Comparative Analysis of Pre-Germination and Post-Germination Inoculation Treatments of Zea mays L. to Mitigate Chromium Toxicity in Cr-Contaminated Soils

The release of heavy metals in the environment is a serious threat causing health hazards to living beings. Hence, it is essential to remediate chemical contamination for a safe environment. Bioremediation is considered one of the most cost-effective and sustainable agricultural techniques, in contrast with other conventional methods to reduce chromium toxicity in agricultural lands polluted with chromium, as it is a natural way to mitigate the toxic effects of hexavalent chromium with simultaneous amelioration in the growth of plants. In the current study, an attempt was made to reduce toxicity of chromium by using six plant growth-promoting chromium-resistant bacteria (Bacillus pumilus (ALa), Bacillus atrophaeus (BL2), Bacillus cereus (AR), Staphylococcus lentus (E3), T2aii and W6ii) for enhancing the growth of Zea mays L. in soil contaminated with chromium. In this regard, a pot experiment was conducted with pre-germination and post-germination inoculation treatments to Zea mays seeds in the presence of chromium stress, i.e., 200, 400, and 600 mu g/ml. Our results have shown that toxicity of chromium caused a reduction in photosynthetic pigments and protein content together with reduction in growth parameters of plants, while treatments with chromium-resistant PGPB significantly enhanced chromium tolerance in treated plants compared with non-inoculated treatments in the presence of chromium stress. The present investigation suggests that applying post-germination inoculation treatments is an effective technique for improved plant growth and heavy metal alleviation in metal-contaminated soil. Thus, our current work revealed an incentive approach toward the green revolution in the age of industrialization by exploring beneficial chromium-tolerant auxin-producing microbes.