Infra- and Intraspecific Classification of Pseudomonas solanacearum Strains, using Whole Cell Fatty Acid Analysis

Whole cell fatty acid patterns of 69 strains of the plant pathogenic bacterium Pseudomonas solanacearum were determined by capillary gas liquid chromatography (GLC). Strains originated from 17 different hosts from many parts of the world covering four biovars and three (pathogenic)races as well as Zingiber strains. Identity of strains was confirmed by conventional biochemical and pathogenicity tests. Multivariate analysis of fatty acid data produced four infraspecific clusters. Three of these clusters corresponded to races 1, 2 and 3, the fourth consisted of five deviating race 1 biovar 1 strains from the U.S.A. Biovar 4 strains of Zingiber were found in the race 1 cluster. Only one biovar 3 strain from this host behaved differently. In contrast to conventional tests it was possible to discriminate between avirulent strains of different races. From unknown strains the race can be determined, using a reference library. The use of the term 'pathovar' instead of 'race' is discussed. Intraspecific relationships between P. solanacearum and four related species (P. caryophylli, P. cepacia, P. gladioli, P. pickettii)of rRNA group II were studied also, using fatty acid analysis. The taxonomic pattern found in DNA-DNA homology studies of these species was confirmed.