Ameliorative effect of co-application of Bradyrhizobium japonicum EI09 and Se to mitigate chromium stress in Capsicum annum L.

Abstract

The present study was conducted to explore the potential of Bradyrhizobium japonicum EI09 (EI09) and selenium (Se) alone or in combination to mitigate hexavalent chromium (Cr⁶⁺) stress in Capsicum annum L. Chromium stressed plants exhibited significant reduction in biomass, chlorophyll content and gas exchange characteristics. The inoculated seedlings subjected to Cr⁶⁺stress showed improvement in growth, proline content, gas exchange attributes and total soluble proteins. Likewise, inoculated C. annum seedlings exhibited augmented activity of ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) under Cr⁶⁺ stress. The Cr⁶⁺ stress mitigation in inoculated seedlings was ascribed to reduction in malondialdehyde (MDA) content, hydrogen peroxide (H₂O₂) besides increase activity of flavonoids, proline, phenolic content along with modulation of antioxidative enzymes. The growth-enhancing attributes of bacteria such as indole acetic acid (IAA) content and 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity enhanced growth in Cr⁶⁺-stressed plants. Moreover, co-treatment of EI09 and 5 µM Se effectively mitigated Cr (VI) stress in C. annum plants. Current studies provide a novel insight into potential of B. japonicum EI09 and Se in reduction of Cr⁶⁺ toxicity in C. annum plants.

Keywords:

• Antioxidant
• chromium
• stress
• Capsicum annum
• PGPR