Effective plant-endophyte interplay can improve the cadmium hyperaccumulation in Brachiaria mutica

Soil contamination due to cadmium (Cd) is a ubiquitous environmental problem for which inexpensive remediation alternatives are required. Phytoaccumulation, the use of plants to extract and accumulate heavy metals from the contaminated environment, is such an alternative. In this study, we aimed at establishing effective plant-bacteria interplay between Brachiaria mutica and Cd-resistant endophytic bacteria eventually leading to improved phytoremediation. B. mutica was grown in a Cd-contaminated soil and inoculated with three Cd-tolerant endophytic bacteria individually as well as in combination. Plant physiological parameters, biomass production, bacterial colonization, and Cd-accumulation were observed at four different Cd exposures, i.e., 100, 200, 400 and 1000 mg kg^-1 of soil. The combined application of endophytic bacteria was more effective as compared to their individual applications at all concentrations. Nevertheless, highest performance of consortium was seen at 100 mg Cd kg^-1 of soil, i.e., root length was enhanced by 46%, shoot length by 62%, chlorophyll content by 40%, and dry biomass by 64%; which was reduced with the increase in Cd concentration. The bacterial population was highest in the root interior followed by rhizosphere and shoot interior. Concomitantly, plants inoculated with bacterial consortium displayed more Cd-accumulation in the roots (95%), shoots (55%), and leaves (44%). Higher values of BCF_root (> 1), and lower values for BCF_shoot and TF (< 1) indicates capability of B. mutica to accumulate high amounts of Cd in the roots as compared to the aerial parts. The present study concludes that plant-endophyte interplay could be a sustainable and effective strategy for Cd removal from the contaminated soils.