Differential effects of plant growth-promoting bacteria on invasive and native plants.
A total of 390 bacterial strains were obtained from rhizosphere soils of an invasive plant, Ageratina adenophora, and common native plants. These strains were evaluated for their plant growth-promoting (PGP) characteristics, including IAA and siderophore production and phosphate solubilization. These traits were dependent on bacterial phylogenetic position but independent of isolation sources. Twenty-four phylogenetically distinct strains were selected and evaluated for their effects on the plant performance of A. adenophora and the two native plants Fallopia multiflora and Arthraxon lanceolatus. All strains had a neutral influence on germination rate; however, the germination timing and aboveground and belowground growth of the three tested plants were significantly changed. Among all tested strains, 20.8% and 16.7% were beneficial for the aboveground and belowground growth of A. adenophora, but none were beneficial to the two native species. In contrast, no strain negatively affected the performance of A. adenophora, but more than half of the strains showed detrimental effects on the belowground growth of the two native species, and approximately half of them delayed the germination timing of F. multiflora. The phylogenetic position of strains distinctly affected plant performance. The bacteria accumulated in the rhizosphere soil of A. adenophora showed a host-specific growth-promotion of A. adenophora; however, such bacteria showed no more detrimental effects on the growth of the two native species than those inhabiting the native plants. Our data suggested that the increased bacterial number and altered species structure in the soils were able to provide a competitive advantage to A. adenophora after invasion.