Salinity Stress Conditions Research Articles

Physiological and Molecular Responses of Red Amaranth (Amaranthus cruentus L.) and Green Amaranth (Amaranthus hypochondriacus L.) to Salt Stress

AbstractSalinization, as a serious climate change phenomenon, continues to cause critical issues for soils and crops. Abundance of genetic diversity of plants could contribute in solving the impacts of salinity. However, the relations between physiological and molecular traits of plant species need deep investigation and interpretation. Pot experiments were conducted in the greenhouse to investigate the difference in behavior between two amaranth species when they were beforehand subjected to salinity-stress conditions, specifically on some specific physiological and molecular characteristics. After 45 days from transplanting, salt stress was induced using a 150 mM sodium chloride solution. Treatments were arranged in randomized complete block design using three replications. After 0, 2, 6, 10, and 24 h, samples were collected to evaluate physiological data as well as diversity of gene expression. The samples were immediately frozen in liquid nitrogen and stored in -80⁰ C ultralow temperature refrigerators. Findings revealed that the red amaranth species (Amaranthus cruentus) was more tolerant to saline stress than the green amaranth species (Amaranthus hypochondriacus). Result data revealed that malondialdehyde (MDA) content in the red amaranth increased after 2 h then decreased (after 6 and 10 h) before rising again after 24 h. In the green amaranth, MDA content initially decreased after 2 h before increasing and later decreasing in a zigzag pattern ending in an increase after 24 h. There was an initial steep rise in proline content of green amaranth after 2 h which continued to still rise moderately till 24 h. In the red amaranth the initial rise in proline continued after 2, 6 and 10 h before it stopped. Results also showed that red amaranth gave higher value of superoxide dismutase (SOD) activity as compared with green amaranth in all tested salinity exposure times. The investigation on the expression of four genes assessed through quantitative PCR indicated the efficiency of red amaranth in increasing the expression of SOS1, HKT1, NHX1, and DGR2 genes, which encode adaptation-related proteins under salinity stress. In summary, the current work demonstrated that red amaranth could be an efficient genetic resource in improving salt-tolerant genotypes belonging to Amaranthus genus.

Correlation and Path Coefficient Analysis for Yield and its Phenological, Physiological, Morphological and Biochemical Traits under 60 mM Salinity Stress in Chickpea (Cicer arietinum L.)

The investigation was carried out during rabi season (November–April) of 2020–2021 in the polyhouse, Department of Genetics and Plant Breeding, Lovely Professional University, Phagwara, Punjab, India to assess the performance of chickpea genotypes under salinity stress conditions. The experiment was conducted using a Completely Randomized Design (CRD) with three replications under two conditions: saline (pots without holes) and control (pots with holes). Twenty genotypes were collected out of which seventeen from ICRISAT, Hyderabad and three from ARS, SriGanganagar. The salinity stress was created using salts NaCl, which were administered in split doses of 60 mM at the time of sowing and 15 DAS. The study monitored various parameters such as phenological, physiological, morphological, biochemical, and yield parameters to determine the effect of salt stress on genotypes exhibiting different tolerance levels. The results showed that the total proline content increased due to the production of stress-related proteins during salinity stress. However, the yield parameters were reduced under stress conditions, with the highest decrease observed in the 60 mM NaCl treatment group compared to the control group. Based on the results of the study, ICC5439 and GNG 1581 are highly tolerant chickpea genotypes under salinity stress conditions. ICC 6050, ICC 251, ICC 252, and ICC 262 are medium tolerant genotypes, while ICC253, ICC 247, and ICC 249 are highly susceptible genotypes. Remaining are minimum tolerant and sensitive genotypes.

