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β-glucan is an important trait to be improved in barley breeding programs, as it greatly affects the quality of the end products when barley grains are used as raw material of feed or malt production or consumed as food for human. Although the genes associated with β-glucan synthesis have been identified, genetic regulation of β-glucan accumulation in barley grains is still completely unclear. In this study, 100 accessions from International Barley Core Selected Collection (BCS) were planted in two environments for two consecutive years to determine the genotypic variation of grain β-glucan content. A genome-wide association study (GWAS) identified 14 stable marker-trait associations (MTAs) (−Log10(P)> 4) for grain β-glucan content. Significantly positive correlation was found between grain β-glucan content and the number of favorable alleles of 14 stable MTAs. Seven putative candidate genes encoding some enzymes in glucose metabolism were found to be associated with β-glucan content. One of the putative genes, HORVU6Hr1G088380, could be an important gene controlling barely β-glucan content, with the SNPs being closely linked in all tested accessions and divided into two haplotypes. High resolution melting (HRM) analysis of the first SNP suggested that the HRM-SNP marker is valid for marker-assisted selection in barley breeding. This study provides useful information for the genes and markers related to grain β-glucan content in barley. [ABSTRACT FROM AUTHOR]

A low level of available potassium (K) in soils is a major factor restricting crop growth and production. In earlier studies we found that Tibetan wild barley has a wider variation in low K stress tolerance than cultivated barley. In this study, we performed a genome-wide association analysis of 179 Tibetan wild barley (Hordeum vulgare L.) accessions exposed to low K stress and investigated the associations of K uptake rate (KUR), K translocation rate (KTR) and other K metabolism traits with 11,013 diversity arrays technology markers. The results showed that there were significant differences in tissue K concentration and content, KUR and KTR among the wild barley accessions analyzed. Scores for all traits showed a normal distribution. Three significant quantitative trait loci (QTLs) for KUR and KTR were identified and located on 6H and 1H. These QTLs were found to be associated with the cation/H(+) antiporter and cyclic nucleotide gated channel. A number of unique candidate genes associated with K-related signals, including K channels, K transporters and ethylene-related genes, were also identified. The K channels and K transporters involved in K uptake and translocation, respectively, were closely associated with KUR in response to low K stress. The present study highlights the potential of Tibetan wild barley to provide elite candidate genes for the improvement of K use efficiency of barley. [ABSTRACT FROM AUTHOR]

Phenolic acids in plants is receiving more attention because of their nutritive function and essential roles in plant growth. However, the genetics of phenolic acids in barley is still unclear. In this study, two main phenolic acids, i.e. ferulic acid (FA) and p-coumaric acid (p-CA), were analyzed in the grains of a double haploid population derived from XZ153 (Tibetan wild barley) × Hua30 (cultivated cultivar) grown in three locations. A wide variation in the content of phenolic acids was observed among the DH population. Quantitative trait locus (QTL) analysis of phenolic acid content in barley grains from three locations totally identified 4 QTLs associated with p-CA content and 4 QTLs with FA content. Based on the mean phenolic acids content over the three locations, two significant QTLs (M_3261686 for p-CA and M_4184755 for FA), belonging to cytochrome P450 family (HvCYPs) were identified, with the LOD value of 5.33 and 7.01 respectively. These two QTLs could account for 14% of phenotypic variation for FA and 18% for p-CA. Collinearity analysis revealed that HvCYPPA (QTL for p-CA) has duplication events in barley genome. Furthermore, there was no synteny block found for these two genes in barley genome. The current results provide a new knowledge about genetic controlling of phenolic acids synthesis in barley grains. [ABSTRACT FROM AUTHOR]

