Salt-sensitive Variety Research Articles

Effectiveness of salt priming and plant growth-promoting bacteria in mitigating salt-induced photosynthetic damage in melon.

Seed priming and plant growth-promoting bacteria (PGPB) may alleviate salt stress effects. We exposed a salt-sensitive variety of melon to salinity following seed priming with NaCl and inoculation with Bacillus. Given the sensitivity of photosystem II (PSII) to salt stress, we utilized dark- and light-adapted chlorophyll fluorescence alongside analysis of leaf stomatal conductance of water vapour (Gsw). Priming increased total seed germination by 15.5% under salt-stress. NaCl priming with Bacillus inoculation (PB) increased total leaf area (LA) by 45% under control and 15% under stress. Under the control condition, priming (P) reduced membrane permeability (RMP) by 36% and PB by 55%, while under stress Bacillus (BS) reduced RMP by 10%. Although Bacillus inoculation (B) and priming (P) treatments did not show significant effects on some PSII efficiency parameters (FV/FM, ABS/RC, PIABS, FM), the BS treatment induced a significantly higher quantum efficiency of PSII (ΦPSII) and increased Gsw by 159% in the final week of the experiment. The BS treatment reduced electron transport rate per reaction center (ETO/RC) by 10% in comparison to the salt treatment, which showed less reaction centre damage. Bacillus inoculation and seed priming treatment under the stressed condition (PBS) induced an increase in electron transport rate of 40%. Salt stress started to show significant effects on PSII after 12 days, and adversely impacted all morphological and photosynthetic parameters after 22 days. Salt priming and PGPB mitigated the negative impacts of salt stress and may serve as effective tools in future-proofing saline agriculture.

Prohexadione Calcium Improves Rice Yield Under Salt Stress by Regulating Source-Sink Relationships During the Filling Period.

Salt stress is an important factor affecting the growth and development of rice, and prohexadione calcium (Pro-Ca) plays an important role in alleviating rice salt stress and improving rice yield. However, there are few studies on how Pro-Ca improves rice yield under salt stress by regulating the source-sink metabolism. In this study, we used Guanghong 3 (salt-tolerant variety) and Huanghuazhan (salt-sensitive variety) as experimental materials to investigate the dynamic changes in the synthesis and partitioning of nonstructural carbohydrates among source-sink, the dynamic changes in related enzyme activities, the effects of the source-sink metabolism on yield in rice under salt stress and the effect of Pro-Ca during the filling period. The results of this study showed that Pro-Ca improved photosynthetic efficiency by increasing leaf photosynthetic gas exchange parameters and other stomatal factors on the one hand and, on the other hand, promoted sugar catabolism and reduced sugar synthesis by increasing leaf sucrose synthase activity and decreasing sucrose phosphate synthase activity, alleviating the inhibitory effect of high concentrations of sugars in the leaves on photosynthesis. Meanwhile, Pro-Ca promotes the transport of sugars from source (leaves) to sink (seeds), increases the sugar content in the seeds, and promotes starch synthesis in the seeds by increasing starch phosphorylase, which promotes seed filling, thus increasing the number of solid grains on the primary and secondary branches of the panicle in rice, increasing the 1000-grain weight, and ultimately increasing the seed setting rate and yield. These results indicated that Pro-Ca alleviated the inhibitory effect of salt stress on rice leaf photosynthesis through stomatal and non-stomatal factors. Meanwhile, Pro-Ca promotes the transport of rice sugars from source to sink under salt stress, regulates the source-sink relationship during the filling period of rice, promotes starch synthesis, and ultimately improves rice yield.

Enhancing Soybean Salt Tolerance with GSNO and Silicon: A Comprehensive Physiological, Biochemical, and Genetic Study.

