Salt Tolerance Index Research Articles

Response of African eggplant (Solanum macrocarpon L.) cultivars produced in Benin Republic to salt stress at germination stage

In this study, the response of seed germination of six African eggplant cultivars produced in Benin Republic (Dangbo, Kpinman, Adja-Ouèrè, Togan, Côte d’Ivoire and Kombara F1) to salt stress was investigated with the aim to determine their relative salt resistance level. The experiment was laid out in a completely randomized design with four replications. Seeds were subjected in Petri dishes to five NaCl concentrations (0; 30; 60; 90 and 120 mM). Seed germination was checked every day during twenty days incubation period. Germination index (GI), percentage of final germination (PFG) and salt tolerance index (STI) were calculated for each cultivar. Salt stress induced a significant reduction of GI(P < 0.001) and PFG (P <0.05) with a difference among cultivars. A significant difference (P <0.001) was observed among cultivars STI: cultivar Togan showed the highest STI (0.96) followed by Adja-Ouèrè (0.89) and Dangbo (0.76) whereas Côte d’Ivoire (0.38) and Kombara F1 (0.35) showed the weakest STI values. Thus cultivar Togan appeared as the most salt resistant whereas Côte d’Ivoire and Kombara F1were the most salt sensitive. For the first time, we demonstrated a variability of relative salinity resistance among local African eggplant cultivars at germination stage.

Screening of Key Indices and the Gene Transcriptional Regulation Analysis Related to Salt Tolerance in Salix matsudana Seedlings

Pot experiments were performed to comparatively study the differences in 16 salt tolerance indices between the seedlings of six Salix matsudana clones under the stress of various concentrations of NaCl (0, 0.1%, 0.3%, 0.5%, and 0.7%), including the salt injury index, shoot fresh weight, root fresh weight, leaf water content, relative conductivity, malondialdehyde content, and antioxidant enzyme activity. The salt-tolerant clones and key indices of salt tolerance were selected. Transcriptome sequencing analysis was performed on the selected salt-tolerant and salt-sensitive clones under salt stress, and the links between the physiological indices of salt tolerance and gene expression were analyzed. Results: (1) Superoxide dismutase (SOD), peroxidase (POD), chlorophyll, and net photosynthetic rate were closely related to the salt tolerance of Salix matsudana at the seedling stage. The regression equation was constructed as follows: salt tolerance index (y) = 0.224x10 + 0.216x11 + 0.127x12 + 0.191x7 − 0.187 (x10 = chlorophyll, x11 = SOD, x12 = POD, x7 = net photosynthetic rate). (2) The number of differentially expressed genes between the seedlings of salt-tolerant and salt-sensitive clones varied with the time of exposure (0 h, 4 h, 12 h, and 24 h) to 200 mmol·L−1 NaCl stress. The most differentially expressed genes in Sm172 were detected upon 24 h vs. 4 h of salt treatment, while the most in Sm6 were in the 24 h vs. 0 h comparison. Gene Ontology analysis and Kyoto Encyclopedia of Genes and Genomes analysis showed that several differentially expressed genes were involved in carotenoid biosynthesis and plant mitogen-activated protein kinase signaling pathways. The nine highly expressed transcription factor genes (Sm172-f2p30-2392, Sm172-f2p28-2386, Sm6-f8p60-2372, Sm6-f2p39-2263, Sm6-f16p60-2374, Sm6-f3p60-931, Sm6-f2p60-1067, Sm172-f3p54-1980, and Sm172-f3p54-1980) were closely correlated with the four key indices of salt tolerance. These genes could become genetic resources for salt tolerance breeding of Salix matsudana.

