First Report of Trunk Canker and Gummosis of Kumquat Caused by <i>Lasiodiplodia theobromae</i> in China

HomePlant DiseaseVol. 104, No. 3First Report of Trunk Canker and Gummosis of Kumquat Caused by Lasiodiplodia theobromae in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Trunk Canker and Gummosis of Kumquat Caused by Lasiodiplodia theobromae in ChinaQing Gui, Jiang Zhao, Zhihe Yu, Wenxiu Sun, Jianyou Mo, Qili Li, Tangxun Guo, Lihua Tang, Suiping Huang, and Tom HsiangQing GuiCollege of Life Sciences, Yangtze University, Jingzhou 434025, Hubei, China, Jiang ZhaoCollege of Life Sciences, Yangtze University, Jingzhou 434025, Hubei, China, Zhihe YuCollege of Life Sciences, Yangtze University, Jingzhou 434025, Hubei, China, Wenxiu Sun†Corresponding authors: W. Sun; E-mail Address: 75102310@qq.com and Q. Li; E-mail Address: 65615384@qq.comCollege of Life Sciences, Yangtze University, Jingzhou 434025, Hubei, China, Jianyou MoInstitute of Plant Protection, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, ChinaGuangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Nanning 530007, Guangxi, China, Qili Li†Corresponding authors: W. Sun; E-mail Address: 75102310@qq.com and Q. Li; E-mail Address: 65615384@qq.comhttp://orcid.org/0000-0001-5775-8910Institute of Plant Protection, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, ChinaGuangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Nanning 530007, Guangxi, China, Tangxun GuoInstitute of Plant Protection, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, ChinaGuangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Nanning 530007, Guangxi, China, Lihua Tanghttp://orcid.org/0000-0001-5972-0166Institute of Plant Protection, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, ChinaGuangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Nanning 530007, Guangxi, China, Suiping Huanghttp://orcid.org/0000-0001-9484-3487Institute of Plant Protection, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, ChinaGuangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Nanning 530007, Guangxi, China, and Tom HsiangSchool of Environmental Sciences, University of Guelph, Guelph N1G 2W1, Ontario, Canada AffiliationsAuthors and Affiliations Qing Gui1 Jiang Zhao1 Zhihe Yu1 Wenxiu Sun1 † Jianyou Mo2 3 Qili Li2 3 † Tangxun Guo2 3 Lihua Tang2 3 Suiping Huang2 3 Tom Hsiang4 1College of Life Sciences, Yangtze University, Jingzhou 434025, Hubei, China 2Institute of Plant Protection, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, China 3Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Nanning 530007, Guangxi, China 4School of Environmental Sciences, University of Guelph, Guelph N1G 2W1, Ontario, Canada Published Online:22 Jan 2020https://doi.org/10.1094/PDIS-02-19-0424-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Kumquat (Fortunella margarita [Lour.] Swingle) is widely cultivated in southern China. In June 2016, trunk cankers and gummosis were observed in four kumquat orchards in Yangshuo County, Guangxi Province, China, with an average of 10% disease incidence (DI) and a maximum of 30% DI in nearby locations. Initially, small brown circular lesions (1 to 2 cm) were observed above graft unions, which then became 10 to 30 cm long and 3 to 14 cm wide in 1 to 4 months. Gummosis then appeared and increased along with increasing lesion sizes, resulting eventually in the death of 2.5-m-tall trees in 2 to 3 years under high temperature and high rainfall conditions. Diseased trunks were collected from each of four orchards in Yangshuo County, and symptomatic bark tissue was cut into 5 × 5-mm pieces, surface sterilized with 75% ethanol for 10 s and 2% sodium hypochlorite for 1 min, rinsed three times in sterile water, plated on potato dextrose ager (PDA), and incubated at 25°C in the dark until colonies developed. Fungal cultures with similar morphology on PDA (19 isolates) were consistently recovered from symptomatic samples. A representative isolate (J4-1), grew quickly (53 mm/day) at 