Soil salinity is a major global challenge affecting agricultural productivity and food security. This study explores innovative strategies to improve salt tolerance in soybean (Glycine max), a crucial crop in the global food supply. This study investigates the synergistic effects of S-nitroso glutathione (GSNO) and silicon on enhancing salt tolerance in soybean (Glycine max). Two soybean cultivars, Seonpung (salt-tolerant) and Cheongja (salt-sensitive), were analyzed for various physiological, biochemical, and genetic traits under salt stress. The results showed that the combined GSNO and Si treatment significantly improved several key traits, including plant height, relative water content, root development, nodule numbers, chlorophyll content, and stomatal aperture, under both control and salt stress conditions. Additionally, this treatment optimized ion homeostasis by enhancing the Na/K ratio and Ca content, while reducing damage markers such as electrolyte leakage, malondialdehyde, and hydrogen peroxide. The stress-responsive compounds, including proline, ascorbate peroxidase, and water-soluble proteins, were elevated under stress conditions, indicating improved tolerance. Gene expression analysis revealed significant upregulation of genes such as GmNHX1, GmSOS2, and GmAKT1, associated with salt stress response, while GmNIP2.1, GmNIP2.2, and GmLBR were downregulated in both varieties. Notably, the salt-sensitive variety Cheongja exhibited higher electrolyte leakage and oxidative damage compared to the salt-tolerant Seonpung. These findings suggest that the combination of GSNO and silicon enhances salt tolerance in soybean by improving physiological resilience, ion homeostasis, and stress-responsive gene expression.

Genome-wide identification, gene cloning, subcellular location and expression analysis of the OPR gene family under salt stress in sweetpotato

BackgroundThe 12-oxo-phytodienoic acid reductase (OPR) enzyme is crucial for the synthesis of jasmonates (JAs), and is involved in the plant stress response. However, the OPR gene family in sweetpotato, an important horticultural crop, remains unidentified.ResultsIn this study, we employed bioinformatics techniques to identify nine IbOPR genes. Phylogenetic analysis revealed that these genes could be divided into Group I and Group II. Synteny analysis indicated that IbOPR evolution was driven by tandem duplication, whole-genome duplication (WGD), and segmental duplication events. The promoter sequences of IbOPRs were found to be associated with stress and hormonal responses. Additionally, we successfully cloned four IbOPRs from "Haida HD7791" and "Haida HD7798" using homologous cloning technology. These sequences were 1203 bp, 1200 bp, 1134 bp, and 1137 bp in length and encoded 400, 399, 377, and 378 amino acids, respectively. The protein sequence similarity between the salt-tolerant variety "Haida HD7791" and the salt-sensitive variety "Haida HD7798" was determined to be 96.75% for IbOPR2, 99.75% for IbOPR3, 92.06% for IbOPR6, and 98.68% for IbOPR7. Phylogenetic analysis categorized IbOPR2 and IbOPR3 proteins into Group II, while IbOPR6 and IbOPR7 proteins belonged to Group I. Subcellular localization experiments showed IbOPR2 protein present in the peroxisome, while IbOPR3, IbOPR6, and IbOPR7 proteins were found in the cytoplasm and nucleus. Salt stress induction experiments demonstrated that IbOPR2, IbOPR3, and IbOPR7 were significantly upregulated only in 'Haida HD7791' after 6 h. In contrast, IbOPR6 was induced in 'Haida HD7798' at 6 h but inhibited in 'Haida HD7791' at later time points (12, 24, 48, and 72 h), highlighting functional differences in salt stress responses.ConclusionsOur findings suggest that IbOPR2 may play a crucial role in sweetpotato's response to salt stress by participating in JAs synthesis. These results provide a foundation for future functional analyses of OPR genes in sweetpotato.

Unveiling Salt Tolerance Mechanisms and Hub Genes in Alfalfa (Medicago sativa L.) Through Transcriptomic and WGCNA Analysis.

