Salinity Tolerance In Wheat Research Articles

Population structure and genome-wide association analysis for salinity tolerance in wheat using SNP, SSR and SCoT marker assays.

Wheat is an essential staple food in the developing world, where demand is projected to grow exponentially in the future; simultaneously, climate changes are projected to reduce supply in the near future. One of the main consequences of climate change is salinity, which negatively impacts the world's cultivated area and therefore affects the global wheat production. Our objectives are to study the population structure of several Egyptian and international wheat accessions and to identify the genetic factors controlling the salinity stress response of b wheat. In addition, we have attempt to identify genes that control some important agronomic parameters of wheat under salinity stress were identified. The wheat germplasm panel consisted of 70 accessions obtained from Egypt, Syria and Iran. The assessment of salinity tolerance was conducted over the years of 2018 and 2019 in the field and in the greenhouse. The genome association analysis (GWAS) and population structure analysis was conducted using six SCoT, five SSR and 93 SNP markers. Analysis of the population structure using allele frequency and phylogenetic analysis indicated that the studied wheat accessions were belong to four population groups. Where, for the most portion, Egyptian, Syrian and Iranian accessions are clustered depending on their country of origin. The GWAS analysis revealed 13 SNP markers that were significantly associated with morpho-agronomic wheat traits during salinity stress. These markers were closely related to genes that are known to have a direct link to wheat response to salinity stress such as CYP709B2, MDIS2, STAY-GREEN, PIP5K9, and MSSP2 genes. This study revealed the genetic structure of adapted and imported wheat accessions, which could be used to select potential wheat accessions for local breeding programs. In addition, the SNP genotyping assay is a very potential technology that could be efficiently applied to detect genes that control bread wheat response to salinity stress.

Genetic basis of ion exclusion in salinity stressed wheat: implications in improving crop yield

Productivity of food crops like wheat, a staple food of major portion of the world, is hampered due to salinity stress, thereby threatening food security. With the advancements in plant physiology and molecular biology based techniques, a number of structural and regulatory genes (transcription factors, miRNA, siRNA etc.) have been identified that contribute to inducing salinity tolerance responses. Location of these salt tolerant genes or genetic loci on specific chromosomes has also been partially characterized through QTL mapping. This information helps in efficient transfer of these genes into other crop cultivars through molecular breeding tools. Although plant salt tolerance mechanisms include osmotic adjustment, ion exclusion, ion inclusion, efficient antioxidant system, hormonal signaling etc., ion exclusion has long been recognized as central to salinity tolerance in wheat. Ion exclusion involves highly coordinated activity of a variety of channels, pumps and antiporters at parenchyma cells in root, stem and leaves associated with xylem. A number of molecular markers have been identified which are associated with ion exclusion or Na+ exclusion. However, some of them are associated with undesirable traits thereby producing lower crop productivity, e.g. Kna1. Thus, it is imperative to assess novel sources of ion exclusion with subsequent characterization before their introgression into other crop cultivars. In this review, recent advancements in identifying novel sources of ion exclusion in wheat have been discussed at length. In addition, up to what extent marker assisted breeding using these ion exclusion sources will help improve crop salt tolerance in wheat, thereby reducing global food security threat. An effective new paradigm is the targeted identification of specific genetic determinants of stress adaptation that have evolved in nature and their precise introgression into elite varieties.

Perennial growth and salinity tolerance in wheat × wheatgrass amphiploids varying in the ratio of wheat to wheatgrass genomes

AbstractSince wheat and other annual cereal crops are often harvested for forage instead of grain in California, replacing them with perennial crops could save energy and reduce the release of heat‐trapping gases. To assess the potential for perennial crops based on wheat, biomass yield and stand persistence were studied for nine wheat×wheatgrass amphiploids (8x to 14x) and five wheatgrass species (2x to 10x) over three seasons in the Central Valley, California. The 8x and 10x amphiploids died after one biomass harvest and a single summer period. In contrast, the 14x amphiploids, which were sterile, continued producing biomass over the entire period of the trial. They were also highly salt‐stress tolerant with little decline in biomass production in response to an increase in salinity from 100 and 250 mM NaCl in a solution‐culture study. The development of a salt‐stress‐tolerant perennial crop based on wheat for the California‐type climate will require either a substantial improvement in perennial growth of low‐ploidy (8x) amphiploids or the development of technology for efficient vegetative propagation of the sterile high‐ploidy (14x) amphiploids.

