Salt-sensitive Cultivar Research Articles

Role of mineral nutrients, antioxidants, osmotic adjustment and PSII stability in salt tolerance of contrasting wheat genotypes

Global food production is threatened due to increasing salinity and can be stabilized by improving salt tolerance of crops. In the current study, salt tolerance potential of 40 local wheat cultivars against 150 mM NaCl stress was explored. Salt treatment at seedling stage caused less reduction in biomass, K+ and P while more decline of Na+ in tolerant cultivars due to reduced translocation and enhanced exclusion of Na+ from leaves. Principal component analysis based selected S-24, LU-26S, Pasban-90 (salt tolerant) and MH-97, Kohistan-97, Inqilab-91 and Iqbal-2000 (salt sensitive) cultivars were evaluated at adult stage applying 150 mM salinity. Osmotic adjustment by accumulation of soluble sugars and proline and accelerated antioxidant enzymes activities caused efficient scavenging of reactive oxygen species making S-24 and LU-26S tolerant while in MH-97 and Kohistan-97, high MDA represent greater membrane damage due to oxidative stress making them salt sensitive. Chlorophyll a fluorescence transients confirmed better efficiency of photosystem II in S-24 and LU-26S based on energy fluxes (ABS/RC, TRo/RC, ETo/RC and DIo/RC), performance index (PIABS) and maximum quantum yield (Fv/Fm). These findings can be correlated using molecular techniques to identify genes for salt exclusion, osmotic adjustment and photosynthetic activity for use in molecular breeding programs.

​Early Identification of Salt-tolerant Genotypes in Finger Millet (Eleusine coracana L.) at Germination stage by Observing the Morphological Characters

Background: The major abiotic stress limiting the plant growth and productivity across the globe is salinity. This may be overwhelmed by growing salt tolerant varieties. Hence, the present study has been figured out to sort out the salt tolerant and salt sensitive cultivars of finger millet. Methods: In this study 15 cultivars of finger millet (Eleusine coracana L.) seeds were grown at different NaCl concentrations (50 mM, 100 mM, 150 mM and 200 mM) on germination stage. Germination percentage, root length, shoot length, fresh weight, dry weight and vigour index of the seedlings were measured using different concentrations of NaCl. Result: Salt tolerant cultivars were discovered to be GPU 28, GPU 67, ML 365, Udurumallige, PYR1 and GPU 48 at 150 Mm and ML 365 at 200 Mm salt accumulation, while cultivars such as VL 400 and KM252 were very much sensitive to NaCl. Accessions with tolerance to salinity are precious genetic material for future crop improvement program.

Effect of salicylic acid seed priming on morpho-physiological responses and yield of baby corn under salt stress

Rising salinity in the arable lands is a substantial threat to crop production. Exogenously-applied salicylic acid (SA) alleviates the negative impacts of salinity on plants. A factorial pot experiment, consisted of two baby corn hybrid cultivars (PAC 571: salt-tolerant and SG 17 Super: salt-sensitive), three doses of SA (0 [hydropriming], 1, and 2 mM) applied as a seed priming material, and four levels of salinity (0.7 [control], 6, 9, and 12 dS m–1), was conducted to evaluate the impact of SA on baby corn under salt stress. Data on growth, physiological traits, cob yield, and ion content in leaf tissues were collected, which revealed that an increasing salinity level was equally detrimental for the two tested cultivars with varying intensities. At the highest salinity level (12 dS m–1), both cultivars produced no cob, and the same salinity level caused a reduction of 67%, 14%, 42%, 87%, and 37% in shoot dry matter, leaf relative water content, membrane stability index, net photosynthetic rate, and leaf potassium content, respectively, compared with the control across cultivars and SA levels. The same salinity level caused about 3-fold, 10-fold, and 6-fold increases in electrolyte leakage, free proline content, and leaf sodium content, respectively. Seed priming with SA was effective, and 1 mM provided more promising results with an increase of 43%, 45%, 5%, and 7% in root dry matter, cob yield, leaf relative water content, and free proline content at 6 dS m–1 than 0 mM SA at the same salinity level. Salt-tolerant cultivar (PAC 571) had significantly higher cob number plant–1 (30%) and cob yield (34%) than salt-sensitive cultivar (SG 17 Super) at 6 dS m–1. However, there was largely no effect of SA seed priming on other evaluated parameters at 9 and 12 dS m–1 salinity levels. Priming of seeds with 1 mM SA could be a promising approach for baby corn production under a moderate salinity level up to 6 dS m–1. However, harmful effects of extreme salinity (9 and 12 dS m–1) cannot be completely compensated for SA seed priming.