Enhancing salt tolerance in rice genotypes through exogenous melatonin application by modulating growth patterns and antistress agents

Melatonin is a bioactive molecule with an important role in plants responding to various abiotic and biotic stresses. This study aims to determine the role of melatonin in rice under salt stress. This study used a factorial completely randomized design. The first factor was local rice varieties (IR64 and Silaun), and the second factor was plant treatments (control, 1 µM melatonin, 150 mM NaCl, 150 mM NaCl + 1µM melatonin). This study shows that exogenous melatonin can increase plant growth, such as plant height, root length, stem length, leaf length, leaf area, and plant biomass under salt stress compared to treatment without melatonin. Exogenous melatonin can increase the total chlorophyll content, relative water content, and proline content, reduce the total sodium content, and increase potassium absorption under conditions of salinity stress. Melatonin is also able to scavenge ROS in plants, resulted the decrease in ROS and MDA content. In terms of gene expression, OsAPX1 and cytosolic APX exhibited the highest expression in IR64 under combined salt and melatonin treatment, while GPOD, Mn-SOD, and Cu/Zn-SOD were upregulated under various conditions in both varieties. Additionally, OsLEA showed high expression in both varieties under control conditions, and CAT was significantly upregulated under salt stress. Our findings indicate that exogenous melatonin has the potential to enhance various factors under salt stress and helping in the recovery of rice plants from sodium (Na+) damage.

Genotype-by-Trait (GT) biplot analysis and ranking of rice genotypes in salinity stress conditions

Estimation of plant tolerance values for agronomic traits, in addition to being genetically influenced, can also be influenced by the plant’s growing environment. Effective screening at the generative stage can only be carried out on land directly affected by salinity. However, the challenge lies in the fact that salinity levels vary widely on farmers’ land and are difficult to predict. The GT biplot analysis is a statistical method used in plant breeding to evaluate the performance of different genotypes based on various supporting traits. e three groups of biplots used are genotype by trait evaluation, genotype ranking analysis, and mega-environment analysis. There were differences in genotype responses based on yield component variables in each experimental environment. IRRI-IL12 and IRRI-IL09 are stable salinity-tolerant rice genotypes. IRRI-IL07 and IRRI-IL16 are adaptive in the optimum environment (L1), IRRI-IL07 and IRRI-IL10 are adaptive in the greenhouse salinity environment (L2), and IRRI-IL13 is adaptive in the salinated intrusion (L3).

Cerium Oxide Nanoparticles (CeO2 NPs) Enhance Salt Tolerance in Spearmint (Mentha spicata L.) by Boosting the Antioxidant System and Increasing Essential Oil Composition

Salinity represents a considerable environmental risk, exerting deleterious effects on horticultural crops. Nanotechnology has recently emerged as a promising avenue for enhancing plant tolerance to abiotic stress. Among nanoparticles, cerium oxide nanoparticles (CeO2 NPs) have been demonstrated to mitigate certain stress effects, including salinity. In the present study, the impact of CeO2 NPs (0, 25, and 100 mg L−1) on various morphological traits, photosynthetic pigments, biochemical parameters, and the essential oil profile of spearmint plants under moderate (50 mM NaCl) and severe (100 mM NaCl) salinity stress conditions was examined. As expected, salinity reduced morphological parameters, including plant height, number of leaves, fresh and dry weight of leaves and shoots, as well as photosynthetic pigments, in comparison to control. Conversely, it led to an increase in the content of proline, total phenols, malondialdehyde (MDA), hydrogen peroxide (H2O2), and antioxidant enzyme activities. In terms of CeO2 NP applications, they improved the salinity tolerance of spearmint plants by increasing chlorophyll and carotenoid content, enhancing antioxidant enzyme activities, and lowering MDA and H2O2 levels. However, CeO2 NPs at 100 mg L−1 had adverse effects on certain physiological parameters, highlighting the need for careful consideration of the applied concentration of CeO2 NPs. Considering the response of essential oil compounds, combination of salinity stress and CeO2 treatments led to an increase in the concentrations of L-menthone, pulegone, and 1,8-cineole, which are the predominant compounds in spearmint essential oil. In summary, foliar application of CeO2 NPs strengthened the resilience of spearmint plants against salinity stress, offering new insights into the potential use of CeO2 NP treatments to enhance crop stress tolerance.

Exploring the Potential of Bacillus subtilis IS1 and B. amyloliquificiens IS6 to Manage Salinity Stress and Fusarium Wilt Disease in Tomato Plants by Induced Physiological Responses.

