Bacillus thuringiensis Strains Isolated from Agricultural Soils in Mali Tested for Their Potentiality on Plant Growth Promoting Traits

Aims: To screen of the multiple plant growth promoting activities of some Bacillus thuringiensis strains isolated from Malian Agricultural soils and evaluate their ability to improve maize seed germination and seedling vigor in vitro.

Study Design: Strains of Bacillus thuringiensis (Bt) used in this study belong to collection of the Laboratory of Research in Microbiology and Microbial Biotechnology (LaboREM-Biotech) isolated from different agricultural soils of Mali.

Methodology: Different tests, namely: Phosphate solubilization, Siderophore production, Indol acetic acid cellulase and chitinase production tests were performed to confirm the PGP characteristic of the insecticidal B. thuringiensis strains screened. In vitro test was performed in the laboratory to confirm the capacity of these bacteria to enhance maize germination and seedling vigor.

Results: All tested Bacillus strains solubilize efficiently insoluble phosphate, but BtI4" showed the highest clearance zone around its colony. In this study, except in BtI4’, the siderophore production was significantly elevated in the other Bt strains tested. Only BtD5 was able to produce Indol acetic acid. Contrary, except BtD5, all the isolates produce chitinase and cellulase. Exept IAA, the isolate BtI4" produce all the tested compounds and showed the highest % seed germination and seedling vigor.

Conclusion: In the current study, plant growth promotion analysis of three B. thuringiensis strains from Malian agricultural soils were assessed in relation with maize seed germination and seedling vigor. These tested Bt strains showed several plant growth-promoting characteristics. These activities may allow the use of these isolates for plant growth promotion. Future work will address the applications of the selected bacteria in biocontrol and plant growth promotion. Insect pest biocontrol, enhancement of plant nutrition and production of phytohormon are the mechanisms involved.