Assessment of Morpho-Physiological, Biochemical and Antioxidant Responses of Tomato Landraces to Salinity Stress

Effect of Biochar Application on Morpho-Physiological Traits, Yield, and Water Use Efficiency of Tomato Crop under Water Quality and Drought Stress

The use of saline water under drought conditions is critical for sustainable agricultural development in arid regions. Biochar is used as a soil amendment to enhance soil properties such as water-holding capacity and the source of nutrition elements of plants. Therefore, the experiment was conducted to evaluate the effects of biochar application on the morpho-physiological traits and yield of tomatoes under combined salinity and drought stress in greenhouses. There were 16 treatments consist two water quality fresh and saline (0.9 and 2.3 dS m^-1), three deficit irrigation levels (DI) 80, 60, and 40% addition 100% of Evapotranspiration (ETc), and biochar application by rate 5% (BC_5%) (w/w) and untreated soil (BC_0%). The results indicated that the salinity and water deficit negatively affected morphological, physiological, and yield traits. In contrast, the application of biochar improved all traits. The interaction between biochar and saline water leads to decreased vegetative growth indices, leaf gas exchange, the relative water content of leaves (LRWC), photosynthetic pigments, and yield, especially with the water supply deficit (60 and 40% ETc), where the yield decreased by 42.48% under the highest water deficit at 40% ETc compared to the control. The addition of biochar with freshwater led to a significantly increased vegetative growth, physiological traits, yield, water use efficiency (WUE), and less proline content under all various water treatments compared to untreated soil. In general, biochar combined with DI and freshwater could improve morpho-physiological attributes, sustain the growth of tomato plants, and increase productivity in arid and semi-arid regions.

Salt stress resilience in plants mediated through osmolyte accumulation and its crosstalk mechanism with phytohormones

Salinity stress is one of the significant abiotic stresses that influence critical metabolic processes in the plant. Salinity stress limits plant growth and development by adversely affecting various physiological and biochemical processes. Enhanced generation of reactive oxygen species (ROS) induced via salinity stress subsequently alters macromolecules such as lipids, proteins, and nucleic acids, and thus constrains crop productivity. Due to which, a decreasing trend in cultivable land and a rising world population raises a question of global food security. In response to salt stress signals, plants adapt defensive mechanisms by orchestrating the synthesis, signaling, and regulation of various osmolytes and phytohormones. Under salinity stress, osmolytes have been investigated to stabilize the osmotic differences between the surrounding of cells and cytosol. They also help in the regulation of protein folding to facilitate protein functioning and stress signaling. Phytohormones play critical roles in eliciting a salinity stress adaptation response in plants. These responses enable the plants to acclimatize to adverse soil conditions. Phytohormones and osmolytes are helpful in minimizing salinity stress-related detrimental effects on plants. These phytohormones modulate the level of osmolytes through alteration in the gene expression pattern of key biosynthetic enzymes and antioxidative enzymes along with their role as signaling molecules. Thus, it becomes vital to understand the roles of these phytohormones on osmolyte accumulation and regulation to conclude the adaptive roles played by plants to avoid salinity stress.

Crataegus oxyacantha Extract as a Biostimulant to Enhance Tolerance to Salinity in Tomato Plants

Salinity is a severe abiotic problem that has harmful impacts on agriculture. Recently, biostimulants were defined as bioprotectant materials that promote plant growth and improve productivity under various stress conditions. In this study, we investigated the effect of Crataegus oxyacantha extract as a biostimulant on tomato plants (Solanum lycopersicum) grown under salt stress. Concentrations of 20 mg/L, 30 mg/L, and 70 mg/L of C. oxyacantha extract were applied to tomato plants that were grown under salt stress. The results indicated that plants that were treated with C. oxyacantha extract had a higher ability to tolerate salt stress, as demonstrated by a significant (p < 0.05) increase in plant growth and photosynthetic pigment contents, in addition to a significant increase in tomato soluble sugars and amino acids compared to the control plants. In the stressed tomato plants, malondialdehyde increased and then decreased significantly with the different concentrations of C. oxyacantha extract. Furthermore, there was a significant improvement in the antioxidant enzyme activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), and glutathione reductase (GR) in the stressed plants, especially after treatment with 70 mg/L of the extract. Overall, our results suggest that C. oxyacantha extract could be a promising biostimulant for treating tomato plants under salinity stress.

