Evaluating the contribution of osmotic and oxidative stress components on barley growth under salt stress

Effect of Selenium and Garlic Extract Treatments of Seed-Addressed Lettuce Plants on Biofortification Level, Seed Productivity and Mature Plant Yield and Quality

The enhancement of the plant seed yield and quality represents the basis of the successful productivity of the deriving crop. The effect of single and combined foliar treatments of lettuce plants with sodium selenate and garlic bulb extract on seed yield and quality and on mature plant biochemical characteristics was investigated using four lettuce cultivars (Bouquet, Picnic, Moskovsky parnikovy and Cavalier). The seed production of plants treated with Se increased by 20-41%, compared to the untreated control plants, while the augmentation was as much as 10-23% and 17-27% under garlic extract and the joint application of Se and garlic, respectively. Garlic extract stimulated the accumulation of Se in lettuce seeds, which rose by 1.21-1.29 times compared to the Se-treated plants. The proline levels in lettuce seeds exceeded the corresponding values recorded in the control ones by 1.32-1.64 times in the case of the Se supply, 1.10-1.47 times upon garlic extract application and 1.09-1.31 times under the combined Se/garlic treatment. All the treatments given to lettuce plants increased the leaf weight by 1.10-1.30 times, compared to the untreated control. The seed Se levels positively correlated with the leaf weight (r = 0.621; p < 0.005), chlorophyll (r = 0.672, p < 0.002) and total antioxidant activity (AOA; r = 0.730, p < 0.001) of plants grown from these seeds. Positive correlations were also recorded between the seed proline content and lettuce plant leaf weight, chlorophyll and AOA (r = 0.868, 0.811 and 0.815, respectively, at p < 0.001). Lettuce yield was positively correlated with the leaf AOA, chlorophyll and ascorbic acid content (r = 0.942, 0.921 and 0.665, respectively, at p < 0.001). The results indicate high prospects of Na2SeO4 and garlic extract application to seed-addressed lettuce plants, to improve seed productivity and quality, as well as lettuce yield and quality.

Maternal Effects of Habitats Induce Stronger Salt Tolerance in Early-Stage Offspring of Glycyrrhiza uralensis from Salinized Habitats Compared with Those from Non-Salinized Habitats

(1) Wild Glycyrrhiza uralensis Fisch (licorice) seeds from different habitats are often mixed for cultivation. However, differences in the responses of seeds from different habitats to salt at the early-stage offspring stage are unclear. (2) Our objective was to evaluate the salt tolerance of G. uralensis germplasms by comparing differences in seed germination and seedling vigor in salinized (abandoned farmland and meadow) and non-salinized (corn farmland edge) soil habitats under different sodium chloride (NaCl) concentrations. (3) The germination rates and germination indexes of seeds from the two salinized habitats with 0-320 mmol·L-1 NaCl were higher and their germination initiation times were earlier. Only seeds from salinized habitats were able to elongate their germs at 240 mmol·L-1 NaCl. Seedlings from salinized habitats had higher fresh weights and relative water contents, while they exhibited lower accumulation of malondialdehyde and less cell electrolyte leakages. Under NaCl treatment, seedlings from the salinized habitats displayed higher superoxide dismutase, catalase, and peroxidase (SOD, CAT, and POD) activities and lower superoxide anion and hydrogen peroxide (O2- and H2O2) contents. Their comprehensive scores showed that the vigor of licorice seeds from salinized habitats was higher. (4) The salt tolerances of different wild G. uralensis seeds were different, and the offspring of licorice from salinized habitats had stronger early-stage salt tolerances.