Synergistic effect of arbuscular mycorrhizal fungi and poultry manure to significantly increase proximal structure and physiological parameters of Cucurbita maxima and Telfairia occidentalis under soil salinity

This research was carried out to assess the potential impacts of arbuscular mycorrhizal fungi (AMF) complex (Glomus geosporum and Rhizophagus irregularis) synergy with poultry manure (PM) on the survival of Cucurbita maxima and Telfairia occidentalis grown under salt stress conditions. This experiment was set up in a completely randomized design with all treatments replicated thrice for both test plants. Analysis of the saline and garden soils used in this study revealed significant (P ≤ 0.05) variations in their soil physico-chemical parameters. Increase in parameters such as pH (7.75 for saline soil; 6.78 for garden soil), EC (SS 7.80 dS.m.-1; GS 0.32) and Ex Na+ (SS 8.81 cmol.kg-1; GS 0.4181 cmol.kg-1) was observed in the saline soil while there was a decrease in organic carbon, total nitrogen and available phosphorus in saline soil. Proximate analysis of C. maxima and T. occidentalis leaves revealed that fiber, carbohydrate, and caloric value were slightly reduced in saline soil treatments while ash, protein and lipids contents were slightly increased. AMF inoculation and PM application had significant effect on proximate composition of these plant leaves but caloric value which was significantly (P ≤ 0.05) increased in non-saline soil treatments. Physiological parameters such as leaf turgid weight (LTW), leaf relative water content (LRWC), vigor index (VI), and salt tolerance index (STI) were significantly reduced by salinity, while electrolyte leakage (EL) was higher in saline soil treatments than non-saline soil treatments. However, inoculation with AMF in combination with PM amendment significantly increased LTW, LRWC, VI, and STI in both saline and non-saline soil treatments above single treatment with mycorrhizal species and poultry manure. However, EL reduced with mycorrhizal inoculation. The results of this work have shown that AMF and PM can enhance plants ability to tolerate salinity possibly through some morphological and physiological changes which improved water and nutrients uptake.

EVALUATION OF WHEAT GENOTYPES FOR SALINITY TOLERANCE BASED ON AGRONOMIC TRAITS

Salinity stress is one of the important constraints to wheat (Triticum aestivum L.) production globally. Breeding for salinity tolerance using novel genetic resources is an important mitigation strategy. This study aimed to identify and select the best wheat genotypes that are tolerant to salinity stress and provide them to researchers and wheat breeders for more intense evaluation and screening. Twenty two wheat genotypes, as well as two commercial cultivars, were regenerated and evaluated for salinity tolerance. Highly significant effects were detected for the measured traits for years, genotypes and treatment under normal and salinity stress conditions over all the two years. Interaction between treatments and genotype and interaction between genotypes and years were highly significant for all studied characters overall the two years and conditions, except plant height. Genotypes 13, 14 and Giza 168 showed the highest grain yield (ton/ha) under normal soil over two seasons, Also, genotypes 19, 20 and Giza 168 showed the highest grain yield (ton/ha) under salinity soil. The highest SSI value was detected for genotype 14, followed by genotypes 15 and 10 which had the highest values. Based on STI, MP and GMP indices, Giza 168, genotypes 19, 7 and 21 had the highest values. Grain yield under normal conditions (YP) was significantly and positively correlated with an STI, MP, GMP, TOL and SSPI. Grain yield under salt-stressed (YS) was significantly and positively correlated with an STI, MP, GMP, YSI, YI and HM. These results suggest that indices, STI, MP and GMP were able to identify high-yielding wheat genotypes under both normal and salt-stressed conditions. Frist PC accounted for about 7.42% of the variation in salt tolerance indices and the second PC for 3.57% by using biplots genotypes 20, 19 and Giza 168 were identified as the most stable high yielding genotypes under salinity stress.

