<i>Alternaria alternata</i> Causing Leaf Spot on <i>Magnolia grandiflora</i> in China

HomePlant DiseaseVol. 103, No. 10Alternaria alternata Causing Leaf Spot on Magnolia grandiflora in China PreviousNext DISEASE NOTES OPENOpen Access licenseAlternaria alternata Causing Leaf Spot on Magnolia grandiflora in ChinaJ. Liu, J. Xiao, J. Zhou, G. Cai, X. Li, and J. LuJ. Liuhttp://orcid.org/0000-0003-3831-2774Key Laboratory of Industrial Biotechnology of Ministry of Education, National Engineering Laboratory for Cereal Fermentation Technology, Jiangsu Provincial Research Center for Bioactive Product Processing Technology, School of Biotechnology, Jiangnan University, Wuxi 214122, China, J. XiaoKey Laboratory of Industrial Biotechnology of Ministry of Education, National Engineering Laboratory for Cereal Fermentation Technology, Jiangsu Provincial Research Center for Bioactive Product Processing Technology, School of Biotechnology, Jiangnan University, Wuxi 214122, China, J. ZhouKey Laboratory of Industrial Biotechnology of Ministry of Education, National Engineering Laboratory for Cereal Fermentation Technology, Jiangsu Provincial Research Center for Bioactive Product Processing Technology, School of Biotechnology, Jiangnan University, Wuxi 214122, China, G. CaiKey Laboratory of Industrial Biotechnology of Ministry of Education, National Engineering Laboratory for Cereal Fermentation Technology, Jiangsu Provincial Research Center for Bioactive Product Processing Technology, School of Biotechnology, Jiangnan University, Wuxi 214122, China, X. Li†Corresponding authors: X. Li; E-mail Address: xiaomin@jiangnan.edu.cn and J. Lu; E-mail Address: jlu@jiangnan.edu.cnKey Laboratory of Industrial Biotechnology of Ministry of Education, National Engineering Laboratory for Cereal Fermentation Technology, Jiangsu Provincial Research Center for Bioactive Product Processing Technology, School of Biotechnology, Jiangnan University, Wuxi 214122, China, and J. Lu†Corresponding authors: X. Li; E-mail Address: xiaomin@jiangnan.edu.cn and J. Lu; E-mail Address: jlu@jiangnan.edu.cnKey Laboratory of Industrial Biotechnology of Ministry of Education, National Engineering Laboratory for Cereal Fermentation Technology, Jiangsu Provincial Research Center for Bioactive Product Processing Technology, School of Biotechnology, Jiangnan University, Wuxi 214122, ChinaAffiliationsAuthors and Affiliations J. Liu J. Xiao J. Zhou G. Cai X. Li † J. Lu † Key Laboratory of Industrial Biotechnology of Ministry of Education, National Engineering Laboratory for Cereal Fermentation Technology, Jiangsu Provincial Research Center for Bioactive Product Processing Technology, School of Biotechnology, Jiangnan University, Wuxi 214122, China Published Online:20 Aug 2019https://doi.org/10.1094/PDIS-04-19-0828-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Southern magnolia (Magnolia grandiflora) is a popular evergreen tree, planted especially as an ornamental for landscaping. During September 2016 to October 2018, ∼41 to 45% of leaves of M. grandiflora plants (a total of about 300 plants) displayed a severe foliar disease in Jiangnan University campus in Wuxi, Jiangsu, China (31.48°N, 120.46°E). Leaf symptoms consisted of dark brown, circular to irregular lesions, surrounded by a yellowish border. The symptomatic leaf tissues were surface sterilized in 75% ethanol for 30 s and then in 1% sodium hypochlorite for 1 min, rinsed three times in sterile distilled water, plated onto potato dextrose agar, and incubated at 25°C in the dark for 5 days. The fungal colonies were olivaceous to dark olive, wool-like, with whitish mycelium borders. Conidiophores were septate, branched or unbranched, and measured 19.7 to 49.3 × 2.1 to 4.2 μm. Conidia, produced in single or branched chains, were obclavate or ovoid, measured 7.2 to 57.8 × 5.1 to 20.4 μm (n = 50) and showed two to five transverse and zero to three longitudinal septa. Based on the morphological characteristics, the pathogen was identified as Alternaria alternata (Simmons 2007). To confirm the identification, total genomic DNA