Clavibacter: a new genus containing some phytopathogenic coryneform bacteria, including Clavibacter xyli subsp. xyli sp. nov., subsp. nov. and Clavibacter xyli subsp. cynodontis subsp. nov., pathogens that cause ratoon stunting disease of sugarcane and Bermudagrass stunting disease.
The 23 strs. of coryneform bacteria examined comprised 17 sugarcane strs. from Fla., La., South Africa, Brazil and Japan and 6 Bermudagrass [Cynodon dactylon] strs. from Fla. and Taiwan. All contained 2,4-diaminobutyric acid, rhamnose and fucose in their cell walls, suggesting a relationship to some other phytopathogenic corynebacteria and related organisms with similar cell wall compositions. The cellular protein patterns of the sugarcane and Bermudagrass strs. after polyacrylamide gel electrophoresis resembled patterns of Corynebacterium michiganense sspp. more than those of some other diaminobutyric acid-containing taxa. The protein patterns of the sugarcane strs. were distinct from those of the Bermudagrass strs. examined. The guanine + cytosine contents of the DNA of 2 sugarcane strs. and 1 Bermudagrass str. were 66 mol%. The sugarcane and Bermudagrass strs. formed a homogeneous group based on morphological characteristics and most biochemical characteristics. All of the sugarcane strs. were nonpigmented (white) and grew more slowly in culture than the yellow Bermudagrass strs. The latter, unlike the former, hydrolyzed starch and utilized citrate and malate. It is proposed that coryneform bacteria with 2,4-diaminobutyric acid in the peptidoglycans of their cell walls (including C. michiganense) be reclassified in Clavibacter. The sugarcane and Bermudagrass pathogens are described as C. xyli ssp. xyli and ssp. cynodontis respectively.