Enhanced Plant Performance in Cicer arietinum L. Due to the Addition of a Combination of Plant Growth-Promoting Bacteria

Current agriculture is based on external fertilizers that jeopardize soil fertility. Alternative fertilization systems might come from the use of soil-borne bacteria with plant growth enhancing ability. Here, six bacterial strains that produce varying concentrations of indole acetic acid (IAA) were tested individually and in consortia for plant growth promotion and fitness-related traits of Cicer arietinum. The nitrogen fixer Mesorhizobium ciceri consistently increased biomass production and N content. In the absence of this strain, IAA Psedomonas putida and Bacillus megaterium hindered plant growth and fitness-related traits. The application of mixes of the three strains always resulted in better plant performance when M. ciceri was present. Mixes that included a P. putida strain that produced low levels of IAA appeared more likely to promote plant growth than mixes that included P. putida strains that produced high levels of IAA or mixes that included B. megaterium. The low levels of IAA produced by the selected strains, compared to the high IAA-producing strains had a significantly greater positive effect on plant biomass accumulation, flower, pod, and seed production, and total plant nitrogen and nitrogen concentrations in seeds.