Tomato responses to salinity stress: From morphological traits to genetic changes

Enhancement of plant growth in lentil (Lens culinaris) under salinity stress by exogenous application or seed priming with salicylic acid and hydrogen peroxide

This study was conducted in order to test the effect of seed pretreatment or exogenous application through the rooting medium of 0.1 mM Salicylic Acid (SA) and 0.1 mM hydrogen peroxide (H2O2) on growth, nutritional behavior and some biochemical parameters (photosynthetic pigments, gas exchange parameters, oxidative stress indicators and antioxidant enzymes activities) of lentil plants (Lens culinaris) under 75 mM salt stress. Our results demonstrated that salt stress noticeably reduced shoot and root DWs by 39.01 and 42.81%, respectively, as compared to controls. This reduction was associated with a significant decrease in all photosynthetic parameters, including Chlorophyll (Chl) and carotenoid (Car), net assimilation of photosynthesis (A), stomatal conductance (gs), transpiration (E) and internal CO2 level (Ci), an accumulation of Na+ and Cl- and a decrease of K+ and Ca2+ concentrations in plant shoots and roots. In addition, relative to control plants, salt stress remarkably increased the malondialdehyde MDA and H2O2 contents especially in roots and increased GPOX and SOD activities, especially in plant shoots. Both methods of SA and H2O2 application recovered the plant growth, enhanced shoot and root DWs (increase of 67.65 and 82.36% in shoots and roots, respectively, as compared to salt-stressed plants) and increased all parameters that were reduced by NaCl treatment. Nevertheless, the most prominent effects of SA and H2O2 on plant growth were obtained with the seed priming method. Thus, SA and H2O2 applications, especially the H2O2 seed priming method, induced the antioxidant system, improved the membrane stability and ameliorated the gas exchange parameters. As compared to salt plant stressed, Na+ and Cl- contents were significantly decreased and K+ and Ca2+ were significantly increased in shoots and roots following SA and H2O2 applications, especially with the H2O2 seed priming method. Similarly, this method was more efficient in alleviating the adverse effects of salt stress on all photosynthetic pigment contents and measured gas exchange parameters. Compared to salt stressed plants, it significantly decreased the H2O2 and MDA contents and further stimulated GPOX and SOD activities. Our results indicated that the seed priming method, particularly with H2O2, could be recommended for obtaining better growth of lentil seedlings under salt-affected soil conditions.

CLC gene family in Solanum lycopersicum: genome-wide identification, expression, and evolutionary analysis of tomato in response to salinity and Cd stress

Introduction

Chloride channels (CLCs) play critical roles in anion transport, stress adaptation, and ion homeostasis in plants. Whereas their genomic wide indentification and functional divergence in tomato (Solanum lycopersicum) remain largely unexplored.

Methods and results

In this study, we identified nine CLC genes in the tomato genome, classifying them into two evolutionarily distinct clades (Group I and II) based on phylogenetic analysis. Structural dissection revealed conserved transmembrane domains (9-12 TMDs) and motif patterns (e.g., motifs 3/7/9 in Group I), with SlCLC02 exhibiting the largest gene size (27,041 bp). Promoter analysis indicated the presence of key abiotic stress-responsive cis-elements (ABRE, MYB, MYC), aligning with the pronounced transcriptional dynamics of SlCLCs under salinity stress. Notably, qRT-PCR analysis demonstrated that most SlCLC genes (particularly SlCLC05, an ortholog to AtCLC-g) exhibited rapid upregulation within 1-4 hours followed by downregulation in roots under salinity treatment, suggesting early stress signaling roles. Likewise, preliminary expression profiling under cadmium stress further identified specific induction of SlCLC07, proposing gene-specific roles in heavy metal detoxification. Strikingly, SlCLC09 lacked collinearity with Arabidopsis/potato homologs, implying lineage-specific diversification.

Discussion

These findings elucidate the SlCLC family's structural diversity, evolutionary constraints, and stress-responsive regulation, providing a framework for targeting specific SlCLC genes (e.g., SlCLC05) to enhance chloride homeostasis in crops under combined salinity and cadmium stress. This study will open a new research direction for genetic crop improvement to ensure protected vegetable production.

Enhancing Salt Tolerance in Tomato Plants Through PEG6000 Seed Priming: Inducing Antioxidant Activity and Mitigating Oxidative Stress

Salt stress is a major constraint to crop productivity, negatively affecting plant physiology and fruit quality. This study hypothesized that seed priming with polyethylene glycol (PEG6000) might enhance antioxidant activity by mitigating oxidative stress in Solanum lycopersicum 'Micro-Tom' under salt stress. Seeds primed with -1.2 MPa PEG6000 were grown in Rockwool and treated with 0, 50, 100, 150, and 200 mM NaCl. Primed plants showed a 32% increase in leaf potassium (K+) and a 28% decrease in sodium (Na+) accumulation compared to non-primed plants under 150 mM NaCl. Glucose, fructose, and sucrose contents increased by 25%, 22%, and 19%, respectively, in primed fruits, while citric acid decreased by 15%. Malondialdehyde (MDA) and electrolyte leakage were reduced by 35% and 29%, respectively, in primed plants under moderate salinity. Antioxidant enzyme activities-SOD, POD, CAT, and APX were enhanced by 30-45% in primed plants under 100 and 150 mM NaCl, compared to non-primed controls. Abscisic acid (ABA) levels increased by 40% in primed roots under salt stress. Activities of polyamine-related enzymes (DAO, PAO, and ADC) also rose significantly. Priming improved protein content by 20% and relative water content by 18%. These results suggest that PEG6000 seed priming enhances salt tolerance by boosting antioxidant defense, regulating osmotic balance, and improving ion homeostasis, offering a viable strategy for sustaining tomato productivity under salinity.

