Interactive Effects of Rhizobium and Arbuscular Mycorrhizal Fungi Reduced Heavy Metal Uptake and Enhanced Antioxidants and Yield in Cicer arietinum L. Grown in Metal Contaminated Sewage Sludge-amended Soil

Reusing sewage sludge as organic amendment and nutrient source for plants is a promising method for managing organic waste; however, its high heavy metal content poses a risk to crop productivity and food security. Synergistic microbial interaction exhibits considerable potential for the bioremediation of heavy metals in sewage sludge. This study evaluated the roles of symbiotic microbes viz. Rhizobium and arbuscular mycorrhizal fungi (AMF) (Funneliformis caledonius and Glomus bagyarajii), on growth, antioxidant enzyme activity, heavy metal uptake, and yield attributes in chickpea grown either in sterilized soil alone (S) or soil amended with 20% sewage sludge (SS). Application of sewage sludge alone significantly increased the antioxidant enzyme activities, MDA content, and heavy metal uptake in chickpea plants. However, co-inoculation of the sludge-amended soil with Rhizobium and AMF reduced the metal uptake and restricted their translocation to the shoots. Dual microbial inoculation also resulted in the highest yield attributes in the chickpea. Heavy metal concentrations were highest in chickpea shoots grown in soil amended with sewage sludge without microbial inoculation, whereas they were lowest in soil inoculated with the combination of Rhizobium + G. bagyarajii. These findings demonstrate that synergistic inoculation of Rhizobium and AMF can effectively mitigate metals stress while improving antioxidant capacity and yield of chickpea grown in sewage sludge amended soil.