Salt-sensitive Cultivar Research Articles

RNA-Seq and WGCNA Analyses Reveal Key Regulatory Modules and Genes for Salt Tolerance in Cotton.

The problem of soil salinization has seriously hindered agricultural development. Cotton is a pioneering salinity-tolerant crop, so harvesting its key salinity-tolerant genes is important for improving crop salt tolerance. In this study, we analyzed changes in the transcriptome expression profiles of the salt-tolerant cultivar Lu Mian 28 (LM) and the salt-sensitive cultivar Zhong Mian Suo 12 (ZMS) after applying salt stress, and we constructed weighted gene co-expression networks (WGCNA). The results indicated that photosynthesis, amino acid biosynthesis, membrane lipid remodeling, autophagy, and ROS scavenging are key pathways in the salt stress response. Plant-pathogen interactions, plant hormone signal transduction, the mitogen-activated protein kinase (MAPK) signaling pathway, and carotenoid biosynthesis are the regulatory networks associated with these metabolic pathways that confer cotton salt tolerance. The gene-weighted co-expression network was used to screen four modules closely related to traits, identifying 114 transcription factors, including WRKYs, ERFs, NACs, bHLHs, bZIPs, and MYBs, and 11 hub genes. This study provides a reference for acquiring salt-tolerant cotton and abundant genetic resources for molecular breeding.

Metabolic adaptations leading to an enhanced lignification in wheat roots under salinity stress.

Analysis of salinity tolerance processes in wheat has focused on salt exclusion from shoots while root phenotypes have received limited attention. Here, we consider the varying phenotypic response of four bread wheat varieties that differ in their type and degree of salt tolerance and assess their molecular responses to salinity and changes in root cell wall lignification. These varieties were Westonia introgressed with Nax1 and Nax2 root sodium transporters (HKT1;4-A and HKT1;5-A) that reduce Na+ accumulation in leaves, as well as the 'tissue tolerant' Portuguese landrace Mocho de Espiga Branca that has a mutation in the homologous gene HKT1;5-D and has high Na+ concentration in leaves. These three varieties were compared with the relatively more salt-sensitive cultivar Gladius. Through the use of root histochemical analysis, ion concentrations, as well as differential proteomics and targeted metabolomics, we provide an integrated view of the wheat root response to salinity. We show different metabolic re-arrangements in energy conversion, primary metabolic machinery and phenylpropanoid pathway leading to monolignol production in a genotype and genotype by treatment-dependent manner that alters the extent and localisation of root lignification which correlated with an improved capacity of wheat roots to cope better under salinity stress.

Enhancing Bean (Phaseolus vulgaris L.) Resilience: Unveiling the Role of Halopriming against Saltwater Stress

Common bean (Phaseolus vulgaris L.), one of the most important cultivated legumes, requires a high level of water. It is included among the most sensitive species to climate change; drought and salinity cause a reduction in photosynthesis, metabolic and enzymatic alterations, and oxidative stress. To improve crop tolerance to salt, seed priming and acclimation can be useful tools. To test the salt tolerance of beans, a preliminary screening was undertaken on four cultivars of P. vulgaris (Black Turtle, Cargamanto, Bola Roja, Borlotto) by exposing the seeds to different levels of salinity. The salt-sensitive cultivar Borlotto was chosen for experimental greenhouse trials to study the effects of halopriming and acclimation. Primed and non-primed seeds were sown in non-saline soil and acclimated for 2 weeks; then, the plants were watered with non-saline and saline solutions for 4 weeks. At the end of this growth period, the primed plants showed a marked increase in salt stress tolerance, improving the chlorophyll content, phenolic compounds, and many enzymes’ activities, in turn reducing the effect of salt on growth and fruit production compared to the non-primed controls. In conclusion, halopriming can be considered a useful tool to enhance salinity tolerance in beans and other salt-sensitive crops.

