Physiological and transcriptional responses of contrasting alfalfa (Medicago sativa L.) varieties to salt stress

Alfalfa (Medicago sativa L.) acts as a most important legume forage crop and is widely cultivated in various environments. Salt stress is one of the major abiotic stresses in cultivation of alfalfa worldwide. Development of alfalfa cultivars for adaptable to salt environments can provide sustainable solutions. In the present study, we selected two varieties with contrasting salt tolerance-211609 and Xinjiang Daye-from 14 alfalfa varieties. Under salt stress condition, 211609 showed higher leaf water content, less severe cell membrane damage (Electrolyte leakage) and lower accumulation of reactive oxygen species than Xinjiang Daye which exhibited lower GSH content and less antioxidant enzyme activities. In addition, significantly higher expression levels of NHX1, ZFG, CBF4 and HSP23 genes were found in 211609 than those in Xinjiang Daye upon exposure to salt stress. Collectively, these results proved that 211609 showed higher tolerance to salt stress than Xinjiang Daye through regulation of physiological and transcriptional pathways. It could play an important role in breeding program of alfalfa varieties with improved stress tolerance in future.