Abstract: To select new wheat germplasm materials with high salt and alkali resistance, we investigated the salt and alkali tolerance of five wheat-Leymus mollis derivative lines (designated as H9, H24, H29, H30, and H47). Salt and alkali stress conditions were simulated using 25, 50, and 100 mmol·L^-1 solutions of NaCl (neutral sodium salt) and NaHCO₃ (basic sodium salt). The variables related to seed germination and seedling physiology were measured. The results showed that under salt and alkali stress, the germination energy (GE), germination rate (GR), germination index (GI), germination salt/alkali resistance index (GSRI/GARI), root length (RL), bud length (BL) of the five wheat germplasm materials all showed a downward trend. The inhibitory effect positively related with the magnitude of stress. The inhibitory effect of NaHCO₃ on seed germination and growth was more significant than that of NaCl (P<0.05). The chlorophyll (Chl) content showed a decreasing trend due to Chl degradation caused by ion toxicity under salt and alkali stress. H29 had the lowest decrease in Chl content at 50 and 100 mmol·L^-1 NaCl treatment (20.9% and 67.4%) compared with the CK. H47 had the lowest decrease at 25 mmol·L^-1 NaCl treatment (14.8%), and its decreases at 50 and 100 mmol·L^-1 NaCl treatment were second only to H29. Under the NaHCO₃ stress of 25, 50 and 100 mmol·L^-1, H29 showed 11.6%, 25.6%, and 37.2% reductions, respectively, indicating the least inhibition of Chl content among the five wheat materials. The contents of malondialdehyde and proline generally showed an upward trend with the increases of NaCl and NaHCO₃ concentrations. The higher the salt and alkali concentrations, the greater the differences (P<0.05). Under the same salt and alkali concentration, NaHCO₃ alkali stress caused more serious membrane damage and osmotic stress than NaCl salt stress. Principal component analysis showed that the growth indicators of GI, GR, RL, BL, and GSRI/GARI could be used as the main indicators for salt and alkali tolerance of wheat materials. The evaluation results using the membership function method on the salt and alkali tolerance of the five wheat materials showed that H29 had the highest comprehensive evaluation value for salt resistance  and H47 had the highest comprehensive evaluation value for alkali resistance. H29 and H47 could be used as new germplasm materials with good adaptation to saline and alkaline land, respectively.

Key words: wheat, salt stress, alkali stress, germination index, physiological characteristics