Phaseolus vulgaris is nodulated by phosphate solubilizing strains of Sinorhizobium meliloti in Canary Island soils

Phaseolus vulgaris is nodulated by phosphate solubilizing strains of Sinorhizobium meliloti in Canary Island soils

José Luis Zurdo-Piñeiro¹, Alvaro Peix², Raúl Rivas¹, Milagros León-Barrios², Ana Garrido-Martín³, Ricardo Pérez-Galdona², Pedro F. Mateos¹, Eustoquio Martínez-Molina¹ and Encarna Velázquez¹

¹Departamento de Microbiología y Genética, Facultad de Farmacia, Universidad de Salamanca. SPAIN.

²Departamento de Producción Vegetal. IRNA. CSIC. Salamanca. SPAIN

³Departamento de Microbiología y Biología Celular, Facultad de Farmacia, Universidad de La Laguna, 38071 La Laguna, Tenerife, SPAIN.

⁴Servicio Insular de Agricultura, Cabildo Insular de Lanzarote. SPAIN

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Several strains were isolated from Phaseolus vulgaris plants growing in a soil from Canary Islands. These strains showed a high ability to nodulate and to fix nitrogen in common beans. TP-RPD patterns showed that all strains isolated from highly effective nodules display the same pattern indicating that they belong to the same bacterial species. Sequencing of 16S rRNA was performed in a representative strain, GVPV12, and showed a 99.9% similarity with the type strain of Sinorhizobium meliloti. However, unlike the type strain of Sinorhizobium meliloti all strains isolated in this study were able to solubilize phosphate in vitro. It is remarkable that, although Phaseolus vulgaris is a promiscuous legume that is nodulated by several genera and species of rhizobia including Sinorhizobium fredii, here we described for the first time its nodulation by Sinorhizobium meliloti. This species has been considered for decades as a very specific endosymbiont of the cross-inoculation group of alfalfa. Moreover, until now, the strains of Sinorhizobium fredii nodulating Phaseolus have shown a low effectiveness in symbiosis with this legume. However, the data obtained in this work showed that the strains from S. meliloti isolated in Canary Islands form more nodules per plant and fixes more nitrogen than Rhizobium etli that nodulates Phaseolus vulgaris in American soils.