Phenotypic and genetic diversity of Pseudomonas syringae isolates recovered from different host plants

Abstract

Seventy three isolates of fluorescent Pseudomonas recovered in Asturias (Spain) from plants with disease symptoms were characterized. Diversity was revealed by results of nutritional and biochemical tests, and by PCR amplifications of genes involved in the biosynthesis of levan (lsc) and phytotoxin production (phtE, syrB1-syrB2, and syrD). The isolates were grouped in two main clusters by comparison of 26 features. Cluster A (S = 0.90) included 35 isolates and a control strain of pathovar (pv) phaseolicola. Cluster B displayed a higher heterogeneity, with most isolates (29) grouping in one subcluster (B3) together with a control strain of pv syringae (S = 0.83). Three other subclusters included isolates that differed from pv syringae by being negative for lipodepsipeptide production (B1), positive for pectinolytic activity (B2), or negative for levan production and/or lsc genes (B4). However, they were still related to pv syringae at S = 0.78-0.72, and analysis of their 16S rDNA sequences supported their assignation to P. syringae.