Elicitation of salt stress-tolerant mutants in bread wheat (Triticum aestivum L.) by using gamma radiation

BackgroundGiven the strategic importance of wheat being the staple food for the vast majority of people, it was necessary to know reasons for the contraction and decline of its area globally and consequently its lower yield. Among the most important of these problems is the problem of a high level of salinity in both soil and irrigation water coming at the forefront of environmental challenges that hinder its production process at the local and global levels. Therefore, the genetic improvement of wheat for salinity tolerance was one of the most important priorities of this investigation.ResultsThe seven wheat accessions (Sakha 8 and its six M5 derived mutants) succeeded in drawing unique cases of salinity tolerance and were excellent especially mutants 1, 2, 3, and 5. The rest genotypes were coming in the second rank for this purpose and were very good in this regard. The promising wheat genotypes which recorded high salinity tolerance in the recent investigation exhibited also high genetic stability. This fact was proved after estimating some agro-morphological and physiological traits related to salinity tolerance based on evaluating some important genetic parameters besides salinity tolerance indices under stress experiment compared to the control treatment within two seasons. Data evaluated of expected genetic advance (GA) based on 5% selection proved that all values calculated during the two seasons under both treatments appeared low for all studied traits in this regard. However, it reflects the success of breeding for salinity tolerance in wheat using mutations but in relative terms. Molecular marker analysis profile using the six ISSR primers exhibited a total of 173 markers, 12 of them were monomorphic, while that 161 bands appeared polymorphic included 56 unique bands or positive markers and 7 negative markers with 93.06 % (polymorphism).ConclusionThe original wheat variety (Sakha 8) and its six M5 derived mutants exhibited high tolerance of salinity stress in all studied traits based on all genetic parameters and salinity tolerance indices calculated for both seasons under salinity treatment compared to the normal conditions. DNA fingerprinting analysis as well for the six wheat mutants besides the local variety proved that these genotypes were recorded highly genetic differences among them.

Resemblance and Difference of Seedling Metabolic and Transporter Gene Expression in High Tolerance Wheat and Barley Cultivars in Response to Salinity Stress.

To elucidate inter-specific similarity and difference of tolerance mechanism against salinity stress between wheat and barley, high tolerant wheat cv. Suntop and sensitive cv. Sunmate and tolerant barley cv. CM72 were hydroponically grown in a greenhouse with 100 mM NaCl. Glutathione, secondary metabolites, and genes associated with Na+ transport, defense, and detoxification were examined to discriminate the species/cultivar difference in response to salinity stress. Suntop and CM72 displayed damage to a lesser extent than in Sunmate. Compared to Sunmate, both Suntop and CM72 recorded lower electrolyte leakage and reactive oxygen species (ROS) production, higher leaf relative water content, and higher activity of PAL (phenylalanine ammonia-lyase), CAD (cinnamyl alcohol dehydrogenase), PPO (polyphenol oxidase), SKDH (shikimate dehydrogenase), and more abundance of their mRNA under salinity stress. The expression of HKT1, HKT2, salt overly sensitive (SOS)1, AKT1, and NHX1 was upregulated in CM72 and Suntop, while downregulated in Sunmate. The transcription factor WRKY 10 was significantly induced in Suntop but suppressed in CM72 and Sunmate. Higher oxidized glutathione (GSSG) content was accumulated in cv. CM72 and Sunmate, but increased glutathione (GSH) content and the ratio of GSH/GSSG were observed in leaves and roots of Suntop under salinity stress. In conclusion, glutathione homeostasis and upregulation of the TaWRKY10 transcription factor played a more important role in wheat salt-tolerant cv. Suntop, which was different from barley cv. CM72 tolerance to salinity stress. This new finding could help in developing salinity tolerance in wheat and barley cultivars.