Effects of Salinity Stress at Reproductive Growth Stage on Rice (Oryza sativa L.) Composition, Starch Structure, and Physicochemical Properties.

This study aimed to investigate the changes in polished rice composition, starch structure, and physicochemical properties from three rice cultivars treated with medium and high salinity stress at the reproductive growth stage. The results showed that salt stress led to poor milling and appearance quality, higher total starch content, protein content, higher proportion of the medium, and long chains of amylopectin, as well as gelatinization temperature (GT) but lower amylose content and lower proportion of the short chain of amylopectin. Compared with salt-sensitive cultivars, the salt-tolerant cultivars exhibited lower GT and gelatinization enthalpy, better pasting properties, and more stable crystal structure; therefore, their eating and cooking quality (ECQ) was less affected. The above results imply that salt stress at the reproductive growth stage can degrade ECQ and can slightly increase the pasting property of starch from salt-tolerant rice cultivar.

Physiological and Proteomic Analysis Responsive Mechanisms for Salt Stress in Oat.

Oat is considered as a moderately salt-tolerant crop that can be used to improve saline and alkaline soils. Previous studies have focused on short-term salt stress exposure, and the molecular mechanisms of salt tolerance in oat have not yet been elucidated. In this study, the salt-tolerant oat cultivar Vao-9 and the salt-sensitive oat cultivar Bai5 were treated with 6 days of 0 and 150 mmol L−1 salt stress (nNaCl:nNa2SO4 = 1:1). Label-Free technology was then used to analyze the differentially expressed proteins in leaves under 0 and 150 mmol L−1 salt stress. The obtained results indicated that total of 2,631 proteins were identified by mass spectrometry in the four samples. The salt-tolerant cultivar Vao-9 mainly enhances its carbohydrate and energy metabolism through the pentose and glucuronate interconversions, and carbon fixation pathways in prokaryotes, thereby reducing the damage caused by salt stress. In addition, the down-regulation of ribosomes expression and the up-regulated expression of HSPs and CRT are all through the regulation of protein synthesis in response to salt stress. However, GABA metabolism presents a different synthesis pattern in Bai5 and Vao-9. The main KEGG function of differential expressed protein (DEP) in Bai5 is classified into protein processing in the endoplasmic reticulum, estrogen signaling pathway, antigen processing and presentation, longevity regulating pathway-multiple species, arginine and proline metabolism, beta-alanine metabolism, vitamin B6 metabolism, salmonella infection, chloroalkane and chloroalkene degradation, and limonene and pinene degradation. Moreover, the main KEGG functions of DEP in Vao-9 are classified as ribosome and carbon fixation pathways in prokaryotes, pentose and glucuronate interconversions, GABA ergic synapse, and taurine and hypotaurine metabolism. The results obtained in this study provide an important basis for further research on the underlying mechanisms of salt response and tolerance in oat and other plant species.

Comparative Transcriptional Analysis of Two Contrasting Rice Genotypes in Response to Salt Stress

Improving rice salt-tolerance is an effective way to deal with the increasing food demand caused by soil salinization and population growth. Nevertheless, the molecular mechanisms of rice salt-tolerance remain elusive. In this study, comparative transcriptomic analyses were performed to identify salt-tolerance genes that were either specifically regulated or more changed in salt-tolerant cultivar FL478 relative to salt-sensitive cultivar 93-11. In total, 1423, 175, and 224 salt-tolerance genes were identified under 200 mM NaCl treatment for 6 h, 24 h, and 72 h, respectively. These genes were commonly enriched in transport and peroxidase/oxidoreductase activity across all timepoints, but specially enriched in transcription regulator activity at 6 h under salt stress. Further analysis revealed that 53 transporters, 38 transcription factors (TFs), and 23 reactive oxygen species (ROS) scavenging enzymes were involved in salt adaptation of FL478, and that overall, these salt-tolerance genes showed a faster transcriptional expression response in FL478 than in 93-11. Finally, a gene co-expression network was constructed to highlight the regulatory relationships of transporters, TFs, and ROS scavenging genes under salt-stress conditions. This work provides an overview of genome-wide transcriptional analysis of two contrasting rice genotypes in response to salt stress. These findings imply a crucial contribution of quickly transcriptional changes to salt tolerance and provide useful genes for genetic improvement of salt tolerance in rice.

