Rhizobium leguminosarum symbiovar viciae strains associated with wheat roots display root development stimulating activity and a cooperative behavior with arbuscular mycorrhiza fungi

Rhizobacteria play an unequivocal role in plant health and growth. Although rhizobia establishing a nitrogen-fixing symbiosis with legumes can promote growth in non-legumes, studies on rhizobia associated with wheat roots are scarce. We searched for rhizobia naturally competent for wheat roots colonization using a legume-nodule trapping approach. We isolated rhizobia and tested their ability to colonize wheat roots when co-inoculated with phylogenetically related rhizobia. We found that Rhizobium leguminosarum symbiovar viciae (Rlv) strains isolated from wheat roots as well as a strain previously isolated from pea nodules, were more efficient than other Rlv strains to colonize wheat roots, when co-inoculated. Competitive strains had higher wheat root endophytic colonization ability and were able to stimulate root development and to AM. Non-legumes can be alternative hosts for rhizobia and Rlv might play an important role in wheat root development and establishment of the AM.