AimsThis study aimed to evaluate the effect of five cadmium-tolerant endophytic plant growth-promoting bacteria (PGPB) strains on the biomass and cadmium tolerance, and accumulation of the bioenergy plant switchgrass (Panicum virgatum L.) under cadmium (Cd)-contaminated conditions. Methods and ResultsFive bacterial strains (Bj05, Le14, Ps14, So02 and Bo03) that could tolerate up to 2000moll(-1) CdCl2 with a high Cd-binding capacity were isolated from plants grown in Cd-contaminated soil. These strains could promote the growth of switchgrass in the presence of 20moll(-1) CdCl2. Under Cd stress, both the root and shoot length and biomass in two switchgrass cultivars, Alamo and Cave-in-Rock (CIR), increased significantly after treatment with PGPB (P ? 005). Of the five PGPB strains, Bj05 and Le14 most effectively alleviated the Cd-induced growth inhibition of Alamo plants. Interestingly, the five PGPB strains increased Cd tolerance and decreased the accumulation and translocation factor (TF) of Cdin switchgrass when grown in the presence of 20moll(-1) CdCl2. The Cd concentrations in roots and shoots of Alamo and CIR plants were significantly reduced (P?005) compared with noninoculated plants. By 16S rRNA sequencing, these PGPB strains were classified as Pseudomonas putida Bj05, Pseudomonas fluorescens Ps14, and Enterobacter spp. Le14, So02 and Bo03. ConclusionInoculation with PGPB protects plants from the inhibitory effects of Cd, improves plant growth and decreases Cd concentration. These observations suggest that these strains could be used to promote growth and lower the bioavailability of Cd in switchgrass. Significance and Impact of the StudyThese strains are potential candidates for the development of low Cd-accumulating switchgrass, particularly in areas of Cd contamination and pollution, and could be used efficiently for the bioremediation of contaminated soil.