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First Report of Leaf Spot on Paphiopedilum micranthum Caused by Neopestalotiopsis saprophytica in China

2020; American Phytopathological Society; Volume: 104; Issue: 10 Linguagem: Inglês

10.1094/pdis-02-20-0275-pdn

1943-7692

Qian Qin, Zhixiang Lu, Zuzheng Lu, Liqiong Ding, Zhaojin Chi, Bing Shan,

Fungal Plant Pathogen Control

HomePlant DiseaseVol. 104, No. 10First Report of Leaf Spot on Paphiopedilum micranthum Caused by Neopestalotiopsis saprophytica in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Leaf Spot on Paphiopedilum micranthum Caused by Neopestalotiopsis saprophytica in ChinaQian Qin, Zhixiang Lu, Zuzheng Lu, Liqiong Ding, Zhaojin Chi, and Bing ShanQian Qinhttp://orcid.org/0000-0001-9770-5004Guangxi Subtropical Crops Research Institute, Nanning, Guangxi, 530001, China, Zhixiang LuShanghai Jiao Tong University School of Agriculture and Biology, Shanghai, 200240, China, Zuzheng LuGuangxi Subtropical Crops Research Institute, Nanning, Guangxi, 530001, China, Liqiong DingGuangxi Subtropical Crops Research Institute, Nanning, Guangxi, 530001, China, Zhaojin ChiGuangxi Subtropical Crops Research Institute, Nanning, Guangxi, 530001, China, and Bing Shan†Corresponding author: B. Shan; E-mail Address: [email protected]Guangxi Subtropical Crops Research Institute, Nanning, Guangxi, 530001, ChinaAffiliationsAuthors and Affiliations Qian Qin1 Zhixiang Lu2 Zuzheng Lu1 Liqiong Ding1 Zhaojin Chi1 Bing Shan1 † 1Guangxi Subtropical Crops Research Institute, Nanning, Guangxi, 530001, China 2Shanghai Jiao Tong University School of Agriculture and Biology, Shanghai, 200240, China Published Online:30 Jul 2020https://doi.org/10.1094/PDIS-02-20-0275-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat As a high-value ornamental plant, Paphiopedilum micranthum is planted in many provinces in China. In December 2018, a leaf spot disease on P. micranthum was observed in the gardens of Leye County (N 24.78°, E 106.55°), in Guangxi province. At the onset of the infection, brown spots appeared on leaves. Subsequently, tissues around the spots gradually dried up, and the spots gradually expanded to form necrotic areas. In severe cases, these areas connected to form a large dry rot area on the surface of the leaves, which destroyed the ornamental value. This disease was seen year-round, with maximum incidence (∼30%) in July and August. It was also found in Nanning (N22.82°, E108.37°) and Yulin (N22.63°, E110.17°) and has been spreading in other parts of Guangxi province. To isolate the pathogen, leaf sections (5 × 5 mm) were prepared, surface sterilized with 75% ethanol for 30 s and 2% NaOCl for 1.5 min, and rinsed five times with sterilized water. They were placed on PDA with 300 μg/ml of ticarcillin sodium and clavulanate potassium and incubated at 28°C for 2 days. The hyphae grown from the sections were transferred to new PDA and incubated in the dark until conidia were produced. A single conidium was transferred to new medium for a pure culture. The isolated strains were cultured on PDA for 7 days at 28°C. The colony attained 80- to 90-mm diameter, with an undulate edge, was white colored with dense aerial mycelium on the surface, and the reverse was similar in color. After 10 to 15 days, brown gregarious conidiomata were produced on the surface of the mycelium. Conidiomata were globose, confluent, and erumpent, exuding globose conidial masses. Conidia (18 to 28 × 4 to 7 μm) (n = 10) were fusoid and straight to slightly curved, with four septa. The apical cell was hyaline and cylindrical to subcylindrical, with two to three filiform apical appendages arising from the apical crest. The three cells in the middle were brown, and the cell near the basal cell was lighter than the others. The basal cell was also hyaline, with a single appendage that was easy to abscise. These morphological characteristics resembled Neopestalotiopsis spp. (Maharachchikumbura et al. 2014). For further identification, the total genomic DNA was extracted with the CTAB method. For phylogenetic analyses, the internal transcribed spacer 1, 5.8S ribosomal RNA gene and internal transcribed spacer 2 partial region, partial β-tubulin gene, and partial translation elongation factor 1-alpha gene were amplified with primer pairs ITS5/ITS4, T1/Bt-2b, and EF1-728F/EF-2 (Maharachchikumbura et al. 2014). Finally, the pathogen was identified as Neopestalotiopsis saprophytica based on a phylogenetic tree by maximum parsimony analysis. Most isolated strains (70%) were this species. Other isolated strains were saprophytic fungi such as Alternaria. The pathogenicity of these strains was verified by Koch's postulates. A 30-ml conidial suspension (106 spores/ml) of strains was used to inoculate healthy P. micranthum plants, with sterile distilled water as a control. The conidial suspension was smeared on five healthy leaves of each plant. Five pots of P. micranthum were used in each inoculation and control treatment. The experiment was repeated three times. These treated plants were cultured at room temperature (26 to 34°C) for appearance of symptoms. After 2 gap days, brownish spots appeared on the leaf surfaces. All N. saprophytica treatments showed similar symptoms as observed in the field; the other strains and control treatment did not. A similar pathogen was reisolated from the necrotic areas. The reisolations were identified as N. saprophytica by morphological and phylogenetic analyses. According to other research, N. saprophytica could cause leaf spots on Calanthe sinica in China (Rang 2017) and Elaeis guineensis in Malaysia (Ismail et al. 2017). This is the first report of N. saprophytica causing leaf spot on P. micranthum in China. Furthermore, it is necessary to develop effective management strategies for controlling this disease.The author(s) declare no conflict of interest.References:Ismail, S. I., et al. 2017. Plant Dis. 101:1821. https://doi.org/10.1094/PDIS-02-17-0271-PDN Link, Google ScholarMaharachchikumbura, S. S. N., et al. 2014. Stud. Mycol. 79:121. https://doi.org/10.1016/j.simyco.2014.09.005 Crossref, ISI, Google ScholarRang, S. F. 2017. The identification and phylogenetic analyses for fungal pathogens of mainly Orchidaceae in southwest of China. Dissertation, Guizhou University. http://cdmd.cnki.com.cn/Article/CDMD-10657-1017877305.htm Google ScholarThe author(s) declare no conflict of interest.Funding: This work was supported by Basic Research Special Project of Guangxi Subtropical Crops Research Institute (GRY201704).DetailsFiguresLiterature CitedRelated Vol. 104, No. 10 October 2020SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionSymptoms of yellow leaf disease of Areca catechu caused by areca palm velarivirus 1 (H. X. Wang et al.). Photo credit: X. Huang. Fungal fruiting bodies of Phyllachora maydis on corn foliage resemble spots of tar (J. 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