Tolerant Barley Research Articles

Detailed Genetic Analysis for Identifying QTLs Associated with Drought Tolerance at Seed Germination and Seedling Stages in Barley.

Drought induces several challenges for plant development, growth, and production. These challenges become more severe, in particular, in arid and semiarid countries like Egypt. In terms of production, barley ranks fourth after wheat, maize, and rice. Seed germination and seedling stages are critical stages for plant establishment and growth. In the current study, 60 diverse barley genotypes were tested for drought tolerance using two different treatments: control (0-PEG) and drought (20%-PEG). Twenty-two traits were estimated for seed germination and seedling parameters. All traits were reduced under drought stress, and a significant variation was found among genotypes under control and stress conditions. The broad-sense heritability estimates were very high under both control and drought for all traits. It ranged from 0.63 to 0.97 under the control condition and from 0.89 to 0.97 under drought, respectively. These high heritabilities suggested that genetic improvement of drought tolerance in barley at both stages is feasible. The principal component analysis revealed that root-related parameters account for the largest portion of phenotypic variation in this collection. The single-marker analysis (SMA) resulted in 71 quantitative trait loci (QTLs) distributed across the seven chromosomes of barley. Thirty-three QTLs were detected for root-length-related traits. Many hotspots of QTLs were detected for various traits. Interestingly, some markers controlled many traits in a pleiotropic manner; thus, they can be used to control multiple traits at a time. Some QTLs were constitutive, i.e., they are mapped under control and drought, and targeting these QTLs makes the selection for drought tolerance a single-step process. The results of gene annotation analysis revealed very potential candidate genes that can be targeted to select for drought tolerance.

Integrated Multi-criteria Land Suitability Evaluation and Mapping for Scaling Malt Barley Varieties in Rain-Fed Production Areas of Ethiopia

Information on variety specific land suitability analysis was not available in Ethiopia. Therefore, integrated multi-criteria land suitability analysis and mapping for contrasting malt barley varieties was carried out to identify where and how much potentially suitable land exists in the country. The main factors considered for analysis include rainfall and temperature during the growing period, length of growing period, digital elevation models, (altitude and slope data) and soil characteristics (types, pH, depth, texture and drainage). The malt barley varieties included are late maturing Bekoji-1, EH1847 and Holker; and early maturing Grace, IBON 174/03 and Sabini. For classification of the data layers according to the degree of suitability for each variety, various reports and other relevant information were reviewed and used in defining the limits of the suitability ranges of malt barley varieties. The overall suitability was computed by multiplying the selected criteria weight by the assigned sub-criteria score and summing these values in the ArcGIS Model Builder. The analysis showing the extent and patterns of suitable land area available for the selected malt barley varieties are presented in the form of tabular data and maps. Highly suitable areas for these varieties include: 125,332 ha for Bekoji-1; 124,004 ha for EH1847; 775,312 ha for Grace; 125,356 ha for Holker; 1,677,388 ha for IBON 174/03; and 307,952 ha for Sabini. The results suggest that current improved malt barley varieties can be targeted for scaling out in the identified land suitability classes in the highlands of Ethiopia. Results also suggest that future research and development works should give priority for developing early maturing, acidic and waterlogging soil tolerant malt barley varieties. The results can be useful for policy and decision making to ensure land resources are used in the most productive and sustainable ways and solve the mismatches between current land use and land suitability for malt barley varieties in the country.

Wheat and Barley: Acclimatization to Abiotic and Biotic Stress

Twelve articles (ten research papers and two reviews) included in the Special Issue entitled “Wheat and Barley: Acclimatization to Abiotic and Biotic Stress” are summed up here to present the latest research on the molecular background of adaptation to environmental stresses in two cereal species. Crucial research results were presented and discussed, as they may be of importance in breeding aimed at increasing wheat and barley tolerance to abiotic and biotic stresses.