Characterization and Comprehensive Evaluation of Phenotypic and Yield Traits in Salt-Stress-Tolerant Peanut Germplasm for Conservation and Breeding

Salt stress is a limiting factor affecting the growth, development, and yield of peanuts. Breeding improvement is a possible solution to overcome salt stress. The salt tolerance of 57 peanut cultivars in Northeast China was identified using indoor simulation at the germination stage, the seedling stage, and field natural identification. At the germination stage, 75 mM NaCl was the most suitable screening concentration, and the seed vitality index of 57 cultivars was analyzed using the membership function and cluster analysis. Among these cultivars, 11 were identified as salt-tolerant and 19 were salt-sensitive during germination. In the seedling stage, six salt tolerance coefficients (STCs) showed significant correlation. A gray relational analysis was used in combination with evaluation grading, resulting in the identification of 14 salt-tolerant cultivars and 12 salt-sensitive cultivars. In the field screening, a comprehensive analysis was conducted using a principal component analysis of nine indices, including agronomic characteristics, yield characteristics, and SPAD. This analysis led to the determination of three comprehensive indices. The weighted membership function was used for comprehensive evaluation. Finally, three salt-tolerant cultivars and four salt-sensitive cultivars suitable for planting in Northeast China were screened out to provide an excellent germplasm for researching the salt-tolerant mechanism of peanuts.

Impact of Various Levels of Salinity Stress on Growth Attributes of Some Salt-Sensitive and Tolerant Varieties of Mung Bean

Salinity stress poses a significant threat to crop productivity, and understanding the mechanisms of ion uptake and distribution in different cultivars is crucial for developing salt-tolerant varieties. This study investigates the patterns of ion uptake and distribution in salt-sensitive and salt-tolerant cultivars of Vigna radiata, commonly known as mung bean. Hydroponic experiments were conducted under controlled conditions to assess the responses of two contrasting cultivars to varying salt concentrations. The study reveals distinct differences in the ion uptake and distribution between salt-sensitive and salt-tolerant cultivars of V. radiata. Salt-sensitive cultivars exhibited increased sodium (Na+) accumulation in both roots and shoots under saline conditions, leading to disrupted ion homeostasis. In contrast, salt-tolerant cultivars demonstrated efficient ion regulation mechanisms, with a higher capacity for potassium (K+) retention and a lower Na+ to K+ ratio. The study also shed light on the involvement of ion transporters and channels in facilitating differential ion accumulation, highlighting the molecular mechanisms contributing to salt tolerance in Vigna radiata. These findings provide valuable insights into the adaptive strategies of salt-tolerant cultivars, offering a basis for targeted breeding programs aimed at enhancing salinity resilience in this economically significant legume. In summary, this research deepens our understanding of the intricate relationship between ion uptake and distribution in Vigna radiata varieties with varying salt tolerance. It lays the groundwork for developing robust crop varieties capable of thriving in saline environments.

Salt Stress Induces Contrasting Physiological and Biochemical Effects on Four Elite Date Palm Cultivars (Phoenix dactylifera L.) from Southeast Morocco.

Understanding the response of date palm (Phoenix dactylifera L.) cultivars to salt stress is essential for the sustainable management of phoeniculture in Tafilalet, Morocco. It offers a promising avenue for addressing the challenges presented by the increasing salinity of irrigation waters, especially because farmers in these regions often lack the necessary knowledge and resources to make informed decisions regarding cultivar selection. This study addresses this issue by investigating the performance of the most relied on cultivars by farmers in Tafilalet, namely Mejhoul, Boufeggous, Nejda, and Bouskri. These cultivars were exposed to a sodium chloride treatment of 154 mM, and their performances were evaluated over a three-month period. We examined the growth rate, photosynthesis-related parameters, pigments, water status in plants, and biochemical compounds associated with oxidative stress, osmotic stress, and ionic stress. Principle component analysis (PCA) effectively categorized the cultivars into two distinct groups: salt-sensitive (Mejhoul and Nejda) and salt-tolerant (Boufeggous and Bouskri). These findings provide valuable insights for farmers, highlighting the advantages of cultivating Boufeggous and Bouskri cultivars due to their superior adaptation to salt conditions. These cultivars exhibited moderate decrease in shoot growth (25%), enhanced catalase activity, a smaller increase in anthocyanin content, and greater enhancement in organic osmolytes compared with salt-sensitive cultivars like Mejhoul (experiencing an 87% reduction in shoot elongation) and Nejda (exhibiting the highest reduction in leaf area). Furthermore, the Na+/K+ ratio was positively influenced by salt stress, with Mejhoul and Nejda recording the highest values, suggesting its potential as an indicator of salt stress sensitivity in date palms.

