Salt Tolerance Evaluation Of Soybean Germplasm Resources

At present,China’s soybean planting area is seriously insufficient,and soybean production is far from meeting China’s demand for soybeans.Soybean is a moderately salt-tolerant crop.A large number of saline-alkali land in China has not been developed and utilized.If this part of saline-alkali land can be used to grow soybeans,it will greatly alleviate the serious shortage of soybeans in China.Screening soybean salt-tolerant germplasm is an important prerequisite for ensuring soybean planting in saline-alkali land.In this study,74 soybean varieties were used as materials,and the differences of germination rate,growth characteristics,photosynthetic index,ion content,stress resistance,field yield and nutritional quality of 74 soybean varieties under salt stress were evaluated by indoor simulation and field experiment.The results are as follows:（1）Compared with the salt-free control treatment,the salt tolerance of 74 soybean varieties treated with 120 mmol·L^-1 Na Cl was significantly different,and the seed germination rate and radicle length showed a downward trend.After salt treatment,the germination rate decreased by 33.15%compared with the control treatment,and the radicle length decreased by 53.48%compared with the control treatment.Among them,27 varieties had strong salt tolerance,and the germination rate could reach 55.93%after salt treatment.（2）120 mmol·L^-1 Na Cl treatment had a significant effect on the growth characteristics of different soybean varieties.The stem length,stem diameter,root length,leaf area and root-shoot ratio of all tested soybeans were significantly lower than those of the control.With the increase of soil salt content,soybean yield decreased significantly,but there were differences among varieties.After salt treatment,the stem length decreased by 21.15%,the stem diameter decreased by 4.86%,the total root length decreased by 4.9%,the leaf area decreased by 13.13%,and the root-shoot ratio decreased by 6.88%.With the soil salt content from 2.12‰,2.84‰to4.12‰,soybean yield decreased from 193.62 kg/acre to 116.39 kg/acre,until 52.95 kg/acre.The soil salt content decreased from 2.12‰to 4.12‰,and the soybean yield decreased by72.65%.（3）After 120 mmol·L^-1 Na Cl treatment,the chlorophyll content,proline content,malondialdehyde content,Na⁺content and Na⁺/K⁺of soybean leaves were significantly higher than those of CK treatment,and the gas exchange parameters were significantly lower than those of CK treatment.Antioxidant enzyme activity and nutritional quality of seeds varied with varieties,and different varieties showed different trends.After salt treatment,SPAD increased by 5.91%,proline content increased by 7.31 times,and malondialdehyde content increased by49.21%.After salt treatment,Na⁺was mainly enriched in leaves,K⁺was mainly enriched in leaves,Ca²⁺was mainly enriched in leaves,and Mg²⁺was mainly enriched.Intercellular CO₂concentration decreased by 24.74%,stomatal conductance decreased by 74.22%,net photosynthetic rate decreased by 45.23%,transpiration rate decreased by 24.74%.（4）According to the growth characteristics,stress resistance and other traits,seven soybean varieties such as Qihuang 34,Jidou 12,Daoqiu 19,Wandou 28,Xudou 14,Shengdou5,Huadou 16 were selected to have better salt tolerance at seedling stage.Under field conditions,three soybean varieties,Qihuang 34,Daoqiu 19 and Xudou 14,have strong salt tolerance.When the soil salt content is 4.12‰,the yield can reach 90 kg/acre.Based on the related indexes of germination stage,seedling stage and whole growth stage,Qihuang 34,Daoqiu 19 and Xudou 14 had the best salt tolerance among the tested soybean varieties.