Plant growth-promoting rhizobacteria enhanced induced systemic resistance of tomato against Botrytis cinerea phytopathogen

Introduction

Botrytis cinerea is one of the pathogenic fungi causing major problems worldwide in crops such as tomato. Some Plant Growth-Promoting Rhizobacteria (PGPR) can activate induced systemic resistance (ISR) pathways in crops, reducing the need for antifungals.

Methods

Three strains belonging to the species Peribacillus frigoritolerans (CD_FICOS_02), Pseudomonas canadensis (CD_FICOS_03), and Azotobacter chroococcum (CD_FICOS_04), which exhibit outstanding PGPR properties, were evaluated for their ability to protect tomato plants against B. cinerea infection by ISR via soil inoculation.

Results

The strains CD_FICOS_02 and CD_FICOS_03 reduced B. cinerea incidence and plant oxidative stress. The first strain mainly increased the expression of genes related to the salicylic acid pathway, while the second increased the expression of genes related to the jasmonic acid/ethylene hormonal pathway, indicating preferential ISR activation by each of these pathways. In addition, CD_FICOS_03 was able to increase the root and aerial biomass production of infected plants compared to the control. Interestingly, although the strain CD_FICOS_04 did not reduce the damage caused by B. cinerea, it increased the biomass of infected plants.

Discussion

Our results suggest that the best strategy for biocontrol of B. cinerea is to combine the ability to promote plant growth with the ability to induce systemic resistance, as demonstrated by strains P. frigoritolerans CD_FICOS_02 and P. canadensis CD_FICOS_03.

Transcriptional Profiling to Assess the Effects of Biological Stimulant Atlanticell Micomix on Tomato Seedlings Under Salt Stress

Recent environmental changes in the Mediterranean region, attributable to anthropogenic climate change, present a substantial challenge to the adaptive evaluation of crops and the development of novel improvement strategies. In this study, we established a hydroponic tomato cultivation protocol under in vitro conditions to analyze the transcriptomic profile of seedlings exposed to salinity stress. The study also examined the impact of Atlanticell Micomix, a biological stimulant derived from a mixture of mycorrhizal microorganisms and rhizobacteria, on plant growth and development under standard conditions and in response to moderate salinity. Our transcriptomic analysis indicated a differential effect of biostimulant inoculation compared to the effect induced by salinity stress, involving genes such as GOX3 or DIR1, which are associated with the plant's defense response to adverse conditions. In addition, the presence of a cross-regulatory module between jasmonic acid and auxin, involving potential orthologs of IAA29 and JAZ, was proposed. The application of the biostimulant demonstrated a potential priming effect on the tomato seedlings, which might be useful in reversing the transcriptomic effects caused by salt stress. A comprehensive analysis of the pathways differentially affected by the treatments facilitates further investigation into the mechanisms underlying these effects.

Melatonin Alleviates Photosynthetic Injury in Tomato Seedlings Subjected to Salt Stress via OJIP Chlorophyll Fluorescence Kinetics

The tomato is among the crops with the most extensive cultivated area and greatest consumption in our nation; nonetheless, secondary salinization of facility soil significantly hinders the sustainable growth of facility agriculture. Melatonin (MT), as an innovative plant growth regulator, is essential in stress responses. This research used a hydroponic setup to replicate saline stress conditions. Different endogenous levels of melatonin (MT) were established by foliar spraying of 100 μmol·L-1 MT, the MT synthesis inhibitor p-CPA (100 μmol·L-1), and a combination of p-CPA and MT, to investigate the mechanism by which MT mitigates the effects of salt stress on the photosynthetic efficiency of tomato seedlings. Results indicated that after six days of salt stress, the endogenous MT content in tomato seedlings drastically decreased, with declines in the net photosynthetic rate and photosystem performance indices (PItotal and PIabs). The OJIP fluorescence curve exhibited distortion, characterized by anomalous K-band and L-band manifestations. Exogenous MT dramatically enhanced the gene (TrpDC, T5H, SNAcT, and AcSNMT) expression of critical enzymes in MT synthesis, therefore boosting the level of endogenous MT. The application of MT enhanced the photosynthetic parameters. MT treatment decreased the fluorescence intensities of the J-phase and I-phase in the OJIP curve under salt stress, attenuated the irregularities in the K-band and L-band performance, and concurrently enhanced quantum yield and energy partitioning ratios. It specifically elevated φPo, φEo, and ψo, while decreasing φDo. The therapy enhanced parameters of both the membrane model (ABS/RC, DIo/RC, ETo/RC, and TRo/RC) and leaf model (ABS/CSm, TRo/CSm, ETo/CSm, and DIo/CSm). Conversely, the injection of exogenous p-CPA exacerbated salt stress-related damage to the photosystem of tomato seedlings and diminished the beneficial effects of MT. The findings suggest that exogenous MT mitigates salt stress-induced photoinhibition by (1) modulating endogenous MT concentrations, (2) augmenting PSII reaction center functionality, (3) safeguarding the oxygen-evolving complex (OEC), (4) reinstating PSI redox potential, (5) facilitating photosynthetic electron transport, and (6) optimizing energy absorption and dissipation. As a result, MT markedly enhanced photochemical performance and facilitated development and salt stress resilience in tomato seedlings.

