This study was conducted to screen the concentration of soda saline-alkali stress solution and the determination index of saline-alkali tolerance, to establish the identification method of saline-alkali tolerance to large-scale identification of sorghum germplasms. The saline-alkali tolerance of the core germplasms of grain sorghum were comprehensively evaluated, and the saline-alkali tolerant germplasms were identified and selected to provide a germplasm basis for further breeding of saline-alkali tolerant parents and hybrids.

The main components of saline-alkali soil of in The Songnen Plain are Na₂CO₃ and NaHCO₃. This experiment used 50 mmol·L^-1 NaHCO₃∶Na₂CO₃=9∶1 as a stress solution to simulate the moderate saline-alkali environment in Songnen Plain, the pH is 9.19, Salinity is 0.21%. Eight traits, including seedling height, root length, seedling fresh weight, root fresh weight, seeding dry weight, root dry weight, root-shoot ratio fresh weight and root-shoot ratio dry weight were used as measurement indexes and the saline-alkali tolerance characteristics of 285 sorghum core germplasms at seedling stage were identified. Principal component analysis was used to screen the salt-alkali tolerance identification indexes of grain sorghum at seedling stage and establish a mathematical model for salt-alkali tolerance evaluation at seedling stage. The saline-alkaline tolerance of 285 sorghum germplasms was classified by cluster analysis, and the germplasms with strong saline-alkaline tolerance were screened.

50 mmol·L^-1 saline-alkali stress showed inhibitory effects on 8 indexes of 285 sorghum germplasms, the average values of saline -alkali resistance coefficients are 0.794, 0.785, 0.565, 0.554, 0.802, 0.638, 0.978, and 0.841. Under saline alkali stress, 8 indexes showed significant positive correlations; the seedling height and root fresh weight could be used as the indexes for the identification and evaluation of soda saline-alkali stress in sorghum seedling stage by principal component analysis; The evaluation model of saline-alkali tolerance characteristics of sorghum seedlings was summarized by multiple linear regression analysis Y=0.097X4+0.171X2+0.201X6+0.157X1+0.105X3-0.147, it can be used for comprehensive evaluation of multiple indicators. 285 grain sorghum core collections were divided into 5 grades by cluster analysis, strong saline-alkali tolerance, saline-alkali tolerance, intermediate type, sensitive type and extremely sensitive type, Among them, there were 8 strong salt-tolerant germplasms, 8 salt-tolerant germplasms, 112 intermediate germplasms, 134 sensitive germplasms and 23 extremely sensitive germplasms. The saline-alkali tolerant germplasm and extremely sensitive germplasm were planted in the moderate saline-alkali soil (pH 8.5-9.5, Salinity 0.3%) for verification in Zhenlai County of western Jilin Province. The average seedling emergence rate of strong saline-alkali tolerant germplasm was 45.4%, and the average seedling height was 23 cm. The average seedling emergence rate of salt-tolerant germplasm was 31.3%, and the average height was 20.9 cm. The average emergence rate of extremely sensitive germplasm was 20%, and the average seedling height was 12.3 cm.

8 strong soda saline-alkali tolerant germplasms and 8 saline-alkali tolerant germplasms were screened out from 285 sorghum germplasms resources with 50 mmol·L^-1 soda saline-alkali concentration (NaHCO₃∶Na2CO₃=9∶1). The seedling height and root fresh weight could be used as the preferred evaluation indexes for the identification of saline-alkali tolerance at seedling stage.