Abstract
Salinity is one of the most significant environmental stresses for sustainable crop production in major arable lands of the globe. Thus, we conducted experiments with 27 tomato genotypes to screen for salinity tolerance at seedling stage, which were treated with non-salinized (S1) control (18.2 mM NaCl) and salinized (S2) (200 mM NaCl) irrigation water. In all genotypes, the elevated salinity treatment contributed to a major depression in morphological and physiological characteristics; however, a smaller decrease was found in certain tolerant genotypes. Principal component analyses (PCA) and clustering with percentage reduction in growth parameters and different salt tolerance indices classified the tomato accessions into five key clusters. In particular, the tolerant genotypes were assembled into one cluster. The growth and tolerance indices PCA also showed the order of salt-tolerance of the studied genotypes, where Saniora was the most tolerant genotype and P.Guyu was the most susceptible genotype. To investigate the possible biochemical basis for salt stress tolerance, we further characterized six tomato genotypes with varying levels of salinity tolerance. A higher increase in proline content, and antioxidants activities were observed for the salt-tolerant genotypes in comparison to the susceptible genotypes. Salt-tolerant genotypes identified in this work herald a promising source in the tomato improvement program or for grafting as scions with improved salinity tolerance in tomato.
Highlights
Among the environmental stresses, elevated salinization is identified as a severe detrimental one, mostly in desert and semi-desert climatic countries, triggering large yield losses for most of the domesticated plants across the globe
The control without any stress was successful in growing more leaf area and higher leaf numbers, highly stable leaf tissue membrane, higher leaf relative water content, longer and heavier shoots, higher relative chlorophyll content or soil plant analysis development (SPAD) values with more chlorophylls (a, b), and high K+/Na+ ratios compared to the salt stress treated plants
As a result of higher sodium accumulating in leaves, the lower ratio of K+/Na+ was found in salt-treated plants, but for most of the genotypes, the root to shoot length and weight ratio (RSR or RSDWR) were higher relative to the control with non-salinized conditions (Figure S1)
Summary
Among the environmental stresses, elevated salinization is identified as a severe detrimental one, mostly in desert and semi-desert climatic countries, triggering large yield losses for most of the domesticated plants across the globe. Impaired water uptake, germination disruption, stunted growth, photosynthesis retardation, oxidative stress, and yield reduction are the key effects of salinity on crop plants. Major adverse effects of salt stress are decreases in hydraulic potential leading to osmotic stress, ionic imbalance due to Na+ and Cl− harmfulness on plants’ physiological and biochemical functions, cellular energy dynamics, and disturbance of essential element supply and uptake [5,6,7]. Salt can negatively impact the functions of chloroplasts and leaf metabolites, as well as have a detrimental effect in the functions and units of photosynthesis in plants [6]
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