Overview of Deep Learning and Nondestructive Detection Technology for Quality Assessment of Tomatoes

Tomato, as the vegetable queen, is cultivated worldwide due to its rich nutrient content and unique flavor. Nondestructive technology provides efficient and noninvasive solutions for the quality assessment of tomatoes. However, processing the substantial datasets to achieve a robust model and enhance detection performance for nondestructive technology is a great challenge until deep learning is developed. The aim of this paper is to provide a systematical overview of the principles and application for three categories of nondestructive detection techniques based on mechanical characterization, electromagnetic characterization, as well as electrochemical sensors. Tomato quality assessment is analyzed, and the characteristics of different nondestructive techniques are compared. Various data analysis methods based on deep learning are explored and the applications in tomato assessment using nondestructive techniques with deep learning are also summarized. Limitations and future expectations for the quality assessment of the tomato industry by nondestructive techniques along with deep learning are discussed. The ongoing advancements in optical equipment and deep learning methods lead to a promising outlook for the application in the tomato industry and agricultural engineering.

The Pyrus sinkiangensis Yu PsLEA4 Gene Enhances the Cold Resistance of Solanum lycopersicum

Plants have large amounts of the late embryogenesis abundant protein (LEA) family of proteins, which is involved in osmotic regulation. The Korla Pear (Pyrus sinkiangensis Yu) is an uncommon pear species that thrives in Xinjiang and can survive below-freezing conditions. We found that the PsLEA4 gene was more expressed after cold treatment by looking at the transcriptome data of the Korla Pear. In order to evaluate the biological function of the PsLEA4 protein under low-temperature stress and its potential for use in agricultural breeding, we cloned the PsLEA4 gene from the Korla Pear, made a plant overexpression vector, and transformed it into a tomato via Agrobacterium transformation. When exposed to low temperatures, we found that PsLEA4 overexpression can regulate proline metabolism and antioxidant enzyme activity in tomatoes compared to wild tomatoes. Because of this, transgenic tomatoes are more resilient to cold temperatures and produce more than their wild counterparts. Thus, expressing PsLEA4 has multiple advantages: (1) Improving frost resistance and reducing plant damage. (2) Increasing crop yield. Therefore, this study provides a theoretical basis for the role of the PsLEA4 protein in plants' resilience to low temperatures, as well as for its potential application in crop breeding.

Long-Term Salinity-Responsive Transcriptome in Advanced Breeding Lines of Tomato

Soil salinity and the scarcity of freshwater resources are two of the most common environmental constraints that negatively affect plant growth and productivity worldwide. The tomato (Solanum lycopersicum Mill.) plant is moderately sensitive to salinity. The identification of salinity-responsive genes in tomato that control long-term salt tolerance could provide important guidelines for its breeding programs and genetic engineering. In this study, a holistic approach of RNA sequencing combined with measurements of physiological and agronomic traits were applied in two advanced tomato breeding lines (susceptible L46 and tolerant L56) under long-term salinity stress (9.6 dS m-1). Genotype L56 showed the up-regulation of known and novel differentially expressed genes (DEGs) that aid in the salinity tolerance, which was supported by a high salt tolerance index (81%). Genotype L46 showed both similar and different gene families of DEGs. For example, 22 paralogs of CBL-interacting kinase genes were more up-regulated in L56 than in L45. In addition, L56 deployed more SALT OVERLY SENSITIVE paralogs than L45. However, both genotypes showed the up-regulation of ROS-detoxifying enzymes and ROS-scavenging proteins under salinity stress. Therefore, L56 was more effective in conveying the stress message downstream along all available regulatory pathways. The salt-tolerant genotype L56 is genetically robust, as it shows an enhanced expression of a complete network of salt-responsive genes in response to saline conditions. In contrast, the salt-susceptible genotype L46 shows some potential genetic background. Both genotypes have great potential in future breeding programs.

Revisiting the role of light signaling in plant responses to salt stress

As one of the grave environmental hazards, soil salinization seriously limits crop productivity, growth, and development. When plants are exposed to salt stress, they suffer a sequence of damage mainly caused by osmotic stress, ion toxicity, and subsequently oxidative stress. As sessile organisms, plants have developed many physiological and biochemical strategies to mitigate the impact of salt stress. These strategies include altering root development direction, shortening the life cycle, accelerating dormancy, closing stomata to reduce transpiration, and decreasing biomass. Apart from being a prime energy source, light is an environmental signal that profoundly influences plant growth and development and also participates in plants' response to salt stress. This review summarizes the regulatory network of salt tolerance by light signals in plants, which is vital to further understanding plants' adaptation to high salinity. In addition, the review highlights potential future uses of genetic engineering and light supplement technology by light-emitting diode (LED) to improve crop growth in saline-alkali environments in order to make full use of the vast saline land.

Mitigating salinity stress on tomato growth, water regime, gas exchange, and yield with the application of QuitoMax

This study assessed the intensity of salt stress in the two tomato varieties by measuring variables associated with the water regime, chlorophyll content, normalized difference vegetation index, gas exchange, and yield. The cultivars Amalia and Claudia, which represent tolerance and susceptibility to salinity, were evaluated. Three treatments were established in plastic pots, using a completely randomized design: T1, saline soil (ECse = 6.9 dS m-1 without QuitoMax application); T2, nonsaline soil (ECse = 0.95 dS m -1 with QuitoMax application); and T3, saline soil (ECse = 6.9 dS m-1) with QuitoMax application. The QuitoMax was applied at a rate of 300 mg L-1, during the flowering phenophase. QuitoMax caused an increase in the variables evaluated in both varieties (tolerant and susceptible) of tomato, with a lower contribution of QuitoMax to the variables related to water regime and the greatest contributions to chlorophyll content and photosynthetic activity. QuitoMax contributed positively to all variables and was superior to stress intensity for most of the variables evaluated in the tolerant variety (Amalia), except for stem thickness and the number of flowers per bunch. In the susceptible variety (Claudia), the five variables of stress intensity exceeded the contribution of QuitoMax, with the strongest effects on osmotic potential, fruit mass, and yield per plant. The present work demonstrates the feasibility of using this biostimulant to increase the tolerance of tolerant varieties and maintain tolerance in tomato varieties susceptible to salinity, reducing the intensity of saline stress and increasing plant performance under salinity conditions.

