First Report of Stemphylium lycopersici and Stemphylium vesicarium causing Leaf Spot on Lettuce (Lactuca sativa) in China

HomePlant DiseaseVol. 103, No. 11First Report of Stemphylium lycopersici and Stemphylium vesicarium causing Leaf Spot on Lettuce (Lactuca sativa) in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Stemphylium lycopersici and Stemphylium vesicarium causing Leaf Spot on Lettuce (Lactuca sativa) in ChinaH. Liu, H. Wang, J. Zhong, X. Lu, X. T. Pan, H. J. Zhu, and Q. ZhouH. Liuhttp://orcid.org/0000-0001-6168-3579Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha 410128, China, H. WangHunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha 410128, China, J. ZhongHunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha 410128, China, X. LuAgricultural Science Institute of XiangXi Tujia and Miao Autonmous Prefecture, 416000, China, X. T. PanHunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha 410128, China, H. J. ZhuHunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha 410128, China, and Q. Zhou†Corresponding author: Q. Zhou; E-mail Address: zhouqian2617@hunau.edu.cnHunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha 410128, ChinaAffiliationsAuthors and Affiliations H. Liu1 H. Wang1 J. Zhong1 X. Lu2 X. T. Pan1 H. J. Zhu1 Q. Zhou1 † 1Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University, Changsha 410128, China 2Agricultural Science Institute of XiangXi Tujia and Miao Autonmous Prefecture, 416000, China Published Online:5 Sep 2019https://doi.org/10.1094/PDIS-05-19-1052-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Lettuce (Lactuca sativa L.) is a globally important leafy vegetable. Since 2015, a new leaf spot disease of lettuce has been observed in Changsha (28.12°N, 112.59°E), Hunan Province, China. More than 90% of plants in the field were affected. Initial symptoms were small, multiple, irregular to oval, yellow leaf spots, which enlarged to brown lesions later. As the disease progressed, lesions expanded and merged, resulting in withering of the whole leaves. Small sections (5 × 5 mm) excised from margins of spots were surface sanitized in 75% ethanol for 5 s and then transferred to a 0.1% mercuric chloride solution for 30 s. After rinsing three times with sterile distilled water, the sections were plated on potato dextrose agar (PDA) in Petri dishes. The putative fungal pathogen was transferred to V-8 juice agar (V8A) plates and incubated at 25°C for 25–30 days under black light blue (BLB) irradiation with a 12-h light-dark cycle to promote sporulation. All isolates were purified using a single spore isolation technique. Two kinds of colony morphology were observed and a representative strain from each kind (SlHN-10 and SvHN-02) was selected for further studies. Strain SlHN-10 cultured on PDA developed cottony raised colonies with entire margins, white to light brownish yellow in obverse and deep red in reverse, and a vivid red mycelial pigmentation that diffused into the culture medium. Strain SvHN-02 developed cottony and raised colonies but with undulated margins, light orange mycelial pigmentation and diffusion of light orange pigment into the culture medium. Conidia of the SlHN-10 were dark brown, solitary, oblong with a conical end at the apex, bluntly rounded at the base, each 48.8–75.2 μm long and 17.8–20.2 μm wide (n = 50), the L/W ratio of conidia was 2.7–3.1, and had 2–3 darkened constrictions, 3–5 transverse and 1–2 longitudinal septa. Conidia of the SvHN-02 were brown, oblong to oval, 25.2–35.2 long and 13.8–19.2 μm wide (n = 50), the L/W ratio of conidia was 1.5–2.5, 1–3 transverse constrictions, 2–4 transverse septa and 1–3 longitudinal septa. For molecular identification of the fungal species, the ITS (ITS4/ITS5) (White et al. 1990) and GPD (Franco et al. 2017) sequences were amplified and sequenced. The ITS sequence of SlHN-10 (MF357692) showed 99% identity with S. lycopersici strain CBS 122503 (GenBank MH863236) and the GPD sequence (MF356304) showed 100% identity with S. lycopersici strain CBS 124981 (KU850760). The ITS sequence of strain SvHN-02 (MF356304) showed 99% identity with several Stemphylium spp., while its GPD sequences (MK674611) revealed 100% identity with S. vesicarium strain CBS138138 (KU850735). Based on cultural, morphological, and molecular characteristics, strain SlHN-10 and SvHN-02 were identified as S. lycopersici and S. vesicarium. A pathogenicity test was conducted to confirm Koch’s postulates. Detached lettuce leaves were inoculated with freshly grown mycelial plugs and controls were inoculated with sterile PDA plugs, followed by incubation at 25°C with 90% RH. In addition, conidia were collected from 30-day-old V8A cultures grown at 25°C under BLB irradiation with a 12-h light-dark cycle, then suspended in sterilized distilled water at 105 conidia/ml. Detached leaves were inoculated by spraying with conidia; control leaves were sprayed with sterilized water. Treated leaves were placed on moist filter paper in sealed plastic boxes and incubated at 25°C with 90% RH and a 12-h light-dark cycle. After 5 days of inoculation, pathogenicity was assessed by the presence or absence of lesions. Experiments were conducted at least three times. Whether inoculated with spore suspension or mycelial plugs, symptoms developed by strain SlHN-02 and SvHN-02 were visible ∼4 and 5 days post inoculation, respectively. No symptoms were observed on control leaves. The two fungal isolates were reisolated from the symptomatic tissue on the inoculated leaves. Although S. lycopersici and S. vesicarium were widespread fungi causing leaf spot disease on plants, to our knowledge, this is the first report of natural infection by S. lycopersici and S. vesicarium on lettuce in China. The occurrence of this disease in China is a serious threat and prevention strategies should be developed to mitigate possible outbreaks in the vegetable garden.The author(s) declare no conflict of interest.References:Franco, M. E. E., et al. 2017. Eur. J. Plant Pathol. 149:983. https://doi.org/10.1007/s10658-017-1248-z Crossref, Google ScholarWhite, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA. Google ScholarH. Liu and H. Wang contributed equally to this work.The author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Vol. 103, No. 11 November 2019SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionAdvanced symptoms of bacterial blotch disease on mushroom caps (Osdaghi et al.). Photo credit: C. Bull. Powdery mildew caused by Golovinomyces neosalviae on Salvia fruticosa (Soylu et al.). Photo credit: S. Soylu. Metrics Article History Issue Date: 4 Nov 2019Published: 5 Sep 2019First Look: 4 Jul 2019Accepted: 2 Jul 2019 Page: 2957 Information© 2019 The American Phytopathological SocietyKeywordsleaf spot diseaselettuceStemphylium lycopersiciStemphylium vesicariumThe author(s) declare no conflict of interest.Cited byCharacterization and pathogenicity of Stemphylium symphyti causing leaf spot on pennyroyal ( Mentha pulegium L.)18 August 2022 | Archives of Phytopathology and Plant Protection, Vol. 55, No. 14Pathogenic Process-Associated Transcriptome Analysis of Stemphylium lycopersici from TomatoInternational Journal of Genomics, Vol. 2022Stemphylium lycopersici Nep1-like Protein (NLP) Is a Key Virulence Factor in Tomato Gray Leaf Spot Disease18 May 2022 | Journal of Fungi, Vol. 8, No. 5Stemphylium vesicarium (onion leaf blight)CABI Compendium, Vol. CABI CompendiumStemphylium lycopersici (grey leaf spot)CABI Compendium, Vol. CABI CompendiumFirst Report of Leaf and Stem Spot on Common Bean Caused by Stemphylium lycopersici in ChinaY. 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