Rhizoglomus intraradices and associated Brevibacterium frigoritolerans enhance the competitive growth of Flaveria bidentis

Our aim was to determine whether there is a synergistic interaction between the arbuscular mycorrhizal (AM) fungus Rhizoglomus intraradices and the bacterium Brevibacterium frigoritolerans, and to understand how R. intraradices and B. frigoritolerans affect the competitive growth of Flaveria bidentis (L.) Kuntze in nutrient-deficient soil. Pot culture of F. bidentis and Eclipta prostrata (L.) L. under nutrient-limited soil conditions was used to test the effect of R. intraradices and B. frigoritolerans on the competitive growth of F. bidentis. Inoculation with B. frigoritolerans and co-inoculation with R. intraradices and B. frigoritolerans increased the biomass of F. bidentis, and a single inoculation of B. frigoritolerans gave E. prostrata a competitive advantage over F. bidentis. However, we found higher R. intraradices colonization of exotic F. bidentis roots than native E. prostrata roots. R. intraradices and B. frigoritolerans probably play different roles in the invasion of F. bidentis. R. intraradices may give the invader a competitive advantage through the accumulation of higher foliar levels of N, and B. frigoritolerans may facilitate the uptake of available N from the soil. Therefore, the results support the hypothesis that the AM fungus-soil bacteria cooperation makes N available to F. bidentis and facilitates its competitive growth.