Dissection of major QTLs and candidate genes for seedling stage salt/drought tolerance in tomato

BACKGROUND

As two of the most impactful abiotic stresses, salt and drought strongly affect tomato growth and development, especially at the seedling stage. However, dissection of the genetic basis underlying salt/drought tolerance at seedling stage in tomato remains limited in scope.

RESULTS

Here, we reported an analysis of major quantitative trait locus (QTL) and potential causal genetic variations in seedling stage salt/drought tolerance in recombinant inbred lines (n = 201) of S. pimpinellifolium and S. lycopersicum parents by whole genome resequencing. A total of 5 QTLs on chromosome 1, 3, 5, 7 and 12 for salt tolerance (ST) and 15 QTLs on chromosome 1, 3, 4, 8, 9, 10, 12 for drought tolerance (DT) were identified by linkage mapping. The proportion of phenotypic variation explained (PVE%) by these QTLs ranged from 4.91 to 15.86. Two major QTLs qST7 and qDT1-3 were detected in both two years, for which two candidate genes (methionine sulfoxide reductase SlMSRB1 and brassinosteroid insensitive 1-like receptor SlBRL1) and the potential functional variations were further analyzed. Taking advantage of the tomato population resequencing data, the frequency changes of the potential favorable QTL allele for seedling stage ST/DT during tomato breeding were explored.

CONCLUSIONS

These results will be beneficial for the exploration of salt/drought tolerance genes at seedling stages, laying a foundation for marker-assisted breeding for seedling stage salt/drought tolerance.

A glutathione S-transferase regulates lignin biosynthesis and enhances salt tolerance in tomato

Salt stress adversely affects the growth and yield of crops. Glutathione S-transferases (GSTs) are involved in plant growth and responses to biotic and abiotic stresses. In this study, 400 mm NaCl stress significantly induced the expression of Glutathione S-transferase U43 (SlGSTU43) in the roots of the wild-type tomato (Solanum lycopersicum L.) plants. Overexpressing SlGSTU43 enhanced the ability of scavenging reactive oxygen species in tomato leaves and roots under NaCl stress, while SlGSTU43 knock-out mutants showed the opposite performance. RNA sequencing analysis revealed that overexpressing SlGSTU43 affected the expression of genes related to lignin biosynthesis. We demonstrated that SlGSTU43 can regulate the lignin content in tomato through its interaction with SlCOMT2, a key enzyme involved in lignin biosynthesis, and promote the growth of tomato plants under NaCl stress. In addition, SlMYB71 and SlWRKY8 interact each other, and can directly bind to the promoter of SlGSTU43 to transcriptionally activate its expression separately or in combination. When SlMYB71 and SlWRKY8 were silenced in tomato plants individually or collectively, the plants were sensitive to NaCl stress, and their GST activities and lignin contents decreased. Our research indicates that SlGSTU43 can enhance salt stress tolerance in tomato by regulating lignin biosynthesis, which is regulated by interacting with SlCOMT2, as well as SlMYB71 and SlWRKY8. This finding broadens our understanding of GST functions.

Editing and genome-wide analysis upstream open reading frames contributes to enhancing salt tolerance in tomato

The salinization of soil constitutes a substantial hindrance to the advancement of sustainable agriculture. Our research seeks to elucidate the role of a Rab GTPase-activating protein (RabGAP) family member, SlRabGAP22, in salt tolerance and its translational regulation under salt stress in tomatoes, employing gene-editing techniques and ribosome profiling methodologies. Findings demonstrate that SlRabGAP22 acts as a positive regulator of tomato salt tolerance, with four predicted upstream open reading frames (uORFs) classified into three categories. Functional uORFs were found to be negative regulation. Editing these uORFs along with altering their classifications and characteristics mitigated the inhibitory effects on primary ORFs and fine-tuned gene expression. Enhanced tomato salt tolerance was attributed to improved scavenging of reactive oxygen species, reduced toxicity Na+, and diminished osmotic stress effects. Furthermore, we conducted genome-wide analysis of ORFs to lay the foundation for further research on uORFs in tomatoes. In summary, our findings offer novel perspectives and important data for the enhancement of genetic traits via uORF-based strategies and translational regulation against the backdrop of salt stress.

Optimizing Tomato (Lycopersicon esculentum) Yield Under Salt Stress: The Physiological and Biochemical Effects of Foliar Thiourea Application

A pot experiment was conducted to investigate the role of thiourea exogenous application (0 mg/L and 100 mg/L) on the morphological, physiological, and yield traits of two varieties of tomato (Naqeeb and Nadir) under different salt stress treatments (0, 60, and 120 mM) in completely randomized design (CRD). The imposition of salinity by rooting medium showed that salt stress reduced plant height by 20%, fresh shoot weight by 50%, dry shoot weight by 78%, fresh root weight by 43%, dry root weight by 84%, root length by 34%, shoot length by 32%, shoot K+ by 47%, Ca2+ by 70%, chlorophyll a by 30%, chlorophyll b by 67%, and the number of seeds per berry by 53%, while shoot Na+ ions were increased by 90% in comparison to those grown with control treatment. However, the exogenous application of thiourea significantly enhanced dry root weight by 25% and the number of seeds per berry by 20% in comparison to untreated plants with thiourea when grown under salt stress. Salt stress resulted in a reduction in the number of berries, weight per berry, number of seeds per berry, and seed weight in both varieties, while thiourea foliar application increased these yield parameters. On the other hand, the Nadir variety surpassed Naqeeb in plant height (+13%), root length (+31%) and shoot length (+11%), fresh shoot weight (+42%) and dry shoot weight (+11%), fresh root weight (+29%), dry root weight (+25%), area of leaf (+26%), chlorophyll a (+32%), and chlorophyll b (+24%). In conclusion, the exogenous application of thiourea can be used to mitigate salt stress in tomato plants since it can improve the growth, physiological, and yield traits of this strategic crop.