The intensified concerns related to agrochemicals' ecological and health risks have encouraged the exploration of microbial agents as eco-friendly alternatives. Some members of Bacillus spp. are potential plant-growth-promoting agents and benefit numerous crop plants globally. This study aimed to explore the beneficial effects of two Bacillus strains (B. subtilis strain IS1 and B. amyloliquificiens strain IS6) capable of alleviating the growth of tomato plants against salinity stress and Fusarium wilt disease. These strains were able to significantly promote the growth of tomato plants and biomass accumulation in pot trials in the absence of any stress. Under salinity stress conditions (150 mM NaCl), B. subtilis strain IS1 demonstrated superior performance and significantly increased shoot length (45.74%), root length (101.39%), fresh biomass (62.17%), and dry biomass (49.69%) contents compared to control plants. Similarly, B. subtilis strain IS1 (63.7%) and B. amyloliquificiens strain IS6 (32.1%) effectively suppressed Fusarium wilt disease and significantly increased plant growth indices compared to the pathogen control. Furthermore, these strains increased the production of chlorophyll, carotenoid, and total phenolic contents. They significantly affected the activities of enzymes involved in antioxidant machinery and the phenylpropanoid pathway. Hence, this study effectively demonstrates that these Bacillus strains can effectively alleviate the growth of tomato plants under multiple stress conditions and can be used to develop bio-based formulations for use in the fields.

Genome-wide association study of salt tolerance at the seed germination stage in lettuce.

Developing lettuce varieties with salt tolerance at the seed germination stage is essential since lettuce seeds are planted half an inch deep in soil where salt levels are often highest in the salinity-affected growing regions. Greater knowledge of genetics and genomics of salt tolerance in lettuce will facilitate breeding of improved lettuce varieties with salt tolerance. Accordingly, we conducted a genome-wide association study (GWAS) in lettuce to identify marker-trait association for salt tolerance at the seed germination stage. The study involved 445 diverse lettuce accessions and 56,820 single nucleotide polymorphism (SNP) markers obtained through genotype-by-sequencing technology using lettuce reference genome version v8. GWAS using two single-locus and three multi-locus models for germination rate (GR) under salinity stress, 5 days post seeding (GR5d_S) and a salinity susceptibility index (SSI) based on GR under salinity stress and control conditions, 5 days post seeding (SSI_GR5d) revealed 10 significant SNPs on lettuce chromosomes 2, 4, and 7. The 10 SNPs were associated with five novel QTLs for salt tolerance in lettuce, explaining phenotyping variations of 5.85%, 4.38%, 4.26%, 3.77%, and 1.80%, indicating the quantitative nature of these two salt tolerance-related traits. Using the basic local alignment search tool (BLAST) within 100 Kb upstream and downstream of each of the 10 SNPs, we identified 25 salt tolerance-related putative candidate genes including four genes encoding for major transcription factors. The 10 significant salt tolerance-related SNPs and the 25 candidate genes identified in the current study will be a valuable resource for molecular marker development and marker-assisted selection for breeding lettuce varieties with improved salt tolerance at the seed germination stage.

Germination of chief fire seeds cockscomb cultivar under saline stress conditions induced by sodium chloride

Cockscomb plant, Chief fire cultivar, is used as an ornamental, medicinal and non-conventional food plant (NCFP) and is cultivated from the north to the center-west of Brazil; however, these areas suffer from adverse environmental factors such as salinity stress. The objective of this study was to evaluate the seed germination performance and vigor of Celosia cristata L. var. Chief Fire seedlings exposed to salinity during the germination phase. To carry out the work, C. cristata seeds were sown in gerboxes conditioned to increasing doses of sodium chloride (NaCl), obtained by dissolving the salt in distilled water, obtaining electrical conductivities of 2.0; 4.0; 6.0 and 8.0 dS.m-1, constituting the treatments. An additional group was treated only with distilled water and was used as a control for the experiment. The experiment was conducted in a completely randomized design, with a total of five treatments and four replicates of 25 seeds. The parameters assessed were: first germination count, germination, germination speed index (GVI), mean germination time (MGT), length of aerial part and primary root. The data was submitted to analysis of variance and the means were compared using the Scott-Knott test at 5% significance. Based on the results obtained, it can be concluded that the conditions of salt stress induced by NaCl were not harmful to the germination of C. cristata, presenting itself as a species tolerant to water salinity during seed germination, since the variables analyzed showed no signs of deleterious effects as the salt concentration was increased.

