Abstract:
The symbiotic interaction between soybean plants and rhizobacteria can be severely
affected by drought, which results in a reduction in symbiotic nitrogen fixation and
ultimately decreased yields. The aim of our research was to determine whether symbiotically efficient rhizobia that can better tolerate soil water deficits can improve
nodule performance in plants subjected to drought. Firstly, rhizobial strains were
selected that exhibited differences in tolerance to salt (NaCl) or water deficit (PEG
6000). Sinorhizobium fredii strain SMH12 showed the highest tolerance to these
treatments while Bradyrhizobium diazoefficiens strain WB74‐1 showed the lowest
tolerance. Greenhouse‐grown Prima 2000 soybean plants were then inoculated with
either SMH12 or WB74‐1 and subjected to two water deficit regimes. Different nodule and plant growth traits were determined, including nodule number, dry weight,
water potential, and the accumulation of malondialdehyde and ureide. Plants inoculated with SMH12 had significantly more nodules under water deficit conditions than
those inoculated WB74‐1, despite having lower root and shoot biomass. SMH12‐inoculated plants had higher nodule water potentials and lower malondialdehyde contents than the WB74‐1‐inoculated plants. These results demonstrate that inoculation
of soybean plants with the more water deficit‐tolerant S. fredii strain improved nodule characteristics when plants were grown under water deficit conditions. However,
these improved nodule characteristics do not always directly translate into better
plant growth.