Promoting tomato resilience: effects of ascorbic acid and sulfur-treated biochar in saline and non-saline cultivation environments

The resilience of tomato plants under different cultivation environments, particularly saline and non-saline conditions, was investigated by applying various treatments, including 0.5% Ascorbic Acid (AsA) and 1% Sulphur-treated Biochar (BS). The study evaluated parameters such as fruit length, diameter, yield per plant and pot, Total Soluble Solids (TSS) content, chlorophyll content, electrolyte leakage, enzyme activities (Superoxide Dismutase - SOD, Peroxidase - POD, Catalase - CAT), and nutrient content (Nitrogen - N%, Phosphorus - P%, Potassium - K%). Under saline conditions, significant enhancements were observed in fruit characteristics and yield metrics with the application of AsA and BS individually, with the combined treatment yielding the most substantial improvements. Notably, AsA and BS treatments exhibited varying effects on TSS levels, chlorophyll content, electrolyte leakage, and enzyme activities, with the combination treatment consistently demonstrating superior outcomes. Additionally, nutrient content analysis revealed notable increases, particularly under non-saline conditions, with the combined treatment showcasing the most significant enhancements. Overall, the study underscores the potential of AsA and BS treatments in promoting tomato resilience, offering insights into their synergistic effects on multiple physiological and biochemical parameters crucial for plant growth and productivity.

The Optimal Drought Hardening Intensity and Salinity Level Combination for Tomato (Solanum lycopersicum L.) Cultivation under High-Yield, High-Quality and Water-Saving Multi-Objective Demands

The extreme weather and the deteriorating water environment have exacerbated the crisis of freshwater resource insufficiency. Many studies have shown that salty water could replace freshwater to partly meet the water demand of plants. To study the effects of early-stage drought hardening and late-stage salt stress on tomatoes (Solanum lycopersicum L.), we conducted a 2-year pot experiment. Based on the multi-objective demands of high yield, high quality, and water saving, yield indicators, quality indicators, and a water-saving indicator were selected as evaluation indicators. Three irrigation levels (W1: 85% field capacity (FC), W2: 70% FC, W3: 55% FC) and three salinity levels (S2: 2 g/L, S4: 4 g/L, S6: 6 g/L) were set as nine treatments. In addition, a control treatment (CK: W1, 0 g/L) was added. Each treatment was evaluated and scored by principal component analysis. The results for 2022 and 2023 found the highest scores for CK, W2S2, W3S2 and CK, W2S4, W2S2, respectively. Based on response surface methodology, we constructed composite models of multi-objective demands, whose results indicated that 66-72% FC and 2 g/L salinity were considered the appropriate water-salt combinations for practical production. This paper will be beneficial for maintaining high yield and high quality in tomato production using salty water irrigation.

Mitigating Salt Stress with Biochar: Effects on Yield and Quality of Dwarf Tomato Irrigated with Brackish Water

The increase in the frequency and magnitude of environmental stresses poses a significant risk to the stability of food supplies. In coastal areas of the Mediterranean, brackish water has long been considered a limitation on horticultural production. In this scenario, the use of biochar in agriculture could be considered a valuable tool to cope with the deleterious effects of salt stress. This work aimed to investigate, in a protected environment, the effects of different concentrations of biochar (0, 1, and 2% v/v) obtained from poplar (Populus L.) biomass on the yield and quality of dwarf San Marzano ecotype tomatoes irrigated with saline water at different concentrations of NaCl (0, 40 and 80 mM). The increase in salt concentration from 0 to 80 mM NaCl reduced the total yield (-63%) and the number of fruits (-25%), but improved the main quality parameters such as dry matter (+75%), total soluble solids (+56%), and polyphenol content (+43%). Compared to control conditions, biochar supplementation improved the total yield (+23%) and number of fruits (+26%) without altering the functional and organoleptic characteristics of the fruits. The promising results underscore the potential of biochar as a sustainable solution to amend soils in order to improve tomato production under unfavorable conditions such as high salinity. However, there is a need to clarify which adaptation mechanisms triggered by biochar amending improve production responses even and especially under suboptimal growing conditions.

A Novel MsEOBI-MsPAL1 Module Enhances Salinity Stress Tolerance, Floral Scent Emission and Seed Yield in Alfalfa

Alfalfa (Medicago sativa L.) is an important and widely cultivated forage legume, yet its yield is constrained by salinity stress. In this study, we characterized an R2R3-MYB transcription factor MsEOBI in alfalfa. Its salt tolerance function and regulatory pathways were investigated. The nuclear-localized MsEOBI functions as a transcriptional activator, enhancing salinity tolerance by promoting the biosynthesis of flavonoids and lignin, as well as facilitating the scavenging of reactive oxygen species (ROS). Additionally, MsEOBI promotes pollinator attraction and increases seed yield by activating the biosynthesis of volatile phenylpropanoids. Yeast one-hybrid (Y1H), dual-luciferase reporter and chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) assays demonstrated that MsEOBI directly binds to the promoter regions of MsPAL1, a key gene in the phenylpropanoid pathway, thereby activating its expression. Overexpression of MsPAL1 enhances salinity tolerance in alfalfa. These findings elucidate the role of the MsEOBI-MsPAL1 regulatory module and provide valuable genetic resources for the future breeding of salt-tolerant alfalfa varieties.

