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Abstract
Immunodiffusion and an enzyme-linked immunosorbent assay (ELISA) were used to reveal serological relationships between coryneform bacteria responsible for annual ryegrass toxicity (ARGT) and other plant-pathogenic corynebacteria, particularly those associated with similar diseases of grasses, Clavibacter iranicum, Clavibacter rathayi, and Clavibacter tritici. Antisera were raised in rabbits against one strain each of C. iranicum, C. rathayi, C. tritici, and the ARGT bacterium. The antisera were tested against 26 strains belonging to that group of species and one strain each of eight other species of plant-pathogenic corynebacteria. Immunodiffusion with antiserum against the ARGT bacterium did not show cross-reactions with any of the other species tested, whereas, antisera against C. iranicum, C. rathayi, and C. tritici all showed some heterologous cross-reactions. The ELISA revealed cross-reactions undetected by immunodiffusion and allowed the organisms to be grouped by hierarchical cluster analysis. The results indicate that coryneform bacteria pathogenic to Lolium rigidum and responsible for its toxicity to livestock are serologically distinct from the other plant-pathogenic corynebacteria causing similar diseases of grasses. Amino acid analysis of the ARGT bacterium cell wall revealed the presence of 2,4-diaminobutyric acid, indicating that this bacterium should be classified in the genus Clavibacter.
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