Isolation, Characterization and Evaluation of the Growth-Promoting Properties of Rhizosphere Bacteria in Tomato Plants in Burkina Faso

Abstract

Soil degradation is a major constraint on agricultural productivity. However, the use of rhizobacteria as biofertilizers. Enabling the sustainable recovery of infertile soils. The objective of this study is to evaluate the plant growth-promoting properties of rhizobacteria from tomato plants, for using as biofertilizers. To this end, bacteria were isolated from the tomato rhizosphere using standard laboratory methods. Tests for nitrogen fixation, phosphate solubilization, ammonia, indoleacetic acid, cellulase, and hydrogen cyanide production were performed to evaluate the growth-promoting properties of the bacteria.  A germination test was also performed on two tomato varieties (Mongal and Cobra) using the bacteria as inoculum. The morphological, biochemical, and physiological parameters of the isolates were assessed, and their probable identity was determined using ABIS online software. A total of 225 rhizobacteria were isolated. Preliminary screening allowed the selection of 21 isolates, notably isolates A3, A30, A56, B1, B15, B30, T9, T6, T3, KOM3, KOM1, KOM9, Le13, Le18, Le6, KO15, KO1, KO2, Ki1, and Ki3. These bacteria were capable of both nitrogen fixation, indoleacetic acid production, and ammonia production. Among the selected isolates, 47.61%, 42.85%, and 81.75% were capable of solubilizing phosphate, producing hydrogen cyanide, and synthesizing cellulase, respectively. The vigor index of inoculated grains increased from 755 to 838 compared to the non-inoculated control (750) for the Cobra variety. For the Mongal variety, the vigor indices of the inoculated grains ranged from 605 to 863, compared to the non-inoculated control (548), with 95% of the inoculated isolates showing the best vigor indices. Strains B30 and B1 yielded the highest vigor indices for the Cobra and Mongal varieties, respectively. The ABIS software allowed the isolates to be classified into the genera Pseudomonas (52.38%), Bacillus (28.57%), and Enterobacter (19.05%). These results highlight the potential of these rhizobacterial isolates to be used as biofertilizers to increase tomato production.