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Curtobacterium flaccumfaciens pv. beticola, A New Pathovar of Pathogens in Sugar Beet

Bacterial leaf spot of sugar beet was first discovered in 1995 in Inner Mongolia of China. The pathogen was shown to be a bacterium with properties of gram-positive bacteria: small irregular rods, lateral flagella, aerobic, and catalase-positive. The colonies of sugar beet strains produced a pale-yellow pigment. The optimum temperature for the bacteria to grow was 24 to 27°C. The bacteria could utilize a wide range of organic compounds, including hydrolyzed casein, starch, esculin and Tween 80, and released H₂S from cysteine, cystine, and Na₂S₂O₃·5H₂O, but could not produce urease, oxidase, or indole. The cell wall peptidoglycan was based on ornithine (type B2β). The predominant menaquinone was MK-9. Polar lipids contained several glycosyldiacyl-glycerols. The DNA G+C content of a type strain of the new pathovar, T30^T, was 67.5%. DNA-DNA homology between T30^T and Curtobacterium flaccumfaciens pv. flaccumfaciens (International Collection of Micro-Organisms from Plants, New Zealand [ICMP] 2584) was 70.1%. The new pathovar and C. flaccumfaciens pv. flaccumfaciens had 99.9% identity in DNA sequence of 16S rRNA. Close genetic relatedness was observed for the representatives of the species Curtobacterium flaccumfaciens, but a low level of similarity between the different pathovars was found. Based on these physiological, biochemical, chemotaxonomic, phylogenetic, and genetic characteristics, we demonstrate that the pathogen represents a new pathovar of C. flaccumfaciens, for which we propose the name Curtobacterium flaccumfaciens pv. beticola pv. nov. The type strain is T30^T (=ATCC BAA-144^T).