Variation in Virulence of Goss’s Bacterial Wilt and Blight Pathogen Clavibacter michiganensis subsp. nebraskensis Strains in the Maize Inbred Lines

Goss’s bacterial wilt and blight is caused by gram positive bacterium Clavibacter michiganensis subsp. nebraskensis (Cmn).  The disease was observed in 1969 in the state of Nebraska following which it spread to the neighboring states including Kansas, Colorado and Wyoming.  Goss’s wilt was only seen occasionally until it reemerged in 2006 with widespread range in the western Corn Belt and raised concerns among the corn industry.  Previous studies have indicated the existence of population structure and genetic diversity among the Cmn strains.  The objective of this study is to assess the Cmn strain - maize line interaction to characterize the variation in virulence of Cmn strains in maize inbred lines with different tolerance levels to Goss’s wilt.  We conducted pathogenicity assay with five geographically and genetically diverse Cmn strains and four maize inbred lines with varying tolerance levels to the disease.  Results revealed that the Cmn strains vary significantly in their virulence across the maize inbred lines and the maize lines have significant differences in the level of tolerance to Cmn.   However, the Cmn strain - maize line interaction was not significant.  Selection of Cmn strains appears to be important for artificial inoculations in genetic and breeding studies with Goss’s wilt.  Recently, the studies have been initiated to understand the Cmn genome and to characterize the population structure of Cmn strains.