Genome-Wide Association Analysis for Salt–Induced Phenotypic and Physiologic Responses in Rice at Seedling and Reproductive Stages

Salinity is one of the main adverse environmental factors severely inhibiting rice growth and decreasing grain productivity. Developing rice varieties with salt tolerance (ST) is one of the most economical approaches to cope with salinity stress. In this study, the salt tolerance of 220 rice accessions from rice diversity panel l (RDP1), representing five subpopulations, were evaluated based on 16 ST indices at both seedling and reproductive stages under salt stress. An apparent inconsistency was found for ST between the two stages. Through a gene-based/tightly linked genome-wide association study with 201,332 single nucleotide polymorphisms (SNPs) located within genes and their flanking regions were used, a total of 214 SNPs related to 251 genes, significantly associated with 16 ST-related indices, were detected at both stages. Eighty-two SNPs with low frequency favorable (LFF) alleles in the population were proposed to hold high breeding potential in improving rice ST. Fifty-four rice accessions collectively containing all these LFF alleles were identified as donors of these alleles. Through the integration of meta-quantitative trait locus (QTL) for ST and the response patterns of differential expression genes to salt stress, thirty-eight candidate genes were suggested to be involved in the regulation of rice ST. In total, the present study provides valuable information for further characterizing ST-related genes and for breeding ST varieties across whole developmental stages through marker-assisted selection (MAS).

Alleviating adverse effects of irrigation by saline water on growth, productivity and fruit quality of strawberry by using some salinity reducers

This experiment was carried out during two successive seasons of 2019/2020 and 2020/2021 at the Experimental Farm of El-Kassasein, Hort. Res. Station, Ismailia Governorate, Egypt, to study the effect of irrigation water sources (ground water, EC= 1254 ppm) and (Nile River water, EC =282 ppm) and treating plants with some salinity reducers (plant growth promoting rhizobacteria, Salt Free as salinity reducer with water irrigation at 2 liter /fad. each and trehalose as foliar application at 2 ml /l) on growth, some plant water relationships, yield and fruit quality of strawberry under sandy soil conditions. Under the irrigation with ground water conditions, treating strawberry plants with some salinity reducers (plant growth promoting rhizobacteria, Salt Free with water irrigation and trehalose as foliar application) increased plant growth, yield and fruit quality compared to control (without salinity reducers) and gave similar results with the plants which irrigated with Nile River water only. In this concern, foliar spray with trehalose at 2 ml/l gave the highest values of dry weight of shoots, total water, free water, total chlorophyll in leaf tissues, salt tolerance index, average fruit weight, yield / plant and total yield/fad., fruit firmness, total soluble solids and vitamin C contents in fruits.

Effect of salinity on growth traits in sorghum (Sorghum bicolor)

The experiment was conducted to study the effect of salinity on growth characters in sorghum at Punjab Agricultural University, Ludhiana during Kharif 2020. In this experiment, 40 sorghum genotypes were grown hydroponically under control (EC 2.0 dS/m) and three salt stress concentrations (EC 6.8 dS/m, EC 11.4 dS/m and EC 16.2 dS/m). To study the effect of salt stress, the data was recorded on six growth parameters viz., per cent germination, seedling shoot/root ratio, seedling fresh weight, seedling dry weight, stress tolerance vigour index I and stress tolerance vigour index II with respect to seed vigor index. Based on germination percentage, it was noticed that 19 genotypes failed to germinate at EC 16.2 dS/m. It was further observed that the increase in salt concentration had drastic effect on all the growth characters studied. The genotype with minimum decrease in shoot/root ratio under salt stress was SCL3. Based on salt tolerance indices with respect to seedling vigor index, SPSSV40 was found to be most tolerant. Further, the cluster analysis performed on the basis of mean comparisons of all growth traits grouped the genotypes into six categories viz., highly tolerant, moderately tolerant, tolerant, susceptible, moderately susceptible and highly susceptible. Eleven genotypes among the 40 genotypes studied were found to be tolerant with four genotypes being highly tolerant to salt stress. The genotypes SPSSV40, PV2068, SCL3 and UK081 were found to be highly tolerant which can be used in further breeding programs while developing genotypes for salt stress tolerance.

