Can a diazotrophic endophyte originally isolated from lodgepole pine colonize an agricultural crop (corn) and promote its growth?

• Paenibacillus polymyxa P2b-2R bacteria colonized corn rhizosphere & root tissues endophytically.
• Significant growth promotion in P2b-2R inoculated corn seedlings.
• P2b-2R inoculated corn seedlings derived 20% of foliar N from atmosphere.
• Results suggest that this bacterial strain might have a broad range of plant hosts.

Several diazotrophic Paenibacillus strains were isolated from extracts of surface-sterilized lodgepole pine seedling and tree tissues. One strain, Paenibacillus polymyxa P2b-2R, was found to fix high amounts of nitrogen when reintroduced to the gymnosperms, lodgepole pine and western red cedar. We wanted to determine if P. polymyxa P2b-2R could colonize rhizosphere and internal tissues, fix N and promote growth of corn (Zea mays L), an important agricultural crop. We inoculated corn seeds with P. polymyxa strain P2b-2R and grew seedlings for 30 days. Corn seedlings were harvested 10, 20 and 30 days after inoculation for evaluation of endophytic and rhizospheric colonization as well as nitrogen fixation and growth promotion. P2b-2R successfully colonized the rhizosphere as well as internal root tissues of corn (i.e., endophytically) with population densities near 106 cfu. Corn seedling growth was promoted significantly by inoculation with P2b-2R with an increase of up to 35% in length and up to 30% in biomass after 30 days of inoculation. Seedlings inoculated with P2b-2R derived up to 20% of foliar nitrogen from atmosphere after 30 days of inoculation, which is significant considering the fact that this was a short growth trial. These results suggest that P. polymyxa P2b-2R might have a broad range of plant hosts and is able to fix N and promote the growth of at least one important agricultural crop i.e. Corn.

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