Water and nutrient availability modulate the salinity stress response in Olea europaea cv. Arbequina

Salinity stress represents a key factor for global agriculture. Plants can respond to salinity stress by adapting their physiology in different ways with the aim of limiting reductions in growth and development. Importantly, moisture retention capacity, permeability and nutrient availability of substrates represent critical variables for plants as they may further influence the effect of osmotic stress. Here, a multidisciplinary approach was applied to evaluate the role of two different substrates, peat and perlite, on 2-year-old potted cuttings of Olea europaea (cultivar Arbequina) under different salinity stress conditions (0, 100 and 200 mM NaCl). Biometric and physiological data indicate that plants potted in perlite (AP) generally present lower growth and photosynthetic rates when compared with peat (AS) in combination with salinity stress. Ion measurements indicate a rise in Na+ accumulation with increasing stress severity, which alters the ion ratio in both substrates. In addition, differences occurred in polyphenol contents, with a general increase in quinic acid and rutin contents in AS and AP samples, respectively. Metabolomic and biometric data were also coupled with metabarcoding analysis, which indicates that the moderate salinity treatment (100 mM NaCl, T100) reshaped the endophytic community of plants grown on both substrates. Taken together, the data suggest that the strategy used by a glycophytic species such as the olive tree to cope with salinity stress seems to be highly related to availability of water and nutrients. The lack of both may be simulated by perlite, enhancing the effect of salinity stress response in woody plants. Lastly, applying the beneficial endophytic bacterial taxa identified here could represent a step forward in increasing plant defence and nutrient uptake and reducing inputs for modern and more sustainable agriculture.

Tolerance of local gogo rice sprouts under salinity stress conditions

The expansion of rice planting areas in the future needs to be carried out outside Java, as fertile land in Java is shrinking due to land conversion. Most of the land outside Java consists of marginal land, such as areas with high salinity. High salinity levels in the soil cause a decrease in plant germination, growth, and production. The research aimed to examine the tolerance of each cultivar at each level of NaCl concentration, to obtain cultivars that were tolerant to salinity stress, and to determine the NaCl concentration that suppresses the germination of local upland rice. The research was structured using a completely randomized design with a two-factor factorial pattern. The first was the six upland rice cultivars, namely, dongan, jahara, Pulu Konta, pomegranate, kalendeng, and pulu tau leru, while the second factor was the NaCl concentration consisting of 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1%. Thus, there were 36 experimental units, which were repeated three times so that there were 108 experimental units. The results of the research showed that there was no interaction with all germination variables; cultivar and concentration had a significant effect on maximum growth potential, germination capacity, germination time, plumule length, radicle length and dry weight of sprouts, while cultivar affected the wet weight of sprouts. Kalendeng has a high salinity tolerance. The use of NaCl concentrations of up to 0.6% has been able to reduce the germination capacity of local upland rice. The conclusion of the research showe that there was no interaction between all germination variables.

Fulvic and Salicylic Acids Improve Morpho-Physio-Biochemical Attributes, Yield and Fruit Quality of Two Mango Cultivars Exposed to Dual Salinity and Heat Stress Conditions

