First Report of Tar Spot on Corn Caused by Phyllachora maydis in the Great Plains

HomePlant DiseaseAhead of PrintFirst Report of Tar Spot on Corn Caused by Phyllachora maydis in the Great Plains PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Tar Spot on Corn Caused by Phyllachora maydis in the Great PlainsR. D. Moura, K. C. Broderick, M. Shires, K. Andersen Onofre, E. De Wolf, T. A. Jackson-Ziems, and R. B. OnofreR. D. MouraDepartment of Plant Pathology, Kansas State University, Manhattan, KS 66506, K. C. BroderickDepartment of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583-0722, M. ShiresDepartment of Agronomy, Horticulture, and Plant Sciences, South Dakota State University, Brookings, SD 57007, K. Andersen OnofreDepartment of Plant Pathology, Kansas State University, Manhattan, KS 66506, E. De Wolfhttps://orcid.org/0000-0002-9339-1543Department of Plant Pathology, Kansas State University, Manhattan, KS 66506, T. A. Jackson-ZiemsDepartment of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583-0722, and R. B. Onofre†Corresponding author: R. B. Onofre; E-mail Address: [email protected]https://orcid.org/0000-0002-1789-347XDepartment of Plant Pathology, Kansas State University, Manhattan, KS 66506AffiliationsAuthors and Affiliations R. D. Moura1 K. C. Broderick2 M. Shires3 K. Andersen Onofre1 E. De Wolf1 T. A. Jackson-Ziems2 R. B. Onofre1 † 1Department of Plant Pathology, Kansas State University, Manhattan, KS 66506 2Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583-0722 3Department of Agronomy, Horticulture, and Plant Sciences, South Dakota State University, Brookings, SD 57007 Published Online:28 Jul 2023https://doi.org/10.1094/PDIS-01-23-0183-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleTar spot caused by the fungus Phyllachora maydis Maubl. is a significant foliar disease of corn (Zea mays L.). Threatening corn production across the Americas, this disease can reduce the quality of silage and grain yield (Rocco da Silva et al. 2021; Valle-Torres et al. 2020). Lesions caused by P. maydis are usually black and glossy, with raised stromata on the leaf surface and occasionally on the husk (Liu 1973; Rocco da Silva et al. 2021). Samples consistent with tar spot of corn were collected between September and October of 2022 from 6 fields in Kansas, 23 in Nebraska, and 6 in South Dakota. One sample was selected from each of the three states for further microscopic evaluation and molecular analysis. Signs of the fungus were visually and microscopically confirmed in eight Nebraska counties in October 2021; however, in the 2021 season, tar spot signs were not found in Kansas and South Dakota. In the 2022 season, disease severity varied by location; some fields in Kansas had <1% incidence, whereas in South Dakota, disease incidence approached 1 to 2%, and in Nebraska between <1 and 5%. Stromata were present on both green and senescing tissues. Morphological characteristics of the pathogen were similar and consistent with the description of P. maydis (Parbery 1967) from all examined leaves across all locations. Asexual spores (conidia) were produced in pycnidial fruiting bodies ranging in size from 1.29 to 2.82 × 8.84 to 16.95 μm (n = 40, average 1.98 × 13.30 μm). The pycnidial fruiting bodies were often found adjacent to perithecia within the stromata. For molecular confirmation, stromata were aseptically removed from leaves collected at each location, and DNA was extracted using a phenol chloroform method. The internal transcribed spacer (ITS) regions of the ribosomal RNA gene were sequenced using ITS1/ITS4 universal primers (Larena et al. 1999). Amplicons were Sanger sequenced (Genewiz, South Plainfield, NJ), and a consensus sequence for each sample was deposited in GenBank: Kansas (OQ200487), Nebraska (OQ200488), and South Dakota (OQ200489). Using the BLASTn, sequences from Kansas, Nebraska, and South Dakota showed 100% homology with 100% query cover to other P. maydis GenBank accessions (MG881848.1; OL342916.1; OL342915.1). Koch’s postulates were not performed given the obligate nature of the pathogen (Müller and Samuels 1984). This report documents the first confirmation of tar spot on corn in Kansas, Nebraska, and South Dakota (Great Plains).The author(s) declare no conflict of interest.References:Larena, I., et al. 1999. J. Biotechnol. 75:187. https://doi.org/10.1016/S0168-1656(99)00154-6 Crossref, ISI, Google ScholarLiu, L.-J. 1973. J. Agric. Univ. P. R. 57:211. https://doi.org/10.46429/jaupr.v57i3.10745 Google ScholarMüller, E., and Samuels, G. J. 1984. Nova Hedwig. 40:113. ISI, Google ScholarParbery, D. G. 1967. Aust. J. Bot. 15:271. https://doi.org/10.1071/BT9670271 Crossref, ISI, Google ScholarRocco da Silva, C., et al. 2021. Plant Health Prog. 22:596. https://doi.org/10.1094/PHP-04-21-0074-RP Link, ISI, Google ScholarValle-Torres, J., et al. 2020. Plant Dis. 104:2541. https://doi.org/10.1094/PDIS-02-20-0449-FE Link, ISI, Google ScholarFunding: This research was supported by the Kansas State University and the Kansas Agricultural Experiment Station (contribution no. 23-213-J).The author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Just PublishedSubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Published: 28 Jul 2023First Look: 7 Mar 2023Accepted: 1 Mar 2023 Information© 2023 The American Phytopathological SocietyFundingKansas State UniversityKansas Agricultural Experiment StationGrant/Award Number: 23-213-JKeywordscornGreat PlainsPhyllachora maydistar spotThe author(s) declare no conflict of interest.PDF download