Linkage and association mapping of wild soybean (Glycinesoja) seeds germinating under salt stress

Salinity threatens soybean germination, growth and production. The germination stage is a key period in the life of soybean. Wild soybean contains many genes related to stress resistance that are valuable resources for the genetic improvement of soybean. To identify the genetic loci of wild soybean that are active during seed germination under salt stress, two populations, a soybean interspecific hybrid population comprising 142 lines and a natural population comprising 121 wild soybean accessions, were screened for three germination-related traits in this study. By using single-nucleotide polymorphism (SNP) markers with three salt tolerance indices, 25 quantitative trait loci (QTLs), 21 significant SNPs (–log10(P)≥4.0) and 24 potential SNPs (3.5<−log10(P)<4.0) were detected by linkage mapping and a genome-wide association study (GWAS) in two environments. The key genetic region was identified based on these SNPs and QTLs. According to the gene functional annotations of the W05 genome and salt-induced gene expression qRT-PCR analysis, GsAKR1 was selected as a candidate gene that responded to salt stress at the germination stage in the wild soybean. These results could contribute to determining the genetic networks of salt tolerance in wild soybean and will be helpful for molecular marker-assisted selection in the breeding of salt-tolerant soybean.

Genome-Wide Association Analysis of Salt-Tolerant Traits in Terrestrial Cotton at Seedling Stage.

Soil salinization is the main abiotic stress factor affecting agricultural production worldwide, and salt stress has a significant impact on plant growth and development. Cotton is one of the most salt-tolerant crops. Therefore, the selection and utilization of salt-tolerant germplasm resources and the excavation of salt resistance genes play important roles in improving cotton production in saline–alkali soils. In this study, we analysed the population structure and genetic diversity of a total 149 cotton plant materials including 137 elite Gossypium hirsutum cultivar accessions collected from China and 12 elite Gossypium hirsutum cultivar accessions collected from around the world. Illumina Cotton SNP 70 K was used to obtain genome-wide single-nucleotide polymorphism (SNP) data for 149 elite Gossypium hirsutum cultivar accessions, and 18,430 highly consistent SNP loci were obtained by filtering. It was assessed by using PCA principal component analysis so that the 149 elite Gossypium hirsutum cultivar accessions could be divided into two subgroups, including subgroup 1 with 78 materials and subgroup 2 with 71 materials. Using the obtained SNP and other marker genotype test results, under salt stress, the salt tolerance traits 3d Germination potential, 3d Radicle length drop rate, 7d Germination rate, 7d Radicle length drop rate, 7d Germination weight, 3d Radicle length, 7d Radicle length, Relative Germination potential, Relative Germination rate, 7d Radicle weight drop rate, Salt tolerance index 3d Germination potential index, 3d Radicle length index, 7d Radicle length index, 7d Radicle weight index and 7d Germination rate index were evaluated by GWAS (genome-wide association analysis). A total of 27 SNP markers closely related to the salt tolerance traits and 15 SNP markers closely related to the salt tolerance index were detected. At the SNP locus associated with phenotyping, Gh_D01G0943, Gh_D01G0945, Gh_A01G0906, Gh_A01G0908, Gh_D08G1308 and Gh_D08G1309 related to plant salt tolerance were detected, and they were found to be involved in intracellular transport, sucrose synthesis, osmotic pressure balance, transmembrane transport, N-glycosylation, auxin response and cell amplification. This study provides a theoretical basis for the selection and breeding of salt-tolerant upland cotton varieties.

RAV transcription factor regulatory function in response to salt stress in two Iranian wheat landraces

