Evaluating the Necessity of a Control Treatment for Assessing Salt Tolerance in Wheat Genotypes Based on Agro-Physiological Traits in Real-Field Conditions

Evaluating salt tolerance based on agro-physiological traits is resource-intensive when testing numerous genotypes under both control and saline conditions. Focusing specifically on stress conditions may streamlines the process while effectively revealing the physiological mechanisms underlying salt tolerance in genotypes. This study investigated whether control treatments are necessary for accurate salt tolerance assessment by analyzing 22 wheat genotypes under real field conditions with control and 150 mM NaCl salinity. Genotypes were grouped based on absolute trait values of ionic and agro-physiological traits under normal or salinity stress conditions separately, as well as stress tolerance indices (STIs) that consider the genotypes' performance under stress compared to non-stress conditions. Heatmap clustering of ionic, physiological, or growth and yield traits under salinity stress successfully differentiated between salt-tolerant (Sakha 93) and sensitive (Sakha 61) genotypes. In contrast, the heatmap of ionic and physiological traits under control conditions or STIs of ionic and growth and yield traits failed to distinguish between the two genotypes. When categorized based on control-condition values or STIs, the Sakha 93 group performed similarly or worse than the Sakha 61 group. However, under salinity stress, the Sakha 93 group consistently outperformed the Sakha 61 group. Salinity-stress trait values provided significant insights into the salt tolerance mechanisms of the tested genotypes, whereas control condition data offered no meaningful contribution to understanding salinity tolerance. In summary, assessing ionic and agro-physiological traits under salinity stress alone can accurately evaluate the salt tolerance of wheat genotypes in real field conditions, eliminating the necessity of determining them under control conditions. This method not only saves effort, time, and resources when evaluating the salt tolerance of a large number of genotypes, but also offers a reliable way to understand the mechanisms of salt tolerance through agro-physiological traits.