Comparative Evaluation of Antioxidant Status and Mineral Composition of Diploschistes ocellatus, Calvatia candida (rostk.) Hollós, Battarrea phalloides and Artemisia lerchiana in Conditions of High Soil Salinity

Natural reserves play a fundamental role in maintaining flora and fauna biodiversity, but the biochemical characteristics of such ecosystems have been studied in an extremely fragmentary way. For the first time, mineral composition and antioxidant status of three systematic groups of organisms, lichens (Diplischistes ocellatus), mushrooms (Calvatia candida and Battarrea phalloides) and wormwood (Artemisia lerchiana) have been described at the territory of Bogdinsko-Baskunchak Nature Reserve (Astrakhan region, Russia), characterized by high salinity and solar radiation, and water deficiency. Through ICP-MS, it was determined that scale lichen D. ocellatus accumulated up to 10-15% Ca, 0.5% Fe, 15 mg kg^-1 d.w. iodine (I), 54.5 mg kg^-1 Cr. Battarrea phalloides demonstrated anomalously high concentrations of B, Cu, Fe, Mn Se, Zn, Sr and low Na levels, contrary to Calvatia candida mushrooms accumulating up to 10,850 mg kg^-1 Na and only 3 mg kg^-1 Sr. The peculiarity of A. lerchiana plants was the high accumulation of B (22.23 mg kg^-1 d.w.), Mn (57.48 mg kg^-1 d.w.), and antioxidants (total antioxidant activity: 68.6 mg GAE g^-1 d.w.; polyphenols: 21.0 mg GAE g^-1 d.w.; and proline: 5.45 mg g^-1 d.w.). Diploschistes ocellatus and Calvatia candida demonstrated the lowest antioxidant status: 3.6-3.8 mg GAE g^-1 d.w. total antioxidant activity, 1.73-2.10 mg GAE g^-1 d.w. polyphenols and 2.0-5.3 mg g^-1 d.w. proline. Overall, according to the elemental analysis of lichen from Baskunchak Nature Reserve compared to the Southern Crimean seashore, the vicinity of Baskunchak Salty Lake elicited increased environmental levels of Cr, Si, Li, Fe, Co, Ni and Ca.

Physio-biochemical and transcriptomic analysis reveals that the mechanism of Bacillus cereus G2 alleviated oxidative stress of salt-stressed Glycyrrhiza uralensis Fisch. seedlings

Salt stress severely affects the growth and productivity of Glycyrrhiza uralensis. Our previous research found that the endophyte Bacillus cereus G2 alleviated the osmotic and oxidative stress in G. uralensis exposed to salinity. However, the mechanism is still unclear. Here, a pot experiment was conducted to analyse the change in parameters related to osmotic adjustment and antioxidant metabolism by G2 in salt-stressed G. uralensis at the physio-biochemistry and transcriptome levels. The results showed that G2 significantly increased proline content by 48 %, glycine betaine content by 75 % due to activated expression of BADH1, and soluble sugar content by 77 % due to upregulated expression of α-glucosidase and SS, which might help to decrease the cell osmotic potential, enable the cell to absorb water, and stabilize the cell's protein and membrane structure, thereby alleviating osmotic stress. Regarding antioxidant metabolism, G2 significantly decreased malondialdehyde (MDA) content by 27 %, which might be ascribed to the increase in superoxide dismutase (SOD) activity that facilitated the decrease in the superoxide radical (O₂^‾) production rate; it also increased the activities of catalase (CAT), ascorbate peroxidase (APX) and glutathione peroxidase (GPX), which helped stabilize the normal level of hydrogen peroxide (H₂O₂). G2 also increased glutathione (GSH) content by 65 % due to increased glutathione reductase (GR) activity and GSH/GSSG ratio, but G2 decreased oxidized glutathione (GSSG) content by 13 % due to decreased activity of dehydroascorbate reductase (DHAR), which could provide sufficient substrates for the ascorbate-glutathione (AsA-GSH) cycle to eliminate excess H₂O₂ that was not cleared in a timely manner by the antioxidant enzyme system. Taken together, G2 alleviated osmotic stress by increasing proline, soluble sugar, and glycine betaine contents and alleviated oxidative stress by the synergistic effect of antioxidant enzymes and the AsA-GSH cycle. Therefore, the results may be useful for explaining the mechanism by which endophyte inoculation regulates the salt tolerance of crops.

