Abstract: 【Objective】 In order to obtain valuable salt-tolerance soybean germplasms, the productive potential of TaNHX2（wheat Na⁺/H⁺ transporter code gene）over-expression transgenic soybeans was studied through observing their salt induced phenotype, photosynthetic intensity and agronomic traits under salt stress.【Method】The T₄ generation of TaNHX2 over-expression transgenic soybeans, which the transgenic authenticity confirmed by Glufosinate-resistance assay, PCR and RT-PCR detections at V₃ stage were chosen as materials. The positive individuals were then treated with NaCl solution at V₄ stage, during the treatment phase, the salt induced phenotype of transgenic and wild-type plants was observed. Furthermore, the photosynthetic intensity of the soybeans at R₃ stage was measured. Finally, the plant height, node number on main stem, pod number per plant, seed number per plant and seed weight per plant of soybean plants which harvested at R₈ stage were measured. Two concentrations of NaCl solution (0 and 200 mmol·L^-1) were applied in Beipuchang research site, while three concentrations were applied (0, 150 and 200 mmol·L^-1) in Changping, Beijing. The observation of salt induced phenotype and measurement of photosynthetic intensity were only carried out at Beipuchang research site. 【Result】 The successful expression of foreign gene TaNHX2 was confirmed by molecular identification, its inheritance was stable. Transgenic soybean and wild-type plants had similar growth vigor, leaf size and photosynthetic intensity under normal growing condition. While both the transgenic soybean and wild-type plants became shorter under 200 mmol·L^-1 NaCl treatment, their leaves became smaller and their photosynthetic intensity decreased. When compared with wild-type, the transgenic soybean lines (C12, C21 and C19) had lower dwarf degree, larger leaf size and photosynthetic intensity, the photosynthetic rate (Pn) of lines C12 and C21 significantly larger than wild-type. In addition, the yield related agronomic trait value of transgenic soybean lines and wild-type were comparable under normal condition, while under 150 mmol·L^-1 and 200 mmol·L^-1 NaCl stress, the agronomic trait values of transgenic soybean lines were larger than wild-type. Under 150 mmol·L^-1 NaCl stress (Changping), seed weight per plant of lines C12, C21 and C19, pod number per plant of line C19 had a significant difference with wild-type. Under 200 mmol·L^-1 NaCl stress (Changping), pod number per plant, seed number per plant and seed weight per plant of lines C12, C21 and C19, plant height of lines C12 and C19 had a significant difference with wild-type. At Beipuchang research site, plant height of lines C12, C21 and C19, seed number per plant and seed weight per plant of line C19 were significantly larger than wild-type. 【Conclusion】Compared with wild-type, transgenic soybean lines (C12, C21 and C19) had lower salt damage degree, kept a higher photosynthesis and certain yield under salt stress, line C19 had an excellent yield potential both at two research sites, therefore, it is practical valuable for breeding and production.

Key words: TaNHX2 over-expression transgenic soybean, salt stress, yield potential, application in production