Candidate genes for salinity tolerance in barley revealed by RNA-seq analysis of near-isogenic lines

Salinity stress is one of the major abiotic stresses which affects grain yield and quality in barley. A major QTL QSl.TxNn.2H has been identified from a Chinese Landrace variety TX9425 on chromosome 2H. To assist in the identification of candidate genes, the roots of a pair of near-isogenic lines (NILs) containing the major salinity tolerance QTL (QSl.TxNn.2H) were analysed by RNA-seq after exposing the plants to 300 mM NaCl for 48 h. In total, 1256 and 809 differentially expressed genes were identified in the salt-tolerant and sensitive lines, T46 and N33, respectively. Of these genes, 572 were specifically up-regulated and 326 down-regulated in the salt-tolerant line T46, while 170 genes were specifically up-regulated and 281 down-regulated in the sensitive line N33. There are 146 genes in the QSl.TxNn.2H mapping region. Among them the transcript expression levels of 11 genes were changed in either N33 or T46 under salinity stress. A gene encoding a heat shock protein 90 (HSP90) was up-regulated more in the tolerant line T46 compared to the sensitive line N33 while a gene encoding a protein kinase WAK was up-regulated only in T46. Both may confer barley salinity tolerance by participating in Ca2+ signaling and hormone metabolism, maintaining the integrity of cell wall, regulating ion homeostasis, participating in lipid metabolism and regulating nitrogen and sugar transportation.

Genome-wide association mapping reveals putative candidate genes for drought tolerance in barley

Drought is one of the most important abiotic stresses limiting yield production in cereal crops which deleteriously affects food security worldwide. The study aimed to identify marker-trait associations (MTAs) and putative candidate genes underlying agronomic and seed related traits under post-anthesis drought stress in a set of 183 spring barley gene bank accessions from 23 countries that were genotyped with a 9 K SNP chip. Plants were grown in the field in two consecutive years and post-anthesis drought stress was simulated by spraying 1% KI ten days after anthesis. The treatment caused a significant reduction in total biomass by 10.7 %, in kernel number by 2.5 %, in kernel weight per spike by 21.4 % and in thousand kernel weight (TKW) by 16.7 %, whereby most tolerant accessions were HOR 5970, HOR 6606 and HOR 6560. GWAS analysis of best linear unbiased estimators (BLUEs) revealed 97 significant MTAs associated with kernel number and kernel weight per spike and confirmed prominent regions such as 2H (18.9 cM), 6H (54.8 cM) and 7H (70.5-71.0 cM) for drought response and were co-localized with ten putative candidate genes. Gene annotation indicates that genes for the plant respiratory burst oxidase homologs (rboh) family, the carotenoid cleavage dioxygenase 1 (CCD1) and RNA-binding proteins (RBPs) might be involved in tolerance and stress response mechanisms during post-anthesis drought stress. In conclusion, the study provides essential information about significant MTAs and candidate genes related to drought tolerance which can be further used for marker-assisted selection. More drought tolerant barley accessions may be used as pre-bred material to widen the genetic diversity of cultivated barley and to meet the demands for cultivars in world’s areas which suffer post-anthesis drought stress.

Cytoplasmic glucose-6-phosphate dehydrogenase plays an important role in the silicon-enhanced alkaline tolerance in highland barley

Glucose-6-phosphate dehydrogenase (G6PDH), as a key enzyme in the pentose phosphate pathway, extensively responds to the biotic and abiotic stresses. In this study we focussed on the G6PDH role in the alleviation of alkaline stress induced by silicon (Si) in highland barley. Application of Si reduced the water loss and malondialdehyde (MDA) and reactive oxygen species (ROS) contents, improved the fresh weight, photosynthesis, K+ content, and the superoxide dismutase (SOD) and catalase (CAT) activities, thus alleviating the damage caused by alkaline stress. The G6PDH activity, especially the cytoplasmic G6PDH, significantly increased under alkaline stress, and was further stimulated by the addition of exogenous Si. Meanwhile, the levels of NADPH and reduced glutathione (GSH) showed similar profiles to G6PDH activity under NaHCO3 and NaHCO3 + Si treatments. The inhibition of G6PDH activity by glucosamine abolished the relieving effect of Si on alkaline stress, which was manifested in the increase of ROS and the decrease of GSH content. Together, our results suggest that Si-enhanced tolerance of alkaline stress may be related to the regulation of GSH levels by the cytoplasmic G6PDH in highland barley.

