Improving the growth, P uptake and quality characteristics of 'Lollo Rosso' lettuce in the nutrient solution by Bacillus subtilis in different phosphorus concentrations

The use of plant-growth-promotion rhizobacteria will play a vital role in phosphorus (P) fertilizers management because of the restricted P resources within the world. In this regard, a greenhouse experiment was performed to evaluate the effect of Bacillus subtilis (B. subtilis) in different concentrations of P (12.5, 25, 37.5, 50 and 62.5 mg L-1) on growth, P uptake and quality characteristics of 'Lollo Rosso' lettuce in hydroponic condition. The results showed that the effect of B. subtilis on growth, biochemical attributes and P concentration in plant tissues was significant. So that, only the fresh weight of leaves in bacterial treatments increased by about 21% compared to the control. Without B. subtilis, P application enhanced multiple plant growth indices, P uptake and antioxidant compounds in 'Lollo Rosso' plants. The finding of this experiment also clearly indicated that in inoculated plants with a 25% reduction in P consumption in nutrient solution (37.5 mg L-1 treatment) quality characteristics of lettuce such as flavonoids and vitamin C contents and also root and shoot P concentrations were not significantly different from the 50 mg L-1. Our results recommend that the utilization of B. subtilis in hydroponic condition can improve growth, quality characteristics, and P uptake and ultimately decrease the use of P fertilizers, which can be an efficient tool for sustainable agriculture.