Foliar applied fullerol differentially improves salt tolerance in wheat through ion compartmentalization, osmotic adjustments and regulation of enzymatic antioxidants.

Earlier we reported that seed pre-treatment with PHF promoted early seedling growth and salinity tolerance in wheat. As a way forward, experiments were conducted to investigate whether and to what extent foliar spray of fullerol could influence growth and physio-biochemical responses in salt stressed wheat. Ina control experiment, seeds were sown in sand filled pots (500g) under control and 150mM NaCl stress. After 15days, foliar spray of fullerol at 0, 10, 40, 80 and 120nM concentrationwas applied and the data for various morpho-biochemical attributes recorded after 2weeks. Fullerol caused improvements in shoot growth attributes while had least effect on root growth traits. Increase in total chlorophyll while reduction in Car/Chl ratio was evident under salinity in response to fullerol spray. Only 40 and 80nM spray treatments improved antioxidant activities and reduced H2O2 contents while MDA contents which increased due to salt stress, remained unaffected by foliar spray. Fullerol spray also improved sugars, proline and free amino acids under salinity. During second experimentunder natural conditions, 60day old plants grown in sand filled pots (10kg) under 0 and 150mM NaCl were foliar sprayed with selected concentrations (0, 40 and 80nM) offullerol. Salinity inhibited gas exchange and grain yield attributes while fullerol-sprayed plants exhibited recovery. Fullerol spray resulted in high root and shoot K+ and shoot Ca2+ contents. Also, increase in shoot and root P, while lesser shoot Na+ was recorded due to 80nM spray under salt stress. Overall, 40 and 80nM fullerol spray improved photosynthetic activity, osmolytes accumulation and altered tissue ion compartmentalization which contributed to improvement in grain yield attributes under salinity.

Gas exchange and ionic traits as selection criteria for salinity tolerance in wheat (Triticum aestivum L.) cultivars

Gas exchange and ionic traits as selection criteria for salinity tolerance in wheat (Triticum aestivum L.) cultivars

Expression analysis of stress responsive transcription factors during heat, drought and salinity tolerance in wheat

Expression analysis of stress responsive transcription factors during heat, drought and salinity tolerance in wheat

Genetic and transcriptional variations in NRAMP-2 and OPAQUE1 genes are associated with salt stress response in wheat

Key messageSNP alleles on chromosomes 4BL and 6AL are associated with sensitivity to salt tolerance in wheat and upon validation can be exploited in the development of salt-tolerant wheat varieties.The dissection of the genetic and molecular components of salt stress response offers strong opportunities toward understanding and improving salt tolerance in crops. In this study, GWAS was employed to identify a total of 106 SNP loci (R2 = 0.12–63.44%) linked to salt stress response in wheat using leaf chlorophyll fluorescence, grain quality and shoot ionic (Na+ and K+ ions) attributes. Among them, 14 SNP loci individually conferred pleiotropic effects on multiple independent salinity tolerance traits including loci at 99.04 cM (R2 ≥ 14.7%) and 68.45 cM (R2 ≥ 4.10%) on chromosomes 6AL and 4BL, respectively, that influenced shoot Na+-uptake, shoot K+/Na+ ratio, and specific energy fluxes for absorption (ABS/RC) and dissipation (DIo/RC). Analysis of the open reading frame (ORF) containing the SNP markers revealed that they are orthologous to genes involved in photosynthesis and plant stress (salt) response. Further transcript abundance and qRT-PCR analyses indicated that the genes are mostly up-regulated in salt-tolerant and down-regulated in salt-sensitive wheat genotypes including NRAMP-2 and OPAQUE1 genes on 4BL and 6AL, respectively. Both genes showed highest differential expression between contrasting genotypes when expressions of all the genes within their genetic intervals were analyzed. Possible cis-acting regulatory elements and coding sequence variation that may be involved in salt stress response were also identified in both genes. This study identified genetic and molecular components of salt stress response that are associated with Na+-uptake, shoot Na+/K+ ratio, ABS/RC, DIo/RC, and grain quality traits and upon functional validation would facilitate the development of gene-specific markers that could be deployed to improve salinity tolerance in wheat.

