Using some growth stimuli, a comparative study of salt tolerance in two tomatoes cultivars and a related wild line with special reference to superoxide dismutases and related micronutrients.

Abstract

Salinity is a major global problem that threatens the agricultural sector, especially in areas that suffer from a shortage of water. It motivates ionic toxicity, osmotic and oxidative stresses, which greatly inhibits plant performances and crop productivites. However, micronutrients (MNs) or plant extracts, like germinated maize grain extract (gMGE), have been reported to minimize the effects of salt stress on plant growth and returns. Therefore, this study aimed at evaluating the influences of MNs or gMGE applied as foliar sprays on growth, physio-biochemical indices, and antioxidative system components in three genotypes of tomato plants stressed by 9 dS m−1 NaCl. This salinity level markedly increased Na+ content, lipid peroxidation, ion leakage, and markers related to oxidative stress (superoxide; O2•− and hydrogen peroxide; H2O2). Besides, marked increases in activities of enzymatic (especially different forms of superoxide dismutase; SODs) and non-enzymatic antioxidants and osmoprotectant compounds were also observed. In contrast, growth, photosynthetic capacity including hill reaction activity (HRA), K+/Na+ ratio, tissue cell integrity (e.g., cell water content and membrane stability), and K+ and MNs contents decreased significantly under stress. However, compared to MNs, gMGE significantly improved the activities of the antioxidative system components (particularly SODs) and osmoprotectants, which were reflected in reduced Na+ accumulation, lipid peroxidation, ion leakage, and oxidative stress. These results were coupled with remarkable elevations in photosynthetic capacity including HRA, K+/Na+ ratio, tissue cell integrity, K+ content, and MNs contents, all of which were reflected in the enhancement of plant growth. Compared to local tomato cultivars (e.g., Castle Rock and C10), the wild line “0043-1” had better results. The interaction of three factors; salt stress, promoters, and tomato genotypes was significant. The wild tomato line “0043-1” as the best salt-tolerant is a good candidate for implication in breeding programs for tolerance to salinity to produce salt-tolerant cultivars for use to maximize tomato growth and productivity in saline environments.