Identification and Characterization of Pseudomonas fuscovaginae, the Causal Agent of Bacterial Sheath Brown Rot of Rice, from Madagascar and Other Countries. P. Rott, Plant Pathologist, Laboratoire de Phytopathologie, Institut de Recherches Agronomiques Tropicales et des Cultures Vivrières, CIRAD, BP 5035, 34032 Montpellier, France. J. L. Notteghem, and P. Frossard. Plant Pathologist, Laboratoire de Phytopathologie, Institut de Recherches Agronomiques Tropicales et des Cultures Vivrières, CIRAD, BP 5035, 34032 Montpellier, France, and Plant Pathologist, Laboratoire de Phytobactériologie, GERDAT/CIRAD, BP 5035, 34032 Montpellier, France. Plant Dis. 73:133-137. Accepted for publication 31 May 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0133.

Four unidentified bacterial strains that caused sheath necrosis and sterility of rice spikelets in Madagascar were compared with nine known strains of Pseudomonas fuscovaginae. All 13 strains were pathogenic on rice seedlings and caused symptoms identical to those described for bacterial sheath brown rot. Based on 151 cultural, cytological, physiological, and biochemical characteristics, we demonstrated that the unidentified strains were P. fuscovaginae. Several characteristics distinguish this species from P. marginalis: production of levan, potato soft rot, nitrate reduction, production of 2-ketogluconate, the formation of pits on polypectate gels, and the use of 2-ketogluconate, polygalacturonic acid, and various carbohydrates. The four native strains and nine reference strains of P. fuscovaginae differed in agglutination and indirect immunofluorescence tests using two sera suggesting intraspecies differences. It was possible to distinguish four serological groups. Since various serological results were observed with different reference strains obtained from different collections and originated from the same initial isolation, divergency arising from subculturing must be considered. Four strains of P. marginalis and P. fluorescens tested were only distantly related to P. fuscovaginae, if at all.