Evaluation of Na+ Concentration and K+/Na+ Ratio as A Criterion for Salinity Tolerance in Wheat and Barley

Evaluation of Na+ Concentration and K+/Na+ Ratio as A Criterion for Salinity Tolerance in Wheat and Barley

Salt overly sensitive 1 (SOS1) gene expression can be regulated via Azospirillum brasilense Sp7 in wheat seedlings under saline condition

Salinity stress reduces plant growth via failure of physiological processes mainly due to the abundance of Na+ ion. Salt overly sensitive (SOS) signaling pathway is considered as an important component of Na+/K+ homeostasis system in plants, especially under saline condition. Moreover, it is reported that wheat-Azospirillum associated has resulted in an enhanced salinity tolerance. To evaluate involvement of Azospirillum species in regulation of SOS signaling pathway, inoculated and none-inoculated wheat seedlings with Azospirillum brasilense Sp7 were grown for five days. Then uniform seedlings were transferred into saline hydroponic media with and without 200 mM NaCl. The relative expression of TaSOS1 of root, sheath, and blade as well as Na+/K+ ratio was measured after 6, 24 and 48 hours since inoculated and non-inoculated seedling were transferred to NaCl media. Simultaneously Ca, Fe, proline content, root and shoot dry mass and soluble sugars were measured at 72 hour after application of NaCl. Result showed that salinity increased TaSOS1 gene expression, Na+, prolin and Na+/K+ ratio but Ca and Fe were decreased in root and shoot of wheat seedlings. Although A. brasilense Sp7 could improve salinity tolerance in wheat via reduction of Na uptake and upregulation of TaSOS1 expression, but do not have any effect in sodium distribution within plant parts. Therefore, salinity could increase TaSOS1 expression in the root, sheath and blade and A. brasilense Sp7 also could reduce the adverse effect of salinity via addition of over expression of TaSOS1.

Identification, analysis and development of salt responsive candidate gene based SSR markers in wheat

BackgroundSalinity severely limits wheat production in many parts of the world. Development of salt tolerant varieties represents the most practical option for enhancing wheat production from these areas. Application of marker assisted selection may assist in fast tracking development of salt tolerant wheat varieties. However, SSR markers available in the public domain are not specifically targeted to functional regions of wheat genome, therefore large numbers of these need to be analysed for identification of markers associated with traits of interest. With the availability of a fully annotated wheat genome assembly, it is possible to develop SSR markers specifically targeted to genic regions. We performed extensive analysis to identify candidate gene based SSRs and assessed their utility in characterizing molecular diversity in a panel of wheat genotypes.ResultsOur analysis revealed, 161 SSR motifs in 94 salt tolerance candidate genes of wheat. These SSR motifs were nearly equally distributed on the three wheat sub-genomes; 29.8% in A, 35.7% in B and 34.4% in D sub-genome. The maximum number of SSR motifs was present in exons (31.1%) followed by promoters (29.8%), 5’UTRs (21.1%), introns (14.3%) and 3’UTRs (3.7%). Out of the 65 candidate gene based SSR markers selected for validation, 30 were found polymorphic based on initial screening and employed for characterizing genetic diversity in a panel of wheat genotypes including salt tolerant and susceptible lines. These markers generated an average of 2.83 alleles/locus. Phylogenetic analysis revealed four clusters. Salt susceptible genotypes were mainly represented in clusters I and III, whereas high and moderate salt tolerant genotypes were distributed in the remaining two clusters. Population structure analysis revealed two sub-populations, sub-population 1 contained the majority of salt tolerant whereas sub-population 2 contained majority of susceptible genotypes. Moreover, we observed reasonably higher transferability of SSR markers to related wheat species.ConclusionWe have developed salt responsive gene based SSRs in wheat for the first time. These were highly useful in unravelling functional diversity among wheat genotypes with varying responses to salt stress. The identified gene based SSR markers will be valuable genomic resources for genetic/association mapping of salinity tolerance in wheat.

