Abstract

This study assessed the tripartite symbiosis of common bean (Phaseolus vulgaris L.) with rhizobia and arbuscular mycorrhizal fungi (AMF) in hydroaeroponic culture under sufficient versus deficient P supplies (250 versus75 µmol P plant^-1 week^-1). The effects of three AMF species on the mycorrhizal root colonization, rhizobial nodulation, plant growth and phosphorus useefficiency were compared in the bean recombinant inbred line (RIL) 147 after transfer from initial sand culture. Although Glomus intraradices well colonized roots of RIL147, in both P levels, Gigaspora rosea weakly colonized roots, and no root-colonization was found with Acaulospora mellea. Mycorrhization byGlomus was also obtained by contact with mycorrhized Stylosanthes guianensis. Significant differences among colonization and nodulation of the roots and plant growth were found between AMF species. Although the results showed that the double inoculation induced a significant increase in all parameters whatever the phosphorus supply in comparison to control.Nevertheless, the highest phosphorus use efficiency and plant total nitrogen were found under P deficiency in both AMF treatments (by contact or by inoculant). It is concluded that phosphorus use efficiency for plant growth and nitrogen fixation could be improved by compatibility between both symbionts (AMF and rhizobia) and common bean genotype.

Key words: Acaulospora mellea, Arbuscular mycorrhizal fungi, Glomus intraradices, Gigaspora rosea, nitrogen fixation, Phaseolus vulgaris, phosphorus, rhizobia, Stylosanthes guianensis, symbiosis.