of the isolated fungus was extracted with a Plant/Fungi DNA Isolation Kit (Sigma-Aldrich, Ontario, Canada). Internal transcribed spacer (ITS), translation elongation factor 1-alpha (EF1), β-tubulin gene (Bt), actin gene (ACT), Alternaria major allergen (Alta1), plasma membrane ATPase gene (ATP), and calmodulin gene (CAL) were amplified with primers ITS1/ITS4, EF1-728F/EF1-986R (Carbone and Kohn 1999), Bt1a/Bt1b, ACT512F/783R, Alt-for/Alt-rev, ATPDF1/ATPDR1, and CALDF1/CALDR1 (Lawrence et al. 2013), respectively. The amplicons were sequenced (GenBank accession nos. MK804118 [ITS], MK796125 [EF1], MK804117 [Bt], MK804113 [ACT], MK804114 [Alta1], MK804115 [ATP], and MK804116 [CAL]), and a BLAST search revealed 99.44 to 100% identity with sequences of various A. alternata isolates (MH475292 for ITS, JF835905 for EF1, KF380803 for Bt, MG736306 for ACT, MG525451 for Alta1, JQ811979 for ATP, and KJ920938 for CAL). For pathogenicity tests, one isolate was used for artificial inoculation of detached leaves of 10-year-old M. grandiflora plants, and 500 μl of a spore suspension of 107 conidia/ml was sprayed on 24 healthy leaves. The inoculated leaves were then incubated in an artificial climate chamber at 25°C and 75 to 80% relative humidity under a 12-h photoperiod. Pathogenicity tests were repeated three times, and 5 to 7 days postinoculation, dark brown lesions similar to the original ones developed on all inoculated leaves, whereas control leaves sprayed with sterile distilled water remained symptomless. A. alternata was reisolated from artificially inoculated leaves, confirming Koch's postulates based on morphology and molecular data. There are reports of A. alternata causing leaf spot and postharvest fruit rot on numerous hosts (Farr and Rossman 2017). Nevertheless, to our knowledge, this is the first report of A. alternata causing leaf spots on M. grandiflora in China. Future research will focus on the management of this disease.The author(s) declare no conflict of interest.References:Carbone, I., and Kohn, L. 1999. Mycologia 91:553. https://doi.org/10.1080/00275514.1999.12061051 Crossref, ISI, Google ScholarFarr, D. F., and Rossman, A. Y. 2017. Fungal Databases, Syst. Mycol. Microbiol. Lab., ARS, USDA. https://nt.ars-grin.gov/fungaldatabases/. Google ScholarSimmons, E. G. 2007. Alternaria: An Identification Manual. CBS Fungal Biodiversity Center, Utrecht, the Netherlands. Google ScholarLawrence, D. P., et al. 2013. Mycologia 105:530. https://doi.org/10.3852/12-249 Crossref, ISI, Google ScholarThe author(s) declare no conflict of interest.Funding: This research was supported by the Postgraduate Research and Practice Innovation Program of Jiangsu Province (KYCX19_1830), the Fundamental Research Funds for the Central Universities (JUSRP2191), and the Jiangnan University Postgraduate Overseas Research Project.DetailsFiguresLiterature CitedRelated Vol. 103, No. 10 October 2019SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionBell pepper cv. Bomby infected with zucchini yellow mosaic virus along with cucumber mosaic virus, pepper mild mottle virus, and tobacco mosaic virus (Verma et al.). Photo credit: S. Tripathi. Severe stunting, leaf chlorosis, and horizontal head growth of sunflower infected with Plasmopara halstedii, causal agent of downy mildew (Humann et al.). Photo credit: S. Markell. Metrics Article History Issue Date: 3 Oct 2019Published: 20 Aug 2019First Look: 10 Jun 2019Accepted: 7 Jun 2019 Pages: 2672-2672 Information© 2019 The American Phytopathological SocietyFundingPostgraduate Research and Practice Innovation Program of Jiangsu ProvinceGrant/Award Number: KYCX19_1830Fundamental Research Funds for the Central UniversitiesGrant/Award Number: JUSRP2191Jiangnan University Postgraduate Overseas Research ProjectKeywordsAlternaria alternataleaf spotMagnolia grandifloraThe author(s) declare no conflict of interest.Cited byFungi associated with dead branches of Magnolia grandiflora: A case study from Qujing, China4 August 2022 | Frontiers in Microbiology, Vol. 13

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