Alfalfa (Medicago sativa L.), an important forage crop with high nutritional value and good palatability, plays a vital role in the development of animal husbandry in China. In Northeast China, there are vast areas of saline-alkali land that remain undeveloped. Given that alfalfa is a highly adaptable forage crop, exploring its salt tolerance at the molecular transcriptional level and identifying salt-tolerant genes has great significance for breeding salt-resistant alfalfa varieties. This also provides valuable genetic resources for better utilization of saline-alkali land. In this study, we conducted two rounds of screening on 41 alfalfa varieties and identified WL168 as a salt-sensitive variety and Longmu801 as a salt-tolerant variety. After 7 days of 300 mM salt stress, both varieties showed a decreasing trend in plant height, fresh weight, and dry weight over time, but Longmu801 demonstrated better water retention ability compared to WL168. Chlorophyll content also declined, but chlorophyll a and total chlorophyll levels in Longmu801 were higher than in WL168. Hydrogen peroxide and malondialdehyde levels increased overall, but Longmu801 had significantly lower levels than WL168 under prolonged stress. Both varieties showed increasing trends in soluble sugars, proline, and antioxidant enzymes (SOD, POD, CAT), with Longmu801 significantly outperforming WL168. This suggests that the two varieties share similar growth and physiological response mechanisms, with their differences primarily arising from variations in indicator levels. In the above, comparisons between varieties were conducted based on the relative values of the indicators in relation to their controls. Transcriptomic analysis revealed that under salt stress, Longmu801 had 16,485 differentially expressed genes (DEGs) relative to its control, while WL168 had 18,726 DEGs compared to its control. Among these, 2164 DEGs shared the same expression trend, with GO functions enriched in response to oxidative stress, nucleus, plasma membrane, and others. The KEGG pathways were enriched in phenylpropanoid biosynthesis, protein processing in the endoplasmic reticulum, starch and sucrose metabolism, and others. This suggests that alfalfa's transcriptional response mechanism to salt stress involves these pathways. Additionally, the variety-specific DEGs were also enriched in the same KEGG pathways and GO functions, indicating that the differences between the two varieties stem from their unique stress-responsive DEGs, while their overall mechanisms for coping with stress remain similar. To further identify salt stress-related genes, this study conducted WGCNA analysis using 32,683 genes and physiological indicators. Six modules closely related to physiological traits were identified, and the top five genes ranked by degree in each module were selected as hub genes. Further analysis of these hub genes identified five genes directly related to salt stress: Msa085011, Msa0605650, Msa0397400, Msa1258740, and Msa0958830. Mantel test analysis revealed that these genes showed strong correlations with physiological indicators. This study will provide important insights for breeding salt-tolerant alfalfa varieties.

Identification of salt tolerance of different Chinese kale cultivars under NaCl stress at seedling stage

In order to understand the salt tolerance of different Chinese kale varieties at seedling stage and screen out the varieties with strong salt tolerance at seedling stage, the seeds of 26 Chinese kale varieties were used as materials. The growth indexes, physiological indexes, seedling rate and salt damage index of different Chinese kale varieties were compared and cluster analyzed by means of tissue culture. The results showed that: (1) under 160 mmol∙L−1 NaCl stress, the different Chinese kale varieties at growth indexes, physiological indexes, seedling rate and salt damage index were significantly different, the relative seedling rate of R4, R14 and R32 reached 100.00%, and the salt damage index was the lowest, which was 20.00%; The correlation analysis showed that the relative seedling rate, the relative content of soluble protein, the relative content of soluble sugar and the relative value of Leaf SPAD were all negatively correlated with the salt damage index, and the relative conductivity and the relative content of malondialdehyde were all positively correlated with the salt damage index. (2) The average value of 14 salt tolerance indexes was used to cluster analyze the salt tolerance of 26 Chinese kale varieties. The tested materials were divided into four categories: high salt tolerance, moderate salt tolerance, low salt tolerance and salt sensitivity. R14, R25, R30 and R32 were highly salt tolerant varieties and R24 was salt sensitive varieties, which laid a foundation for further breeding and genetic research of salt tolerant varieties.

Marker-Assisted Selection of Jacalin-Related Lectin Genes OsJRL45 and OsJRL40 Derived from Sea Rice 86 Enhances Salt Tolerance in Rice.

Soil salinization limits rice growth and is an important restriction on grain yield. Jacalin-related lectins are involved in multiple stress responses, but their role in salt stress responses and use as molecular markers for salt tolerance remain poorly understood. Salt stress treatments and RT-qPCR analyses of Sea Rice 86 (SR86), 9311, and Nipponbare (Nip) showed that OsJRL45 and OsJRL40 enhanced tolerance of salt stress in SR86. Molecular markers based on sequence differences in SR86 and the salt-sensitive variety, 9311, in the intergenic region between OsJRL45 and OsJRL40 were validated in recombinant inbred lines derived from SR86 and 9311, hybrid populations, and common rice varieties. Yeast two-hybrid and bimolecular fluorescence complementation demonstrated that OsJRL45 and OsJRL40 interacted. Co-transformation of Nip with OsJRL45 and OsJRL40 derived from SR86 had no effect on the mature phenotype in T2 plants; however, salt stress at the three-leaf stage led to significant increases in CAT, POD, SOD, and Pro contents, but reduced MDA content in transgenic plants. Transcriptomic analysis identified 834 differentially expressed genes in transgenic plants under salt stress. GO and KEGG enrichment analyses indicated that metabolic pathways related to antioxidant responses and osmotic balance were crucial for salt-stress tolerance. Thus, molecular markers based on nucleotide differences in OsJRL45 and OsJRL40 provide a novel method for identifying salt-tolerant rice varieties.

