Propagation Host Affects the Mycorrhiza-Mediated Cd Toxicity Alleviation in Cocoa (Theobroma cacao L.) Seedlings and Restoration of Soil Aerobic Mesophyll Microflora

The contamination of agricultural soil represents an environmental and human health risk factor. Arbuscular mycorrhizal (AM) fungi have shown great potentials as toxic metal bioalleviator in agricultural settings. Nonetheless, the field response of AM fungi-mediated toxic metal tolerance in important agricultural crops has been jeopardized owing to limited understanding of complex interactions undergone between the formers and the components of the mycorrhizosphere. An experiment was conducted to evaluate the response of a consortium of AM fungi inoculum resulting from various propagation hosts and/or host systems on cocoa growth, Cd uptake, and antioxidant system as well as soil microbial restoration under Cd stress. The data demonstrated Cd buildup in cocoa shoots in proportion to soil Cd intoxication levels. Following AM fungi colonization into seedlings’ roots, Cd uptake and translocation in shoot parts decreased dramatically, with varying patterns with regard to propagation systems. A significantly low root-to-shoot translocation of Cd (TF = 0.09) was recorded upon producing the inoculum with a combination of sorghum (S. bicolor) and groundnut (A. hypogaea L). The principal component analysis disclosed a negative correlation between Cd retention and soluble flavonoid biosynthesis (− 36.15%) as well as a drop in specific activities of superoxide dismutase (SOD, − 43.05%), phenylalanine ammonia-lyase (PAL, − 21.73%), guaiacol peroxidase (GPX, − 99.74%), and fumarase (− 77.77%). Also, a significant increase of soil aerobic mesophyll microflora was recorded (+ 925.98%). These findings unveil a promising track toward standardization of mycorrhizal efficiency through propagation host.