Abstract Purpose The present research’s main objective was to explore the potential stimulative effect of fulvic acid (FA) as a soil conditioner and salicylic acid (SA) as foliar spraying on morpho-physio-biochemical attributes, fruit yield, and quality of ‘Sediek’ and ‘Ewais’ mango cultivars (cvs.) grown under saline calcareous soil and heat stress conditions Methods Eight treatments, namely, 200 (FA200) and 400 (FA400) g FA tree−1 as a soil addition, 200 (SA200) or 400 (SA400) mg SA L−1 as foliar spraying, and their bilateral combinations (e.g., FA200 + SA200, FA200 + SA400, FA400 + SA200, and FA400 + SA400) compared to untreated control on morpho-physio-biochemical attributes, yield, and fruit quality of ‘Sediek’ and ‘Ewais’ mango cvs. grown under saline calcareous soil and heat stress conditions were assessed. These treatments were carried out using a split-plot arrangement in a randomized complete block design replicated three times during the 2022 and 2023 seasons. Results Cultivar Sediek had higher SPAD value, leaf proline and phenolic content, leaf area, fruit weight, yield and vitamin C than Ewais which had higher tree water status and shoot length. Saline calcareous and heat-stressed mango trees without FA or/and SA treatment had a significant decline in their water status, photosynthetic traits, biochemical responses that adversely affected growth and yield and fruit quality. However, soil FA addition and foliar SA spraying alone or in combination at any application level attenuated the negative effects of saline calcareous and heat-stress conditions via enhancing the morpho-physio-biochemical attributes, positively reflecting in tree growth, yield, and fruit quality. FA treatment alone improved tree water status (membrane stability index; MSI and relative water content; RWC), photosynthetic traits (SPAD value and maximum photochemical efficiency; Fv/Fm), leaf area, fruit weight, fruit yield, and fruit vitamin C (fruit vit.C), while SA treatment alone enhanced leaf proline and phenolic content, shoot length, and fruit total soluble solids (fruit TSS) compared to the non-FA or SA-treated control. Moreover, co-application of FA400 and SA400 effectively alleviated the harmful impacts of dual stress of heat and salinity on mango trees by improving MSI, RWC, SPAD value, Fv/Fm, proline and phenolic content, fruit weight, fruit yield, fruit TSS, fruit vit.C by 19.7, 26.1, 46.7, 18.7, 101.7, 390.7, 42.7, 6.8, 22.6, 69.6% (averages of the two seasons), respectively, compared to the non-FA or SA-treated trees. Conclusion It is recommended to add 400 g FA tree−1 to soil integrated with 400 mg SA L−1 foliar spraying four times at 30-day intervals for improving water status and photosynthetic traits, proline and phenolic accumulation, thereby growth, yield, and fruit quality of mango trees exposed to dual stress of heat and salinity under arid conditions.

Analysis of the Application of Vitamin B1 on the Response of Salinity Stress Resistance in Several Varieties of Rice (Oryza Sativa L.)

One of the most common stresses in rice cultivation is salinity. Rice plants stressed by salinity exhibit changes such as yellowing leaves, drying tips, and chlorosis. The efforts made by the government and farmers so far include implementing cultivation scheduling techniques, planting patterns, and using stress-resistant varieties, as well as improving soil to increase water-holding capacity through lime application. Each of these efforts comes with its own risks. Another approach to enhance the growth and yield of rice plants is the application of vitamins. Providing vitamins can stimulate the growth of plant organs, as they play a crucial role in the growth process by acting as catalysts for metabolism. Research has indicated that vitamin B1 can significantly promote plant growth under stressful conditions. This study aims to investigate the positive effects of various concentrations of vitamin B1 on the growth and yield of rice plants while also reducing salinity stress. The method used involved planting three varieties of rice—IR-46, Inpari-32, and Pokkali—in planting buckets using the TABELA system. Vitamin B1 was applied at concentrations of 0, 5, and 10 mM during the peak vegetative phase, with salinity stress of 6 dS/m introduced one day after vitamin application. The plants were maintained under salinity stress conditions until harvest, during which morphological and phytochemical analyses were conducted. Morphological analysis included measurements of plant height, number of tillers, number of productive tillers, number of grains per panicle, and percentage of healthy grains. Biochemical parameters measured included total chlorophyll and electrolyte leakage analysis. The results indicate that vitamin B1 can effectively reduce stress in plants affected by salinity.

Assessing of sugar beet Seed adaptation under salt and drought stress conditions with coating technology based on Fuzzy inference system

