Effects of boron-treated rhizobial inoculum on soluble sugar concentration in alfalfa roots, stems, and leaves

We aimed to explore the effects of boron-treated rhizobial inocula on the soluble sugar content in the roots, stems, and leaves in different periods. Medicago sativa ‘Gannong No.5’ alfalfa was used as the test material; two rhizobial solutions (from Sinorhizobium meliloti LZgn5f and S. meliloti 12531f) containing different boron concentrations (0, 0.05, 1.5, 10, and 100 mg·L⁻¹) were inoculated into alfalfa seedling roots, and no boron and inoculum were used as the control. The results showed that after inoculation with exogenous rhizobia 12531f containing 1 mg·L⁻¹ boron and endogenous rhizobia gn5f containing 100 mg·L⁻¹ boron, the soluble sugar content in alfalfa roots and stems at different sampling periods was higher than that in both the control and no-boron inoculation treatments and could promote the accumulation of soluble sugars in the roots and stems of alfalfa in different periods. In summary, under suitable boron treatment concentrations, the two strains could promote the accumulation of soluble sugars in the leaves to roots and stems in different growth periods and maintain the dynamic balance of soluble sugars in the roots, stems, and leaves.