In vitro exploration of Acinetobacter strain (SG-5) for antioxidative potential and phytohormone biosynthesis in...

Cadmium (Cd) poses serious threats to plant growth and development, whereas the use of plant growth-promoting rhizobacteria (PGPR) has emerged a promising approach to diminish Cd retention in crops. A pot experiment was conducted to evaluate the effect of Cd tolerant strain Acinetobacter sp. SG-5 on growth, phytohormonal response, and Cd uptake of two maize cultivars (3062 and 31P41) under various Cd stress levels (0, 5, 12, 18, 26, and 30 μM CdCl₂). The results revealed that CdCl₂ treatment significantly suppressed the seed germination and growth together with higher Cd retention in maize cultivars in a dose-dependent and cultivar-specific manner with pronounced negative effect in 31P41. However, SG-5 strain exerted positive impact by up-regulating seed germination traits, plant biomass, photosynthetic pigments, enzymatic and non-enzymatic antioxidants, endogenous hormone level indole-3-acetic acid (IAA), abscisic acid (ABA), and sustained optimal nutrient's levels in both cultivars but predominantly in Cd-sensitive one (31P41). Further, Cd-resistant PGPR decreased the formation of reactive oxygen species in terms of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) verified through 3, 3'-diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) analysis in conjunction with reduced Cd uptake and translocation in maize root and shoots in comparison to controls, advocating its sufficiency for bacterial-assisted Cd bioremediation. In conclusion, both SG-5 inoculated cultivars exhibited maximum Cd tolerance but substantial Cd tolerance was acquired by Cd susceptible cultivar-31P41 than Cd-tolerant one (3062). Current work recommended SG-5 strain as a promising candidate for plant growth promotion and bacterial-assisted phytomanagement of metal-polluted agricultural soils.