In this study, Rhizobium rhizogenes-mediated root proliferation system in Sedum alfredii has been established.Twenty strains of R. rhizogenes were screened for root proliferation. A significant difference (P < 0.01) wasobserved in plant morphological characters under influence of different bacterial strains. The highest root freshweight (3.236 g/plant) was observed with strain AS12556. Furthermore, significant difference (P < 0.05) wasobserved in the chemical composition of organic acids, Tartaric acid (TA), Succinic acid (SA), Malic acid (MA),Citric acid (CA) and Oxalic acid (OA), pH, Total Nitrogen (TN), Total Organic Carbon (TOC) and soluble sugars inroot exudates with different R. rhizogenes mediated roots. Furthermore, a series of hydroponics experiments wereconducted with varying concentrations of Cd (25, 50 and 75 μM) and Zn (100, 200 and 500 μM) to assess thephytoextraction efficiency of proliferated roots with Rhizobium. Several plants with proliferated roots showedenhanced growth and improved metal extraction efficiency. Five strains (LBA 9402, K599, AS12556, MSU440and C58C1) were identified as potential strains for root proliferation in Sedum alfredii. R. rhizogenes strainAS12556 improved Cd/Zn phytoextraction by exogenous production of phytochemicals to promote root proliferation,improved shoot biomass, lowered oxidative damage and enhanced phytoextraction efficiency inS. alfredii. Therefore, it has been selected as a potential microbial partner of S. alfredii to develop extensiverooting system for better growth and enhanced phytoremediation potential. Results suggest that R. rhizogenesmediated root proliferation system can be used for optimizing metal extraction from contaminated soils.