Sustainability in crop production is highly dependent on favorable indicators of germination and seedling establishment. In this research seed coating different treatments data prepared and membership function defined in fuzzy inference system then used rule editor tool for determining parameters weight for achieved the best coating treatment in salinity and drought stress conditions. Seed coating formulations were investigated in laboratory and greenhouse experiments for their potential to increase maximum germination, germination rate, germination uniformity, and seedling growth of sugar beet seeds. Sugar beet seeds were coated with different compounds and combinations, including micro- (Fe, Zn, Cu, Mn, Co, Mo) and macro- (N, P, K) nutrients, humic acid, gibberellic acid, kaolin, and chitosan. Coated and non-coated sugar beet seeds were evaluated for germination and seedling growth after 10 and 21 days, respectively. In total, 30 different treatments were used to assess the effects of seed coating treatments. In laboratory experiments, sugar beet seeds were placed on paper in Petri dishes and maintained in a germinator at 25 °C. Sodium chloride and polyethylene glycol 8000 were used to apply salinity and drought stresses at three levels each and achieve the results of seed coatings on reducing the effects of salinity and drought stresses. To determine the indices related to emergence and establishment, cultivation trays were utilized with four replications for each treatment. The trays were kept inside a greenhouse. Coating treatments significantly improved total germination percentage, germination rate, seedling growth, and uniformity compared with the non-treated controls. In all treatments, polyvinylpyrrolidone was utilized as a binder. The best treatment with respect to germination and seedling growth indices was number 21 (micro and macronutrients, humic acid, gibberellic acid) in salinity and drought stress conditions. The results by fuzzy inference system illustrated that micronutrients, humic acid, and gibberellic acid create the best seed coating for sugar beet seeds, especially when combined at the specified amounts.

Metabolic Response in the Gill Tissue of Juvenile Black-Shelled Pearl Oyster (Pinctada fucata martensii) under Salinity Stress

Salinity significantly affects shellfish metabolism and growth. In this study, we evaluated the characterization of metabolomic differences in the juvenile black-shelled pearl oyster, Pinctada fucata martensii, under 15‰ (LSG), 25‰ (CG), and 35‰ (HSG) salinity conditions. Non-targeted metabolomics analyses revealed that salinity stress altered the metabolism of pearl oyster. A total of 229 significant differential metabolites (SDMs) were identified between LSG and CG via an in-house MS2 database, 241 SDMs were identified between LSG and HSG, and 50 SDMs were identified between CG and HSG. The pathway analysis showed that 21 metabolic pathways were found between LSG and CG, such as arginine and proline metabolism, glycerophospholipid metabolism, and pentose and glucuronide interconversion. A total of 23 metabolic pathways were obtained between LSG and HSG, such as aspartate, alanine, and glutamate metabolism. Only aminoacyl-tRNA biosynthesis, cysteine and methionine metabolism, and biotin metabolism were enriched between CG and HSG. A further integrated analysis suggested that amino acid metabolism might participate in osmoregulation and energy metabolism to respond to salinity stress in P. f. martensii, and the metabolic pathways differed under varying salinity stress conditions. In addition, low salinity stress might promote apoptosis in pearl oysters. Altogether, these results clarify the salinity tolerance mechanism of pearl oysters.

Enhancing salinity stress tolerance in corn salad (Valerianella locusta L.) through melatonin or salicylic acid-functionalized chitosan seed priming: A smart delivery approach

Soil salinity represents a significant environmental stressor that impairs crop production and yield. A wide range of treatments have been used to reduce the effects of salinity in plants. Among the treatments used, functionalized nanoparticles (NPs) have shown great results. In light of recently demonstrated beneficial effects of chitosan-melatonin nanoparticles (CTS-Mel NPs) and chitosan-salicylic acid nanoparticles (CTS-SA NPs) in mitigating the deleterious consequences of major stress factors and boosting secondary metabolite biosynthesis, the current study aimed to investigate their potential as seed priming coatings to enhance plant performance under both control and salinity stress conditions. For this purpose, CTS (0.1% w/v), Mel (50 µM), SA (0.5 mM), CTS-Mel NPs and CTS-SA NPs were applied as seed priming agents on corn salad (Valerianella locusta) seeds, and subsequently key morphophysiological and biochemical properties were assayed under salinity conditions (0, 30 and 60 mM NaCl). Accordingly, salinity stress caused significant reduction in fresh and dry weights (FW and DW) of leaves, chl a, total chl, SPAD and enhancement in content of proline, phenolics, MDA, as well as protein content, and activities of SOD and CAT antioxidant enzymes. Concerning the phenolic compounds analyzed, salinity stress did not affect the dominant phenolic constituents with the exception of naringine. Regarding the protective effects of the various priming treatments, the adverse effects of salinity stress were ameliorated with the application of most of the applied treatments, and with CTS-Mel NPs in particular, by enhancing biomass, pigments, total phenols, protein, SOD and CAT antioxidant enzymatic activities, as well as the content of some dominant constituents of phenolic profile. CTS-Mel NPs enhanced chlorogenic acid, naringine, o-coumaric acid and catechin hydrate under both control and salinity conditions. Overall, CTS-Mel NPs outperformed CTS-SA NPs as a seed priming coating and could potentially be widely introduced as an innovative, sustainable approach to mitigate the effects of salinity and other abiotic stress conditions in crop plants.

