Investigation of PGPR's potential to promote growth in maize (Zea mays L.) under chromium and cadmium stress

Corn is an important cereal crop after wheat and rice in various regions of the world. It is used by animals as well as human beings. Industrialization, urbanization and other anthropogenic activities have significantly elevated the concentration of heavy metals in the biosphere. Agricultural crops are facing heavy metal contamination. Cadmium (Cd) and chromium (Cr) are particularly concerning heavy metals due to their documented phytotoxicity and zootoxicity even at low levels. In this regard, plant growth promoting rhizobacteria (PGPR) offer a clean and green solution of bioremediation of these heavy metals. During the current study, already isolated chromium and cadmium resistant bacterial strains i.e., Pseudomonas aeruginosa (EH2), Pseudomonas songnensis (GR3), Bacillus bingmayongensis (KH3) and Bacillus tropicus (LS5) were selected to observe their beneficial impact on the increase production of corn in chromium and cadmium stress (150 & 250 µg/mL). Minimum inhibitory concentration (MIC) of these bacterial isolates was recorded for chromium and cadmium stress. Plant microbe experiment was conducted and various growth as well as biochemical parameters were measured. Results showed that these PGPR significantly alleviated the toxic effects of chromium and cadmium stress and improved the production. Maximum possible enhancement in growth parameters i.e., root and shoot length, number of leaves and fresh weight was observed up to 47, 41, 70 and 56% in plants treated with P. songnensis (GR3), B. bingmayongensis (KH3), P. songnensis (GR3) and B. bingmayongensis (KH3) respectively. Enhancement in total chlorophyll and protein content of treated plants with P. aeruginosa (EH2) was noted up to 21 and 13% respectively as compared to control. In chromium and cadmium contaminated soil, these bacterial strains can be employed to ameliorate plant growth and reduce heavy metal phytotoxicity