Amongst the transcription factor groups, the AP2/ERF (Apetala2/Ethylene Response Factor) superfamily is one of the main groups in plants and plays an essential role in tolerating abiotic and biotic stresses. The AP2/ERF superfamily consists of ERF, AP2, RAV, and Soloist families based on the AP2 domain number. The RAV (Related to ABI3/VP1) family members have been revealed to be stimulate by a number of biotic and abiotic environmental incentives; including pathogen infection, salicylic acid, osmotic stress, cold, high salinity, wounding, and exogenous hormone application. However, limited data are available on the contributions of RAV transcription factors in wheat (Triticum aestivum L.). In the present study, a total of 26 RAV genes were identified in wheat from a genome-wide search against the latest wheat genome data. Phylogenetic and sequence alignment analyses divided the wheat RAV genes into 4 clusters, I, II, III and IV. Chromosomal distribution, gene structure and motif composition were subsequently investigated. The 26 TaRAV genes were unevenly distributed on 21 chromosomes. After cloning and sequencing of 7 TaRAVs candidate genes the expression levels of two TaRAVs, TaRAV4 and TaRAV5, were validated through qPCR analyses in two salt-tolerant Iranian landraces of wheat. Our results showed that the TaRAV4 and TaRAV5 were co-expressed in wheat tissues and were highly correlated to salt tolerance indices such as the K+/Na+ ratio. Protein interaction revealed that the TaRAV4 and TaRAV5 were related to vital proteins such as PK4 and PP2C, and MYB and Zinc finger transcription factors, and Gigantea proteins. This study improved our knowledge of the RAV gene family function in wheat and the probable role of RAVs in salt tolerance mechanisms to improve crop production under changing environments. Also, the two relatively salt-tolerant landraces of wheat that were examined in this study could be suitable candidates for future breeding studies.

Characterization of Maize Hybrids (Zea mays L.) for Detecting Salt Tolerance Based on Morpho-Physiological Characteristics, Ion Accumulation and Genetic Variability at Early Vegetative Stage.

Increasing soil salinity due to global warming severely restricts crop growth and yield. To select and recommend salt-tolerant cultivars, extensive genotypic screening and examination of plants’ morpho-physiological responses to salt stress are required. In this study, 18 prescreened maize hybrid cultivars were examined at the early growth stage under a hydroponic system using multivariate analysis to demonstrate the genotypic and phenotypic variations of the selected cultivars under salt stress. The seedlings of all maize cultivars were evaluated with two salt levels: control (without NaCl) and salt stress (12 dS m−1 simulated with NaCl) for 28 d. A total of 18 morpho-physiological and ion accumulation traits were dissected using multivariate analysis, and salt tolerance index (STI) values of the examined traits were evaluated for grouping of cultivars into salt-tolerant and -sensitive groups. Salt stress significantly declined all measured traits except root–shoot ratio (RSR), while the cultivars responded differently. The cultivars were grouped into three clusters and the cultivars in Cluster-1 such as Prabhat, UniGreen NK41, Bisco 51, UniGreen UB100, Bharati 981 and Star Beej 7Star exhibited salt tolerance to a greater extent, accounting for higher STI in comparison to other cultivars grouped in Cluster-2 and Cluster-3. The high heritability (h2bs, >60%) and genetic advance (GAM, >20%) were recorded in 13 measured traits, indicating considerable genetic variations present in these traits. Therefore, using multivariate analysis based on the measured traits, six hybrid maize cultivars were selected as salt-tolerant and some traits such as Total Fresh Weight (TFW), Total Dry Weight (TDW), Total Na+, Total K+ contents and K+–Na+ Ratio could be effectively used for the selection criteria evaluating salt-tolerant maize genotypes at the early seedling stage.

Evaluation and screening of elite wheat germplasm for salinity stress at the seedling phase.