Evaluation of salt tolerance of oat cultivars and the mechanism of adaptation to salinity

Soil salinity is a threat to agricultural production worldwide. Oat (Avena sativa L.) is an irreplaceable crop in areas with fragile ecological conditions. However, there is a lack of research on salt tolerance evaluation of oat germplasm resources. Therefore, the purpose of this work was to evaluate the salt tolerance of oat cultivars and investigate the mechanism of salt-tolerant oat cultivars’ adaptation to salinity. Salt tolerance of 100 oat cultivars was evaluated, and then two salt-tolerant cultivars and two salt-sensitive cultivars were used to compare their physiological responses and expression patterns of Na+- and K+-transport-related genes under salinity. Principal component analysis and membership function analysis had good predictability for salt tolerance evaluation of oat and other crops. The 100 oat cultivars were clustered into three categories, with three salt tolerance levels. Under saline condition, salt-tolerant cultivars maintained higher growth rate, leaf cell membrane integrity, and osmotic adjustment capability via enhancing the activities of antioxidant enzymes and accumulating more osmotic regulators. Furthermore, salt-tolerant cultivars had stronger capability to restrict root Na + uptake through reducing AsAKT1 and AsHKT2;1 expression, exclude more Na+ from root through increasing AsSOS1 expression, compartmentalize more Na + into root vacuoles through increasing AsNHX1 and AsVATP-P1 expression, and absorb more K+ through increasing AsKUP1 expression, compared with salt-sensitive cultivars. The evaluation procedure developed in this work can be applied for screening cereal crop cultivars with higher salt tolerance, and the elucidated mechanism of oat adaptation to salinity lays a foundation for identifying more functional genes related to salt tolerance.

Foliar Application of Spermidine Reduced the Negative Effects of Salt Stress on Oat Seedlings.

The effects of foliar application of spermidine (Spd) on the physiological aspects of salt-stressed oat seedlings were studied under greenhouse conditions. At the seedling stage, the salt-sensitive variety, namely, Caoyou 1 and the salt-tolerant variety, namely, Baiyan 2 were treated with 70 and 100 mM of salt, followed by the foliar application of 0.75 mM Spd or distilled water. Results showed that Spd application increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and reduced the rate of O2⋅– production and the accumulation of H2O2 and malondialdehyde (MDA). In addition, it increased the level of zeatin riboside (ZR) and the content of endogenous polyamines. The application of Spd increased the contents of soluble sugar, soluble protein, and free proline and helped maintain the osmotic balance of oat leaves. At the same time, foliar Spd treatment helped in maintaining the ion nutrition balance. Specifically, it reduced the content of Na+ and thereby stabilized the ratio of Na+/K+, Na+/Ca2+, and Na+/Mg2+. The effects of Spd application were more obvious for the salt-sensitive cultivar Caoyou 1 and under the lighter 70 mM salt stress.

Biomolecular evaluation of three contrasting rice cultivars (Oryza sativa L.) in salt stress response at seedling stage.

Salt contamination of soils due to climate change faces a severe environmental issue that affects crop production today. However, the response mechanism in plants to salt stress is not fully understood. The present study investigated molecular and biochemical changes under salt stress in rice seedlings of three rice cultivars, i.e., AGPPS114 (salt-tolerant), OM6967 (moderately tolerance), VD20 (salt-sensitive). Increasing salt concentration leads to a reduction in shoot/root length but different levels among the cultivars. In contrast, reactive oxygen species (ROS) accumulation and lipid peroxidation increased progressively with increasing salt concentration and time course treatment. However, at 250 ?M of NaCl, these parameters were more adversely affected in VD20 than AGPPS114 and OM6967. Using ICP showed that Na+ accumulation in rice root increased gradually with increasing NaCl concentrations in all cultivars under salt treatment but was low in salt-sensitive cultivar VD20 compared to other cultivars. Antioxidant enzyme activity analysis indicated catalase (CAT) and superoxide dismutase (SOD) were induced during salt treatment in all cultivars. The results also showed greater proline and glycine betaine accumulation in the AGPPS114 than OM6976 and VD20. qPCR indicated a significant difference in transcript levels of the Na+-transporter gene OsSOS1, OsNHX1 and OsHKT1s in AGPPS114 and OM6967 cultivars compared to VD20 cultivar. In summary, the active regulation of genes related to Na+ transport at the transcription level and with high glycine betaine and proline accumulation levels may be involved in salt tolerance mechanisms and thus might be useful for selecting tolerant plants.

