Genetic Diversity Among Pseudomonad Strains Associated with Cereal Diseases in Russian Federation

Basal glume rot, caused by Pseudomonas syringae pv. atrofaciens (PSA), has emerged as a major bacterial disease of wheat, barley, and rye in Russia. Forty-nine suspect strains of PSA isolated from diseased cereal plants from different regions of Russia were tentatively identified by production of a fluorescent pigment and confirmed by pathogenicity tests on the host of origin. Each strain was then grouped according to LOPAT (levan, oxidase, potato rot, arginine dihydrolase, and tobacco hypersensitivity) assays. Ten strains were assigned to LOPAT group 1a, 13 to group 1b, 5 to group 2, 4 to group 3, and 16 to group 5. Strains of each group were then characterized by 16S-23S rRNA Intergenic Transcribed Region (ITR) sequencing and fingerprinted by restriction fragment length polymorphism of ITR, and repetitive PCR using REP, ERIC, and BOX primers. A phylogenetic tree constructed from ITR sequence data revealed two discrete clusters, designated “syringae” and “fluorescens”. ERIC-PCR did not work well. However, BOX PCR produced very useful differential genomic fingerprints. There was a high correlation between LOPAT group 1a and BOX PCR patterns. The remaining groups showed a low correlation to BOX PCR patterns and a high level of genetic diversity.