Phenotypic and biochemical responses of high-yield tomato varieties to salinity and drought stress

Abiotic stresses can influence plant growth and productivity by causing physiological, biochemical, molecular, and morphological changes. Salinity and drought are increasing in frequency and intensity because of climate change. Therefore, this study assessed four high-yield tomato cultivars under 150 mM NaCl and 260 mM mannitol treatments to characterize physiological (i.e., chlorophyll level, root/shoot length, and relative water content) and biochemical responses (i.e., GLY I/II and DLDH enzyme activities, proline, and hydrogen peroxide). Results indicated that the four BARI tomato varieties showed genotype- and treatment-specific physiological and biochemical responses rather than a single uniform tolerance pattern. BARI tomato 2 maintained relatively higher shoot growth and showed strong proline accumulation under stress, whereas BARI tomato 16 showed higher chlorophyll retention, RWC, and lower H2O2 accumulation. GLY I, GLY II, and DLDH activities were significantly affected by variety, treatment, and their interaction, with reduced activities in several stress treatments after 120 h exposure. Moreover, there was a significant accumulation of proline and hydrogen peroxide in the plant leaves. These results showed that MG detoxification-related enzyme activities are useful biochemical markers for comparing tomato responses to salinity and drought. Thus, this research can provide stress-response profiles of high-yielding BARI tomato varieties at the seedling stage and reveal DLDH as an unexplored downstream component of MG detoxification-related metabolism during salinity and drought stress.