Novel underlying regulatory mechanism of the MsDAD2-mediated salt stress response in alfalfa

Alfalfa (Medicago sativa L.), a crucial and widely grown forage legume, faces yield and quality challenges due to salinity stress. The defender against apoptotic death (DAD) gene, recognized initially as an apoptosis suppressor in mammals, plays a pivotal role in catalyzing N-glycosylation, acting as a positive regulator for protein folding and endoplasmic reticulum (ER) export. Here, we found that the MsDAD2 gene was specially induced in the salt-tolerant alfalfa cultivar (DL) under salinity stress, but not in the salt-sensitive cultivar (SD). Overexpression of MsDAD2 enhanced the salinity resistance of transgenic alfalfa by promoting NAD(P)H-quinone oxidoreductase (NQO1) and cytochrome b6f complex subunit (Cyt b6/f) expression, thereby mitigating reactive oxygen species (ROS) production. ChIP-qPCR analysis suggested that the differential expression of MsDAD2 in DL and SD under salinity stress may be linked to dynamic histone modifications in its promoter. Therefore, our findings elucidate a novel regulatory mechanism of MsDAD2 in alfalfa's response to salinity stress, underscoring its significance as a target for alfalfa breeding to enhance salt tolerance.

Comparative transcriptome analysis of gene responses of salt-tolerant and salt-sensitive rice cultivars to salt stress

Salt stress is one unfavorable factor of global climate change that adversely affects rice plant growth and yield. To identify novel salt-tolerant genes and new varieties of salt-tolerant rice, a better understanding of the molecular regulation mechanism of salt tolerance in rice is needed. In this study we used transcriptome analyses to examine changes in gene expression of salt-tolerant and salt-sensitive rice plants. The salt-tolerant cultivar HH11 and salt-sensitive cultivar IR29 were treated with 200 mM NaCl solution for 0 h, 6 h, 24 h and 48 h at the three leaf stage. Physiological parameters and transcriptome were measured and analyzed after each treatment. Activity of SOD and POD, as well as the MDA and protein content of the two rice cultivars generally increased with increasing time of exposure to NaCl. Meanwhile, the APX activity first increased, then decreased in both cultivars, with maximum values seen at 6 h for IR29 and at 24 h for HH11. The GR and GPX activity of HH11 were stronger than that of IR29 in response to salt stress. The H2O2 content first increased at 0–6 h, then decreased at 6–24 h, and then increased again at 24–48 h under salt stress. Compared with IR29, SOD, POD and APX activity of HH11 was more sluggish in response to salt stress, reaching the maximum at 24 h or 48 h. The MDA, H2O2 and proline content of HH11 was lower than that of IR29 under salt stress. Relative to untreated HH11 plants (0 h) and those exposed to salt for 6 h, 24 h, and 48 h (H0-H6, H0-H24 and H0-H48), 7462, 6363 and 6636, differentially expressed genes (DEGs), respectively, were identified. For IR29, the respective total DEGs were 7566, 6075 and 6136. GO and KEGG enrichment analysis showed that metabolic pathways related to antioxidative responses and osmotic balance played vital roles in salt stress tolerance. Sucrose and starch metabolism, in addition to flavonoid biosynthesis and glutathione metabolism, showed positive responses to salt stress. Expression of two SPS genes (LOC_Os01g69030 and LOC_Os08g20660) and two GST genes (LOC_Os06g12290 and LOC_Os10g38740) was up-regulated in both HH11 and IR29, whereas expression of LOC_Os09g12660, a glucose-1-phosphate adenylyltransferase gene, and two SS genes (LOC_Os04g17650 and LOC_Os04g24430) was up-regulated differential expression in HH11. The results showed that HH11 had more favorable adjustment in antioxidant and osmotic activity than IR29 upon exposure to salt stress, and highlighted candidate genes that could play roles in the function and regulation mechanism of salt tolerance in rice.

Overexpression of TCP9-like gene enhances salt tolerance in transgenic soybean.

TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) transcription factors are a plant-specific family and play roles in plant growth, development, and responses to biotic and abiotic stresses. However, little is known about the functions of the TCP transcription factors in the soybean cultivars with tolerance to salt stress. In this study, TCP9-like, a TCP transcription factor, was identified in the soybean cultivars exposed to salt stress. The expression of TCP9-like gene in the roots of salt-tolerant soybean cultivars was higher than that in salt-sensitive cultivars treated with NaCl. The overexpression of TCP9-like enhanced the salt tolerance of the salt-sensitive soybean cultivar 'DN50'. In T2 generation, the plants with TCP9-like overexpression had significantly lower Na+ accumulation and higher K+ accumulation than the WT plants exposed to 200 or 250 mmol/L NaCl. The K+/Na+ ratio in the plants overexpressing TCP9-like was significantly higher than that in WT plants treated with 200 mmol/L NaCl. Meanwhile, the overexpression of TCP9-like up-regulated the expression levels of GmNHX1, GmNHX3, GmSOS1, GmSOS2-like, and GmHKT1, which were involved in the K+/Na+ homeostasis pathway. The findings indicated that TCP9-like mediated the regulation of both Na+ and K+ accumulation to improve the tolerance of soybean to salt stress.

A Review on Understanding the Effects and Mechanisms of Salinity Tolerance in Rice (Oryza sativa L.)

Salinity, along with drought, is one of the key abiotic stressors that has posed a danger to the advancement and evolution of cereal crops like rice and wheat. Water shortage and a lack of irrigation water availability are the main causes of salty soil formation. Rice is salt sensitive and glycophyte, wheat is moderately salt tolerant. Wild tolerant cultivars like Oryza coarctata and Oryza alta are more tolerant than traditional cultivars such as Pokkali and Nona Bokra in rice. Salt stress affects crop plants’ processes like ionic imbalance, osmotic and oxidative stress. Na+ should be low in the shoots of the plant which is restricted by various transporters in the cell membrane of the roots in soil. High K+ & Na+/K+ homeostasis should be maintained. Many RILs and NILs have been developed which acts as a donor for salinity tolerant genes. FL478 is a recombinant inbred line in which candidate genes are situated in the Saltol region of chromosome 1 region which is obtained by a cross between Pokkali x IR29. Increase in world’s population, rice output must be increased by at least 25% by 2030 and 50% by 2050.Salinity stress is a polygenic character which involves several genes works in harmony. For evolution of salinity tolerant cultivars, we need to access the physiological, biochemical genetic responses of the crop plant which helps in transfer of candidate genes from donor parents to elite high yielding salt sensitive cultivars. Especially in rice salt tolerant mechanisms like, Ion equilibrium regulation, Adjustment of osmotic potential, Reduction of ROS, Nutrient disequilibrium, and Regulation of PGRs. Conventional, MABC, MAS and direct gene transfer by transgenic methods. This review paper's main objective is to understand the mechanisms of the crop plants to salinity effects and development of salt tolerant cultivars by modern approaches which fulfill the food scarcity of staple food crops with increasing population.

Physiological traits and metabolic profiles of contrasting rice cultivars under mild salinity stress during the seedling stage

This study aimed to investigate the effects of mild salinity stress on some physiological traits and metabolic profiles of rice during the seedling stage. Three rice cultivars differing in salinity stress response, ‘KDML105’ (salt-sensitive, local Thai jasmine rice), ‘IR29’ (salt-sensitive rice), and ‘Pokkali’ (salt-tolerant rice), were subjected to mild salinity stress by flood-irrigated with 40 mM NaCl. Salinity stress significantly reduces the growth and biomass of the sensitive cultivars. Electrolyte leakage in ‘KDML105’ and ‘IR29’ also increased significantly while the relative water content (RWC) decreased. However, salinity stress did not affect growth, electrolyte leakage, and RWC in the tolerant cultivar. Salinity significantly increased Na+/K+ ratio in shoot and root of all cultivars. Nevertheless, the increase of Na+/K+ ratio in ‘KDML105’ and ‘IR29’ was higher than that of ‘Pokkali’. The metabolic profile analysis of ‘KDML105’ showed that uracil, L-proline, malonate, L-carnitine, L-lactate, and guanine were significantly increased, but the levels of dihydroxyacetone and glycine were significantly decreased under salinity conditions. In ‘IR29’, L-proline, melatonin, gamma-aminobutyrate, and acetate were significantly increased. In ‘Pokkali’, however, sugar alcohols and sugars were slightly increased when exposed to salinity conditions. The metabolic pathway analysis revealed one involved metabolic pathway of ‘KDML105’: aminoacyl-tRNA biosynthesis, and three involved those of ‘IR29’: arginine proline metabolism, sulfur metabolism, and butanoate metabolism. The difference in the metabolic profile of the salt-tolerance salt-sensitive cultivars provides new insights to identify additional novel biomarkers that will help better understand the mechanisms for salt tolerance in rice.