25°C on PDA, with abundant white fluffy aerial mycelium, which turned gray-black after 9 days. Conidia were elliptical, single celled, hyaline, and produced when exposed to 280 to 400 nm wavelength UV light on PDA for 20 days with 12 h of light/12 h of dark. By 30 days, spores turned dark brown and were two-celled with longitudinal striations on the surface, averaging 23.7 × 12.8 μm. The fungus was identified as Lasiodiplodia theobromae based on the morphological characteristics (Phillips et al. 2013). Sequences of the internal transcribed spacer, elongation factor 1-α, and β-tubulin showed ≥99% identity with L. theobromae type isolate CBS 164.96. These sequences were deposited in GenBank (MK478882, MK423878, and MN172230), and L. theobromae isolate J4-1 was deposited in the China Center for Type Culture Collection (CCTCC AF 2019011). Pathogenicity of isolate J4-1 was tested on asymptomatic trunks and branches of three 2-year-old kumquat trees in a greenhouse in Nanning, Guangxi Province, China. For each tree, a wound was made on the trunk and on a branch. For each wound, six adjacent needle punctures were made in a 5-mm-diameter circular area using a sterilized needle. Then a 5-mm-diameter PDA culture plug was placed on each wound, covered with sterile wet cotton padding, and wrapped with Parafilm. Sterile PDA plugs were used as controls. After 2 weeks, typical brown lesions were clearly visible on the wound-inoculated trunks and branches, and sap oozed from the infected wounds forming gummosis. No symptoms were observed on the controls. The fungus was reisolated from inoculated symptomatic bark tissue but not from controls, thus completing Koch's postulates. It has been reported that L. theobromae can cause wilt and tree gummosis on kumquat in Taiwan (Ko et al. 2004) and gummosis in lemon (Citrus limon) in Chile (Guajardo et al. 2018). In China, L. theobromae caused fruit rot on pomelo (C. grandis) (Luo et al. 2011). However, to our knowledge, this is the first report of L. theobromae causing trunk cankers and gummosis on kumquat in mainland China. This finding allows a better understanding of kumquat diseases for local growers and for disease management, as well as facilitating future research.The author(s) declare no conflict of interest.References:Guajardo, J., et al. 2018. Plant Dis. 102:818. https://doi.org/10.1094/PDIS-09-17-1517-PDN Link, ISI, Google ScholarKo, W. H., et al. 2004. Plant Dis. 88:1383. https://doi.org/10.1094/PDIS.2004.88.12.1383A Link, ISI, Google ScholarLuo, M., et al. 2011. Plant Dis. 95:1190. https://doi.org/10.1094/PDIS-03-11-0214 Link, ISI, Google ScholarPhillips, A. J. L., et al. 2013. Stud. Mycol. 76:51. https://doi.org/10.3114/sim0021 Crossref, ISI, Google ScholarThe author(s) declare no conflict of interest.Funding: The research was supported by Guangxi Natural Science Foundation (2016GXNSFCB380004 and 2017GXNSFBA198218) and Foundation for Development of Science and Technology of Guangxi Academy of Agricultural Sciences (31860482).DetailsFiguresLiterature CitedRelated Vol. 104, No. 3 March 2020SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionPathogenicity of Lasiodiploidia pseudotheobromae in a coffee plant 3 days after inoculation (R. L. Freitas-Lopes et al.). Photo credit: U. P. Lopes. Seedling blight of soybean caused by soilborne pathogens (J. R. Lamichhane et al.). Photo credit: M. I. Chilvers. Metrics Downloaded 2,101 times Article History Issue Date: 3 Mar 2020Published: 22 Jan 2020First Look: 10 Dec 2019Accepted: 5 Dec 2019 Pages: 971-971 Information© 2020 The American Phytopathological SocietyFundingGuangxi Natural Science FoundationGrant/Award Number: 2016GXNSFCB380004Grant/Award Number: 2017GXNSFBA198218Foundation for Development of Science and Technology of Guangxi Academy of Agricultural SciencesGrant/Award Number: 31860482KeywordsLasiodiplodia theobromaegummosiskumquatcankertrunkThe author(s) declare no conflict of interest.

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