Diagnostic species are crucial for the functioning of plant associations in inland salt marshes

Salt marsh vegetation is considered unique and valuable and has been legally protected in Europe for years but is still declining. Its protection is related to vegetation syntaxonomical units. The characteristic combination of diagnostic species is used to create this syntaxonomical system. The aim of our novel study was to assess whether diagnostic species are sufficient for characterising vegetation functioning. Moreover, we included biochemical traits not considered to date in vegetation ecology. We hypothesised that (1) diagnostic species are crucial for the functioning of inland salt marsh vegetation and (2) their morphological and biochemical traits define the functioning of typical salt marsh associations. We chose three typical inland associations to test our hypotheses and measured the morphological and biochemical functional traits of their diagnostic plant species. Our research has shown that diagnostic species play a crucial role not only in distinguishing typical inland salt marsh associations but also in determining their functioning. Among the analysed associations, Salicornietum ramosissimae was the most adaptable to osmotic and oxidative stress under soil salinity. Triglochino maritimae-Glaucetum maritimae showed the lowest salt resistance, as indicated by the highest osmotic and oxidative stress and stress responses. Our findings may facilitate the practical application of new approaches and protection strategies for inland salt marsh habitats.

Alleviating salinity stress in canola (Brassica napus L.) through exogenous application of salicylic acid

Canola, a vital oilseed crop, is grown globally for food and biodiesel. With the enormous demand for growing various crops, the utilization of agriculturally marginal lands is emerging as an attractive alternative, including brackish-saline transitional lands. Salinity is a major abiotic stress limiting growth and productivity of most crops, and causing food insecurity. Salicylic acid (SA), a small-molecule phenolic compound, is an essential plant defense phytohormone that promotes immunity against pathogens. Recently, several studies have reported that SA was able to improve plant resilience to withstand high salinity. For this purpose, a pot experiment was carried out to ameliorate the negative effects of sodium chloride (NaCl) on canola plants through foliar application of SA. Two canola varieties Faisal (V1) and Super (V2) were assessed for their growth performance during exposure to high salinity i.e. 0 mM NaCl (control) and 200 mM NaCl. Three levels of SA (0, 10, and 20 mM) were applied through foliar spray. The experimental design used for this study was completely randomized design (CRD) with three replicates. The salt stress reduced the shoot and root fresh weights up to 50.3% and 47% respectively. In addition, foliar chlorophyll a and b contents decreased up to 61-65%. Meanwhile, SA treatment diminished the negative effects of salinity and enhanced the shoot fresh weight (49.5%), root dry weight (70%), chl. a (36%) and chl. b (67%). Plants treated with SA showed an increased levels of both enzymatic i.e. (superoxide dismutase (27%), peroxidase (16%) and catalase (34%)) and non-enzymatic antioxidants i.e. total soluble protein (20%), total soluble sugar (17%), total phenolic (22%) flavonoids (19%), anthocyanin (23%), and endogenous ascorbic acid (23%). Application of SA also increased the levels of osmolytes i.e. glycine betaine (31%) and total free proline (24%). Salinity increased the concentration of Na+ ions and concomitantly decreased the K+ and Ca2+ absorption in canola plants. Overall, the foliar treatments of SA were quite effective in reducing the negative effects of salinity. By comparing both varieties of canola, it was observed that variety V2 (Super) grew better than variety V1 (Faisal). Interestingly, 20 mM foliar application of SA proved to be effective in ameliorating the negative effects of high salinity in canola plants.

RNA-seq analysis reveals transcriptome reprogramming and alternative splicing during early response to salt stress in tomato root

Salt stress is one of the dominant abiotic stress conditions that cause severe damage to plant growth and, in turn, limiting crop productivity. It is therefore crucial to understand the molecular mechanism underlying plant root responses to high salinity as such knowledge will aid in efforts to develop salt-tolerant crops. Alternative splicing (AS) of precursor RNA is one of the important RNA processing steps that regulate gene expression and proteome diversity, and, consequently, many physiological and biochemical processes in plants, including responses to abiotic stresses like salt stress. In the current study, we utilized high-throughput RNA-sequencing to analyze the changes in the transcriptome and characterize AS landscape during the early response of tomato root to salt stress. Under salt stress conditions, 10,588 genes were found to be differentially expressed, including those involved in hormone signaling transduction, amino acid metabolism, and cell cycle regulation. More than 700 transcription factors (TFs), including members of the MYB, bHLH, and WRKY families, potentially regulated tomato root response to salt stress. AS events were found to be greatly enhanced under salt stress, where exon skipping was the most prevalent event. There were 3709 genes identified as differentially alternatively spliced (DAS), the most prominent of which were serine/threonine protein kinase, pentatricopeptide repeat (PPR)-containing protein, E3 ubiquitin-protein ligase. More than 100 DEGs were implicated in splicing and spliceosome assembly, which may regulate salt-responsive AS events in tomato roots. This study uncovers the stimulation of AS during tomato root response to salt stress and provides a valuable resource of salt-responsive genes for future studies to improve tomato salt tolerance.

The efficiency of chlorophyll fluorescence as a selection criterion for salinity and climate aridity tolerance in barley genotypes

Introduction

In the Near East and North Africa (NENA) region, crop production is being affected by various abiotic factors, including freshwater scarcity, climate, and soil salinity. As a result, farmers in this region are in search of salt-tolerant crops that can thrive in these harsh environments, using poor-quality groundwater. The main staple food crop for most of the countries in this region, Tunisia included, is barley.

Methods

The present study was designed to investigate the sensitivity and tolerance of six distinct barley genotypes to aridity and salinity stresses in five different natural field environments by measuring their photosynthetic activity.