Seed priming mitigates high salinity impact on germination of bread wheat (Triticum aestivum L.) by improving carbohydrate and protein mobilization.

Salinity is increasingly considered as a major environmental issue, which threatens agricultural production by decreasing yield traits of crops. Seed priming is a useful and cost-effective technique to alleviate the negative effects of salinity and to enable a fast and uniform germination. In this context, we quantified the effects of priming with gibberellic acid (GP), calcium chloride (CP), and mannitol (MP) on seed germination of three bread wheat cultivars and investigated their response when grown at high salinity conditions (200 mM NaCl). Salt exposure strongly repressed seed imbibition and germination potential and extended germination time, whereas priming enhanced uniformity and seed vigor. Seed preconditioning alleviated the germination disruption caused by salt stress to varying degrees. Priming mitigating effect was agent-dependent with regard to water status (CP and MP), ionic imbalance (CP), and seed reserve mobilization (GP). Na+ accumulation in seedling tissues significantly impaired carbohydrate and protein mobilization by inhibiting amylase and proteases activities but had lesser effects on primed seeds. CP attenuated ionic imbalance by limiting sodium accumulation. Gibberellic acid was the most effective priming treatment for promoting the germination of wheat seeds under salt stress. Moreover, genotypic differences in wheat response to salinity stress were observed between varieties used in this study. Ardito, the oldest variety, seems to tolerate better salinity in priming-free conditions; Aubusson resulted the most salt-sensitive cultivar but showed a high germination recovery under priming conditions; Bologna showed an intermediate behavior.

Evaluation of Amino Acid Profiles of Rice Genotypes under Different Salt Stress Conditions.

Amino acids are building blocks of proteins that are essential components of a wide range of metabolic pathways in plant species, including rice species. Previous studies only considered changes in the amino acid content of rice under NaCl stress. Here, we evaluated profiles of essential and non-essential amino acids in four rice genotype seedlings in the presence of three types of salts, namely NaCl, CaCl2, and MgCl2. Amino acid profiles in 14-day-old rice seedlings were determined. The total essential and non-essential amino acid contents in cultivar Cheongcheong were considerably increased upon NaCl and MgCl2 application, whereas total amino acids were increased upon NaCl, CaCl2, and MgCl2 application in the cultivar Nagdong. The total amino acid content was significantly lower in the salt-sensitive cultivar IR28 and salt-tolerant Pokkali under different salt stress conditions. Glycine was not detected in any of the rice genotypes. We observed that cultivars with the same origin respond similarly to each other under salinity stress conditions: cultivars Cheongcheong and Nagdong were found to show increased total amino acid content, whereas the content in foreign cultivars IR28 and Pokkali was found to decrease. Thus, our findings showed that the amino acid profile of each rice cultivar might depend on the origin, immune level, and genetic makeup of the respective cultivar.

Transcriptome-Wide Identification and Functional Characterization of CIPK Gene Family Members in Actinidia valvata under Salt Stress.

Fruit plants are severely constrained by salt stress in the soil due to their sessile nature. Ca2+ sensors, which are known as CBL-interacting protein kinases (CIPKs), transmit abiotic stress signals to plants. Therefore, it is imperative to investigate the molecular regulatory role of CIPKs underlying salt stress tolerance in kiwifruit. In the current study, we have identified 42 CIPK genes from Actinidia. valvata (A.valvata). All the AvCIPKs were divided into four different phylogenetic groups. Moreover, these genes showed different conserved motifs. The expression pattern analysis showed that AvCIPK11 was specifically highly expressed under salt stress. The overexpression of AvCIPK11 in 'Hongyang' (a salt sensitive commercial cultivar from Actinidia chinensis) enhanced salt tolerance by maintaining K+/Na+ homeostasis in the leaf and positively improving the activity of POD. In addition, the salt-related genes AcCBL1 and AcNHX1 had higher expression in overexpression lines. Collectively, our study suggested that AvCIPK11 is involved in the positive regulation of salt tolerance in kiwifruit.

Potassium ameliorates cotton (Gossypium hirsutum L.) fiber length by regulating osmotic and K+ /Na+ homeostasis under salt stress.

