First Report of Corynespora cassiicola Causing Leaf Spot of Strobilanthes cusia in China

HomePlant DiseaseVol. 107, No. 2First Report of Corynespora cassiicola Causing Leaf Spot of Strobilanthes cusia in China PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Corynespora cassiicola Causing Leaf Spot of Strobilanthes cusia in ChinaB. C. Liu, J. Y. Chen, W. J. Zhang, Y. Z. Huang, and Y. Q. ZhaoB. C. Liuhttps://orcid.org/0000-0001-9436-3897Institute of Agricultural Bio-resource, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, ChinaResearch Center for Medicinal Plant, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, China, J. Y. Chen†Corresponding author: J. Y. Chen; E-mail Address: [email protected]Institute of Agricultural Bio-resource, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, ChinaResearch Center for Medicinal Plant, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, China, W. J. ZhangInstitute of Agricultural Bio-resource, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, ChinaResearch Center for Medicinal Plant, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, China, Y. Z. HuangInstitute of Agricultural Bio-resource, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, ChinaResearch Center for Medicinal Plant, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, China, and Y. Q. ZhaoInstitute of Agricultural Bio-resource, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, ChinaResearch Center for Medicinal Plant, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, ChinaAffiliationsAuthors and Affiliations B. C. Liu1 2 J. Y. Chen1 2 † W. J. Zhang1 2 Y. Z. Huang1 2 Y. Q. Zhao1 2 1Institute of Agricultural Bio-resource, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, China 2Research Center for Medicinal Plant, Fujian Academy of Agricultural Sciences, Fuzhou 350003, Fujian, China Published Online:9 Feb 2023https://doi.org/10.1094/PDIS-03-22-0635-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleStrobilanthes cusia (Nees) Kuntze is a vital medicinal and industrial herb, planted extensively in southern China (Hu et al. 2011). In July and August of 2021, leaf spot incidence on >60% plants and reduced yields >20% for fresh leaves were observed in S. cusia 'Malan No.1' across the whole Shufeng Township, Xianyou County, Fujian province. Initial symptoms on leaves were observed as small, dark-brown spots surrounded by a yellow halo, expanding irregularly or into semicircular spots. As symptoms developed, the spots became dark brown, thin, and fragile, forming small holes. In severe cases plants were defoliated. The pathogen was isolated from the margin of 60 symptomatic leaf lesions, surface sterilized with 75% ethanol for 45 s, rinsed three times with sterile water, air dried, and cultured on potato dextrose agar (PDA) at 25°C in the dark. Pure cultures were obtained by single-spore isolation after subculture. Ten representative single-spore isolates (MY-1 to MY-10) from 154 pathogens in 10 sampling points were selected for morphological characterization and identification. After 7 days, mycelial colonies were gray to dark gray with few aerial hyphae. Conidia (32.3 to 132.8 × 5.8 to 8.4 μm, average 81.4 × 6.3 μm, n = 50) were pale to brown, erect or curved, solitary or in chains, with 0 to 15 pseudosepta. Based on morphological characteristics, the isolates were preliminarily identified as Corynespora cassiicola. Genomic DNA of isolate MY-2 (randomly selected from 10 isolates as representative) was extracted from mycelia using the Ezup DNA extraction kit (Sangon Biotech Co., Shanghai, China). The internal transcribed spacer (ITS) region of rDNA, translation elongation factor 1 alpha (TEF1-α), and beta-tubulin (TUB2) genes were amplified and sequenced with primers ITS4/ITS5, EF1-728F/EF-986R (Wang et al. 2021), and Bt2a/Bt2b (Glass and Donaldson 1995), respectively. BLASTN sequence analyses of ITS (538 bp), TEF1-α (302 bp), and TUB2 (436 bp) of isolate MY-2 (GenBank accessions OK355515, OM339443, and OM339442) showed 100, 97.6, and 100% identity with C. cassiicola in GenBank (accession nos. JX908713, MW961421, and AB539228). A neighbor-joining phylogenetic analysis based on ITS and TEF1-α sequences using MEGA7 showed that MY-2 clustered in the same clade with C. cassiicola. For pathogenicity tests, five S. cusia plants were inoculated on the adaxial surface of leaves with mycelial plugs from 10 isolates of 8-day-old cultures on PDA. Five leaves per plant were inoculated, covered with wet cotton, and kept in a controlled greenhouse (26 to 33°C, 80 to 90% relative humidity). Leaves inoculated with sterile PDA plugs served as a negative control. At 3 to 5 days postinoculation, all 25 inoculated leaves of each isolate showed leaf spot lesions similar to those observed in the field, and control leaves were symptomless. C. cassiicola was successfully reisolated from the diseased leaves. The pathogenicity tests were repeated three times under the same conditions, and similar results were observed. In view of morphology, pathogenicity, and sequence results, the isolates were identified as C. cassiicola, a pathogen reported from many important crops (Lu et al. 2021). This is the first report of C. cassiicola as a pathogen in China, which poses a potential threat to leaf production and S. cusia processing.The author(s) declare no conflict of interest.References:Glass, N. L., and Donaldson, G. C. 1995. Appl. Environ. Microbiol. 61:1323. https://doi.org/10.1128/aem.61.4.1323-1330.1995Crossref, ISI, Google ScholarHu, J. Q., et al. 2011. Page 407 in: Flora of China, Vol. 19. Science Press, Beijing, China.Google ScholarLu, P.-K, et al. 2021. Plant Dis. 105:3753. https://doi.org/10.1094/pdis-02-21-0277-pdnLink, ISI, Google ScholarWang, S. H., et al. 2021. For. Pathol. 51:1.ISI, Google ScholarFunding: Funding was provided by Collaborative Innovation of the Fujian Provincial People's Government (XTCXGC2021003), Fujian Provincial Finance Special Project to Science and Technology Innovation Team of Fujian Academy of Agricultural Sciences (CXTD2021014-2), Project of Fujian Academy of Agricultural Sciences (A2017-5), and Young Talents in Science and Technology Project of Fujian Academy of Agricultural Sciences (YC2021005).The author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Vol. 107, No. 2 February 2023SubscribeISSN:0191-2917e-ISSN:1943-7692 Download Cover Image Metrics Article History Issue Date: 28 Feb 2023Published: 9 Feb 2023First Look: 8 Jul 2022Accepted: 4 Jul 2022 Page: 561 Information© 2023 The American Phytopathological SocietyFundingCollaborative Innovation of the Fujian Provincial People's GovernmentGrant/Award Number: XTCXGC2021003Fujian Provincial Finance Special Project to Science and Technology Innovation Team of Fujian Academy of Agricultural SciencesGrant/Award Number: CXTD2021014-2Project of Fujian Academy of Agricultural SciencesGrant/Award Number: A2017-5Young Talents in Science and Technology Project of Fujian Academy of Agricultural SciencesGrant/Award Number: YC2021005KeywordsCorynespora cassiicolaetiologyfungal diseaseleaf spotmedicinal plantsStrobilanthes cusiaThe author(s) declare no conflict of interest.PDF download