Analysis Of Soybean Physiological Responses To Salinity Stress And Mapping Of Salt Tolerance Gene At Seeding Stage

Salinity is one of the main abiotic stresses for crop production worldwide. One of the most important approach to deal with this serious problem is to cultivate crops with high salt tolerance. The research on selection methods of salt-tolerant soybean is crucial for physiological mechanism research and developing of salt tolerant cultivars. Thus, the objective is to study the relationship of ion content in different organs and physiological trait with salt tolerance under long-term and short-term salt stresses, by using one salt tolerant and one salt sensitive soybean cultivars. A simple method for salt tolerance in soybean germplasm was developed by screening 29 cultivated soybean by testing Na~+ content in leaves and cotyledons in hydroponics. This method was also applied to screen 22 wild soybean for salt tolerance. The salt tolerant gene was fine mapped in 300 cultivated soybean germplasm by association mapping.The main results are as follows:1. Lower Na~+ content in leaves and cotyledons has relationship with salt tolerance of soybean Dry biomass and chlorophyll content in both cultivars were significantly reduced by 1-9 d of 100 mmol L-1 NaCl stress. The content of Na~+ in leaves and cotyledons determines the salt tolerance. The combination of salinity and cotyledon removal before salt stress had the more negative effects on Peking than on Wenfeng 7, reducing the survival time of Peking by 2 days. The removal of cotyledons also enhanced Na~+ accumulation and K~+ reduction in leaves of both cultivars, indicating that cotyledons, as storage and photosynthetic organs, play an important role in regulation of K~+ and Na~+ content under salt stress.2. Both the root and shoot determined the salt tolerance and accumulation of Na~+ in soybean plantSoybean shoot was more tolerant to NaCl and had lower Na~+ content when Wenfeng 7 was used as rootstocks regardless of the scion. The Wenfeng 7 scion was tolerance than Peking scion when the same rootstocks were used. The leaf Na~+ content is lower in Wenfeng 7 scion when Peking was used as rootstocks. The result indicated that both the root and shoot can control the Na~+ accumulation.3. Correlation between Na~+ contents in different organs of soybean and salt tolerance at the seedling stageNa~+ contents in leaves and cotyledons can distinguish salt tolerance and salt sensitive soybean of 29 cultivars. Therefore, a quantitative index method as Na~+ contents in leaves and cotyledons was established to screen soybean germplasm for salt tolerance. But it is not clear if this method can be applied to screen wild soybean for salt tolerance.4. The salt tolerant gene was fine mapped to a 60kb region by association mappingTwenty five markers from a 495kb region on Linkage group N, covering the salt tolerant QTL region of soybean, were used to screen 300 soybean accessions. We finally identified a 60kb as candidate region for the salt tolerant related gene by association mapping.