Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/27/2006
Publication Date: N/A
Technical Abstract: The bacterium Acidovorax avenae causes disease in a wide range of monocotyledonous and dicotyledonous plants, including corn, rice, watermelon, and orchids. The organism is currently classified as several subspecies of A. avenae. To determine the phylogenetic relatedness among strains of A. avenae subsp. avenae, A. avenae subsp. citrulli, and A. avenae subsp. cattleyae, 16S-23S rDNA internally transcribed spacer (ITS) region sequencing, DNA/DNA reassociation assays, and amplified fragment length polymorphism (AFLP) analyses were conducted. Results of ITS sequencing showing a similarity of 97.3% or greater was found among all the strains. The DNA/DNA reassociation assays revealed two distinct species-level taxa among strains of A. avenae subsp. avenae; taxon A included six A. avenae subsp. avenae strains from corn which interrelated at a mean reciprocal similarity of 81.1 % and taxon B included six A. avenae subsp. avenae strains from rice interrelated at a mean reciprocal similarity of 97.0%. A. avenae subsp. citrulli consisted of a single taxon containing 11 strains from cucurbits interrelated at a mean reciprocal similarity of 88.4%. A. avenae subsp. cattleyae consisted of a single taxon containing four strains from orchids which interrelated at a mean similarity of 98.3%. The mean reciprocal relatedness between the four taxa was less than 70%, suggesting species-level relatedness. The AFLP analysis revealed the same four groups (taxa) at a similarity of 40-50%. On the basis of these and previous genetic and phenotypic results, we suggest strains of the four Acidovorax taxa be re-classified at the species rank.