"Goss's wilt, a bacterial disease of corn caused by Clavibacter michiganensis subsp. nebraskensis (Cmn), has re-emerged in the corn belt of the USA, since 2006. Corn fields in Michigan and Indiana were scouted from 2014 to 2016 for Goss's wilt, and putative Cmn isolates were obtained from corn leaf tissue. Known isolates were obtained from cultures or diseased leaf tissue from Indiana, Iowa, Missouri, and a culture collection at Michigan State University. All Cmn isolates were separated into three virulence groups and biofilm formation for each was observed in vitro. Biofilm formation of a highly virulent and a moderately virulent Cmn isolate was observed in vivo. All isolates produced strong biofilms on TEM grids and the slightly virulent isolate FN produced the most biofilm on glass coverslips. The highly virulent isolate GIL1 exhibited an aggregation phenotype in planta, while the moderately virulent isolate GW-20-E was observed forming biofilms within and around xylem vessels. Examination of epiphytic and endophytic was done to determine if there was any correlation to virulence. Populations of spontaneous rifampicin-resistant mutants of Cmn isolates that differed in virulence were tracked over time on Goss's wilt susceptible hybrids. There was no correlation between virulence and endophytic or epiphytic survival of Cmn."--Page ii.
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