Morphological, physiological, and biochemical responses of three different soybean (Glycine max L.) varieties under salinity stress conditions.

Salinity is one of the most detrimental factors for the growth performance and productivity of crops worldwide. Therefore, understanding crop responses or growth potentials and their effectiveness in salinity mitigation is highly important for the selection of salinity-tolerant plant varieties. In this study, the effects of salinity at various stress levels (0 mM, 50 mM, 100 mM, and 150 mM NaCl) on the morphological, physiological, and biochemical parameters of three soybean varieties ('Afigat', 'Gishama', and 'Pawi-2') were investigated. The results showed that salinity significantly reduced morphological traits including plant height, number of leaves per plant, stem thickness, shoot and root length, and fresh and dry weight. This reduction was more prominent in the 'Afigat' variety for all of these traits except shoot and root length. The concentrations of chlorophyll a and b decreased with increasing salinity. In addition, salinity significantly increased leaf electrolyte leakage (EL), lipid peroxidation, proline accumulation, and phenol and flavonoid content. The 'Pawi-2' variety was more tolerant than the other studied varieties in terms of membrane stability (less EL and a low malondialdehyde content) and proline, phenol, and flavonoid accumulation. Therefore, 'Pawi-2' may be considered as the most salt-tolerant variety in comparison with the other studied soybean varieties. Further complementary studies in field conditions including anatomical parameters are needed to confirm these findings.

Overexpression of dehydroascorbate reductase gene IbDHAR1 improves the tolerance to abiotic stress in sweet potato.

Dehydroascorbate reductase (DHAR), an indispensable enzyme in the production of ascorbic acid (AsA) in plants, is vital for plant tolerance to various stresses. However, there is limited research on the stress tolerance functions of DHAR genes in sweet potato (Ipomoea batatas [L.] Lam). In this study, the full-length IbDHAR1 gene was cloned from the leaves of sweet potato cultivar Xu 18. The IbDHAR1 protein is speculated to be located in both the cytoplasm and the nucleus. As revealed by qRT-PCR, the relative expression level of IbDHAR1 in the proximal storage roots was much greater than in the other tissues, and could be upregulated by high-temperature, salinity, drought, and abscisic acid (ABA) stress. The results of pot experiments indicated that under high salinity and drought stress conditions, transgenic Arabidopsis and sweet potato plants exhibited decreases in H2O2 and MDA levels. Conversely, the levels of antioxidant enzymes APX, SOD, POD, and ACT, and the content of DHAR increased. Additionally, the ratio of AsA/DHA was greater in transgenic lines than in the wild type. The results showed that overexpression of IbDHAR1 intensified the ascorbic acid-glutathione cycle (AsA-GSH) and promoted the activity of the related antioxidant enzyme systems to improve plant stress tolerance and productivity.

Lifetime of forage cactus submitted to different water and saline levels

Forage cactus is mostly grown in hot climates, where water deficit is quite common, consequently they end up suffering from saline stress, as the waters of these regions have high concentrations of salts. The buildup of salts in the soil promotes an unfavorable environment for the development of plants, as it negatively alters the growth of crops, reducing the productivity of forage plants in agricultural areas. The objective was then to evaluate the lifetime of Nopalea cochenillifera cactus under water and saline stress conditions. This research was conducted from September 2021, to August 2022, in the forage farming sector of the Federal Rural University of Pernambuco. The design used was completely randomized, in a factorial scheme, being composed of two clones of cactus (Clones Giant and Little Sweet), two levels of water irrigation (0.5 and 1L weekly), five levels of saline stress (0, 2, 4, 6 and 8 dS m-1), with four replications. The lifetime of forage cactus was evaluated using the statistical methodology of survival analysis by Kaplan-Meier method. The plant mortality rate of N. cochenillifera clone Giant Sweet at 257 days after planting was of 20%, while the clone Little Sweet showed a mortality rate of 15%. When irrigated with 0.5 liter of water, the plants of the clone Giant Sweet presented a mortality rate of 5.0%, whereas the clones Little Sweet showed no mortality. When using 1.0 liter of irrigation water, the clones Giant and Little Sweet showed a mortality rate of 35.0 and 30.0%, respectively.

