Competitiveness and symbiotic effectiveness of a R. gallicum strain isolated from root nodules of Phaseolus vulgaris

• Published in: European journal of agronomy Vol. 22; no. 2; pp. 209 - 216
• Main Authors: Mrabet, Moncef, Mhamdi, Ridha, Tajini, Fatma, Tiwari, Ravi, Trabelsi, Mustapha, Aouani, Mohamed Elarbi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-02-2005; Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; beans; Biological and medical sciences; competitive ability; Competitiveness; crop yield; Economic plant physiology; Field inoculation; Fundamental and applied biological sciences. Psychology; inoculum; microbial competition; nitrogen fertilizers; nitrogen fixation; nodulation; Phaseolus vulgaris; pods; Rhizobium; Rhizobium gallicum; root nodules; Soil-core microcosms; strain differences; strains; symbiosis; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); yield response; Tunisia; Rhizobium; Soil-core microcosms; Field inoculation; Phaseolus vulgaris; Competitiveness; Symbiotic relation; Root; Microcosm; Plant nodule; Symbiont; Grain legume; Soils; Inoculation; Leguminosae; Vegetable crop; Dicotyledones; Angiospermae; Bacteria; Spermatophyta; Rhizobiaceae
• ISSN: 1161-0301; 1873-7331
• DOI: 10.1016/j.eja.2004.02.006

The rhizobia strain
R. gallicum bv.
gallicum 8a3 was isolated from root nodules of
Phaseolus vulgaris cultivated in Tunisian soils. This strain was selected on the basis of its high symbiotic effectiveness in laboratory conditions. In order to assess its ability to compete indigenous rhizobia, this strain was labelled with
gusA gene. Conservation of initial effectiveness and competitiveness by transconjugants was tested. A transconjugant was introduced in three soil-core microcosms originating from different geographical and agronomic regions. Nodulation monitoring showed that the labelled transconjugant was able to occupy more than 90% of nodules at 30 days after inoculation. The nodule occupancy by the introduced strain was high even in the soil sample of Mateur which showed an MPN value of 10
3
rhizobia/g of dry soil. A significant improvement of plant productivity by inoculation was observed with the three soil samples in green house. Field inoculation with the parental strain showed a significant increase in nodule number, pod number and seed dry weight. The improvement of plant productivity in green house or in field conditions was equal or better than nitrogen fertilisation.