QTL-Seq identified a genomic region on chromosome 1 for soil-salinity tolerance in F2 progeny of Thai salt-tolerant rice donor line "Jao Khao".

Owing to advances in high-throughput genome sequencing, QTL-Seq mapping of salt tolerance traits is a major platform for identifying soil-salinity tolerance QTLs to accelerate marker-assisted selection for salt-tolerant rice varieties. We performed QTL-BSA-Seq in the seedling stage of rice from a genetic cross of the extreme salt-sensitive variety, IR29, and "Jao Khao" (JK), a Thai salt-tolerant variety. A total of 462 F2 progeny grown in soil and treated with 160 mM NaCl were used as the QTL mapping population. Two high- and low-bulk sets, based on cell membrane stability (CMS) and tiller number at the recovery stage (TN), were equally sampled. The genomes of each pool were sequenced, and statistical significance of QTL was calculated using QTLseq and G prime (G') analysis, which is based on calculating the allele frequency differences or Δ(SNP index). Both methods detected the overlapping interval region, wherein CMS-bulk was mapped at two loci in the 38.41-38.85 Mb region with 336 SNPs on chromosome 1 (qCMS1) and the 26.13-26.80 Mb region with 1,011 SNPs on chromosome 3 (qCMS3); the Δ(SNP index) peaks were -0.2709 and 0.3127, respectively. TN-bulk was mapped at only one locus in the overlapping 38.26-38.95 Mb region on chromosome 1 with 575 SNPs (qTN1) and a Δ(SNP index) peak of -0.3544. These identified QTLs in two different genetic backgrounds of segregating populations derived from JK were validated. The results confirmed the colocalization of the qCMS1 and qTN1 traits on chromosome 1. Based on the CMS trait, qCMS1/qTN1 stably expressed 6%-18% of the phenotypic variance in the two validation populations, while qCMS1/qTN1 accounted for 16%-20% of the phenotypic variance in one validation population based on the TN trait. The findings confirm that the CMS and TN traits are tightly linked to the long arm of chromosome 1 rather than to chromosome 3. The validated qCMS-TN1 QTL can be used for gene/QTL pyramiding in marker-assisted selection to expedite breeding for salt resistance in rice at the seedling stage.

Overexpression of GhGSTF9 Enhances Salt Stress Tolerance in Transgenic Arabidopsis.

Soil salinization is a major abiotic stress factor that negatively impacts plant growth, development, and crop yield, severely limiting agricultural production and economic development. Cotton, a key cash crop, is commonly cultivated as a pioneer crop in regions with saline-alkali soil due to its relatively strong tolerance to salt. This characteristic renders it a valuable subject for investigating the molecular mechanisms underlying plant salt tolerance and for identifying genes that confer salt tolerance. In this study, focus was placed on examining a salt-tolerant variety, E991, and a salt-sensitive variety, ZM24. A combined analysis of transcriptomic data from these cotton varieties led to the identification of potential salt stress-responsive genes within the glutathione S-transferase (GST) family. These versatile enzyme proteins, prevalent in animals, plants, and microorganisms, were demonstrated to be involved in various abiotic stress responses. Our findings indicate that suppressing GhGSTF9 in cotton led to a notably salt-sensitive phenotype, whereas heterologous overexpression in Arabidopsis plants decreases the accumulation of reactive oxygen species under salt stress, thereby enhancing salt stress tolerance. This suggests that GhGSTF9 serves as a positive regulator in cotton's response to salt stress. These results offer new target genes for developing salt-tolerant cotton varieties.

Comparative Physiological and Transcriptomic Profiling Reveals the Characteristics of Tissue Tolerance Mechanisms in the japonica Rice Landrace Under Salt Stress

