Salt tolerance of two different varieties of tobacco under NaCl stress

Abstract

Background In the context of increasing global soil salinization, reducing the damage caused by soil salinity and improving the salt tolerance of crops has become an urgent issue in modern agriculture. However, few studies have reported on the different salt tolerance performances of different varieties of tobacco crops under salinity stress due to the gradual evolution of geographical separation. Results The aim of this study was to investigate the different performances of Basma (Spice tobacco) and K326(Flue-cured tobacco) under NaCl stress in order to find a more effective method to improve salt tolerance in tobacco. In this study, Basma and K326 were treated with a 150 mM NaCl solution, and a blank control treatment was included. Physiological indicators such as root length growth, antioxidant enzyme activity, ion concentration, hormone content, and related gene expression were measured. In the plate medium, the root length growth of K326 under NaCl stress treatment was only 60% of that of Basma, which had higher salt tolerance. The reasons for this difference mainly concentrated on three aspects. Firstly, in Basma, the accumulation of reactive oxygen species caused by salt stress is scavenged by increasing the activity of antioxidant enzymes, and the damage to the plasma membrane is decreased. Secondly, the ion toxicity caused by salt stress is relieved by increasing the expression of the SOS1 gene in the roots, which can balance the intracellular osmotic pressure and maintain ion balance. Lastly, the expression of PIN4, a key gene in growth hormone transport, is upregulated to obtain antigravity transport of growth hormone and increase IAA content in roots, promoting root growth. Conclusion In this study, it was found that oriental tobacco Basma demonstrated greater resistance to salt stress compared to flue-cured tobacco K326. This was primarily observed in the root growth and activity, as well as in significant differences in physiological indexes such as active oxygen accumulation, ion distribution regionalization, and hormone content distribution. The experimental results suggest that Basma achieves strong salt tolerance through three main mechanisms: increasing the activity of antioxidant enzymes to eliminate ROS accumulation, expressing SOS1 to adapt to ion regionalization under salt stress, regulating sodium-potassium ratio, and increasing the expression of IAA polar transporter gene PIN4 to maintain a balance of IAA content.