Identification of novel microRNAs for cold deacclimation in barley

Cold acclimation is crucial for the overwintering process of plants. Cold deacclimation is also important for plant survival in winter, which results in loss of freezing tolerance and initiation of growth. MicroRNAs (miRNAs) play crucial roles in regulating various physiological activities including cold response in plants. However, there is no study on miRNAs and their target genes in response to cold deacclimation in a cold-tolerant crop – barley (Hordeum vulgare L.). Here, we performed high-throughput sequencing of miRNAs of leaves during the cold deacclimation process using two barley cultivars with contrasting cold tolerance (Nure, tolerant and Tremois, sensitive). We found a total of 36 known and 267 novel miRNAs, including 12 known and 112 novel ones that are differentially expressed during cold deacclimation. The number of detected differentially expressed miRNAs was larger in Nure than that in Tremois, and the expression profile of miRNAs was dramatically different between Nure and Tremois. Moreover, we identified 13 known and 97 novel miRNAs, which have putative target genes during cold deacclimation. The putative targets of the novel miRNAs included genes encoding C-repeat binding factor (CBF) transcription factors, phytohormones, antioxidant, osmopretectant and flower development. Our results suggest that barley miRNAs respond quickly to cold deacclimation, and the larger number of miRNAs differentially expressed in the cold tolerant cv. Nure indicating that miRNAs might play an important role in the process of deacclimation. It sets a solid foundation for future studies and breeding programs on low temperature tolerance in barley.

Overexpression of HvAKT1 improves drought tolerance in barley by regulating root ion homeostasis and ROS and NO signaling.

Potassium (K+) is the major cationic inorganic nutrient utilized for osmotic regulation, cell growth, and enzyme activation in plants. Inwardly rectifying K+ channel 1 (AKT1) is the primary channel for root K+ uptake in plants, but the function of HvAKT1 in barley plants under drought stress has not been fully elucidated. In this study, we conducted evolutionary bioinformatics, biotechnological, electrophysiological, and biochemical assays to explore molecular mechanisms of HvAKT1 in response to drought in barley. The expression of HvAKT1 was significantly up-regulated by drought stress in the roots of XZ5-a drought-tolerant wild barley genotype. We isolated and functionally characterized the plasma membrane-localized HvAKT1 using Agrobacterium-mediated plant transformation and Barley stripe mosaic virus-induced gene silencing of HvAKT1 in barley. Evolutionary bioinformatics indicated that the K+ selective filter in AKT1 originated from streptophyte algae and is evolutionarily conserved in land plants. Silencing of HvAKT1 resulted in significantly decreased biomass and suppressed K+ uptake in root epidermal cells under drought treatment. Disruption of HvAKT1 decreased root H+ efflux, H+-ATPase activity, and nitric oxide (NO) synthesis, but increased hydrogen peroxide (H2O2) production in the roots under drought stress. Furthermore, we observed that overexpression of HvAKT1 improves K+ uptake and increases drought resistance in barley. Our results highlight the importance of HvAKT1 for root K+ uptake and its pleiotropic effects on root H+-ATPase, and H2O2 and NO in response to drought stress, providing new insights into the genetic basis of drought tolerance and K+ nutrition in barley.

RESULTS OF IN VITRO ANDROGENESIS UNDER INCREASING SALINITY CONDITIONS FOR THREE MOROCCAN SPRING BARLEY VARIETIES (HORDEUM VULGARE L.)

In vitro androgenesis process under salt pressure is recognized as being a valuable method for quick production of salt stress tolerant doubled haploid lines, enabling yield improvement of plants cultivated in dry climates. This study aimed to investigate the effect of salt stress on in vitro androgenetic regeneration, and the production of salt tolerant barley doubled haploid lines. Moroccan barley varieties, Arig, Asni and Tamelalt were used as RS0, and after one round of selfing (RS1) or two (RS2). These successive generations made possible to verify genetic stability or possible accidental heterozygosity, and to obtain plants presumably more tolerant to salinity. After culture of 11,340 anthers on induction medium, 2,270 calluses or embryos were generated. According to the induction rate of these formations, the three generations of each variety were not significantly different, pointing out the genetic stability after two selfings. Tamelalt and Arig had similar in vitro response, while for Asni, the three generations behaviour differed from the previous ones and constitute a statistically separate group. After transfer of the formations on regeneration medium either salt free, as control, or supplemented by increasing concentrations of NaCl, ranging from 2.5 to 13 g.L-1, 170 regenerants were produced. Asni (RS1) showed to be the most salt tolerant, bearing the maximal NaCl concentration of 12 g.L-1, but the single regenerated plant obtained was albino, as most of the regenerated plants from any genotype and generation. However, RS1 and RS2 generations of Asni regenerated one green plant each, with NaCl concentration of 5 g.L-1, resulting in two new Asni doubled haploid fertile lines.

Antixenosis, Antibiosis, and Potential Yield Compensatory Response in Barley Cultivars Exposed to Wheat Stem Sawfly (Hymenoptera: Cephidae) Under Field Conditions.