Seed Priming and Biopriming in Two Squash Landraces (Cucurbita maxima Duchesne) from Tunisia: A Sustainable Strategy to Promote Germination and Alleviate Salt Stress.

In recent years, seed priming has gained interest, with researchers aiming to enhance seed germination and early growth, especially under abiotic stress conditions. In this study, seeds from two squash landraces (Cucurbita maxima Duchesne; i.e., Galaoui large seeds (Galaoui hereafter) and Batati green (Batati hereafter)) were subjected to different priming methods ((a) 0.3% and 0.4% KNO3 (halopriming); (b) 0.1% and 0.2% GA3 (hormopriming); (c) inoculation with Trichoderma spp. (T. harzianum, T. viride, and T. virens), Bacillus subtilis, and Pseudomonas fluorescens (biopriming) in order to promote germination parameters and seedling growth under salinity stress (0, 100, and 200 mM of NaCl). Our findings indicate the better performance of primed seeds compared to the untreated ones in terms of germination and seedling growth traits, although a varied response depending on the priming method and the landrace was observed. The highest germination percentage (GP) and the lowest mean germination time (MGT) were observed in 0.4% KNO3-primed seeds. The positive effects of 0.4% KNO3 were also depicted in all traits related to seedling growth and the seedling vigor index (SVI), indicating its effectiveness as a priming agent in squash seeds. Under salinity stress conditions, priming with 0.4% KNO3 significantly improved the germination and seedling growth traits for both landraces, while the application of 0.2% GA3 at high salinity significantly improved photosynthetic quantum yield (Fv/Fm ratio). Regarding the effects of biopriming in germination and seedling growth traits, our results indicate that T. harzianum and B. subtilis were the most effective bioagents in promoting germination and seedling growth in Galaoui and Batati seeds, respectively. In conclusion, our findings provide important information regarding the practice of using priming and biopriming agents to enhance the germination and seedling growth capacity of squash seeds, as well to mitigate the negative effects of salinity stress at the critical stages of germination and early growth.

Improved salinity tolerance in cucumber seedlings inoculated with halotolerant bacterial isolates with plant growth-promoting properties

To address salinity stress in plants in an eco-friendly manner, this study investigated the potential effects of salinity-resistant bacteria isolated from saline agricultural soils on the growth of cucumber (Cucumis sativus, cv. Royal) seedlings. A greenhouse factorial experiment was conducted based on a completely randomized design (CRD) with two factors, salinity at four levels and five bacterial treatments, with three replications (n = 3). Initially, fifty bacterial isolates were screened for their salinity and drought tolerance, phosphate solubilization activity, along with production of auxin, siderophore and hydrogen cyanide. Isolates K4, K14, K15, and C8 exhibited the highest resistance to salinity and drought stresses in vitro. Isolates C8 and K15 demonstrated the highest auxin production capacity, generating 2.95 and 2.87 µg mL− 1, respectively, and also exhibited significant siderophore production capacities (by 14% and 11%). Additionally, isolates C8 and K14 displayed greater phosphate solubilization activities, by 184.64 and 122.11 µg mL− 1, respectively. The statistical analysis revealed that the selected four potent isolates significantly enhanced all growth parameters of cucumber plants grown under salinity stress conditions for six weeks. Plant height increased by 41%, fresh and dry weights by 35% and 7%, respectively, and the leaf area index by 85%. The most effective isolate, C8, was identified as Bacillus subtilis based on the 16 S rDNA amplicon sequencing. This study demonstrated that inoculating cucumber seedlings with halotolerant bacterial isolates, such as C8 (Bacillus subtilis), possessing substantial plant growth-promoting properties significantly alleviated salinity stress by enhancing plant growth parameters. These findings suggest a promising eco-friendly strategy for improving crop productivity in saline agricultural environments.