The Relationship between Auxin Producing Rhizobacteria and Wheat Biomass Productivity Alimamy Fornah, Plant and Soil Sciences, Oklahoma State University, Stillwater, OK and Michael P. Anderson, Oklahoma State University, Stillwater, OK. Auxin a plant growth promoting hormone is known to be produced by many if not all bacteria. Some have suggested that auxin is associated with either positive or negative plant growth promotion. We determined the relationship between auxin production capacity in bacteria that are associated with the wheat plants and wheat biomass productivity. A set of 20 wheat plants were randomly selected, grown under greenhouse conditions in two soil types namely, Perkins (Teller fine sandy loam) and Greenhouse soil (Easpur loam). The biomass of all 96 set of plant were recorded. A total of 2880 individual bacteria were isolated from the rhizosphere and endorhizosphere of the Perkins and rhizosphere of the Greenhouse soil. Isolates were dilution plated categorized based on colony diameter as large (> 2mm) and slow (< 2mm) growing bacteria. The bacteria were assayed based on the Salkowski reagent and differences among soil types, colony diameter and biomass association was determined. The relationship between auxin production capacity by bacteria and wheat biomass was negative to non – significant. Auxin production capacity produced by bacteria in the endorhizosphere was significantly higher than in the rhizosphere in the Perkins Soils. Fast growing isolates produced significantly higher auxin capacity than slow growing isolates in both soils. There was a significant relationship between cell growth and auxin production capacity in both fast and slow growing bacteria. There was no significant difference between soils. The result suggests that auxin production capacity by bacteria cannot be used as an indicator rhizobacteria for wheat growth promotion.