Wheat stem sawfly, Cephus cinctus Norton, is an economically serious pest of cereals grown in North America. Barley cultivars were previously planted as resistant crops in rotations to manage C. cinctus, but due to increasing levels of injury to this crop, this is no longer a valid management tactic in Montana. Therefore, we aimed to understand antixenosis (behavioral preference), antibiosis (mortality), and potential yield compensation (increased productivity in response to stem injuries) in barley exposed to C. cinctus. We examined these traits in eight barley cultivars. Antixenosis was assessed by counting number of eggs per stem and antibiosis was assessed by counting infested stems, dead larvae, and stems cut by mature larvae. Potential yield compensation was evaluated by comparing grain yield from three categories of stem infestation: 1) uninfested, 2) infested with dead larva, and 3) infested cut by mature larva at crop maturity. We found the greatest number of eggs per infested stem (1.80 ± 0.04), the highest proportion of infested stems (0.63 ± 0.01), and the highest proportion of cut stems (0.33 ± 0.01) in ‘Hockett’. Seven out of eight cultivars had greater grain weight for infested stems than for uninfested stems. These cultivars may have compensatory responses to larval feeding injury. Overall, these barley cultivars contain varying levels of antixenosis, antibiosis, and differing levels of yield compensation. Our results provide foundational knowledge on barley traits that will provide a framework to further develop C. cinctus resistant or tolerant barley cultivars.

Screening of Worldwide Barley Collection for Drought Tolerance: The Assessment of Various Physiological Measures as the Selection Criteria.

Drought is a devastating environmental constraint affecting the agronomic production of barley. To facilitate the breeding process, abundant germplasm resources and reliable evaluation systems to identify the true drought-tolerant barley genotypes are needed. In this study, 237 cultivated and 190 wild barley genotypes, originating from 28 countries, were screened for drought tolerance under the conditions of both water deficit and polyethylene glycol (PEG)-simulated drought at seedling stage. Drought stress significantly reduced the plant growth of all barley genotypes, but no significant difference in drought-induced reduction in the performance of barley seedlings was observed under these two drought conditions. Both cultivated and wild barley subspecies displayed considerable genotypic variability in drought tolerance, which underpinned the identification of 18 genotypes contrasting in drought tolerance. A comparative analysis of drought effects on biomass, water relation, photosynthesis, and osmotic adjustment was undertaken using these contrasting barley genotypes, in order to verify the reliability of the screening and to obtain the credible traits as screening criteria of drought tolerance in barley. As expected, the selected drought-tolerant genotypes showed much less reduction in shoot biomass than drought-sensitive ones under water deficit, which was significantly positively correlated with the results of large-scale screening, confirming the reliability of the screening for drought tolerance under two drought conditions in this study. Likewise, the traits of water relation, photosynthetic activity, and osmotic adjustment differed greatly between the contrasting genotypes under water deficit stress, and they were highly correlated to the growth of barley seedlings, suggesting the potential of them to be the selection criteria for drought tolerance. The analysis of the variable importance of these traits in drought tolerance indicated that sap osmolality and relative water content in the youngest fully-expanded leaf are the suitable selection criteria of screening for drought tolerance in barley at seedling stage.

The zinc finger transcription factor ATF1 regulates aluminum tolerance in barley.

Aluminum (Al) toxicity is a major abiotic stress that restricts crop production in acid soils. Plants have evolved internal and external mechanisms of tolerance, and among them it is well known that AtSTOP1 and OsART1 are key transcription factors involved in tolerance through regulation of multiple downstream genes. Here, we identified the closest homolog of these two proteins in barley, namely HvATF1, Al-tolerance Transcription Factor 1, and determined its potential function in Al stress. HvATF1 is expressed in the nucleus, and functions in transcriptional activation. The transcription of HvATF1 was found to be constitutive in different tissues, and was little affected by Al stress. Knockdown of HvATF1 by RNAi resulted in increased Al sensitivity. Transcriptomics analysis identified 64 differently expressed genes in the RNAi lines compared to the wild-type, and these were considered as candidate downstream genes regulated by HvATF1. This study provides insights into the different molecular mechanisms of Al tolerance in barley and other plants.

Dissecting new genetic components of salinity tolerance in two-row spring barley at the vegetative and reproductive stages.

