Effect of rhizobacteria on growth and grain protein in wheat

Field-grown wheat, Triticum aestivum L. cv. ProINTA Isla Verde, was inoculated with two Bacillus species, B. simplex and B. firmus, isolated from wheat roots, in four experiments during three years at two sites, Buenos Aires and Castelar, Argentina. Plants were inoculated with a liquid inoculant twenty-two days after sowing, or seeds were pelleted with inoculated peat prior to sowing, according to the experiment. In all experiments a set of plots was left unfertilized, and another set was fertilized with 200 kg N/ha in a split fertilization, 100 kg at sowing and 100 kg at the booting stage. Inoculation affected the results in all experiments, augmenting biomass production by up to 77% in some experiments, through an increase in the number of ears per plot close to 50%. However, as the number of grains per ear was decreased by inoculation by more than 40%, grain yield was not consistently augmented. Inoculation always produced an increase in nitrogen accumulation by the crop, with the inoculated plants showing more than twice the N content of those not inoculated. The most remarkable result due to inoculation was the consistent increase from 9.4% to 15.6% dry matter (DM), with or without N fertilization. Our findings show that inoculation with adequate rhizobacteria consistently increases wheat grain quality and the efficiency of use of the applied fertilizer, with the potential benefit of reducing losses to the environment