QTLs for seedling traits under salinity stress in hexaploid wheat

ABSTRACT: Soil salinity limits agricultural production and is a major obstacle for increasing crop yield. Common wheat is one of the most important crops with allohexaploid characteristic and a highly complex genome. QTL mapping is a useful way to identify genes for quantitative traits such as salinity tolerance in hexaploid wheat. In the present study, a hydroponic trial was carried out to identify quantitative trait loci (QTLs) associated with salinity tolerance of wheat under 150mM NaCl concentration using a recombinant inbred line population (Xiaoyan 54×Jing 411). Values of wheat seedling traits including maximum root length (MRL), root dry weight (RDW), shoot dry weight (SDW), total dry weight (TDW) and the ratio of TDW of wheat plants between salt stress and control (TDWR) were evaluated or calculated. A total of 19QTLs for five traits were detected through composite interval mapping method by using QTL Cartographer version 2.5 under normal and salt stress conditions. These QTLs distributed on 12 chromosomes explained the percentage of phenotypic variation by individual QTL varying from 7.9% to 19.0%. Among them, 11 and six QTLs were detected under normal and salt stress conditions, respectively and two QTLs were detected for TDWR. Some salt tolerance related loci may be pleiotropic. Chromosome 1A, 3A and 7A may harbor crucial candidate genes associated with wheat salt tolerance. Our results would be helpful for the marker assisted selection to breed wheat varieties with improved salt tolerance.

Comparative performance of spectral and thermographic properties of plants and physiological traits for phenotyping salinity tolerance of wheat cultivars under simulated field conditions.

Successful plant breeding in saline environments requires high-throughput phenotyping techniques to differentiate genotypes for salinity tolerance. This study employed advanced, non-destructive sensing technologies to identify traits contributing to salinity tolerance in wheat (Triticum aestivum L.). Plants were grown in large containers to simulate field conditions for control, salinity stress alone, and combined salinity and drought stress treatments. The comparative performance of spectral reflectance sensing, thermography, digital imaging, and the assessment of physiological traits of two wheat cultivars were tested at booting, anthesis and grain filling. Variation in grain yield between the two cultivars was significant for all treatments (controls, P<0.01; others, P<0.001), whereas there were no significant differences in straw DW regardless of treatment. Among the spectral and thermographic assessments, spectral indices were sufficiently sensitive to detect genotypic differences in salinity tolerance among the wheat cultivars after anthesis for the salinity alone and combined treatments. In contrast, physiological traits such as leaf water status and photosynthetic properties demonstrated no differences between the wheat cultivars for either the salinity alone or the combined treatments. These results suggest that spectral sensing has the potential for high-throughput screening of phenotypic traits associated with salinity tolerance of wheat cultivars.

A putative pyruvate transporter TaBASS2 positively regulates salinity tolerance in wheat via modulation of ABI4 expression.

BackgroundHigh salinity adversely affects crop production. Pyruvic acid is the precursor of abscisic acid (ABA) and other chemicals that are synthesized in chloroplast, some of which are involved in the response to salt. The transportation of pyruvic acid into chloroplast is mediated by pyruvate transporters. However, whether pyruvate transporters are involved in salt response has not been studied so far. Here, we answered this issue by assessing the function of a wheat pyruvate transporter in salt response.ResultsA pyruvate transporter TaBASS2 was isolated from salt-tolerant wheat cultivar Shanrong 3. The expression of TaBASS2 was induced by NaCl stress as well as H2O2 and ABA treatments. Constitutive expression of TaBASS2 in Arabidopsis bass2-1 mutant complemented the mevastatin-sensitive phenotype that reflects the deficiency of transporting pyruvic acid into chloroplast. Overexpression of TaBASS2 enhanced salinity tolerance and reactive oxygen species scavenging in wheat. Arabidopsis constitutively expressing TaBASS2 also exhibited enhanced tolerance to salinity and oxidative stress. In Arabidopsis, TaBASS2 repressed the expression of ABA INSENSITIVE 4 (ABI4), a node linking ABA signaling and plastid retrograde signaling pathways. However, the enhanced salinity tolerance of TaBASS2 overexpression Arabidopsis was abolished when ABI4 expression was restored to the level of wild-type through overexpressing ABI4.ConclusionsOur work demonstrates that TaBASS2 enhances salinity tolerance of plants via modulating ABI4 expression. This indicates that pyruvate transporters indeed participate in the interaction of plants with environmental stimuli.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0795-3) contains supplementary material, which is available to authorized users.

