Rhizobium leguminosarum symbiovar viciae strains are natural wheat endophytes and can stimulate root development and colonization by arbuscular mycorrhizal fungi

Abstract

O_LIAlthough rhizobia establishing a nitrogen-fixing symbiosis with legumes are also known to promote growth in non-legumes, studies on rhizobia association with wheat roots are scarce. C_LIO_LIWe searched for Rhizobium leguminosarum symbiovar viciae (Rlv) strains naturally competent for wheat roots colonization. We isolated 20 strains and tested the ability of a subset for wheat roots colonization when co-inoculated with other Rlv. We also measured the effect of these strains on wheat root architecture and Arbuscular Mycorrhizal Fungal (AMF) colonization. C_LIO_LIWe found a low diversity of Rlv in wheat roots compared to that observed in the Rlv species complex. Only a few strains, including those isolated from wheat roots, and one strain isolated from pea nodules, were efficient to colonize wheat roots in co-inoculation conditions. These strains had a high ability for endophytic colonization of wheat root and were able to stimulate root development and AMF colonization in single strain inoculation conditions. C_LIO_LIThese results suggest that wheat is an alternative host for some Rlv; nevertheless, there is a strong competition between Rlv strains for wheat root colonization. Furthermore, our study suggests that the level of endophytic colonization is critical for Rlv ability to promote wheat growth. C_LI