Effect of biofilm-forming plant growth promoting bacterium and tryptophan on yield and Cadmium uptake in Rye (Secale cereale)

Due to the inevitable entry of cadmium into the soils and its high toxicity, it is essential to prevent it from human food chains. Biofilm-forming plant growth-promoting bacteria with the ability of auxin production can prevent the transport of some heavy metals to plants. A hydroponic factorial experiment was designed based on a randomized complete block in three replications to investigate the effect of biofilm-forming plant growth-promoting bacterium and tryptophan on yield and cadmium uptake in Rye. Experimental factors include three levels of cadmium (zero, 50 and, 100 mg.L-1), two bacterial inoculation (with or without Bacillus atrophaeus) and, tryptophan (presence in 100 mgL-1 and absence). The results showed that the addition of tryptophan and bacterial inoculation could increase the yield of rye dry matter by 19% on average vs control. In addition, the co-applying of tryptophan with bacterial inoculation was able to reduce 100% and 62% of the cadmium concentration in rye aerial parts at 50 and 100 mg.L-1, respectively. The use of tryptophan by the improvement of the antioxidant system was able to reduce the amount of malondialdehyde and hydrogen peroxide at 50 mg.L-1 cadmium level up to 30 and 42%, and for 100 mg.L-1 cadmium by 34 and 32%, respectively. Therefore, it seems that with further studies, these treatments can be used to increase the yield and reduce the Cd entry into the food chain in the Cd-contaminated soils.