Differential transcript abundance of salt overly sensitive (SOS) pathway genes is a determinant of salinity stress tolerance of wheat

Salt overly sensitive (SOS) pathway genes, SOS1 (plasma membrane Na+/H+ antiporter), SOS2 (CBL interacting protein kinase 24), and SOS3 (calcineurin B like protein 4) are associated with active efflux of toxic sodium ions (Na+) from cytosol and thus confer salinity tolerance in glycophytic plants such as Arabidopsis. The role of SOS pathway genes SOS2 and SOS3 in salinity tolerance of wheat is rarely studied. One-month-old seedlings of three bread wheat genotypes namely, HD 2009, HD2687 and Kharchia 65 were imposed with two levels of salinity stress (100 and 200 mM NaCl) for 30 days duration. Based on the physiological parameters, genotype Kharchia 65 was highly tolerant, HD 2009 was moderately tolerant and HD 2687 was sensitive to salinity stress. Tolerant genotypes accumulated lesser amount of Na+ in root, stem and leaf tissues. Transcript abundance of SOS1, SOS2 and SOS3 genes was significantly higher in salt tolerant genotypes under long-term salinity and correlated with improved sodium exclusion, and higher potassium/sodium (K+/Na+) ratio. Expression levels of genes involved in vacuolar partitioning of Na+, NHX1 (vacuolar Na+/H+ antiporter) and VP1 (Vacuolar pyrophosphatase) were also higher in salt tolerant wheat genotypes under 200 mM NaCl stress. Partial coding sequences of SOS1, SOS2, SOS3, NHX1 and VP1 genes were cloned and sequenced from the above mentioned three wheat genotypes. The results in the present study demonstrated that SOS pathway of ion homeostasis under salinity stress is conserved across species.

Molecular characterization of salinity tolerance in wheat (Triticum aestivum L.)

Random amplified polymorphic DNA (RAPD) markers were used to estimate the genetical variability of three salt-resistant genotypes, SARC-1, SARC-5 and S-24, exposed to saline environment. High-yielding and salt-sensitive variety MH-97 was used as standard for comparison. The behavior of these genotypes under saline environment was analyzed by using the hydroponics screening methods at the seedling stage. One hundred and fifty primers were tested of which 52 primers revealed differences between SARC-1 and SARC-5, 54 revealed differences between SARC-1 and S-24 and 61 revealed differences between SARC-5 and S-24. Polymorphism differences between MH-97 and SARC-1, MH-97 and SARC-5 and MH-97 and S-24 were 53%, 64% and 42%, respectively. Four primer pairs amplified special fragments, which were located in all the three salt-resistant genotypes but none on the salt-sensitive genotype MH-97. Primer GLD-15 (5ʹ-CCGTGGCATT-3ʹ) generated a prominent fragment of length 1460 bp; primer GLF-18 (5ʹ-ACCCGGAACC-3ʹ) produced a fragment of length nearly 980 bp in the salt-resistant genotype; the primer pair GLE-5 (5ʹ-TTCAAGCCCG-3ʹ) located one polymorphic amplified band of 1290 bp and the primer GLH-9 (5ʹ-ATCCAGGTCA-3ʹ) performed as a weak polymorphic band of 640 bp, respectively.