Biochemical Characteristics and Elemental Composition Peculiarities of Rheum tataricum L. in Semi-Desert Conditions and of European Garden Rhubarb

Biochemical and mineral peculiarities of plants inhabiting desert and semi-desert areas may provide important information about the mechanism of their adaptability and reveal the prospects of their utilization. Rheum tataricum L., known for its high tolerance to drought, salinity, and nutritional deficiency, is the least studied species of wild rhubarb. Using biochemical and ICP-MS analysis, the antioxidant status and mineral composition of R. tataricum were determined. Extremely high levels of antioxidant activity (148–155 mg GAE g−1 d.w.), polyphenols (24.6–25.1 mg GAE g−1 d.w.) and carotenoids (1.94 mg-eq β-carotene g−1 d.w.) were revealed in roots, proline in leaves (71.1 ± 6.2 mg kg−1 d.w.) and malic acid in stems (3.40 ± 0.50 mg g−1 d.w.). Compared to garden rhubarb, R. tataricum demonstrated significant root–leaves translocation of Li, Se, Si, and Mo, known to participate in plant antioxidant defense. Under high levels of Ca, Na, Mg, Fe, Cr and Si in soil, R. tataricum demonstrated the ability to significantly increase the accumulation of these elements in roots, showing a hyperaccumulation ability for Sr. The first broad picture of R. tataricum biochemical and mineral characteristics in semi-desert habitat and its nutritional value indicate the prospects of R. tataricum utilization in plant breeding, medicine, and nutrition.

Salinity Stress Tolerance in Potato Cultivars: Evidence from Physiological and Biochemical Traits

Salinity stress is a major constraint to sustainable crop production due to its adverse impact on crop growth, physiology, and productivity. As potato is the fourth most important staple food crop, enhancing its productivity is necessary to ensure food security for the ever-increasing population. Identification and cultivation of salt-tolerant potato genotypes are imperative mitigating strategies to cope with stress conditions. For this purpose, fifty-three varieties of potato were screened under control and salt stress conditions for growth and yield-related traits during 2020. Salt stress caused a mean reduction of 14.49%, 8.88%, and 38.75% in plant height, stem numbers, and tuber yield, respectively in comparison to control. Based on percent yield reduction, the genotypes were classified as salt-tolerant (seven genotypes), moderately tolerant (thirty-seven genotypes), and salt-sensitive genotypes (nine genotypes). Seven salt-tolerant and nine salt-sensitive genotypes were further evaluated to study their responses to salinity on targeted physiological, biochemical, and ionic traits during 2021. Salt stress significantly reduced the relative water content (RWC), membrane stability index (MSI), photosynthesis rate (Pn), transpiration rate (E), stomatal conductance, and K⁺/Na⁺ ratio in all the sixteen genotypes; however, this reduction was more pronounced in salt-sensitive genotypes compared to salt-tolerant ones. The better performance of salt-tolerant genotypes under salt stress was due to the strong antioxidant defense system as evidenced by greater activity of super oxide dismutase (SOD), peroxidase (POX), catalase (CAT), and ascorbate peroxidase (APX) and better osmotic adjustment (accumulation of proline). The stepwise regression approach identified plant height, stem numbers, relative water content, proline content, H₂O₂, POX, tuber K⁺/Na⁺, and membrane stability index as predominant traits for tuber yield, suggesting their significant role in alleviating salt stress. The identified salt-tolerant genotypes could be used in hybridization programs for the development of new high-yielding and salt-tolerant breeding lines. Further, these genotypes can be used to understand the genetic and molecular mechanism of salt tolerance in potato.

Evaluating Variation in Germination and Growth of Landraces of Barley (Hordeum vulgare L.) Under Salinity Stress

Ongoing climate change is resulting in increasing areas of salinity affected soils, rising saline groundwater and droughts resulting in irrigation with brackish water. This leads to increased salinity stress in crops that are already grown on marginal agricultural lands, such as barley. Tolerance to salinity stress is limited in the elite barley cultivar pools, but landraces of barley hold potential sources of tolerance due to their continuous selection on marginal lands. This study analyzed 140 heritage cultivars and landrace lines of barley, including 37 Scottish Bere lines that were selected from coastal regions, to screen for tolerance to salinity stress. Tolerance to salinity stress was screened by looking at the germination speed and the early root growth during germination, and the pre-maturity biomass accumulation during early growth stages. Results showed that most lines increased germination time, and decreased shoot biomass and early root growth with greater salinity stress. Elite cultivars showed increased response to the salinity, compared to the landrace lines. Individual Bere and landrace lines showed little to no effect of increased salinity in one or more experiments, one line showed high salinity tolerance in all experiments-Bere 49 A 27 Shetland. A Genome Wide Association Screening identified a number of genomic regions associated with increased tolerance to salinity stress. Two chromosomal regions were found, one associated with shoot biomass on 5HL, and another associated with early root growth, in each of the salinities, on 3HS. Within these regions a number of promising candidate genes were identified. Further analysis of these new regions and candidate genes should be undertaken, along with field trials, to identify targets for future breeding for salinity tolerance.

