First Report of Phomopsis Stem Canker of Sunflower (<i>Helianthus annuus</i>) Caused by <i>Diaporthe gulyae</i> in China

HomePlant DiseaseVol. 103, No. 8First Report of Phomopsis Stem Canker of Sunflower (Helianthus annuus) Caused by Diaporthe gulyae in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Phomopsis Stem Canker of Sunflower (Helianthus annuus) Caused by Diaporthe gulyae in ChinaY. Zhang, Y. Yu, M. Li, J. Zhang, K. D. Puri, and J. ZhaoY. Zhanghttp://orcid.org/0000-0003-4656-2001College of Horticulture and Plant Protection, Inner Mongolia Agricultural University, Hohhot, 010018, China, Y. YuDepartment of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada, M. LiCollege of Horticulture and Plant Protection, Inner Mongolia Agricultural University, Hohhot, 010018, China, J. ZhangCollege of Horticulture and Plant Protection, Inner Mongolia Agricultural University, Hohhot, 010018, China, K. D. Purihttp://orcid.org/0000-0001-9165-3282Department of Plant Pathology, University of California, Davis, CA, 93905, U.S.A., and J. Zhao†Corresponding author: J. Zhao; E-mail Address: zhaojun@imau.edu.cnCollege of Horticulture and Plant Protection, Inner Mongolia Agricultural University, Hohhot, 010018, ChinaAffiliationsAuthors and Affiliations Y. Zhang1 Y. Yu2 M. Li1 J. Zhang1 K. D. Puri3 J. Zhao1 † 1College of Horticulture and Plant Protection, Inner Mongolia Agricultural University, Hohhot, 010018, China 2Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada 3Department of Plant Pathology, University of California, Davis, CA, 93905, U.S.A. Published Online:29 May 2019https://doi.org/10.1094/PDIS-01-19-0151-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Sunflower (Helianthus annuus L.) is the fourth most widely grown oilseed crop in China covering approximately 1.2 million ha. Within China, Inner Mongolia is the largest sunflower production region, planting 0.7 million ha. In August 2014, a new disease similar to Phomopsis stem canker was found in a commercial sunflower field in Songjia village, Wulanchabu, Inner Mongolia, China (41°52′N, 112°59′E). The disease incidence was approximately 2%. The symptomatic plants had light-to-dark brown necrotic lesions initiated at the basal leaf nodes that successively grew longer in size (6 to 15 cm) and darker, consistent to the symptoms of Phomopsis stem canker. Other symptoms included pith damage behind the lesions, early plant senescence, and midstem lodging. Five symptomatic plants were randomly sampled and processed for pathogen isolation. Small pieces (0.3 × 0.3 cm) of tissues along the canker margins were plated on potato dextrose agar (PDA) amended with 50 μg/ml of kanamycin sulfate and incubated for 14 days at 25°C with a 12-h photoperiod. An actively growing fungal culture was hyphal tipped and transferred to a new PDA plate to obtain a pure culture isolate, SJC3-2. On PDA, colonies looked tan to gray in color with aerial mycelia covering entire plates within 7 days. Pycnidia were up to 3 mm in diameter, subglobose, occasionally producing beaks up ostiolates, surrounded by black ectostromata. Conidiogeneous cells were cylindrical, hyaline, and approximately 7.5 to 19.2 × 1.3 to 2.7 µm in size. Alpha conidia were 6.4 to 10.3 × 2.4 to 3.8 µm in size, globose, subglobose, ellipsoidal, oval or obovoid in shape, and hyaline, but no beta conidia were observed. These characteristics are typical of Diaporthe spp. (Thompson et al. 2011). Genomic DNA from isolate SJC3-2 was used to amplify the internal transcribed spacer (ITS) and elongation factor 1-alpha (EF1-α) genes using specific primers ITS1/ITS4 (White et al. 1990) and EF1-728F/EF1-986R (Carbone and Kohn 1999), respectively. Sequence comparison in both ITS (GenBank accession no. KX077244) and EF1-α (no. MK408423) using BLAST showed that SJC3-2 had 100% similarity with strain BRIP54025 of Diaporthe gulyae R. G. Shivas S. M. Thompson & A. J. Young, sp. nov. isolated from sunflower (accession nos. NR111615 and JN645803) (Thompson et al. 2011). For pathogenicity testing, ten 4-week-old seedlings grown from sterilized seeds of sunflower variety LD5009 were inoculated at the second internodes by placing a mycelial plug on the wounds pricked with a toothpick (Mathew et al. 2015a). The inoculated seedlings were transferred to a greenhouse maintained at 25°C with 40% relative humidity and a 16-h photoperiod. All inoculated plants showed dark brown lesions 3 days postinoculation (DPI), followed by stems and leaves wilting and complete collapse by 14 DPI. The control plants inoculated with sterile PDA plugs remained symptomless. To complete Koch's postulates, the fungus was reisolated and confirmed as D. gulyae by both morphological and molecular approaches mentioned above. The sunflower Phomopsis stem canker caused by D. gulyae was first reported in Australia in 2011 (Thompson et al. 2011) and then in the United States (Mathew et al. 2015a) and Canada (Mathew et al. 2015b) in 2015. To the best of our knowledge, this is the first report of D. gulyae causing Phomopsis stem canker on sunflower in China. The pathogen is a quarantine problem in China with no known host resistance. Thus, the newly discovered pathogen might pose a threat to sunflower production in China and needs an immediate attention.The author(s) declare no conflict of interest.References:Carbone, I., and Kohn, L. M. 1999. Mycologia 91:553. https://doi.org/10.2307/3761358 Crossref, ISI, Google ScholarMathew, F. M., et al. 2015a. Phytopathology 105:990. https://doi.org/10.1094/PHYTO-11-14-0336-FI Link, ISI, Google ScholarMathew, F. M., et al. 2015b. Plant Dis. 99:160. https://doi.org/10.1094/PDIS-08-14-0858-PDN Link, ISI, Google ScholarThompson, S. M., et al. 2011. Persoonia 27:80. https://doi.org/10.3767/003158511X617110 Crossref, ISI, Google ScholarWhite, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA. Crossref, Google ScholarThe author(s) declare no conflict of interest.Funding: Funding was provided by China Agricultural Research System (grant no. CARS-16) and Major Special Project of Science and Technology in Inner Mongolia.DetailsFiguresLiterature CitedRelated Vol. 103, No. 8 August 2019SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionPistachio fruit infected by Neofusicoccum mediterraneum (Moral et al.). Photo credit: T. J. Michailides. Leaf blight on Hosta ventricosa caused by Pseudomonas syringae pv. syringae (Liu et al.). Photo credit: Z. X. Liu. Metrics Article History Issue Date: 1 Aug 2019Published: 29 May 2019First Look: 5 Apr 2019Accepted: 3 Apr 2019 Pages: 2124-2124 Information© 2019 The American Phytopathological SocietyFundingChina Agricultural Research SystemGrant/Award Number: CARS-16Major Special Project of Science and Technology in Inner MongoliaKeywordssunflower (Helianthus annuus L.)phomopsis stem cankerDisporthe gulyaeThe author(s) declare no conflict of interest.Cited byDiaporthe gulyae (Phomopsis stem canker of sunflower)CABI Compendium, Vol. CABI Compendium

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