The aim of this study was to characterize the tissue tolerance mechanisms of rice under salt stress. Our preliminary experiment identified a japonica rice landrace Shuzenji-kokumai (SZK), which is considered to be tissue-tolerant because it can maintain better growth than salt-sensitive rice varieties while having a high-Na+ concentration in the shoots under salt stress. These mechanisms differ from those of most salt-tolerant rice varieties, which have low Na+ concentrations in the shoots. We compared the physiological and molecular characteristics of SZK with those of FL478, a salt-tolerant variety, and Kunishi, a salt-sensitive variety. Under salt stress conditions, SZK accumulated high levels of Na+ in the roots, leaf sheaths, and leaf blades, which were almost as high as those in the salt-sensitive Kunishi. Simultaneously, SZK maintained better growth and physiological status, as determined by its higher dry weight, lower electrolyte leakage ratio, and lower malondialdehyde concentration. Expressions of OsNHX1 and OsNHX2 were upregulated in the leaf sheaths of SZK, suggesting that Na+ might be compartmentalized in the vacuoles to avoid cytosolic Na+ toxicity. In contrast, FL478 showed upregulation of OsHKT1;5 and OsSOS1 in the roots, which may exclude Na+ from the shoots. RNA-seq analysis showed that 4623 and 1998 differentially expressed genes were detected in the leaf sheaths and leaf blades of SZK, respectively. Among them, the HSP (heat shock protein) gene expression was highly up-regulated only in SZK, indicating that SZK protects against the protein damage caused by Na+ toxicity. Our findings suggest that SZK has atypical survival mechanisms under salt stress conditions. These mechanisms offer potential traits for improving salt tolerance in rice in terms of tissue tolerance.

Regulation of SmEXPA13 expression by SmMYB1R1-L enhances salt tolerance in Salix matsudana Koidz

Expansins, cell wall proteins, play a significant role in plant stress resistance. Our previous study confirmed the expression of the expansin gene SmEXPA13 from Salix matsudana Koidz. enhanced salt tolerance of plants. This report presented an assay that the expression of SmEXPA13 was higher in the salt-resistant willow variety 9901 than in the salt-sensitive variety Yanjiang. In order to understand the possible reasons, a study of the regulation process was conducted. Despite being cloned from both varieties, SmEXPA13 and its promotor showed no significant differences in the structure and sequence. A transcription factor (TF), SmMYB1R1-L, identified through screening the yeast library of willow cDNA, was found to regulate SmEXPA13. Yeast one-hybrid (Y1H) assay confirmed that SmMYB1R1-L could bind to the MYB element at the −520 bp site on the SmEXPA13 promotor. A dual-luciferase reporter assay also demonstrated that SmMYB1R1-L could greatly activate SmEXPA13 expression. The willow calli with over-expression of SmMYB1R1-L exhibited better physiological performance than the wild type under salt stress. Further testing the expression of SmMYB1R1-L displayed it significantly higher in 9901 willow than that in Yanjiang under salt stress. In conclusion, the high accumulation of SmMYB1R1-L in 9901 willow under salt stress led to the high expression of SmEXPA13, resulting in variations in salt stress resistance among willow varieties. The SmMYB1R1-L/SmEXPA13 cascade module in willow offers a new perspective on plant resistance mechanisms.

Alginate Oligosaccharides Alleviate Salt Stress in Rice Seedlings by Regulating Cell Wall Metabolism to Maintain Cell Wall Structure and Improve Lodging Resistance.

Salt stress is one of the major abiotic stresses that damage the structure and composition of cell walls. Alginate oligosaccharides (AOS) have been advocated to significantly improve plant stress tolerance. The metabolic mechanism by which AOS induces salt tolerance in rice cell walls remains unclear. Here, we report the impact of AOS foliar application on the cell wall composition of rice seedlings using the salt-tolerant rice variety FL478 and the salt-sensitive variety IR29. Data revealed that salt stress decreased biomass, stem basal width, stem breaking strength, and lodging resistance; however, it increased cell wall thickness. In leaves, exogenous AOS up-regulated the expression level of OSCESA8, increased abscisic acid (ABA) and brassinosteroids (BR) content, and increased β-galacturonic activity, polygalacturonase activity, xylanase activity, laccase activity, biomass, and cellulose content. Moreover, AOS down-regulated the expression levels of OSMYB46 and OSIRX10 and decreased cell wall hemicellulose, pectin, and lignin content to maintain cell wall stability under salt stress. In stems, AOS increased phenylalamine ammonia-lyase and tyrosine ammonia-lyase activities, while decreasing cellulase, laccase, and β-glucanase activities. Furthermore, AOS improved the biomass and stem basal width and also enhanced the cellulose, pectin, and lignin content of the stem, As a result, increased resistance to stem breakage strength and alleviated salt stress-induced damage, thus enhancing the lodging resistance. Under salt stress, AOS regulates phytohormones and modifies cellulose, hemicellulose, lignin, and pectin metabolism to maintain cell wall structure and improve stem resistance to lodging. This study aims to alleviate salt stress damage to rice cell walls, enhance resistance to lodging, and improve salt tolerance in rice by exogenous application of AOS.

Salt Tolerance Assessment in Triticum Aestivum and Triticum Durum.

