 810500, China, Qiang LinForestry and Grassland Bureau of Qinghai Province, Xining, Qinghai 810016, China, Jinfeng ZhangForestry Bureau of Xining, Xining, Qinghai 810016, China, and Guoxin Chen†Corresponding author: G. Chen; E-mail Address: [email protected]http://orcid.org/0000-0002-7063-678XState Key Laboratory of Plateau Ecology and Agriculture, College of Agriculture and Animal Husbandry, Qinghai University, Xining, Qinghai 810016, ChinaAffiliationsAuthors and Affiliations Luchao Bai1 Yingtai Cao2 Qiang Lin3 Jinfeng Zhang4 Guoxin Chen1 † 1State Key Laboratory of Plateau Ecology and Agriculture, College of Agriculture and Animal Husbandry, Qinghai University, Xining, Qinghai 810016, China 2The Technology Bureau of Huzhu County, Haidong, Qinghai 810500, China 3Forestry and Grassland Bureau of Qinghai Province, Xining, Qinghai 810016, China 4Forestry Bureau of Xining, Xining, Qinghai 810016, China Published Online:22 Jul 2019https://doi.org/10.1094/PDIS-02-19-0251-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Viola delavayi Franch. is a common ornamental plant in China. In August 2018, V. delavayi suffering from heavy powdery mildew infections was found with approximately 70% of the plants affected in Forest Park, Haidong (36.5°N, 102.4°E, altitude 2,200 m), China. Voucher specimens were deposited in the Herbarium of Plant Pathology at Qinghai University under accession number QHU2018056. This powdery mildew is morphologically characterized as follows. Mycelium amphigenous, effuse or in patches, evanescent or persistent, white; often covering the entire surface of leaves and stems; hyphae hyaline, thin-walled, colorless, about 3-6 μm wide; hyphal appressoria nipple-shaped, often poorly developed, conidiophores erect, arising laterally or from the upper surface of hyphal mother cells, and positioned almost centrally or toward one end of the cells, up to about 150 μm long, foot cells straight or often curved in the basal half, 24 to 79 × 8 to 12 μm, followed by one to three shorter cells about 10 to 25 × 11 to 14 μm, forming catenescent conidia in usually short chains, conidia ellipsoid ovoid to doliiform-subcylindrical, 25 to 37 × 12 to 23 μm, length/width ratio usually around 2; chasmothecia scattered, globose or subglobose, blackish brown, 76 to 110 μm diameter, peridium cells irregularly polygonal to daedaleoid, 6 to 20 μm diameter; appendages five to 17, in the lower half of the ascomata, occasionally reaching the upper half, mycelioid, generally unbranched, spirally twisted or sometimes geniculate-sinuous, interlaced with each other and with the mycelium, 0.6 to 2 times as long as the chasmothecial diameter, width irregular, 3 to 5 μm, septate, walls thin, smooth to rough, brown, paler toward the apex; four to eight asci, clavate-saccate, ellipsoid-obovoid, 45 to 64 × 23 to 33 μm, stalked, two- to three-spored; ascospores ellipsoid-ovoid, 15 to 25 × 12 to 15 μm, colorless or yellowish. This fungus was identified as Golovinomyces orontii based on the morphology of its asexual and sexual structures (Braun and Cook 2012). To confirm identification, the internal transcribed spacer (ITS) regions were amplified to confirm the species identification. The ITS5/P3 and PM5/ITS4 primers were used to amplify the ITS regions by nested PCR, and the cloned fragments were sequenced. The ITS regions result sequences of 614 bp were deposited in GenBank (accession no. MK402073) (Takamatsu and Kano 2001). A BLAST search analysis of the two sequences revealed 100% identity with G. orontii infecting Galium spurium var. echinospermon L. in Japan (AB430818). Based on the ITS rDNA phylogenetic tree, the sequences retrieved from the specimen clustered within a strongly supported clade (bootstrap value 96%) with G. orontii (AB430818). Cladistic trees were constructed using the neighbor-joining method with the Kimura two-parameter substitution model in MEGA 5.0. Branch robustness was assessed via bootstrap analysis with 1,000 replicates. Phylogenetic analysis data agree with morphological characters (Takamatsu et al. 1999, 2009). For Koch's postulates, inoculated and noninoculated plants were maintained separately in different rooms of a greenhouse at 22 to 25°C. Inoculated plants developed signs and symptoms after 15 days, whereas control plants remained symptomless. The morphology of the fungus on inoculated leaves was identical to that originally observed on diseased plants. To our knowledge, this is the first report of powdery mildew caused by G. orontii on V. delavayi worldwide. V. delavayi is one kind of ornamental plant, and the powdery mildew seriously affected the quality, reducing the ornamental and economic value.The author(s) declare no conflict of interest.References:Braun, U., and Cook, R. T. A. 2012. Taxonomic Manual of the Erysiphales (Powdery Mildews). CBS Biodiversity Series No. 11. CBS, Utrecht, the Netherlands. Google ScholarTakamatsu, S., et al. 1999. Mycoscience 40:259. https://doi.org/10.1007/BF02463963 Crossref, Google ScholarTakamatsu, S., et al. 2009. Mycol. Res. 113:117. https://doi.org/10.1016/j.mycres.2008.09.006 Crossref, Google ScholarTakamatsu, S., and Kano, Y. 2001. Mycoscience 42:135. https://doi.org/10.1007/BF02463987 Crossref, Google ScholarThe author(s) declare no conflict of interest.Funding: Funding was provided by National Natural Science Foundation of China (grant no. 31600513) and Natural Science Foundation of Qinghai Province (grant no. 2017-ZJ-958Q).DetailsFiguresLiterature CitedRelated Vol. 103, No. 9 September 2019SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionLeaf spot caused by Allophoma tropica on lettuce (Gullino et al.). Photo credit: M. L. Gullino. Red grapevine leaves showing symptoms of 'Candidatus Phytoplasma solani' (Jamshidi et al.). Photo credit: G. Romanazzi. Metrics Article History Issue Date: 30 Aug 2019Published: 22 Jul 2019First Look: 15 May 2019Accepted: 11 May 2019 Page: 2478 Information© 2019 The American Phytopathological SocietyFundingNational Natural Science Foundation of ChinaGrant/Award Number: 31600513Natural Science Foundation of Qinghai ProvinceGrant/Award Number: 2017-ZJ-958QKeywordsGolovinomyces orontiiViola delavayipowdery mildewChinaThe author(s) declare no conflict of interest.Cited byGolovinomyces orontii (powdery mildew)CABI Compendium, Vol. CABI Compendium

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