Salinity is one of the most important constraints for global cereal production, and breeding for salinity tolerance is a challenge. The limited gene pools, merged information regarding osmotic stress/tissue tolerance mechanism(s) including the accumulation of Na+ , over-stressed on the Na+ exclusion mechanism, and inadequate suitable screening methods further weaken the progress. In the present study, an attempt was made to evaluate the salt tolerance in Triticum aestivum lines using the membership function value (MFV) of certain traits viz., the root and shoot length (RL & SL), shoot and root fresh weight (SFW & RFW), shoot and root dry weight (SDW & RDW) and germination percentage (GP). This study screened 314 wheat lines (278 linked top cross population [LTPs] and 36 normal wheat cultivars) under lab conditions to evaluate their salt tolerance. A positive, and the highest, correlation coefficient was recorded between salt tolerance index (STI) of SL and the STI of RL.0.11 highly salt tolerant (HST), 59 salt tolerant (ST), 100 moderately salt tolerant (MST), 137 salt sensitive (SS), and seven highly salt sensitive (HSS) were observed with a distance of 2.2 between each category. The R-square value was maximum (0.836) between the STI of SFW and the mean MFV, which can be used as the most reliable trait for the salinity tolerance in T. aestivum at the germination phase. Wheat tolerant lines had higher tolerance to salt stress in comparison with the used normal wheat cultivars were detected at the seedling stage.

English

Salinity stress is one of the critical factors that limits agricultural productivity particularly in the arid to semi-arid regions worldwide. Elevated concentrations of soluble salts especially NaCl cause osmotic stress, ionic stress and imbalance in the uptake of essential nutrients. Use of salt tolerant rhizobacterial isolates have gained much attention now-a-days on account of their environment friendly nature and effectiveness. Therefore, current study was executed to isolate salt tolerant bacteria from the rhizosphere of maize and check their salt tolerance and plant growth promotion under salinity stress. Selected isolates were further investigated in a growth room trial to compare their efficiency in improving growth and physiology of maize. Salinity stress caused a significant reduction in all the measured traits however, inoculation of rhizobacteria modulated its effects and improved maize growth. Among different strains, SUA-14 caused maximum increment in the shoot length (41%), root length (96%), shoot fresh (1.8 fold) and dry weight (1.3 fold), root fresh (1.76 fold) and dry weight (2 fold), salt tolerance index (1.6 fold), chl ‘a’ contents (2.6 fold) and chl ‘b’ contents (2.3 fold) as compared to its respective uninoculated control. Whereas, rhizobacterial strain SHM-5, SHM-13 and SUA-14 showed statistically nonsignificant response in terms of increasing carotenoid contents by 1.8 fold in comparison with their corresponding control. Pearson correlation coefficient showed a strong positive correlation between growth and physiological attributes under salinity stress. On the basis of PCA, SUA-14 found to be the most efficient strain followed by SHM-13. Using 16 S rRNA sequencing, SUA-14 and SHM-13 were identified as Acinetobacter and Bacillus species respectively.

Pretreatment with H2O2 Alleviates the Negative Impacts of NaCl Stress on Seed Germination of Tartary Buckwheat (Fagopyrum tataricum).

Soil salinization is one of the main abiotic stress factors impacting the growth of crops and the agricultural industry today. Thus, we aimed to investigate the effects of H2O2 pretreatment on seed germination in Tartary buckwheat (Fagopyrum tataricum) seeds under salt stress and to evaluate this species’ salt tolerance. Through the preliminary experiment, this study used 50 mmol L−1 NaCl solution to induce seed stress. After soaking for 12 h in different H2O2 concentrations, seeds were laid in Petri dishes with 50 mmol L−1 NaCl for seven days and the germination parameters and physiological indicators were measured to screen the optimal H2O2 pretreatment concentration and the salt tolerance index. Our results indicated that pretreatment with 5–10 mmol L−1 H2O2 was most effective in alleviating NaCl’s impacts on the seeds’ germination parameters. Furthermore, the growth and material accumulation of seedlings was promoted; catalase, superoxide dismutase activity, and proline content were enhanced; and malondialdehyde content was reduced. Principal component analysis and stepwise regression revealed six key indicators that had a significant impact on the salt tolerance characteristics of F. tataricum, namely, germination potential, shoot fresh weight, root surface area, root average diameter, catalase activity, and superoxide dismutase activity.

