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ARS Home » Midwest Area » St. Paul, Minnesota » Cereal Disease Lab » Research » Publications at this Location » Publication #402598
Research Project: Plant-Fungal Interactions and Host Resistance in Fusarium Head Blight of Barley and Wheat

Location: Cereal Disease Lab

Title: A new and effective method to induce infection of Phyllachora maydis into corn for tar spot studies in controlled environments

Author
item SOLORZANO, JOSE - University Of Minnesota
item ISSENDORF, SHEA - University Of Minnesota
item Drott, Milton
item CHECK, JILL - Michigan State University
item ROGGENKAMP, EMILY - Michigan State University
item CRUZ, C - Purdue University
item KLECZEWKSI, NATHAN - Growmark
item MALVICK, DEAN - University Of Minnesota

Submitted to: Plant Methods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2023
Publication Date: 8/11/2023
Citation: Solorzano, J.E., Issendorf, S.E., Drott, M.T., Check, J.C., Roggenkamp, E.M., Cruz, C.D., Kleczewksi, N.M., Malvick, D.K. 2023. A new and effective method to induce infection of Phyllachora maydis into corn for tar spot studies in controlled environments. Plant Methods. 19. Article 83. https://doi.org/10.1186/s13007-023-01052-8.
DOI: https://doi.org/10.1186/s13007-023-01052-8

Interpretive Summary: Tar spot of corn is a significant and spreading disease in North, Central, and South America. This disease is caused by the fungal plant pathogen Phyllachora maydis. It has not been possible to reliably induce disease symptoms using the causal pathogen in controlled green house or laboratory environments. Here we present a new methodology for infecting plants with Tar spot in the laboratory. The resulting method allows for the infection of plants under controlled conditions with high levels of replicability. This work will enable future efforts to studying the biology of the fungus, the epidemiology of the disease, and breading efforts for resistance.

Technical Abstract: Tar spot of corn is a significant and spreading disease in North, Central, and South America caused by the obligate biotrophic fungus Phyllachora maydis. Advancements in research and management of this disease have been limited by a need for reliable and effective methods to inoculate plants and produce typical signs and symptoms of tar spot. Phyllachora maydis produces conidia and ascospores within stromata that can incite infection under favorable environmental conditions. The goal of this study was to develop an effective and reliable method to consistently inoculate P. maydis into corn and induce tar spot. Using a newly developed vacuum inoculation method, corn seedlings of different genotypes in the V2 growth stage were inoculated in replicated experiments with spores of P. maydis under greenhouse and growth chamber conditions and all inoculated plants developed stromata characteristic of tar spot. Prior to developing this method, previously reported methods for inoculation of corn with P. maydis were evaluated and none were found to be consistently effective. In the new vacuum inoculation method, the latent period from inoculation to stroma development was <12 days in all repetitions of the method. This is a shorter period than previously reported for this pathogen and provides insight into the potential for rapid growth rates of tar spot epidemics under some environmental conditions. With this new method, we report that tar spot can be consistently established in corn. The novel vacuum inoculation method is a consistent, replicable, and effective method for inoculating corn plants to study tar spot. This method is promising for studying the biology of the fungus, the epidemiology of the disease, and for characterizing and identifying host resistance.