Salt stress is a multicomponent phenomenon; it includes many processes that directly or indirectly affect the plant. Attempts have been made to comprehensively consider the processes of salt stress in plants Triticum aestivum (variety Orenburgskaya 22) and Triticum durum (variety Zolotaya). The study used methods of light and fluorescence microscopy, methods of immunofluorodetection, expression of DNA methyltransferase genes, genes of the ion transporter and superoxide dismutase families, as well as biochemical determination of total antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) reagent. According to morphometric indicators, the Orenburgskaya 22 variety showed greater tolerance to the action of 150 mM NaCl than the Zolotaya variety. The level of expression of genes of the HKT ion transporter family in the Orenburgskaya 22 variety is higher than in the Zolotaya variety. It was found that the expression of the DNA methyltransferase gene DRM2.1, which post-translationally methylates cytosine residues, is 22.3 times higher in Zolotaya compared to Orenburg 22 when exposed to salt. The accumulation of toxic ions is accompanied by an increase in reactive oxygen species (ROS) and increased damage to root tissue, especially in the Zolotaya variety. Using fluorescence microscopy using the Carboxy-H2DFF marker in the Orenburgskaya 22 variety at high NaCl concentrations, the highest fluorescence intensity was determined in the cap zone; in the Zolotaya variety-in the zones of the cap and root meristem. Excess ROS is more successfully removed in the Orenburgskaya 22 variety, which has a higher level of antioxidant activity (AOA), as well as the level of expression of the Cu/ZnSOD and MnSOD superoxide dismutase genes. Using programmed cell death (PCD) markers based on the release of cytochrome c from mitochondria into the cytoplasm, DNA breakage and the release of phosphatidylserine from mitochondria, the degree of damage to root cells was assessed in both wheat varieties. It has been proven that wheat cell death occurs through the mitochondrial pathway. It was noted that the salt-sensitive variety Zolotaya had a significant number of necrotic cells. Based on the data obtained, it was concluded that the Orenburgskaya 22 variety exhibits greater resistance to salinity than the Zolotaya variety. These data may be of practical importance for enhancing protective mechanisms under abiotic stress.

Transcriptome Analysis for Salt-Responsive Genes in Two Different Alfalfa (Medicago sativa L.) Cultivars and Functional Analysis of MsHPCA1.

Alfalfa (Medicago sativa L.) is an important forage legume and soil salinization seriously affects its growth and yield. In a previous study, we identified a salt-tolerant variety 'Gongnong NO.1' and a salt-sensitive variety 'Sibeide'. To unravel the molecular mechanism involved in salt stress, we conducted transcriptomic analysis on these two cultivars grown under 0 and 250 mM NaCl treatments for 0, 12, and 24 h. Totals of 336, and 548 differentially expressed genes (DEGs) in response to NaCl were, respectively, identified in the 'Gongnong NO.1' and 'Sibeide' varieties. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathway enrichment analysis showed that the DEGs were classified in carbohydrate metabolism, energy production, transcription factor, and stress-associated pathway. Expression of MsHPCA1, encoding a putative H2O2 receptor, was responsive to both NaCl and H2O2 treatment. MsHPCA1 was localized in cell membrane and overexpression of MsHPCA1 in alfalfa increased salt tolerance and H2O2 content. This study will provide new gene resources for the improvement in salt tolerance in alfalfa and legume crops, which has important theoretical significance and potential application value.

Effects of riboflavin application on rice growth under salinized soil conditions

Salt-sensitive crop varieties suffer from oxidative stress as a consequence of osmotic and ionic stresses in plants under salinity stress. This study is aimed at identifying the effects of riboflavin (RIB) application on uplifting rice growth under salinized soil condition. Two-week-old seedlings of IR29 (a salt-sensitive variety) were supplemented with 0.5 μM of RIB, and 50 mM of NaCl was supplied for 2 weeks, inducing salinized soil conditions. The results indicated that RIB pretreatment (RP) seedlings possessed higher plant biomass, and lower electrolyte leakage ration (ELR), hydrogen peroxide (H2O2) and malondialdehyde (MDA) concentrations, higher chlorophyll, magnesium (Mg), and iron (Fe) concentrations in the leaf blades, a higher proline concentration, and a lower Na+ concentration in the leaf blades. To further understand the mechanisms behind the difference in plant growth between the RP and non-RP seedlings, molecular analysis revealed that RP seedlings upregulated OsNHX1 and OsHKT1;5 expressions were observed in the roots of RP seedlings, regulating Na+ uptake through the transpiration stream and reducing Na+ concentration in the leaf blades. Collectively, these results suggest that RP is a potent method for improving plant growth under salinized soil conditions.