Effects of Salt Stress on Transcriptional and Physiological Responses in Barley Leaves with Contrasting Salt Tolerance

Salt stress negatively impacts crop production worldwide. Genetic diversity among barley (Hordeum vulgare) landraces adapted to adverse conditions should provide a valuable reservoir of tolerance genes for breeding programs. To identify molecular and biochemical differences between barley genotypes, transcriptomic and antioxidant enzyme profiles along with several morpho-physiological features were compared between salt-tolerant (Boulifa) and salt-sensitive (Testour) genotypes subjected to salt stress. Decreases in biomass, photosynthetic parameters, and relative water content were low in Boulifa compared to Testour. Boulifa had better antioxidant protection against salt stress than Testour, with greater antioxidant enzymes activities including catalase, superoxide dismutase, and guaiacol peroxidase. Transcriptome assembly for both genotypes revealed greater accumulation of differentially expressed transcripts in Testour compared to Boulifa, emphasizing the elevated transcriptional response in Testour following salt exposure. Various salt-responsive genes, including the antioxidant catalase 3, the osmoprotectant betaine aldehyde dehydrogenase 2, and the transcription factors MYB20 and MYB41, were induced only in Boulifa. By contrast, several genes associated with photosystems I and II, and light receptor chlorophylls A and B, were more repressed in Testour. Co-expression network analysis identified specific gene modules correlating with differences in genotypes and morpho-physiological traits. Overall, salinity-induced differential transcript accumulation underlies the differential morpho-physiological response in both genotypes and could be important for breeding salt tolerance in barley.

Physiological and Transcriptome Indicators of Salt Tolerance in Wild and Cultivated Barley

Barley is used as a model cereal to decipher salt tolerance mechanisms due to its simpler genome than wheat and enhanced salt tolerance compared to rice and wheat. In the present study, RNA-Seq based transcriptomic profiles were compared between salt-tolerant wild (Hordeum spontaneum, genotype no. 395) genotype and salt-sensitive cultivated (H. vulgare, 'Mona' cultivar) subjected to salt stress (300 mM NaCl) and control (0 mM NaCl) conditions. Plant growth and physiological attributes were also evaluated in a separate experiment as a comparison. Wild barley was significantly less impacted by salt stress than cultivated barley in growth and physiology and hence was more stress-responsive functionally. A total of 6,048 differentially expressed genes (DEGs) including 3,025 up-regulated and 3,023 down-regulated DEGs were detected in the wild genotype in salt stress conditions. The transcripts of salt-stress-related genes were profoundly lower in the salt-sensitive than the tolerant barley having a total of 2,610 DEGs (580 up- and 2,030 down-regulated). GO enrichment analysis showed that the DEGs were mainly enriched in biological processes associated with stress defenses (e.g., cellular component, signaling network, ion transporter, regulatory proteins, reactive oxygen species (ROS) scavenging, hormone biosynthesis, osmotic homeostasis). Comparison of the candidate genes in the two genotypes showed that the tolerant genotype contains higher functional and effective salt-tolerance related genes with a higher level of transcripts than the sensitive one. In conclusion, the tolerant genotype consistently exhibited better tolerance to salt stress in physiological and functional attributes than did the sensitive one. These differences provide a comprehensive understanding of the evolved salt-tolerance mechanism in wild barley. The shared mechanisms between these two sub-species revealed at each functional level will provide more reliable insights into the basic mechanisms of salt tolerance in barley species.