Evaluating salt tolerance in doubled haploid barley lines using a multivariable screening approach

Salt stress is one of the major environmental factors limiting cereal productivity in worldwide agriculture. Evaluating and selecting salt tolerant genotypes are an effective approach to overcome yield losses. This study aimed to characterize and compare phenotypic variability among doubled haploid (DH) barley lines and their parent under different salinity conditions (T1 = 0, T2 = 3, and T3 = 6 g.L −1 NaCl). The DH lines were produced by in vitro selection callus in a regeneration medium supplemented with 5 g.L −1 NaCl. Fifteen measured traits were assessed including physiological, biochemical, and agro-morphological traits. Biplot analysis was used to visualize the relationships among the studied traits and to evaluate the relative performance of each genotype. Pearson's correlation followed by stepwise and path analysis were then performed successively to identify appropriate criteria that most influence grain yield. The results showed a wide range of variation for the measured traits, indicating the existence of a phenotypic variation between the tested genotypes. Salinity significantly affected the parent more than the DH lines. Stepwise regression analysis indicated that 99% of the variation in grain yield was explained by K + /Na + ratio, number of fertile spikes per plant, number of grains per spike, plant height, and proline content. However, the path coefficient revealed that number of fertile spikes per plant and number of grains per spike were indicative of salt tolerance in barley. Based on stepwise and path analysis results, the tested genotypes were ranked using salt tolerance index. The salt tolerant DH lines could be recommended as novel genetic resources in breeding programs. • A set of agro-physiological and biochemical traits was used to differentiate salt tolerant genotypes between doubled haploid barley lines and their parent. • Salt stress caused significant increase in proline, Na + , and decrease K + , stomatal conductance, and chlorophyll contents. • Salt stress reduced significantly yield and yield components. • Fertile tiller number, number of grain per spike, and K + /Na + ratio were the major traits influencing grain yield. • The doubled haploid barley lines exhibited superiority in salinity tolerance compared with their parent.

Evaluation of salt tolerance in maize (Zea mays L.) at seedling stage through morphological characters and salt tolerance index

Evaluation of salt tolerance in maize (Zea mays L.) at seedling stage through morphological characters and salt tolerance index

Genome-wide association mapping reveals key genomic regions for physiological and yield-related traits under salinity stress in wheat (Triticum aestivum L.)

A genome-wide association study (GWAS) was conducted using six different multi-locus GWAS models and 35K SNP array to demarcate genomic regions underlying reproductive stage salinity tolerance. Marker-trait association analysis was performed for salt tolerance indices (STI) of 11 morpho-physiological traits, and the actual concentrations of Na+ and K+, and the Na+/K+ ratio in flag leaf. A total of 293 significantly associated quantitative trait nucleotides (QTNs) for 14 morpho-physiological traits were identified. Of these 293 QTNs, 12 major QTNs with R2 ≥ 10.0% were detected in three or more GWAS models. Novel major QTNs were identified for plant height, number of effective tillers, biomass, grain yield, thousand grain weight, Na+ and K+ content, and the Na+/K+ ratio in flag leaf. Moreover, 48 candidate genes were identified from the associated genomic regions. The QTNs identified in this study could potentially be targeted for improving salinity tolerance in wheat.

Contrasting Responses of Guar Genotypes Shed Light on Multiple Component Traits of Salinity Tolerance Mechanisms

Guar (Cyamopsis tetragonoloba (L.) Taub.) is a legume crop, and gum derived from its seeds has various industrial applications. Due to its tolerance to various abiotic stresses, guar can be grown under water-deficit or high-salinity conditions. In this investigation, four diverse guar genotypes that performed at a similar level in field conditions were evaluated in a salinity experiment in the greenhouse lysimeter system. Based on the salt tolerance index (STI) for shoot biomass, root biomass, shoot length, and root length, Matador and PI 268229 were classified as salt-tolerant, and PI 340261 and PI 537281 as salt-sensitive. Leaf Na concentrations were 4- to 5.5-fold higher, and leaf Cl concentrations were 1.6- to 1.9-fold higher in salt-sensitive lines than salt-tolerant lines under salinity. The strong associations between the leaf K concentrations under salinity compared to the control (K-salinity/K-control) ratio and STI for stem and root length advocate higher importance of K-salinity/K-control than total leaf K concentrations. The expression analyses of genes involved in Na+ and Cl− transport revealed the importance of different component traits of salinity tolerance mechanisms, such as the exclusion of Na+/Cl− from the root, sequestration of Cl− in root vacuoles, retrieval of Na+/Cl− from xylem during salinity stress, root-to-shoot Na+/Cl− translocation, and K+-Na+ homeostasis.