Low apoplastic Na+ and intracellular ionic homeostasis confer salinity tolerance upon Ca2SiO4 chemigation in Zea mays L. under salt stress.

Salinity is known to have a greater impact on shoot growth than root growth. Na+ buildup in plant tissue under salt stress has been proposed as one of the main issues that causes growth inhibition in crops via ionic imbalances, osmotic stress and pH disturbances. However, the evidence for apoplastic Na+ buildup and the role of silicon in Na+ accumulation at the subcellular level is still enigmatic. The current study focuses on the accumulation of Na+ in the apoplast and symplast of younger and older leaves of two maize varieties (Iqbal as salt-tolerant and Jalal as salt-sensitive) using hydroponic culture along with silicon supplementation under short-term salinity stress. Subcellular ion analysis indicated that silicon nutrition decreased Na+ concentration in both apoplastic washing fluid and symplastic fluid of maize under salt stress. The addition of silicon under NaCl treatment resulted in considerable improvement in fresh biomass, relative water content, chlorophyll content, and concentration of important subcellular ions (i.e., Ca2+, Mg2+, and K+). Knowledge of subcellular ion analysis is essential for solving the mechanisms underlying vital cellular functions e.g. in the current study, the soluble Na+ concentration in the apoplast of older leaves was found to be significantly greater (36.1 mM) in the salt-sensitive variety under NaCl treatment, which was 42.4% higher when compared to the Na+ concentration in the salt-tolerant variety under the same treatment which can influence permeability of cell membrane, signal transduction pathways and provides insights into how ion compartmentalization can contributes to salt tolerance. Calcium silicate enrichment can contribute to increased growth and improved ionic homeostasis by minimizing leaf electrolyte leakage, improving mechanical functions of cell wall and reducing water loss, and improved photosynthetic function. In current investigation, increased water content and intracellular ionic homeostasis along with reduced concentration of Na+ in the maize leaf apoplast suggest that calcium silicate can be used to ameliorate the adverse effects of salt stress and obtain yield using marginal saline lands.

Ascophyllum nodosum SWE enhances root anatomy, but not POD activity in both a salt-tolerant and salt-sensitive soybean ( Glycine max) variety exposed to salt stress.

There is growing evidence that seaweed extracts (SWE) may be a solution for mitigating the negative effects of salt stress on crop yield and quality, as they introduce bioactive ingredients able to regulate the expression of growth-inducing and stress-responsive genes. We demonstrate that SWE slightly ameliorated the negative physical growth effects of salt stress, especially in the root anatomy of the salt-sensitive (Clark) variety. The SWE did not stimulate or enhance peroxidase (POD) activity in either the salt-sensitive (Clark) or salt-tolerant variety (Manokin). However, a complete assessment of other antioxidant enzymes (SOD, CAT, APX) involved in the ROS detoxification process is further required.

Transcriptome analysis and physiological changes in the leaves of two Bromus inermis L. genotypes in response to salt stress.

Soil salinity is a major factor threatening the production of crops around the world. Smooth bromegrass (Bromus inermis L.) is a high-quality grass in northern and northwestern China. Currently, selecting and utilizing salt-tolerant genotypes is an important way to mitigate the detrimental effects of salinity on crop productivity. In our research, salt-tolerant and salt-sensitive varieties were selected from 57 accessions based on a comprehensive evaluation of 22 relevant indexes, and their salt-tolerance physiological and molecular mechanisms were further analyzed. Results showed significant differences in salt tolerance between 57 genotypes, with Q25 and Q46 considered to be the most salt-tolerant and salt-sensitive accessions, respectively, compared to other varieties. Under saline conditions, the salt-tolerant genotype Q25 not only maintained significantly higher photosynthetic performance, leaf relative water content (RWC), and proline content but also exhibited obviously lower relative conductivity and malondialdehyde (MDA) content than the salt-sensitive Q46 (p < 0.05). The transcriptome sequencing indicated 15,128 differentially expressed genes (DEGs) in Q46, of which 7,885 were upregulated and 7,243 downregulated, and 12,658 DEGs in Q25, of which 6,059 were upregulated and 6,599 downregulated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the salt response differences between Q25 and Q46 were attributed to the variable expression of genes associated with plant hormone signal transduction and MAPK signaling pathways. Furthermore, a large number of candidate genes, related to salt tolerance, were detected, which involved transcription factors (zinc finger proteins) and accumulation of compatible osmolytes (glutathione S-transferases and pyrroline-5-carboxylate reductases), etc. This study offers an important view of the physiological and molecular regulatory mechanisms of salt tolerance in two smooth bromegrass genotypes and lays the foundation for further identification of key genes linked to salt tolerance.

