Abstract

Leguminous plants and crops subjected to salt stress experience serious adverse conditions, such as ionic toxicity resulting from Na + and Cl − accumulation, and malnutrition including nitrogen deficiency and chlorine imbalances. In this work, using two wild soybean ( Glycine soja L.) accessions, the salt-tolerant BB52 and the salt-sensitive N23227, as the experimental materials, effects of pre-inoculation with Bradyrhizobium japonicum on seedling growth, contents of NH 4 + , NO 3 − , total nitrogen, K + , Cl − and Na + , ratios of Cl − /NO 3 − and Na + /K + , and the transcriptional patterns of NH 4 + , NO 3 − , Na + and Cl − transporter-related genes under NaCl stress were investigated. Results showed that, compared with that on the non-inoculated NaCl-treated soybean seedlings, the salt damage on pre-inoculated seedlings was obviously mitigated as shown by the increased leaf RWC (relative water content) and reduced REL (relative electrolytic leakage) in roots and leaves; in addition, the contents of NH 4 + , NO 3 − , total nitrogen, and K + (except in BB52 roots) in roots, stems and leaves displayed an apparent upward trend, while contents of Cl − and Na + , Cl − /NO 3 − ratio, and Na + /K + ratio (except in BB52 roots) decreased markedly. Generally, the ameliorative effect on the salt-sensitive N23227 seedlings was slightly stronger than that on BB52 seedlings. Furthermore, compared with that in non-inoculated soybean seedlings subjected to 150 mM NaCl for 0, 3, 6, 12 and 24 h, the relative expression levels of most of the ten studied anionic and cationic transporter-related genes, such as GsAMT1.6 , GsAMT2.1 , GSNRT1-2 , GSNRT5-5 , GsNRT2 and GsCLC-C2 , were clearly enhanced in roots and leaves of pre-inoculated BB52 and N23227 seedlings, and the upregulation of GsNRT1-3 , GsNRT1-4 , GsSOS1 , and GsCLC1 varied only at the levels of soybean accessions and plant organs, i.e., roots and leaves. This suggests that the enhanced NaCl toleran