Soil salinity imposes an agricultural and economic burden that may be alleviated by identifying the components of salinity tolerance in barley, a major crop and the most salt tolerant cereal. To improve our understanding of these components, we evaluated a diversity panel of 377 two-row spring barley cultivars during both the vegetative, in a controlled environment, and the reproductive stages, in the field. In the controlled environment, a high-throughput phenotyping platform was used to assess the growth-related traits under both control and saline conditions. In the field, the agronomic traits were measured from plots irrigated with either fresh or saline water. Association mapping for the different components of salinity tolerance enabled us to detect previously known associations, such as HvHKT1;5. Using an "interaction model", which took into account the interaction between treatment (control and salt) and genetic markers, we identified several loci associated with yield components related to salinity tolerance. We also observed that the two developmental stages did not share genetic regions associated with the components of salinity tolerance, suggesting that different mechanisms play distinct roles throughout the barley life cycle. Our association analysis revealed that genetically defined regions containing known flowering genes (Vrn-H3, Vrn-H1, and HvNAM-1) were responsive to salt stress. We identified a salt-responsive locus (7H, 128.35 cM) that was associated with grain number per ear, and suggest a gene encoding a vacuolar H+-translocating pyrophosphatase, HVP1, as a candidate. We also found a new QTL on chromosome 3H (139.22 cM), which was significant for ear number per plant, and a locus on chromosome 2H (141.87 cM), previously identified using a nested association mapping population, which associated with a yield component and interacted with salinity stress. Our study is the first to evaluate a barley diversity panel for salinity stress under both controlled and field conditions, allowing us to identify contributions from new components of salinity tolerance which could be used for marker-assisted selection when breeding for marginal and saline regions.

Phenotypic response of barley landrace and its wild progenitor Hordeum spontaneum from Jordan to salt stress

Populations of barley landrace [Hordeum vulgare (L.)] and wild barley progenitor [Hordeum spontaneum (L.)] were collected from 13 diverse eco-geographical regions in Jordan. In addition to two check varieties (Rum and Acsad 165) were collected from farmers’ fields. In total, 28 genotypes were evaluated during germination, early seedling and maturity stages for salt tolerance. Barley populations were exposed to tap water of 0.85 dS m-1 and saline solutions (NaCl, CaCl2 and MgSO4) of 4, 8, 12 and 16 dS m-1. Final germination percentage, the lengths of shoot and seminal root, growth and yield related traits were significantly decreased by increasing the level of salinity. Proline content was increased by increasing the level of salinity. A high level of salinity of 16 dS m-1 had a strong impact on reduction of grain yield and other agronomic traits in the examined populations. A considerable variation among populations was detectable. Barley landrace and wild barley that were collected from Tafila region were the most tolerant grown populations in Jordan. Interestingly, the ranking pattern of these two populations at the germination and seedling related-traits was consistent with the ranking pattern at the maturity phase. In conclusion, this study indicates that barley landrace and wild barley populations are potential donors for genes of salt tolerance that can be used to enhance salinity tolerance in barley.

Disturbances in the Biosynthesis or Signalling of Brassinosteroids That Are Caused by Mutations in the HvDWARF, HvCPD and HvBRI1 Genes Increase the Tolerance of Barley to the Deacclimation Process

Tolerance to deacclimation is an important physiological feature in plants in the face of global warming, which is resulting in incidents of increases in winter temperatures. The aim of the work was to explore how disturbances in the signalling and synthesis of brassinosteroids (BR) influence the deacclimation tolerance of barley. One group of mutants and their reference cultivars (Bowman and Delisa) was cold-acclimated, deacclimated and then tested for frost tolerance at − 12 °C. After cold acclimation, the second group of plants was additionally exposed to frost (− 6 °C) and then, deacclimated and tested for frost tolerance at − 12 °C. The deacclimated brassinosteroid mutants were characterised by an increased tolerance to frost, and consequently, had a higher tolerance to deacclimation than their wild-type cultivars. The mechanism of this phenomenon may be partly explained by analysing the hormonal homeostasis in the crowns. For all of the tested plants, a characteristic feature of the response to the deacclimation phase was an increase in the growth-promoting hormones and abscisic acid compared to the cold acclimation phase. The increase was greater in the BR-deficient (BW084) and BR-insensitive (BW312) mutants compared to the Bowman reference cultivar. Mutant 522DK was characterised by a lower accumulation of total cytokinins and gibberellins as well as an enhanced auxin deactivation compared to the Delisa. In the second group, when the plants were exposed to a temperature of − 6 °C before deacclimation, the hormonal homeostasis was further altered in both the mutants and reference cultivars, but all of the mutants had a higher frost tolerance than the wild types.