SILICON ENHANCES THE SALT TOLERANCE OF TWO WHEAT CULTIVARS THROUGH DECREASING OXIDATIVE DAMAGE

Using two wheat (Triticum durum) cultivars (cvs. Vitron and Simeto) hydroponic solution experiments were conducted in order to study the genotypic variation in tolerance to NaCl toxicity and to investigate effect of silicon supplied to the nutrient solution on wheat plants grown at salt stress. The experiment was a 2×2 factorial arrangement with two levels of NaCl in nutrient solution, 0 and 100 mM, and two levels of silicon (Si) in nutrient solution, 1 and 2 mM, as Na 2 SiO 3 .9H 2 O. Silicon supplementation has an important role in alleviating salinity injury, however, the definite mechanisms stay scantily understood, and must be examined. The role of silicon application in improving growth, maintaining water status and alleviating oxidative injury of salt affected wheat plants were studied. Indeed, our results indicate salinity induced in wheat plants a notable increase in oxidative biomarkers, reduced plant growth and produced less dry matter content than those without NaCl. However, the reductions of seedling height, dry biomass, and soluble content were greatly alleviated due to Si addition to the culture solution. Thus, the beneficial effects of Si on oxidative biomarkers contents under NaCl stress were genotype-dependent. The beneficial effect of Si on alleviating oxidative stress was much more pronounced in Vitron (salt tolerant cultivar) than in Simeto (salt sensitive cultivar).

Time-series transcriptome comparison reveals the gene regulation network under salt stress in soybean (Glycine max) roots

BackgroundSoil salinity is a primary factor limiting soybean (Glycine max) productivity. Breeding soybean for tolerance to high salt conditions is therefore critical for increasing yield. To explore the molecular mechanism of soybean responses to salt stress, we performed a comparative transcriptome time-series analysis of root samples collected from two soybean cultivars with contrasting salt sensitivity.ResultsThe salt-tolerant cultivar ‘Qi Huang No.34’ (QH34) showed more differential expression of genes than the salt-sensitive cultivar ‘Dong Nong No.50’ (DN50). We identified 17,477 genes responsive to salt stress, of which 6644 exhibited distinct expression differences between the two soybean cultivars. We constructed the corresponding co-expression network and performed Gene Ontology term and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. The results suggested that phytohormone signaling, oxidoreduction, phenylpropanoid biosynthesis, the mitogen-activated protein kinase pathway and ribosome metabolism may play crucial roles in response to salt stress.ConclusionsOur comparative analysis offers a comprehensive understanding of the genes involved in responding to salt stress and maintaining cell homeostasis in soybean. The regulatory gene networks constructed here also provide valuable molecular resources for future functional studies and breeding of soybean with improved tolerance to salinity.

Salinity induced redox metabolic shift influence hormonal profile and germination performance of two contrasting indica rice cultivars

The role of redox deviations under salinity on metabolic dysfunction associated with progression of seed germination is well documented. However, the correlative evaluation of the salinity induced changes in the redox system and hormonal profile in regulating germination are least studied and hence is the subject of present investigation. Imposition of post imbibitional salinity stress (PISS) to two contrasting rice genotypes differing in sensitivity towards salinity (Oryza sativa L., Cultivars Patnai and IR29) caused differential and significant redox-metabolic shift and germination performances. Biomarkers of oxidative stress like, accumulation of total ROS, in situ localization of hydrogen peroxide, radical scavenging property, and lipid peroxidation are assessed for the determination of salinity induced differential changes in redox status of both the experimental cultivars. Salt resistant cultivar Patnai exhibiting better redox regulatory property under PISS in terms of controlled generation of ROS (DCFDA oxidation, H2O2 content) with greater elicitation of total antioxidant capacity (DPPH radical scavenging property), contends lipid peroxidation (accumulation of TBARS) as compared to the salt-sensitive cultivar IR 29. RP-HPLC based estimation of PISS-induced alteration in hormonal pools showed strong correlation between altered redox status (assessed in terms of redox biomarkers) and hormonal profile (endogenous titer of gibberellic acid (GA3), abscisic acid (ABA) and jasmonic acid (JA)) and germination and other physiological phenotypes (t50 value, allocation index, relative water content, and Na+ / K+ ratio) of the experimental rice germplasms, suggesting the influence of differential shift in redox status on germination hormones and early growth performances. Taken as a whole, the work proposes close connection between salinity induced changes in oxidative windows and hormonal profile of germinating seeds, necessary for better management of salinity stress in agriculture.