Potassium (K) application can alleviate cotton salt stress, but the regulatory mechanisms affecting cotton fiber elongation and ion homeostasis are still unclear. A two-year field experiment was conducted to explore the effects of K on the osmolyte contents (soluble sugar, K+ content, and malate) and related enzyme activities during the fiber elongation of two cotton cultivars with contrasting salt sensitivity (CCRI-79; salt tolerant cultivar, and Simian 3; salt-sensitive cultivar). Three K application treatments (0, 150, and 300 kg K2 O ha-1 ) were applied at three soil salinity levels (low salinity, EC=1.73 ± 0.05 dS m-1 ; medium salinity, EC=6.32 ± 0.10 dS m-1 ; high salinity, EC=10.84 ± 0.24 dS m-1 ). K application improved fiber length and alleviated salt stress by increasing the maximum velocity of fiber elongation (Vmax ). The increase rate of K on fiber length decreased with elevating salt stress, and the increase rate of K on Vmax of CCRI-79 was greater than that of Simian3. K application can increase the enzyme activities (phosphoenolpyruvate carboxylase, PEPC, E.C. 4.1.1.31; pyrophosphatase, PPase, E.C. 3.6.1.1; and plasma membrane H+ -ATPase, PM H+ -ATPase, E.C. 3.6.3.14) as well as the content of osmolytes associated with the enzymes mentioned above. K increased the osmolyte contents under salt stress, and the increase in the K+ content of the fibers was much higher than that of soluble sugar and malate. The results of this study indicated K fertilizer application rates regulate the metabolism of osmolytes in cotton fiber development under salt stress, K+ is more critical to fiber elongation.

Impact of salinity on yield-related parameters in two contrasting cultivars ofOryza glaberrimaSteud. in Benin

SummarySalinity is one of the major environmental stresses limiting growth and yield of rice. The objective of the present study was to analyze the impact of NaCl on yield-related parameters ofOryza glaberrima. Two contrasted cultivars ofOryza glaberrimapreviously tested for salt resistance at the vegetative stage [salt-resistant (TOG5307) and salt-sensitive (TOG5949)] were irrigated with a saline solution containing 30 mM NaCl (EC: 3 dS.m−1NaCl). After 6 months of treatments, mineral nutrient and yield-related parameters were assessed. Proline was quantified in the panicle leaf at the start of the grain filling stage. NaCl treatment affected most yield-related parameters: panicle length, panicle leaf dry weight, number of branches per panicle, panicle leaf length, days to 50% heading, straw fresh weight per plant, grain yield per plant, number of spikelets per panicle, and number of filled grains per panicle. The weight of 1,000 grains decreased in the salt-sensitive cultivar only, suggesting that grain filling processes were compromised. The salt-resistant cultivar TOG5307 was less affected than the salt-sensitive TOG5949 and accumulated lower amounts of Na+in the grains. For both cultivars, hulls contained higher concentration of Na+and K+than grains. TOG5307 also contained more proline in the panicle leaf than TOG5949, suggesting that TOG5307 can cope with the osmotic component of salt stress. The cultivar exhibiting the highest salt resistance at the vegetative stage also exhibited the highest resistance at the reproductive one.

Photosynthesis and Salt Exclusion Are Key Physiological Processes Contributing to Salt Tolerance of Canola (Brassica napus L.): Evidence from Physiology and Transcriptome Analysis.

Plant salt tolerance is controlled by various physiological processes such as water and ion homeostasis, photosynthesis, and cellular redox balance, which are in turn controlled by gene expression. In the present study, plants of six canola cultivars (DGL, Dunkled, Faisal Canola, Cyclone, Legend, and Oscar) were evaluated for salt tolerance by subjecting them to 0 or 200 mM NaCl stress. Based on growth, cultivars DGL, Dunkled, and Faisal Canola were ranked as salt tolerant, while cultivars Cyclone, Legend, and Oscar were ranked as salt-sensitive ones. Differential salt tolerance in these canola cultivars was found to be associated with a relatively lower accumulation of Na+ and greater accumulation of K+ in the leaves, lower oxidative damage (MDA), and better antioxidative defense system (Superoxide dismutase, SOD; peroxidase, POD, and catalase, CAT). Cultivar Oscar was the poorest to discriminate Na+ and K+ uptake and accumulation in leaves and had poor antioxidant potential to scavenge ROS. Salt stress did not affect the structural stability of photosystem-II (PSII) till three weeks, thereafter it caused a significant decrease. Salt stress increased the performance index (PIABS) by increasing the density of active reaction centers in Oscar. Salt stress decreased the antenna size thereby lowering the absorption and trapping energy flux, and maintaining the electron transport with an increase in heat dissipation. This may represent a potential mechanism to cope with salt stress. Transcriptome analysis of salt-sensitive cultivar Oscar further revealed that salt stress down-regulated DEGs related to hormonal signal transduction pathways, photosynthesis, and transcription factors, while DEGs related to the biosynthesis of amino acid and ion transport were up-regulated. In conclusion, salt tolerance in canola cultivars was associated with ion exclusion and maintenance of photosynthesis. Salt stress sensitivity in cultivar Oscar was mainly associated with poor control of ion homeostasis which caused oxidative stress and reduced photosynthetic efficiency.