A Wheat Allene Oxide Cyclase Gene Enhances Salinity Tolerance via Jasmonate Signaling

One of the two branches of the α-linolenic acid metabolism pathway is catalyzed by 12-oxo-phytodienoic acid reductase I, and the other is involved in jasmonic acid (JA) synthesis. The former is known to be active in the response to salinity tolerance in wheat (Triticum aestivum), but the participation of the latter in this response has not been established as yet. Here, the salinity-responsive bread wheat gene TaAOC1, which encodes an allene oxide cyclase involved in the α-linolenic acid metabolism pathway, was constitutively expressed in both bread wheat and Arabidopsis (Arabidopsis thaliana). In both species, transgenic lines exhibited an enhanced level of tolerance to salinity. The transgenic plants accumulated a higher content of JA and developed shorter roots. Both the shortened roots and the salinity tolerance were abolished in a background lacking a functional AtMYC2, a key component of the JA and abscisic acid signaling pathway, but were still expressed in a background deficient with respect to abscisic acid synthesis. We provide the first evidence, to our knowledge, suggesting that JA is also involved in the plant salinity response and that the α-linolenic acid metabolism pathway has a regulatory role over this response.

Haplotype analysis of QTLs attributed to salinity tolerance in wheat (Triticum aestivum)

A diverse collection of wheat germplasm, consisting of 100 bread wheat lines with varying levels of salinity tolerance were evaluated based on incomplete block design (lattice) with two replications in field conditions. Plant material was screened for salinity tolerance under normal and saline field conditions. Subsequently in order to assess the haplotype diversity of QTLs attributed to salinity tolerance in wheat (Triticum aestivum), a collection of 30 extremes tolerant and sensitive genotypes among them were selected for genotyping on the basis of morphological, physiological and phenological traits. Genotyping was done using microsatellite markers which had been detected as the flanking regions of large effect QTLs attributed to salinity tolerance on chromosomes 2A, 4D and 3B. Combined analysis of saline and normal conditions revealed that genotypes showed highly significant responses. Association analysis of SSR markers with traits, showed markers Xcfa2121b, Xgwm10 and Xgwm296 on chromosome 2A and markers Xgwm194 and xgwm624 for chromosome 4D, had significant association with most of measured traits. Haplotype diversity analysis showed markers Xgwm10, Xgwm445, Xbarc353.2, Xgwm312, Xgwm515 and Xwmc296 on chromosome 2A as well as markers Xwmc326 and Xgwm345, Xbarc48.4 on chromosomes 3B and 4D were identified as the best markers attributed to salinity tolerance and they can be informative markers for improvement of salinity tolerance through marker-assisted selection programs.

Ability of leaf mesophyll to retain potassium correlates with salinity tolerance in wheat and barley

This work investigated the importance of the ability of leaf mesophyll cells to control K(+) flux across the plasma membrane as a trait conferring tissue tolerance mechanism in plants grown under saline conditions. Four wheat (Triticum aestivum and Triticum turgidum) and four barley (Hordeum vulgare) genotypes contrasting in their salinity tolerance were grown under glasshouse conditions. Seven to 10-day-old leaves were excised, and net K(+) and H(+) fluxes were measured from either epidermal or mesophyll cells upon acute 100 mM treatment (mimicking plant failure to restrict Na(+) delivery to the shoot) using non-invasive microelectrode ion flux estimation (the MIFE) system. To enable net ion flux measurements from leaf epidermal cells, removal of epicuticular waxes was trialed with organic solvents. A series of methodological experiments was conducted to test the efficiency of different methods of wax removal, and the impact of experimental procedures on cell viability, in order to optimize the method. A strong positive correlation was found between plants' ability to retain K(+) in salt-treated leaves and their salinity tolerance, in both wheat and especially barley. The observed effects were related to the ionic but not osmotic component of salt stress. Pharmacological experiments have suggested that voltage-gated K(+) -permeable channels mediate K(+) retention in leaf mesophyll upon elevated NaCl levels in the apoplast. It is concluded that MIFE measurements of NaCl-induced K(+) fluxes from leaf mesophyll may be used as an efficient screening tool for breeding in cereals for salinity tissue tolerance.