PGPB Improve Photosynthetic Activity and Tolerance to Oxidative Stress in Brassica napus Grown on Salinized Soils

Soil salinization, one of the most common causes of soil degradation, negatively affects plant growth, reproduction, and yield in plants. Saline conditions elicit some physiological changes to cope with the imposed osmotic and oxidative stresses. Inoculation of plants with some bacterial species that stimulate their growth, i.e., plant growth-promoting bacteria (PGPB), may help plants to counteract saline stress, thus improving the plant’s fitness. This manuscript reports the effects of the inoculation of a salt-sensitive cultivar of Brassica napus (canola) with five different PGPB species (separately), i.e., Azospirillum brasilense, Arthrobacter globiformis, Burkholderia ambifaria, Herbaspirillum seropedicae, and Pseudomonas sp. on plant salt stress physiological responses. The seeds were sown in saline soil (8 dS/m) and inoculated with bacterial suspensions. Seedlings were grown to the phenological stage of rosetta, when morphological and physiological features were determined. In the presence of the above-mentioned PGPB, salt exposed canola plants grew better than non-inoculated controls. The water loss was reduced in inoculated plants under saline conditions, due to a low level of membrane damage and the enhanced synthesis of the osmolyte proline, the latter depending on the bacterial strain inoculated. The reduction in membrane damage was also due to the increased antioxidant activity (i.e., higher amount of phenolic compounds, enhanced superoxide dismutase, and ascorbate peroxidase activities) in salt-stressed and inoculated Brassica napus. Furthermore, the salt-stressed and inoculated plants did not show detrimental effects to their photosynthetic apparatus, i.e., higher efficiency of PSII and low energy dissipation by heat for photosynthesis were detected. The improvement of the response to salt stress provided by PGPB paves the way to further use of PGPB as inoculants of plants grown in saline soils.

PECULIARITIES OF SALT TOLERANCE OF SUGAR SORGHUM (SORGHUM SACCHARATUM (L.) PERS.) VARIETIES

This article is devoted to the study of the toxic effect of NaCl on sorghum plants, as one of the environmental stress factors and the release of stress-active substance (proline), as one of sensitive response of plant to salinity. The results of the study showed that the Russian variety Larets and the Kazakh variety Kazakhstan-20 germinate and grow well on saline soils. In a comparative study of sorghum varieties, a high degree of salt tolerance was determined in varieties Larets and Kazakhstan-20 and a high sensitivity to salinity of the Chinese variety Kulzha. It was found that the salt-sensitive cultivar Kulzha had a high level of synthesis of stress-active substances. The research results showed that the synthesis of proline, as one of the indicators of resistance to salinity, is not directly related to the accumulation of aboveground biomass. It was noticed that as the concentration of salt in the soil in the variety Kazakhstan-20 increased, the aboveground biomass was high for some time (from 78.22 to 69.82) and the amount of proline was also high for some time, but due to an increase in the concentration of salt in the soil, the content of proline significantly decreased. On the other hand, in the Larets cultivar, on the contrary, with the accumulation of biomass, the synthesis of proline immediately decreased. In the cultivar Kulzha, which is most sensitive to salinity, as the biomass of the stem decreased, the synthesis of proline, on the contrary, increased. This indicates that proline synthesis is not associated with a stress tolerance response in a crop such as sorghum.

Genome-Wide Characterization of Salt-Responsive miRNAs, circRNAs and Associated ceRNA Networks in Tomatoes.

