Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2005
Publication Date: 8/1/2005
Citation: Barta, T.M., Willis, D.K. 2005. Biological and molecular evidence that pseudomonas syringae pathovars coronafaciens, striafaciens, and garcae are likely the same pathovar. Journal of Phytopathology. 153:492-499. Interpretive Summary: We used a combination of molecular, physiological, and disease assays to analyze the relationship among several plant pathogenic bacteria. We discovered that three bacterial pathogens that cause disease on oats and coffee are actually the same bacterium. Although coffee is not grown commercially in the U. S., oats are a major agricultural product. Implications of this work include the possible need to screen imported coffee for potential oat pathogens that could affect agriculture in the grain growing regions of the United States.
Technical Abstract: Using a combination of physiological tests, molecular analysis and pathogenicity assays, we investigated the taxonomic relationship among the oat pathogens Pseudomonas syringae pv. coronafaciens (halo blight) and P. syringae pv. striafaciens (bacterial stripe) and the coffee pathogen P. syringae pv. garcae (bacterial blight). P. syringae pvs. coronafaciens and garcae produce tabtoxin while P. syringae pv. striafaciens is tabtoxin deficient. Physiological tests did not show significant differences among these three pathovars. Analysis using DNA “fingerprint” and Southern blot analysis revealed that P. syringae pvs. coronafaciens, striafaciens and garcae are molecularly very similar except that pv. striafaciens appears to have lost part or all of the tabtoxin biosynthetic region. Significantly, P. syringae pv. garcae was pathogenic on oat leaves and indistinguishable from P. syringae pv. coronafaciens in our laboratory assays. Introduction of tabtoxin biosynthetic region contained on the cosmid pRTBL823 resulted in tabtoxin production by P. syringae pv. striafaciens and the production of lesions on oat leaves that were indistinguishable for those caused by P. syringae pv. coronafaciens. Taken together, our data strongly suggests that the P. syringae pathovars coronafaciens, striafaciens, and garcae are taxonomically redundant.