Wheat straw biochar application improves the morphological, physiological, and yield attributes of maize and the physicochemical properties of soil under deficit irrigation and salinity stress

Soil salinity and water scarcity adversely affect maize productivity. The use of biochar could enhance soil quality and increase the salt and/or drought threshold tolerance and yield of maize. Therefore, a pot experiment was conducted with three biochar addition rates of 0% (BA0), 5% (BA5), and 10% (BA10) concerning salinity stresses of 2.0 (WS2) and 5.0 dS m−1 (WS5) under deficit irrigation comprising three levels at 60% (DI60), 75% (DI75), and 100% (DI100) of the reference evapotranspiration. Compared with the BA0 rate, the BA10 rate improved soil properties and the growth, nutrient uptake, and yield of maize. The DI100 × SW2 × BA10 combination improved plant growth, providing the highest yield (257.7 g/plant) and water productivity (WP) (2.92 kg/m3) values. However, the combination DI60 × SW5 × BA0 decreased plant growth, offering the lowest yield (121.9 g/plant) and WP (1.96 kg/m3) values. While the former combination increased water and nutrient contents in the soil, the latter combination reduced their values. Considering the salt tolerance index, the yield was more tolerant to salinity stress under the BA10 rate as a 3.60% decrease in yield was detected when soil salinity exceeded the threshold value (5.56 dS/m). The drought threshold was declined from 390 L under BA0 to 280 L under BA10 rate. The study suggests that biochar could mitigate the adverse effects of deficit irrigation and salinity stress on maize growth and productivity. Thus, biochar could be used in salt-affected soils or when irrigation water is of low quality to sustain maize production.

Phosphorus Increases K+ in the Shoot and Improves Salinity Tolerance in Sweetsop Seedlings

The use of brackish waters is an alternative for the cultivation of fruit-bearing plants in semi-arid regions; nonetheless, sweetsop trees (Annona squamosa L.) are sensitive to these types of waters. However, phosphate fertilization can be a technique used to mitigate the harmful effects of salinity. Thus, our objective was to evaluate the application of phosphorus to mitigate the salinity in irrigation water. The experiment was conducted in a randomized block design, with six treatments S1 (2.5 dS m−1) S2 = (4 dS m−1), SP1 (2.5 dS m−1 + 1.35 g dm−3 of P2O5), SP2 = (4 dS m−1 + 1.35 g dm−3 of P2O5), T (control), and P (1.35 g dm−3 of P2O5). After 78 days of transplantation, the seedlings were evaluated for the total dry weight (TDW), leaf area (LA), salt tolerance index (STI), water use efficiency (WUE), Na+ and K+ levels in the shoot and root, chlorophylls a and b, maximum (Fm) and variable (Fv) chlorophyll fluorescence, quantum efficiency of photosystem II (Fv/Fm), total soluble sugar (TSS), total free amino acids (TFAA), proline, and glycine betaine (GB). It was observed that plants treated with SP1 and SP2 show higher results of TDW, LA, STI, WUE, and K in the shoot, Chl a, Chl b, Fm, Fv, Fv/Fm, TFAA, proline, GB, and TSS in relation to S1 and S2. The presence of phosphorus under salinity conditions increased the K+ concentration in the shoot, which was responsible for the improvement of pigments as well as increasing the quantum efficiency of photosystem II and carbohydrates, maintaining the growth and, consequently, the salinity tolerance of the sweetsop seedlings.