Characterization of symbiotic plasmids in native peanut rhizobia from Cordoba

PONZIO, M., TAURIAN, T., FABRA, A.

Villa Giardino, Córdoba

Jornada; XV Jornadas Científicas de la Sociedad de Biología de Córdoba; 2005

Sociedad de Biología de Córdoba

Abstract Rhizobial species able to induce nodule formation on leguminous plants belong to the family Rhizobiaceae. Peanut (Arachis hypogaea L.) is a legume that establishes symbiotic relationship with rhizobia. In Argentina 94% of national peanut production is concentrated in the province of Cordoba, being an economically important crop for this region. Previous phenotypic studies of native peanut rhizobia isolated from this region revealed the presence of two populations which group within the slow and fast growing rhizobia. Considering these results and that there are no previous reports describing peanut fast-growing rhizobia, the aim of this study is to analyze if their symbitic genes are localized in autotransmissible plasmids as is described for other fast growing rhizobia. Methods: Bacteria: Rhizobium etli CFN42 pSym-, R.tropici CIAT899  pSym-, Sinorhizobium fredii 192 pSym-, native peanut isolates from Cordoba soils: NCHA22 and NET30. Biparental matings (Simons et al., 1983). Nodulation assays (Vincent, 1970). PCR-nodC (Laguerre et al., 2001). Results and Discussion: Transconjugants were obtained from the mating between NET30 and R. tropici CIAT899 pSym-, which induced efficent nodules in peanut and showed the expected 930 bp band from the nodC-PCR amplification. The transconjugants obtained from the mating of NCHA22 and R. etli CFN42 pSym- were not able to nodulate peanut but gave a 930bp product from nodC-PCR. These results suggest that pSym of isolates NET30 y NCHA22 are autotransmissible. Nevertheless pSym of NCHA22 would not be able to confere peanut nodulation capacity to R. etli CFN42.