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The tripartite symbiosis of common bean (Phaseolus vulgaris L.) recombinant inbred line (RIL) 147 with rhizobia and arbuscular mycorrhizal fungi (AMF) was assessed in sand culture by comparing the effects of three AMF species on the mycorrhizal root colonization, rhizobial nodulation, plant growth and phosphorus use efficiency for symbiotic nitrogen fixation. Although Glomus intraradices well colonized roots of RIL147, Gigaspora rosea and Acaulospora mellea weakly colonized roots-plants. Higher colonization by Glomus was also obtained by contact with mycorrhized Stylosanthes guianensis. Significant differences among colonization and nodulation of the roots and growth were found between AMF species. Although the results showed that the double inoculation, especially with Glomus, induced a significant increase in all parameters whatever the AMF treatments in comparison to the control. In addition, the combined inoculation of Glomus and CIAT899 strains resulted in significantly higher nitrogen and phosphorus accumulation of common bean plants and improved phosphorus use efficiency compared with their controls which were not dually inoculated. It was concluded that phosphorus use efficiency for plant growth and nitrogen fixation could be improved by compatibility with arbuscular mycorrhizal fungi, rhizobial strain and common bean genotype, same under P limited.
Key words: Acaulospora mellea, arbuscular mycorrhizal fungi, Glomus intraradices, Gigaspora rosea, nitrogen fixation, Phaseolus vulgaris, phosphorus, rhizobia, Stylosanthes guianensis, symbiosis.