Burkholderia fungorum promotes common bean growth in a dystrophic oxisol

Burkolderia fungorum and Azospirillum brasilense are species commonly found in soils, and have been shown to be plant growth-promoting rhizobacteria (PGPR). This study examined the effect on the growth of the common bean plant of three strains belonging to B. fungorum and A. brasilense species inoculated alone or co-inoculated with Rhizobium tropici CIAT 899(T) (commercial inoculant strain). The ability of PGPR strains to improve bean growth in the presence of mineral nitrogen was also studied. CIAT 899(T) co-inoculated with B. fungorum UFLA 04-155 and UFLA 04-226 and A. brasilense BR 11001(T) did not show any benefits for bean growth. However, inoculation with B. fungorum UFLA 04-155 alone resulted in increased dry weight of the nodules and shoots, increased foliar contents of P, Mg, Cu, Fe, K, Ca, S, and Zn, and fostered nodulation by the indigenous rhizobia community. Plant growth promotion by B. fungorum UFLA 04-226 was stimulated in the presence of nitrogen fertilizer in experiments using potted plants. The results indicate the potential ability of B. fungorum to promote growth of the common bean plant under natural conditions.