Plant growth-promoting rhizobacteria (PGPR) are known for their potential use as biofertilizers, which can help to reduce the need and cost for synthetic fertilizers. The distribution and quantification of three PGPR in association with corn (Zea mays L.) was determined by the detection of chaperoninQO genes through real-time quantitative PCR. Sphingobacterium canadense, Azospirillum zeae, and Gluconacetobacter azotocaptans were detected at concentrations approaching 106 CFU/g in root tissues and rhizosphere soils in corn-growing regions of Ontario and Québec. Three additional bacterial isolates were recovered from corn rhizosphere soil and roots then identified via colony PCR. Greenhouse trials of all six bacteria as seed inoculants yielded no significant promotion of growth in corn. This study indicated that S. canadense, A. zeae, and G. azotocaptans were detected in locations where previously unknown to be, new PGPR can be isolated, and that a variety of potential PGPR inoculants failed to promote corn growth