Results and discussion

The results revealed that tolerant genotypes were significantly less affected by these stress factors than sensitive genotypes. The genotypes that were more susceptible to salinity and aridity stress exhibited a significant decline in their photosynthetic activity. Additionally, the fluorescence yields in growth phases J, I, and P declined significantly in the order of humid environment (BEJ), semi-arid site (KAI), and arid environment (MED) and became more significant when salt stress was added through the use of saline water for irrigation. The stress adversely affected the quantum yield of primary photochemistry (φP0), the quantum yield of electron transport (φE0), and the efficiency by trapped excitation (ψ0) in the vulnerable barley genotypes. Moreover, the performance index (PI) of the photosystem II (PSII) was found to be the most distinguishing parameter among the genotypes tested. The PI of sensitive genotypes was adversely affected by aridity and salinity. The PI of ICARDA20 and Konouz decreased by approximately 18% and 33%, respectively, when irrigated with non-saline water. The reduction was even greater, reaching 39%, for both genotypes when irrigated with saline water. However, tolerant genotypes Souihli and Batini 100/1B were less impacted by these stress factors.The fluorescence study provided insights into the photosynthetic apparatus of barley genotypes under stress. It enabled reliable salinity tolerance screening. Furthermore, the study confirmed that the chlorophyll a fluorescence induction curve had an inflection point (step K) even before the onset of visible signs of stress, indicating physiological disturbances, making chlorophyll fluorescence an effective tool for identifying salinity tolerance in barley.

Plant Biostimulants Enhance Tomato Resilience to Salinity Stress: Insights from Two Greek Landraces

Salinity, one of the major abiotic stresses in plants, significantly hampers germination, photosynthesis, biomass production, nutrient balance, and yield of staple crops. To mitigate the impact of such stress without compromising yield and quality, sustainable agronomic practices are required. Among these practices, seaweed extracts (SWEs) and microbial biostimulants (PGRBs) have emerged as important categories of plant biostimulants (PBs). This research aimed at elucidating the effects on growth, yield, quality, and nutrient status of two Greek tomato landraces ('Tomataki' and 'Thessaloniki') following treatments with the Ascophyllum nodosum seaweed extract 'Algastar' and the PGPB 'Nitrostim' formulation. Plants were subjected to bi-weekly applications of biostimulants and supplied with two nutrient solutions: 0.5 mM (control) and 30 mM NaCl. The results revealed that the different mode(s) of action of the two PBs impacted the tolerance of the different landraces, since 'Tomataki' was benefited only from the SWE application while 'Thessaloniki' showed significant increase in fruit numbers and average fruit weight with the application of both PBs at 0.5 and 30 mM NaCl in the root zone. In conclusion, the stress induced by salinity can be mitigated by increasing tomato tolerance through the application of PBs, a sustainable tool for productivity enhancement, which aligns well with the strategy of the European Green Deal.

Development of a Multiplex PCR Assay for the Detection of Tomato Wilt Caused by Coinfection of Fusarium brachygibbosum, Fusarium oxysporum, and Ralstonia solanacearum Based on Comparative Genomics

Tomato is consumed worldwide as fresh or processed food products. However, soilborne diseases of tomato plants caused by coinfection of various pathogens result in great economic losses to the tomato industry. It is difficult to accurately identify and diagnose soilborne diseases of tomato plants caused by pathogen complexes. In this study, we investigated field diseases of tomato plants by pathogen isolation and molecular identification and found that tomato wilt was caused by coinfection of Fusarium brachygibbosum, F. oxysporum, and Ralstonia solanacearum. Therefore, developing a method for simultaneous detection of DNA from F. brachygibbosum, F. oxysporum, and R. solanacearum is of great importance to efficiently and accurately monitor disease development at different growth stages of tomato plants. In this study, we performed a comparative genomic analysis of F. brachygibbosum, F. oxysporum, and R. solanacearum and determined the primer sets for simultaneous detection of DNA from these target pathogens. Then, we tested the reagent and condition parameters of multiplex PCR, including primers, dNTP and Mg2+ concentrations, and annealing temperatures, to determine the optimal parameters of a multiplex PCR system. We evaluated the specificity, sensitivity, and stability of the multiplex PCR system based on the optimized reaction conditions. The multiplex PCR system can specifically identify 13 target pathogens from 57 different fungal and bacterial pathogens, at the lower detection limit of the three target pathogens at concentrations of 100 pg/μl. In addition, we can accurately identify the three pathogens in tomato plants using the optimized multiplex PCR method. These results demonstrated that the multiplex PCR method developed in this study can simultaneously detect DNA from F. brachygibbosum, F. oxysporum, and R. solanacearum in a single PCR system to accurately identify and diagnose the pathogen causing tomato wilt.

Identification, Classification, and Transcriptional Analysis of Rab GTPase Genes from Tomato (Solanum lycopersicum) Reveals Salt Stress Response Genes

Salinity in plants generates an osmotic and ionic imbalance inside cells that compromises the viability of the plant. Rab GTPases, the largest family within the small GTPase superfamily, play pivotal roles as regulators of vesicular trafficking in plants, including the economically important and globally cultivated tomato (Solanum lycopersicum). Despite their significance, the specific involvement of these small GTPases in tomato vesicular trafficking and their role under saline stress remains poorly understood. In this work, we identified and classified 54 genes encoding Rab GTPases in cultivated tomato, elucidating their genomic distribution and structural characteristics. We conducted an analysis of duplication events within the S. lycopersicum genome, as well as an examination of gene structure and conserved motifs. In addition, we investigated the transcriptional profiles for these Rab GTPases in various tissues of cultivated and wild tomato species using microarray-based analysis. The results showed predominantly low expression in most of the genes in both leaves and vegetative meristem, contrasting with notably high expression levels observed in seedling roots. Also, a greater increase in gene expression in shoots from salt-tolerant wild tomato species was observed under normal conditions when comparing Solanum habrochaites, Solanum pennellii, and Solanum pimpinellifolium with S. lycopersicum. Furthermore, an expression analysis of Rab GTPases from Solanum chilense in leaves and roots under salt stress treatment were also carried out for their characterization. These findings revealed that specific Rab GTPases from the endocytic pathway and the trans-Golgi network (TGN) showed higher induction in plants exposed to saline stress conditions. Likewise, disparities in gene expression were observed both among members of the same Rab GTPase subfamily and between different subfamilies. Overall, this work emphasizes the high degree of conservation of Rab GTPases, their high functional diversification in higher plants, and the essential role in mediating salt stress tolerance and suggests their potential for further exploration of vesicular trafficking mechanisms in response to abiotic stress conditions.