Variety-driven rhizosphere microbiome bestows differential salt tolerance to alfalfa for coping with salinity stress.

Soil salinization is a global environmental issue and a significant abiotic stress that threatens crop production. Root-associated rhizosphere microbiota play a pivotal role in enhancing plant tolerance to abiotic stresses. However, limited information is available concerning the specific variations in rhizosphere microbiota driven by different plant genotypes (varieties) in response to varying levels of salinity stress. In this study, we compared the growth performance of three alfalfa varieties with varying salt tolerance levels in soils with different degrees of salinization. High-throughput 16S rRNA and ITS sequencing were employed to analyze the rhizosphere microbial communities. Undoubtedly, the increasing salinity significantly inhibited alfalfa growth and reduced rhizosphere microbial diversity. However, intriguingly, salt-tolerant varieties exhibited relatively lower susceptibility to salinity, maintaining more stable rhizosphere bacterial community structure, whereas the reverse was observed for salt-sensitive varieties. Bacillus emerged as the dominant species in alfalfa's adaptation to salinity stress, constituting 21.20% of the shared bacterial genera among the three varieties. The higher abundance of Bacillus, Ensifer, and Pseudomonas in the rhizosphere of salt-tolerant alfalfa varieties is crucial in determining their elevated salt tolerance. As salinity levels increased, salt-sensitive varieties gradually accumulated a substantial population of pathogenic fungi, such as Fusarium and Rhizoctonia. Furthermore, rhizosphere bacteria of salt-tolerant varieties exhibited increased activity in various metabolic pathways, including biosynthesis of secondary metabolites, carbon metabolism, and biosynthesis of amino acids. It is suggested that salt-tolerant alfalfa varieties can provide more carbon sources to the rhizosphere, enriching more effective plant growth-promoting bacteria (PGPB) such as Pseudomonas to mitigate salinity stress. In conclusion, our results highlight the variety-mediated enrichment of rhizosphere microbiota in response to salinity stress, confirming that the high-abundance enrichment of specific dominant rhizosphere microbes and their vital roles play a significant role in conferring high salt adaptability to these varieties.

Genome-wide analysis of the SCAMPs gene family of soybean and functional identification of GmSCAMP5 in salt tolerance

The effect of salt damage on plants is mainly caused by the toxic effect of Na+. Studies showed that the secretory carrier membrane proteins were associated with the Na+ transport. However, the salt tolerance mechanism of secretory carrier protein (SCAMP) in soybean was yet to be defined. In this study, ten potential SCAMP genes distributed in seven soybean chromosomes were identified in the soybean genome. The phylogenetic tree of SCAMP domain sequences of several plants can divide SCAMPs into two groups. Most GmSCAMPs genes contained multiple Box4, MYB and MYC cis-elements indicated they may respond to abiotic stresses. We found that GmSCAMP1, GmSCAMP2 and GmSCAMP4 expressed in several tissues and GmSCAMP5 was significantly induced by salt stress. GmSCAMP5 showed the same expression patterns under NaCl treatment in salt-tolerant and salt-sensitive soybean varieties, but the induced time of GmSCAMP5 in salt-tolerant variety was earlier than that of salt-sensitive variety. To further study the effect of GmSCAMP5 on the salt tolerance of soybean plants, compared to GmSCAMP5-RNAi and EV-Control plants, GmSCAMP5-OE had less wilted leave and higher SPAD value. Compared to empty vector control, less trypan blue staining was observed in GmSCAMP5-OE leaves while more staining in GmSCAMP5-RNAi leaves. The Na+ of GmSCAMP5-RNAi plants leaves under NaCl stress were significantly higher than that in EV-Control plants, while significantly lower Na+ in GmSCAMP5-OE plants than in that EV-Control plants. The contents of leaves K+ of GmSCAMP5-RNAi, EV-Control, and GmSCAMP5-OE plants under NaCl stress were opposite to that of leaves Na+ content. Finally, salt stress-related genes NHX1, CLC1, TIP1, SOD1, and SOS1 in transformed hairy root changed significantly compared with the empty control. The research will provide novel information for study the molecular regulation mechanism of soybean salt tolerance.