title: Agrobacterium strains isolated from root nodules of common bean specifically reduce nodulation by Rhizobium gallicum.
abstract: In a previous work, we showed that non-nodulating agrobacteria strains were able to colonize root nodules of common bean. Both rhizobia and agrobacteria co-existed in the infected nodules. No impact on symbiosis was found in laboratory conditions when using sterile gravel as a support for growth. In this study, soil samples originating from different geographic and agronomic regions in Tunisia were inoculated with a mixture of agrobacteria strains isolated previously from root nodules of common bean. A significant effect on nodulation and vegetal growth of common bean was observed. Characterization of nodulating rhizobia and comparison with non-inoculated controls showed a biased genetic structure. It seemed that Rhizobium gallicum was highly inhibited, whereas nodulation by Sinorhizobium medicae was favored. Co-inoculation of non-sterile soils with R. gallicum and agrobacteria confirmed these findings. In vitro antibiosis assays indicated that agrobacteria exercised a significant antagonism against R. gallicum.
authors.affiliation: Laboratoire Interactions Légumineuses-Microorganismes, INRST, Hammam-lif, Tunisia.
authors.forename: Moncef
authors.initials: M
authors.lastname: Mrabet
authors.forename: Bacem
authors.initials: B
authors.lastname: Mnasri
authors.forename: Samir Ben
authors.initials: SB
authors.lastname: Romdhane
authors.forename: Gisèle
authors.initials: G
authors.lastname: Laguerre
authors.forename: Mohamed Elarbi
authors.initials: ME
authors.lastname: Aouani
authors.forename: Ridha
authors.initials: R
authors.lastname: Mhamdi
mesh_terms: D000898:Antibiosis; D027805:Phaseolus / Q000254:growth & development / Q000382:microbiology*; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology; D012231:Rhizobium / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification* / Q000502:physiology*; D020579:Sinorhizobium / Q000254:growth & development / Q000502:physiology; D014416:Tunisia