Wastewater irrigation and Trichoderma colonization in tomato plants: effects on plant traits, antioxidant activity, and performance of the insect pest Macrosiphum euphorbiae

The scarcity of freshwater for agriculture in many regions has led to the application of sewage and saline water for irrigation. Irrigation with non-conventional water sources could become a non-harmful process for plant cultivation, and the effects of their use on crops should be monitored in order to develop optimal management strategies. One possibility to overcome potential barriers is to use biostimulants such as Trichoderma spp. fungi. Tomato is a crop of great economic importance in the world. This study investigated the joint effects of Trichoderma afroharzianum T-22 on tomato plants irrigated with simulated unconventional waters. The experiment consisted of a control and three water treatments. In the control, the plants were watered with distilled water. The three water treatments were obtained by using an irrigation water added with nitrogen, a wastewater effluent, and a mixed groundwater-wastewater effluents. Potted tomato plants (variety Bobcat) were grown in a controlled growth chamber. Antioxidant activity, susceptibility to the aphids Macrosiphum euphorbiae, and tomato plant growth parameters were estimated. Trichoderma afroharzianum T-22 had a positive effect on plant growth and antioxidant defenses when plants were irrigated with distilled water. Instead, no significant morphological effects induced by T. afroharzianum T-22 on plants were observed when unconventional water was used for irrigation. However, inoculation with T. afroharzianum T-22 activated a stress response that made the colonized plants more susceptible to aphid development and increased their fecundity and longevity. Thanks to this study, it may be possible for the first time to open a new discussion on the practical possibility of using reclaimed wastewater for crop irrigation with the addition of a growth-promoting fungal symbiont.

Hydrogen Peroxide Alleviates Salt Stress Effects on Gas Exchange, Growth, and Production of Naturally Colored Cotton

Cotton is one of the most exploited crops in the world, being one of the most important for the Brazilian Northeast. In this region, the use of irrigation is often necessary to meet the water demand of the crop. Water is often used from underground wells that have a large amount of salt in their constitution, which can compromise the development of crops, so it is vital to adopt strategies that reduce salt stress effects on plants, such as the foliar application of hydrogen peroxide. Thus, the objective of this study was to evaluate the effects of foliar application of hydrogen peroxide on the gas exchange, growth, and production of naturally colored cotton under salt stress in the semi-arid region of Paraíba, Brazil. The experiment was carried out in a randomized block design in a 5 × 5 factorial scheme, with five salinity levels of irrigation water-ECw (0.3, 2.0, 3.7, 5.4 and 7.1 dS m-1)-and five concentrations of hydrogen peroxide-H2O2 (0, 25, 50, 75 and 100 μM), and with three replicates. The naturally colored cotton 'BRS Jade' had its gas exchange, growth, biomass production, and production reduced due to the effects of salt stress, but the plants were able to produce up to the ECw of 3.97 dS m-1. Foliar application of hydrogen peroxide at the estimated concentrations of 56.25 and 37.5 μM reduced the effects of salt stress on the stomatal conductance and CO2 assimilation rate of cotton plants under the estimated ECw levels of 0.73 and 1.58 dS m-1, respectively. In turn, the concentration of 12.5 μM increased water-use efficiency in plants subjected to salinity of 2.43 dS m-1. Absolute and relative growth rates in leaf area increased with foliar application of 100 μM of hydrogen peroxide under ECw of 0.73 and 0.3 dS m-1, respectively. Under conditions of low water salinity (0.3 dS m-1), foliar application of hydrogen peroxide stimulated the biomass formation and production components of cotton.

Exopolysaccharides from endophytic Glutamicibacter halophytocota KLBMP 5180 functions as bio-stimulants to improve tomato plants growth and salt stress tolerance

Microbial exopolysaccharides (EPSs) can promote plants growth and protect them against various abiotic stresses, but the role of actinobacteria-produced EPSs in plant growth promoting is still less known. Here, we aim to explore the effect of EPSs from an endophyte Glutamicibacter halophytocota KLBMP 5180 on tomato seeds germination and seedlings growth under salt stress. Our study revealed that 2.0 g/L EPSs resulted in increased seed germination rate by 23.5 % and 11.0 %, respectively, under 0 and 200 mM NaCl stress conditions. Further pot experiment demonstrated that EPSs significantly promoted seedlings growth under salt stress, with increased height, root length and fibrous roots number. Plant physiological traits revealed that EPSs increased chlorophyll content, enhanced the activity of antioxidant enzymes, soluble sugar, and K+ concentration in seedlings; malondialdehyde and Na+ contents were reduced. Additionally, auxin, abscisic acid, jasmonic acid, and salicylic acid were accumulated significantly in seedlings after EPSs treatment. Furthermore, we identified 1233 differentially expressed genes, and they were significantly enriched in phytohormone signal transmission, phenylpropanoid biosynthesis, and protein processing in endogenous reticulum pathways, etc. Our results suggest that KLBMP 5180-produced EPSs effectively ameliorated NaCl stress in tomato plants by triggering complex regulation mechanism, and showed application potentiality in agriculture.