Mitigation of Salinity-Induced Oxidative Damage, Growth, and Yield Reduction in Fine Rice by Sugarcane Press Mud Application

Salinity stress is one of the major global problems that negatively affect crop growth and productivity. Therefore, ecofriendly and sustainable strategies for mitigating salinity stress in agricultural production and global food security are highly demandable. Sugarcane press mud (PM) is an excellent source of the organic amendment, and the role of PM in mitigating salinity stress is not well understood. Therefore, this study was aimed to investigate how the PM mitigates salinity stress through the regulation of rice growth, yield, physiological properties, and antioxidant enzyme activities in fine rice grown under different salinity stress conditions. In this study, different levels of salinity (6 and 12 dS m-1) with or without different levels of 3, 6, and 9% of SPM, respectively were tested. Salinity stress significantly increased malondialdehyde (MDA, 38%), hydrogen peroxide (H2O2, 74.39%), Na+ (61.5%), electrolyte leakage (40.32%), decreased chlorophyll content (32.64%), leaf water content (107.77%), total soluble protein (TSP, 72.28%), and free amino acids (FAA, 75.27%). However, these negative effects of salinity stress were reversed mainly in rice plants after PM application. PM application (9%) remained the most effective and significantly increased growth, yield, TSP, FAA, accumulation of soluble sugars, proline, K+, and activity of antioxidant enzymes, namely, ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD). Thus, these findings suggest a PM-mediated eco-friendly strategy for salinity alleviation in agricultural soil could be useful for plant growth and productivity in saline soils.

Physiological response and proteomics analysis of Reaumuria soongorica under salt stress

Soil salinity can severely restrict plant growth. Yet Reaumuria soongorica can tolerate salinity well. However, large-scale proteomic studies of this plant’s response to salinity have yet to reported. Here, R. soongorica seedlings (4 months old) were used in an experiment where NaCl solutions simulated levels of soil salinity stress. The fresh weight, root/shoot ratio, leaf relative conductivity, proline content, and total leaf area of R. soongorica under CK (0 mM NaCl), low (200 mM NaCl), and high (500 mM NaCl) salt stress were determined. The results showed that the proline content of leaves was positively correlated with salt concentration. With greater salinity, the plant fresh weight, root/shoot ratio, and total leaf area increased initially but then decreased, and vice-versa for the relative electrical conductivity of leaves. Using iTRAQ proteomic sequencing, 47 177 136 differentially expressed proteins (DEPs) were identified in low-salt versus CK, high-salt versus control, and high-salt versus low-salt comparisons, respectively. A total of 72 DEPs were further screened from the comparison groupings, of which 34 DEPs increased and 38 DEPs decreased in abundance. These DEPs are mainly involved in translation, ribosomal structure, and biogenesis. Finally, 21 key DEPs (SCORE value ≥ 60 points) were identified as potential targets for salt tolerance of R. soongolica. By comparing the protein structure of treated versus CK leaves under salt stress, we revealed the key candidate genes underpinning R. soongolica’s salt tolerance ability. This works provides fresh insight into its physiological adaptation strategy and molecular regulatory network, and a molecular basis for enhancing its breeding, under salt stress conditions.

Analysis of Salinity Tolerance in Tomato Introgression Lines Based on Morpho-Physiological and Molecular Traits

The development of salt-tolerant tomato genotypes is a basic requirement to overcome the challenges of tomato production under salinity in the field or soil-free farming. Two groups of eight tomato introgression lines (ILs) each, were evaluated for salinity tolerance. Group-I and the group-II resulted from the following crosses respectively: Solanum lycopersicum cv-6203 × Solanum habrochaites and Solanum lycopersicum M82 × Solanum pennellii. Salt tolerance level was assessed based on a germination percentage under NaCl (0, 75, 100 mM) and in the vegetative stage using a hydroponic growing system (0, 120 mM NaCl). One line from group I (TA1648) and three lines from group II (IL2-1, IL2-3, and IL8-3) were shown to be salt-tolerant since their germination percentages were significantly higher at 75 and 100 mM NaCl than that of their respective cultivated parents cvE6203 and cvM82. Using the hydroponic system, IL TA1648 and IL 2-3 showed the highest value of plant growth traits and chlorophyll concentration. The expression level of eight salt-responsive genes in the leaves and roots of salt-tolerant ILs (TA1648 and IL 2-3) was estimated. Interestingly, SlSOS1, SlNHX2, SlNHX4, and SlERF4 genes were upregulated in leaves of both TA1648 and IL 2-3 genotypes under NaCl stress. While SlHKT1.1, SlNHX2, SlNHX4, and SlERF4 genes were upregulated under salt stress in the roots of both TA1648 and IL 2-3 genotypes. Furthermore, SlSOS2 and SlSOS3 genes were upregulated in TA1648 root and downregulated in IL 2-3. On the contrary, SlSOS1 and SlHKT1.2 genes were upregulated in the IL 2-3 root and downregulated in the TA1648 root. Monitoring of ILs revealed that some of them have inherited salt tolerance from S. habrochaites and S. pennellii genetic background. These ILs can be used in tomato breeding programs to develop salt-tolerant tomatoes or as rootstocks in grafting techniques under saline irrigation conditions.