Characterization of metabolic responses to salt stress in soybean seedling using gas chromatography-mass spectrometry

Soil salinity is a critical obstacle in modern agriculture which devastates crop growth. Many plants have developed different strategies to sense, transduce, and develop tolerance to salinity. Plant adaptation to salinity stress includes complicated metabolic pathways, genes and molecular networks. Here, we used gas chromatography-mass spectrometry (GC-MS) to understand the metabolic responses of soybean seedlings upon various levels of salt stress treatments. To this end, one salt tolerant and one salt sensitive soybean cultivar, namely Dongnong 69 and Dongnong 63 were used in this study. A total of 10 metabolites, including sugars, amino acids and organic acid, were identified as differential biomarkers. Our results indicated that these biomarkers were closely related to salinity tolerance in soybean seedlings. In particular, three metabolites, namely isoleucine, serine and aspartic acid, were found respond significantly differently between the different soybean cultivars. These three metabolites can be therefore served as potential biomarkers to screen for salt tolerant soybean cultivars. Overall, results of this study help to improve our knowledge with respect to plant salt tolerance in general, and soybean in particular

Impact of Pre-anthesis Salt Stress on Biochemical and Yield Related Traits in Salt Sensitive and Salt Tolerant Genotypes of Triticum aestivum L.

Salinity stress negatively affects the growth and development of wheat leading to diminished grain yield and quality. Salt stress during the reproductive stage is one of the significant factors leading to the drastic reduction in grain yield. The objective of this study was to investigate the biochemical responses of pre-anthesis stage salt stress and yield-related traits in the KRL1-4 salt tolerant and UP2338 salt-sensitive cultivar of wheat. Three different levels of salinity stress (100, 200 and 300 mM NaCl) were induced. Untreated plants were kept in control. Samples were analyzed at pre- anthesis stage (50 DAS and 60 DAS) for various biochemical parameters viz., proline content, total reducing sugar content, total nitrogen content and total protein content. Yield-related traits harvest index, tiller numbers per plant, spike height and spike weight were recorded at the maturity stage. The amount of proline and reducing sugar increased with increasing salinity, the increase being more tolerant than in sensitive cultivar. Total nitrogen and total protein content, however, decreased with increasing salt concentration and reduction being more sensitive than in tolerant cultivar. Yield attributes were affected negatively. The effect was more pronounced in sensitive cultivars compared to tolerant ones.

Identification of Early Salt-Stress-Responsive Proteins in In Vitro Prunus Cultured Excised Roots.

Fruit-tree rootstock selection is a challenge under a scenario of growing environmental stresses in which the soil and climate are greatly affected. Salinization is an increasing global process that severely affects soil fertility. The selection of rootstocks with the ability to tolerate salt stress is essential. Excised root cultures may be an excellent experimental approach to study stress physiology and a predictive tool to assess possible tolerance. In this study, we show how protein changes in response to salt stress evaluated in excised root cultures of Prunus cerasus (moderate salt-sensitive cultivar) could be representative of these changes in the roots of whole plants. The 2D electrophoresis of root extracts and subsequent spot identification by MALDI-TOF/TOF-MS show 16 relevant proteins differentially expressed in roots as a response to 60 mM NaCl. Cytoplasmic isozyme fructose 1,6-bisphosphate aldolase shows relevant changes in its relative presence of isoforms as a response to saline stress, while the total level of enzymes remains similar. Ferredoxin-NADP+ reductase increases as a response to salinity, even though the measured activity is not significantly different. The observed changes are congruent with previous proteomic studies on the roots of whole plants that are involved in protection mechanisms against salt stress.