Role of PGPB and Endomycorrhizae in Growth and Nutrient Uptake in Foxtail Millet and Sorghum

For biofuels to become economically viable, it is important to maximize the biomass of second generation biofuel crops. Moreover, these crops need to be produced on marginal lands to prevent competition with crop lands used for food production. Bacteria and mycorrhiza that assist plant growth, enhance biomass yield and improve nutrient use could help achieve these goals. To test this hypothesis, we grew foxtail millet (Setaria italica) and sorghum (Sorghum bicolor, inbred line BTx623) in combination with microorganisms on copper mining-impacted stamp sands collected from the Torch Lake site in Upper Peninsula, MI. Prior to sowing, the seeds were subjected to three pretreatments: (1) Plant growth promoting bacteria (PGPB) Pseudomonas sp. TLC 6-6.5-4, (2) endomycorrhizae mix (Glomus intraradices, G. mosseae, G. aggregatum and G. etunicatum), and (3) PGPB + endomycorrhizae mix. Control seeds were left untreated. The seeds were planted in either potting soil or stamp sand. The pots were treated once again with the three microbial mixes described above ten days after sowing. Plants were harvested after 60 days; biomass, shoot height, copper concentration and chlorophyll content were measured. Data indicate that treating plants with PGPB alone or PGPB + endomycorrhizae increased height, shoot biomass and copper accumulation in sorghum and foxtail millet significantly when compared to control or endomycorrhizae alone. In contrast, sorghum and foxtail millet showed a significant decrease in shoot and root biomass when treated with endomycorrhizae mix alone. The role of PGPB and endomycorrhizae in promoting plant growth and nutrient uptake will be discussed.