Soil salinization is a major environmental stress that causes crop yield reductions worldwide. Therefore, the cultivation of salt-tolerant crops is an effective way to sustain crop yield. Tomatoes are one of the vegetable crops that are moderately sensitive to salt stress. Global market demand for tomatoes is huge and growing. In recent years, the mechanisms of salt tolerance in tomatoes have been extensively investigated; however, the molecular mechanism through which non-coding RNAs (ncRNAs) respond to salt stress is not well understood. In this study, we utilized small RNA sequencing and whole transcriptome sequencing technology to identify salt-responsive microRNAs (miRNAs), messenger RNAs (mRNAs), and circular RNAs (circRNAs) in roots of M82 cultivated tomato and Solanum pennellii (S. pennellii) wild tomato under salt stress. Based on the theory of competitive endogenous RNA (ceRNA), we also established several salt-responsive ceRNA networks. The results showed that circRNAs could act as miRNA sponges in the regulation of target mRNAs of miRNAs, thus participating in the response to salt stress. This study provides insights into the mechanisms of salt tolerance in tomatoes and serves as an effective reference for improving the salt tolerance of salt-sensitive cultivars.

Genome-wide identification and functional prediction of salt- stress related long non-coding RNAs (lncRNAs) in chickpea (Cicer arietinum L.)

LncRNAs (long noncoding RNAs) are 200 bp length crucial RNA molecules, lacking coding potential and having important roles in regulating gene expression, particularly in response to abiotic stresses. In this study, we identified salt stress-induced lncRNAs in chickpea roots and predicted their intricate regulatory roles. A total of 3452 novel lncRNAs were identified to be distributed across all 08 chickpea chromosomes. On comparing salt-tolerant (ICCV 10, JG 11) and salt-sensitive cultivars (DCP 92–3, Pusa 256), 4446 differentially expressed lncRNAs were detected under various salt treatments. We predicted 3373 lncRNAs to be regulating their target genes in cis regulating manner and 80 unique lncRNAs were observed as interacting with 136 different miRNAs, as eTMs (endogenous target mimic) targets of miRNAs and implicated them in the regulatory network of salt stress response. Functional analysis of these lncRNA revealed their association in targeting salt stress response-related genes like potassium transporter, transporter family genes, serine/threonine-protein kinase, aquaporins like TIP1-2, PIP2-5 and transcription factors like, AP2, NAC, bZIP, ERF, MYB and WRKY. Furthermore, about 614 lncRNA-SSRs (simple sequence repeats) were identified as a new generation of molecular markers with higher efficiency and specificity in chickpea. Overall, these findings will pave the understanding of comprehensive functional role of potential lncRNAs, which can help in providing insight into the molecular mechanism of salt tolerance in chickpea.

TaFLZ2D enhances salinity stress tolerance via superior ability for ionic stress tolerance and ROS detoxification

Salinity stress severely affects plant growth and crop productivity. FCS-like zinc finger family genes (FLZ) play important roles in plant growth and stress responses. But most information of this family obtained was involved in sucrose signaling, limited function has been known in response to salinity stress. In this study, a novel FLZ gene TaFLZ2D has been isolated and characterized in response to salinity stress in wheat. TaFLZ2D was induced by both salinity stress and exogenous abscisic acid (ABA). Its transcript level was substantially higher in the salt resistant wheat cultivar SR3 than in its closely related but salt sensitive cultivar JN177. Transient expression in Nicotiana benthamiana leaf epidermal cells demonstrated TaFLZ2D was localized both in the cytoplasm membrane and nucleus. Constitutive expression of TaFLZ2D in Arabidopsis thaliana improved salinity stress tolerance and ABA sensitivity. Phenotype analysis under KCl and mannitol treatment demonstrated TaFLZ2D increased salinity stress tolerance mainly due to the superior ability to cope with ionic stress. TaFLZ2D over-expressing lines increased abscisic acid synthesis, peroxidase activity and reduced rate of water loss. Transcriptomic analysis demonstrated over-expression of TaFLZ2D regulated ABA-dependent and independent signaling pathway related genes expression and activated antioxidant related genes expression under normal condition and Ca2+ signaling related genes expression under NaCl treatmemt. Taken together, TaFLZ2D is a positive regulator of salinity stress tolerance, which contributes to salinity stress mainly through superior ability for ionic stress tolerance and ROS detoxification.