Molecular Characterization of Betaine Aldehyde Dehydrogenase (BADH) Gene and Proline Estimation in Hordeum vulgare L. in Response to Abiotic Stress

Barley possesses the highest level of salt tolerance among cereals, thus it is used as an important species to investigate mechanisms involved in salt tolerance. The present investigation was conducted to study the effect of salt stress by different NaCl concentrations (0, 9000, 12000, and 15000 ppm) on proline production and it was found that there is a positive correlation between proline production and salinity. Also study the effect of salinity on BADH-1 gene expression by Real-Time PCR,where this gene was performed and it was aligned in GenBank. The sequencing was translated into amino acid sequences and these amino acid sequences were aligned in GenBank. Finally, the secondary structure of BADH-1 enzyme was determined from the most tolerant barley (Giza 2000 and Wadi Sedr) and sensitive barley Giza 129 cultivars, then sequencing translated into amino acid sequences and these sequences were aligned in GenBank. Finally, the secondary structure of BADH-1 enzyme was determined. These isolated genes were submitted in GenBank under accession numbers KX433169, KX342849, KX342850, KX342851, KX433170, and KX433171.

The influence of drought stress on malt quality traits of the wild and cultivated barleys

As a major abiotic stress, drought causes instability and deterioration of malt barley quality. There is distinct difference among barley cultivars in the responses of the main malt quality traits to drought stress. In the previous study, we identified some Tibetan wild barley accessions with relatively less change of malt quality traits under drought. In this study, we examined the impact of drought stress during grain filling stage on grain weight and several important malt quality traits, including total protein content, β-glucan content, limit dextrinase activity, β-amylase activity, and protein fractions in four barley genotypes (two Tibetan wild accessions and two cultivars). Drought treatment reduced grain weight, β-glucan content, and increased total protein content, β-amylase activity. These changes differed among barley genotypes and treatments, and are closely associated with grain filling process and kernel weight. All the results indicated Tibetan wild barley had great potential for developing drought tolerant barley cultivars. Relatively stable kernel weight or filling process under water stress should be highlighted in malt barley breeding in order to reduce the effect of water stress on malt barley quality.

Understanding the mechanistic basis of ameliorating effects of hydrogen rich water on salinity tolerance in barley

Hydrogen gas (H2) is known for its capability to alleviate detrimental effects of salinity in plants. However, the underlying physiological and molecular mechanisms behind this phenomenon remain poorly understood. In this study, we investigated the mechanistic basis of H2 amelioration of the salt stress in barley (Hordeum vulgare). NaCl addition induced significant inhibition of the root elongation and resulted in a loss of the cell viability; these detrimental effects were substantially reversed by treatment with hydrogen reach water (HRW). Electrophysiological experiments using non-invasive ion flux measuring MIFE technique revealed that the beneficial effects of HRW on salinity tolerance could be explained by (1) higher rate of Na+ extrusion from roots mediated by SOS1-like Na+/H+ exchanger in the root epidermis, and (2) better root K+ retention resulting from ability of HRW-treated plants to prevent NaCl-induced membrane depolarization and reduced sensitivity of K+ efflux channels to ROS. Taken together, these two factors resulted in more favorable Na/K ratio and explained beneficial effects of HRW on salinity tolerance in barley.

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.

Combined QTL mapping and RNA-Seq profiling reveals candidate genes associated with cadmium tolerance in barley.

The high toxicity of cadmium (Cd) and its ready uptake by plants has become a major agricultural problem. To investigate the genetic architecture and genetic regulation of Cd tolerance in barley, we conducted quantitative trait loci (QTL) analysis in the phenotypically polymorphic Oregon Wolfe Barley (OWB) mapping population, derived from a cross between Rec and Dom parental genotypes. Through evaluating the Cd tolerance of 87 available doubled haploid lines of the OWB mapping population at the seedling stage, one minor and one major QTL were detected on chromosomes 2H and 6H, respectively. For chlorosis and necrosis traits, the major QTL explained 47.24% and 38.59% of the phenotypic variance, respectively. RNA-Seq analysis of the parental seedlings under Cd treatment revealed 542 differentially expressed genes between Cd-tolerant Rec and Cd-susceptible Dom genotypes. By analyzing sequence variations in transcribed sequences of the parental genotypes, 155,654 SNPs and 1,525 InDels were identified between the two contrasting genotypes and may contribute to Cd tolerance. Finally, by integrating the data from the identified QTLs and RNA-Seq analysis, 16 Cd tolerance-related candidate genes were detected, nine of which were metal ion transporters. These results provide promising candidate genes for further gene cloning and improving Cd tolerance in barley.