Biochemical traits of Bacillus subtilis MF497446: Its implications on the development of cowpea under cadmium stress and ensuring food safety.

ABSTRACT

The present study aimed at assessment of different application methods of Bacillus subtilis MF497446 to induce development of cowpea ensuring food safety under cadmium (Cd) stress. Also, isolation, plant growth promoting (PGP) traits and 16 S rRNA-based identification of Bacillus subtilis MF497446 is documented. Out of 24 Bacillus isolates (AS1-AS24), only four isolates (AS4, AS12, AS14 and AS22) showed greater Cd tolerance up to 18 mg L-1. The greatest PGP traits under Cd stress were displayed by Bacillus isolate (AS12); which, also, enhanced seedling elongation and vigor index of cowpea under Cd stress. Phylogenetic analysis, based on 16 S rRNA, confirmed that this promising Bacillus isolate (AS12) belongs to Bacillus subtilis and is referred to as B. subtilis MF497446. Treatment of inoculation+soaking for 90 min of cowpea seeds by B. subtilis MF497446 resulted in the best development of cowpea plants under Cd stress (up to 9 mg kg-1); as fresh and dry masses of cowpea increased from 6.80 to 1.54 to 12.35 and 2.59 g plant-1, respectively. Moreover, shoot and root lengths were 19.66 and 28.33 cm when cowpea seeds were treated by B. subtilis MF497446 (inoculation+soaking for 90 min) compared to 11.33 and 10.66 cm, respectively, for control (Cd stress only). Application of B. subtilis MF497446 (as inoculation+soaking for 90 min) reduced Cd accumulation and bioconcentration factor in cowpea plants by 29.2 and 28.9%, respectively, compared to control (Cd stress only). These results clearly reveal that applying of B. subtilis MF497446 to crops grown on Cd-contaminated soil enhances plant growth and eliminates (or at least diminishes) the risks to human health ensuring food safety.