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 HS from cysteine, cystine, and NaSO·5HO, 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, was 67.5%. DNA-DNA homology between T30 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 (=ATCC BAA-144).