VIEW ARTICLE

Genetics

Diversity of Pseudomonas fuscovaginae and Other Fluorescent Pseudomonads Isolated from Diseased Rice. T. Jaunet, UR-PHYMA, CIRAD-CA, 2477 Avenue du Val de Montferrand, B.P. 5035, 34032 Montpellier Cedex 1, France; G. Laguerre(2), P. Lemanceau(3), R. Frutos(4), and J. L. Notteghem(5). (2)(3)Laboratoire de Microbiologie des Sols, and Laboratoire de Recherches sur la Flore Pathogène du Sol, respectively, INRA, 17, rue de Sully, B.V. 1540, 21034 Dijon Cedex, France; (4)BIOTROP-IGEPAM, CIRAD, 2477 Avenue du Val de Montferrand, B.P. 5035, 34032 Montpellier Cedex 1, France; (5)UR-PHYMA, CIRAD-CA, 2477 Avenue du Val de Montferrand, B.P. 5035, 34032 Montpellier Cedex 1, France. Phytopathology 85:1534-1541. Accepted for publication 26 September 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-1534.

Fluorescent pseudomonads associated with sheath brown rot of rice were isolated from rice at low and high elevations in various geographic areas and analyzed for pathogenicity and phenotypic and genetic diversity by biochemical tests and restriction fragment length polymorphism (RFLP) analysis of polymerase chain reaction (PCR)-amplified 16S-rDNA genes. Standard strains of various Pseudomonas species of rRNA homology group I were analyzed along with field-collected isolates. Biochemical characterization revealed 23 groups characterized by different nutritional features. Nineteen of thirty-five rice isolates were identified as P. fuscovaginae (biochemical group G1). Using PCR-RFLP, 25 composite 16S-rDNA haplotypes were found. Parsimony analysis revealed that the P. fuscovaginae isolates were distributed in four 16S-rDNA haplotypes, but they formed a cluster that differentiated them from other rRNA group I Pseudomonas species. All field isolates were pathogenic on rice when introduced by injection. Inoculation of rice without wounding at the booting stage showed that only the four haplotypes of P. fuscovaginae and isolates with haplotypes 7, 9, and 17 were pathogenic. Thus, populations of rice-associated fluorescent pseudomonads comprised both phylogenetically different pathogenic isolates and opportunistic isolates pathogenic on rice only after wounding.