Root Na + Content Negatively Correlated to Salt Tolerance Determines the Salt Tolerance of Brassica napus L. Inbred Seedlings

Soil salinization is a major environmental stressor that reduces the growth and yield of crops. Maintaining the balance of ions under salinity is vital for plant salt tolerance; however, little is known about the correlation between the salt tolerance of crops and the ion contents of their roots and shoots. Here, we investigated the poorly understood salt-tolerance mechanisms, particularly regarding ion contents (particularly Na ), in subsp. L., an agriculturally important species. Twenty inbred lines were randomly chosen from five salt-tolerance categories and treated with increasing concentrations of NaCl (0-200 mmol) for this work. We found that the root Na content is the most correlated limiting factor for the salt tolerance of ; the higher the salt tolerance, the lower the root Na content. Correspondingly, the Ca /Na and K /Na ratios of the roots were highly correlated with salt tolerance, indicating that the selective absorption ability of these ions by the roots and their translocation to the shoots play a pivotal role in this trait. These data provide a foundation for the further study of the molecular mechanisms underlying salt tolerance and for breeding salt-tolerant cultivars.