Agronomy and Horticulture Department


Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professor Tamra A. Jackson. Lincoln, Nebraska: May, 2011

Copyright 2011 Kevin A. Korus


Goss’s wilt and blight of corn, caused by the bacterium Clavibacter michiganensis (Cm) subsp. nebraskensis (Cmn), is currently diagnosed by symptom identification and successful isolation onto CNS selective medium. An ELISA test kit and ImmunoStrips (Agdia®) specific to Cm michiganensis (Cmm) reportedly give a cross-reaction with Cm subspecies. Also, the GEN III OmniLog Identification system (Biolog Inc., Hayward, CA) is said to provide accurate identification of Cm subspecies. These tests would provide a quick and inexpensive method for diagnosis of Cmn but have not been previously validated. ELISA test kits were provided by Agdia for the detection of Cmm, Cm tessellarius (Cmt), and Cm sepedonicus (Cms) as well as ImmunoStrips developed for the detection of Cmm. Also, an ELISA test kit (Neogen®) specific to Cmn was included in the study. For each ELISA and ImmunoStrip, 15 strains of Cmn, 5 Cmm, 5 Cmt, 4 Cms, 3 Cmi and 40 symptomatic leaf samples submitted from widely dispersed commercial corn fields to the UNL Plant & Pest Diagnostic Clinic were tested. The ImmunoStrips were tested with an additional 29 Cmn isolates as well as 17 bacterial isolates outside the genus Clavibacter. All ELISA test kits, except those for Cms, consistently gave positive results for all 40 infected leaf samples. Cmn was confirmed in the leaf samples with Koch’s postulates. When testing cultures, the Cmn, Cmm, and Cmt ELISAs gave consistent positive results. The Cms ELISA gave consistent negative results. ImmunoStrips for Cmm consistently tested positive for cultures of all the Cm subspecies and plant samples infected with Cmn and negative results for those bacteria outside the genus Clavibacter. ELISAs using antibodies specific to Cmm, Cmn and Cmt and ImmunoStrips using antibodies specific to Cmm can be used reliably when testing for the presence of Cmn. Further additions to the GEN III OmniLog ID system may be needed to provide consistent identifications of gram-positive coryneform phytopathogenic bacteria, namely those belonging to the genus Clavibacter