Comprehensive Evaluation of Salt Tolerance in Rice (Oryza sativa L.) Germplasm at the Germination Stage

Salt stress reduces the yield and quality of rice. It is of great significance to screen out salt-tolerant varieties for the development and utilization of saline land. The study was carried out on 114 rice varieties; first, seven varieties were selected and treated with different salt concentrations (0, 50, 85, 120, 155, 190, 225 mM), and seven traits, including germination energy, germination capacity, shoot length, root length, root number, plant fresh weight, and seedling vigor index, were measured. The salt concentration at which the sodium chloride injury index was 50% of the control was considered the optimal salt concentration. Second, 114 rice germplasms were carried out under an optimal salt concentration (120 mM). Then, principal component analysis, fuzzy function analysis, stepwise regression analysis, correlation analysis, and systematic cluster analysis were carried out on each parameter. There was a significant correlation between each parameter and the D-value, and the correlation coefficient between the seedling vigor index and D-value was the highest. D-value = − 0.272 + 1.335 × STI − SVI + 0.549 × STI − RN − 0.617 × STI-RL + 0.073 × STI − GE, R2 = 0.986. Using this equation, the sodium chloride tolerance of rice in the germination experiment could be quickly identified. This study showed that the seedling vigor index was a reliable parameter to identify the salinity tolerance of rice varieties. Five groups were obtained by classification at a Euclidean distance of 5. There were 8 highly salt-tolerant cultivars, 23 salt-tolerant cultivars, 42 cultivars with moderate salt tolerance, 33 salt-sensitive cultivars, and 8 highly salt-sensitive cultivars. In this study, we found that Riguang was the most salt-tolerant rice variety, and Xiangxuejing15 was the most salt-sensitive variety.

Transcriptome analysis reveals key genes in response to salinity stress during seed germination in Setaria italica

Salinity stress severely affects agricultural production. Seed germination is the most critical phase of plant life and is regulated by genetic and environmental factors. Setaria italica is an excellent model system for investigating the response to abiotic stresses. However, the key genes in response to salinity stress during seed germination in S. italica are largely unknown. Here, the transcriptional response of imbibed and radicle-protruded seeds to salinity stress revealed 4090 salinity responsive genes (SRGs) from the salt-tolerant cultivar Chigu 10 (CG) and salt-sensitive cultivar Fenghong 3 (FH) by RNA sequencing. Enrichment and expression pattern analysis indicated that the CG and FH cultivars exhibited specific similarities and preferences in the salinity stress response. Heatmap analysis suggested that S. italica seeds germinated under salinity stress required enhanced hormone regulation, more active primary metabolism and energy production, more cell wall modifications, and higher anticipation of autotrophic growth. Furthermore, functional validation experiments demonstrated that the SiDRM2 and SiKOR1 of SRGs significantly influenced seed germination under salinity stress. Collectively, our findings not only provide new insights into the regulatory mechanisms of seed germination under salinity stress, but also reveal promising gene resources to genetically improve the salt-tolerance capacity of S. italica and other crops.

Morphological Analysis, Protein Profiling and Expression Analysis of Auxin Homeostasis Genes of Roots of Two Contrasting Cultivars of Rice Provide Inputs on Mechanisms Involved in Rice Adaptation towards Salinity Stress

Plants remodel their root architecture in response to a salinity stress stimulus. This process is regulated by an array of factors including phytohormones, particularly auxin. In the present study, in order to better understand the mechanisms involved in salinity stress adaptation in rice, we compared two contrasting rice cultivars—Luna Suvarna, a salt tolerant, and IR64, a salt sensitive cultivar. Phenotypic investigations suggested that Luna Suvarna in comparison with IR64 presented stress adaptive root traits which correlated with a higher accumulation of auxin in its roots. The expression level investigation of auxin signaling pathway genes revealed an increase in several auxin homeostasis genes transcript levels in Luna Suvarna compared with IR64 under salinity stress. Furthermore, protein profiling showed 18 proteins that were differentially regulated between the roots of two cultivars, and some of them were salinity stress responsive proteins found exclusively in the proteome of Luna Suvarna roots, revealing the critical role of these proteins in imparting salinity stress tolerance. This included proteins related to the salt overly sensitive pathway, root growth, the reactive oxygen species scavenging system, and abscisic acid activation. Taken together, our results highlight that Luna Suvarna involves a combination of morphological and molecular traits of the root system that could prime the plant to better tolerate salinity stress.