Pseudomonas salomonii sp. nov., pathogenic on garlic, and Pseudomonas palleroniana sp. nov., isolated from rice

Abstract

A total of 26 strains, including 15 strains isolated from garlic plants with the typical symptoms of 'Café au lait' disease and 11 strains isolated from diseased or healthy rice seeds and sheaths infested by Pseudomonas fuscovaginae, were compared with 70 type or reference strains of oxidase-positive pathogenic or non-pathogenic fluorescent pseudomonads. The strains were characterized by using a polyphasic taxonomic approach. Numerical taxonomy of phenotypic characteristics showed that the garlic and rice strains were related to each other. However, they clustered into separate phenons, distinct from those of the other strains tested, and were different in several nutritional tests. On the basis of DNA-DNA hybridization, the garlic and rice strains constituted two distinct DNA hybridization groups, indicating that they belonged to separate species. The two groups of strains were also well differentiated by siderotyping. Garlic strains were pathogenic to garlic plants and either weakly pathogenic or non-pathogenic on rice; rice strains were either weakly pathogenic or non-pathogenic on rice and non-pathogenic on garlic. A phylogenetic analysis of 16S rRNA gene sequences confirmed that the two groups of strains belonged to the y-Proteobacteria and to the genus Pseudomonas. The names Pseudomonas salomonii sp. nov. and Pseudomonas palleroniana sp. nov. are respectively proposed for the garlic strains and the rice strains. The type strains are P. salomonii CFBP 2022(T) ( = ICMP 14252(T) = NCPPB 4277(T)) and P. palleroniana CFBP 4389(T) (= ICMP 14253(T) = NCPPB 4278(T)).