RHIZOBIUM TROPICI NODULATES FIELD-GROWN PHASEOLUS-VULGARIS IN FRANCE

Two hundred and eighty seven isolates of Rhizobium nodulating Phaseolu s vulgaris L. were sampled in France from four geographically distant field populations. They were characterized by their colony morphology and by plasmid profiles. A representative sample was further character ized: a) by the ability of each isolate to nodulate a potential altern ative host Leucaena leucocephala and to grow on specific media, and b) by RFLP analysis of PCR amplified 16S rRNA genes, On the basis of the ir phenotypic and genetic characteristics the isolates could be assign ed either to Rhizobium leguminosarum bv phaseoli, or to R. tropici. Th e two species co-occurred at three sites. R. leguminosarum bv phaseoli represented 2%, 4%, 72% and 100% of the population at the four differ ent sites. Eighteen and 22 different plasmid profiles were identified within R. tropici and R. leguminosarum bv phaseoli, respectively. Some of them were conserved between distant geographical regions. The fact that R. tropici was found in France shows that this species is not li mited to tropical regions and gives additional evidence of the multi-s pecific nature of the Phaseolus microsymbiont, even over a geographica lly limited area.