Submitted to: Systematic and Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2008
Publication Date: 11/24/2008
Citation: Schaad, N.W., Postnikova, E.N., Claflin, L.E., Vidaver, A.K., Agarkova, I., Sechler, A.J., Ignatov, A., Ramundo, B.A. 2008. Transfer of acidovorax avenae subspecies to mesothermophilus avenae. Systematic and Applied Microbiology. 31:434-446. Interpretive Summary: The bacterium Acidovorax avenae causes disease in a wide range of plants, including, corn, rice, watermelon, melon, pumpkin and orchids. Relatedness between and among plant pathogenic strains and non-phytopathogenic strains and related species was determined by genetic analysis. The analysis showed the plant pathogens to be highly related but only distantly related to non-plant pathogenic Acidovorax strains. DNA similarity assays among the phytopathogenic strains revealed four distinct types of A. avenae, grouped by host range. The relatedness between groups was less than 70% and all four groups were easily differentiated from each other and from A. facilis, the type species of Acidovorax. On the basis of these and previous results, we propose that these groups be removed from the genus Acidovorax and renamed as species of Mesothermophilus.
Technical Abstract: The bacterium Acidovorax avenae causes disease in a wide range of plants, including, corn, rice, watermelon, melon, pumpkin and orchids. Taxonomic relatedness among strains of plant pathogenic A. avenae subspecies avenae, citrulli, and. cattleyae, and between the plant pathogenic strains and non-phytopathogenic A. facilis, Comamonas testosteroni and Pseudomonas pseudoalcaligenes was determined by 16S rDNA and 16S-23S rDNA internally transcribed spacer (ITS) region sequencing, DNA/DNA reassociation assays, amplified fragment length polymorphism (AFLP) analysis, and phenotypic characterization. Results of 16S rDNA and ITS sequencing showed the plant pathogens to be highly related but only distantly related to the non-plant pathogenic Acidovorax strains. The DNA/DNA reassociation assays among the phytopathogenic strains of A. avenae revealed four (A, B, C, and D) distinct genotypes. Taxon A contained only corn strains; taxon B contained only rice strains; taxon C contained only watermenlom, melon, and pumpkin strains and taxon D contained only orchid strains, The mean reciprocal relatedness between taxa A, B, C, and D was less than 70% and all four taxa were easily differentiated phenotypically and by AFLP profiles from each other and from A. facilis, the type species of Acidovorax. On the basis of these and previous genetic and phenotypic results, we propose that taxa A, B, C, and D strains be removed from the genus Acidovorax and renamed as Mesothermophilus avenae gen. nov. comb. nov., M. oryzae gen. nov. sp. nov., M. citrulli gen. nov. comb. nov., and M. cattleyae gen. nov. comb. nov, respectively.