First Report of Alfalfa Leaf Spot Caused by Leptosphaerulina australis in China

HomePlant DiseaseVol. 105, No. 8First Report of Alfalfa Leaf Spot Caused by Leptosphaerulina australis in China PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Alfalfa Leaf Spot Caused by Leptosphaerulina australis in ChinaLi Li Zhang and Yan Zhong LiLi Li Zhanghttps://orcid.org/0000-0001-8659-8290Engineering Research Center of Grassland Industry, Ministry of Education, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Ministry of Agriculture and Rural Affairs, Gansu Tech Innovation Center of Western China Grassland Industry, National Demonstration Center for Experimental Grassland Science Education, State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Gansu Lanzhou 730020, ChinaSearch for more papers by this author and Yan Zhong Li†Corresponding author: Y. Z. Li; E-mail Address: liyzh@lzu.edu.cnEngineering Research Center of Grassland Industry, Ministry of Education, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Ministry of Agriculture and Rural Affairs, Gansu Tech Innovation Center of Western China Grassland Industry, National Demonstration Center for Experimental Grassland Science Education, State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Gansu Lanzhou 730020, ChinaSearch for more papers by this author AffiliationsAuthors and Affiliations Li Li Zhang Yan Zhong Li † Engineering Research Center of Grassland Industry, Ministry of Education, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Ministry of Agriculture and Rural Affairs, Gansu Tech Innovation Center of Western China Grassland Industry, National Demonstration Center for Experimental Grassland Science Education, State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Gansu Lanzhou 730020, China Published Online:22 Sep 2021https://doi.org/10.1094/PDIS-10-20-2136-PDNAboutSectionsView articlePDFPDF PlusSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleA disease was observed on alfalfa cultivar WL168 characterized by white to brown leaf spots of regular to round shapes, in Aluhorqin County, Inner Mongolia, China (120°13′23″ to 120°29′14″ E, 43°27′52″to 43°35′16″ N; 281.71 to 360.13 m altitude) during 2019 to 2020. The disease mainly presented in spring 1 month after regreening, and the incidence was 78.30% in this field. Twenty alfalfa plants with severe symptoms were used for pathogen isolation. The infected tissue was cut into 2 × 2-mm pieces, surface sterilized (in 75% ethanol and 5% commercial bleach [NaClO] for 30 s and 2 min, respectively), rinsed five times with sterilized distilled water, and dried between sterile filter paper (Wang et al. 2019). The diseased tissues from each plant sample were cultured on potato dextrose agar (PDA) and incubated at 25°C with 12 h of light per day for 10 days. A fungus was isolated from the diseased leaves at 100% frequency. Fungal growth on PDA was round with a black surface, radial edge, and a dirty white center. The ascocarps were moved to a clean microscope slide to release asci and ascospores. Ascocarps were spheroidal, subglobose brown, 120 to 160 µm × 160 to 180 µm, which contained several asci. The size of asci was 31.0 to 41.6 × 75.0 to 87.5 μm, and each ascus had eight ascospores. Ascospores were ellipsoid to oblong with a gelatinous sheath, brown, 8.8 to 15.0 × 29.9 to 43.0 µm, with two to three horizontal septa and zero to two vertical septa. A phylogenetic tree was constructed after DNA extraction and PCR with primers to amplify the ITS (VG9, 5′-TTACGTCCCTGCCCTTTGTA-3′; and ITS4, 5′-TCCTCCGCTTATTGATATGC-3′) and LSU (LR7, 5′-TACTACCACCAAGATCT-3′; and LROR, 5′-GTACCCGCTGAACTTAAGC-3′) regions. The LSU (SUB8273071) and ITS (SUB8218291) amplicons showed 99% similarity with Leptosphaerulina australis (EU754166.1) in GenBank. To verify the pathogenicity, fungal plugs were inverted on three compound leaves of 20 alfalfa WL168 for 2 days. Agar plugs (PDA) were inverted on three compound leaves of another 20 alfalfa WL168, which were a control. All plants were maintained at 22°C and 44% relative humidity in a growth chamber. Similar disease symptoms were observed on infected leaves 10 days after inoculation, whereas control plants showed no symptoms. The same fungus was reisolated from the lesions, and further morphological characterization and molecular assays, as described above. L. australis has been reported on various plants, including Prunus armeniaca, Dolichos, Poa, Lolium, and Vitis in Australia (Graham and Luttrell 1961), and also from Korean soil in 2018 (Weilan et al. 2018). Additionally, L. briosiana, which is common in the United States, China, and other countries, causes Leptosphaerulina leaf spot (Samac et al. 2015). L. trifolii is newly reported to occur in China (Liu et al. 2019). To the best of our knowledge, this is the first report of L. australis infecting alfalfa in China. Considering the large planting area in Inner Mongolia, this pathogen may cause losses to alfalfa cultivation. Hence, future studies should explore aspects of effective management of this disease.The author(s) declare no conflict of interest.References:Graham, J. H., and Luttrell, E. S. 1961. Phytopathology 51:680. ISI, Google ScholarLiu, X. P., et al. 2019. Plant Dis. 103:2673. https://doi.org/10.1094/PDIS-04-19-0693-PDN Link, ISI, Google ScholarSamac, D. A., et al. 2015. Plant Dis. 99:614. https://doi.org/10.1094/PDIS-03-14-0240-RE Link, ISI, Google ScholarWang, Q., et al. 2019. Plant Dis. 103:2138. https://doi.org/10.1094/PDIS-01-19-0218-PDN Google ScholarWeilan, L., et al. 2018. Kor. J. Mycol. 46:369. https://doi.org/10.4489/KJM.20180041 Google ScholarThe author(s) declare no conflict of interest.Funding: Funding was financially supported by the Program for Changjiang Scholars and Innovative Research Team in University (IRT_17R50), Gansu Provincial Science and Technology Major Projects (No.19ZD2NA002), China Agriculture Research System (CARS-34), and Academician Workstation of Zhibiao Nan (2018IC074).DetailsFiguresLiterature CitedRelated Vol. 105, No. 8 August 2021SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionComparison of banana plants in silicon-deficient soil amended or nonamended with calcium silicate and infected by Fusarium oxysporum f. sp. cubense (W. Zellner et al.). Photo credit: A. A. Fortunato and F. A. Rodrigues. Infected spicebush tree outer bark showing black vascular discoloration of the sapwood typical of laurel wilt (R. Olatinwo et al.). Photo credit: R. Olatinwo. Maize plants naturally infected by Bipolaris zeicola (S. S. Liu et al.). Photo credit: S. S. Liu. Metrics Downloaded 398 times Article History Issue Date: 1 Dec 2021Published: 22 Sep 2021First Look: 8 Feb 2021Accepted: 4 Feb 2021 Page: 2254 Information© 2021 The American Phytopathological SocietyFundingProgram for Changjiang Scholars and Innovative Research Team in UniversityGrant/Award Number: IRT_17R50Gansu Provincial Science and Technology Major ProjectsGrant/Award Number: 19ZD2NA002China Agriculture Research SystemGrant/Award Number: CARS-34Academician Workstation of Zhibiao NanGrant/Award Number: 2018IC074Keywordsfungiepidemiologydisease development and spreaddisease managementcultivar/resistanceThe author(s) declare no conflict of interest.PDF download