Aims: Cadmium (Cd) is a toxic metal in soils and its accumulation in plants poses severe problems to agricultural production and human health. Most of research has focused on the Cd toxicity to plants, but reports on Cd co-transport and regulation by the major counter ion Chloride (Cl) is limited. This study aims to understand the mechanisms of the interaction between soil Cl and phytol-toxicity of Cd. Methods: We utilised soil chemical, plant physiological, biophysical, and molecular approaches to test the hypothesis that Cl transport increases the mobility and phytol-toxicity of Cd to barley. Results: Cd-sensitive Gairdner utilised high amount of Cl− from soil for optimal growth and yield in the control, but this also caused higher tissue Cd uptake and significantly affected photosynthesis in treatments of Cd-Cl combinations. Net ion fluxes from the root mature zone in Cd treatments and relative expression of transporter genes exhibited striking difference between two genotypes. Our results also highlighted evidence that Cd sensitivity is related to higher Cl− and Cd2+ uptake and lower capacity to regulate root ion homeostasis and gene expression. Conclusions: We present a new finding that soil Cl− and Cd availability and Cd uptake and its interaction with other ions play a major role in barley Cd tolerance. These findings will guide future breeding for low Cl− uptake genotypes to reduce Cd accumulation for barley grown in Cd contaminated soils and for the economically sound and cleaner production of barley for the global feed, food and brewery industry. [ABSTRACT FROM AUTHOR]

The toxicity of many heavy metals in plants is closely associated with its subcellular distribution and chemical forms. The subcellular distribution and chemical forms of cobalt (Co) were investigated using 3 barley genotypes differing in Co toxicity resistance, namely Yan66 (resistant), Ea 52 (sensitive), and Humai 4 (moderate), under two Co levels (25 and 100 µM). Higher Co level in cultural solution significantly increased Co accumulation in all subcellular fractions, with vacuole and cell wall having higher concentration. In comparison with 25 µM Co, 100 µM Co treatment caused significant increase of Co concentration in the forms of F-NaCl (extracted with 1 M NaCl), F-Ac (extracted with 2% HAc), F-HCl (extracted by 0.6 M HCl), and F-residue (residue forms) in both shoots and roots. There was a significant difference among genotypes in Co subcellular distribution and chemical forms, with Ea52 accumulating more Co in organelles and Yan66 accumulating more Co in vacuole and cell wall. Moreover, the inorganic form of Co extracted with 80% ethanol (F-ethanol) and water-soluble form (F-HO) were significantly increased in Ea52, while Yan66 accumulated more Co in the forms of low-bioavailable molecules (F-NaCl, F-HAc, and F-HCl). The results suggest that the vacuolar sequestration and cell wall deposition of Co is a key resistant mechanism for genotype Yan66. [ABSTRACT FROM AUTHOR]

Haze formation in beer is a trait closely related to beer quality and it is largely affected by the haze active proteins (HAPs) in barley ( Hordeum vulgare L.). Up to date, little is known about the genetics of HAPs and relevant genes. In this study, we obtained the beer samples from a Franklin/Yerong double haploid (DH) population and the two parents using micro-malting and micro-brewing, and determined tannin-related HAPs. It was found that there was a wide difference in HAPs among all lines of the DH population, and Yerong had a higher HAPs content than Franklin. Quantitative trait locus (QTL) analysis identified five QTLs associated with HAPs in beer, being located on chromosomes 1HS, 5HL and 6HS, respectively. The loci QHAP1.FrYe- 1H and QHAP2.FrYe- 1H were overlapped in the short arm of chromosome 1H, and they controlled HAP1 and HAP2, respectively. Moreover, the candidate genes were also predicted based on published whole barley genome sequence and corresponding gene annotations. [ABSTRACT FROM AUTHOR]

A hydroponic experiment was conducted to elucidate the difference in growth and cell ultrastructure between Tibetan wild and cultivated barley genotypes under moderate (150 mM NaCl) and high (300 mM NaCl) salt stress. The growth of three barley genotypes was reduced significantly under salt stress, but the wild barley XZ16 (tolerant) was less affected relative to cultivated barley Yerong (moderate tolerant) and Gairdner (sensitive). Meanwhile, XZ16 had lower Na and higher K concentrations in leaves than other two genotypes. In terms of photosynthetic and chlorophyll fluorescence parameters, salt stress reduced maximal photochemical efficiency ( F/ F), net photosynthetic rate (Pn), stomatal conductance (Gs), and intracellular CO concentration (Ci). XZ16 showed relatively smaller reduction in comparison with the two cultivated barley genotypes. The observation of transmission electron microscopy found that fundamental cell ultrastructure changes happened in both leaves and roots of all barley genotypes under salt NaCl stress, with chloroplasts being most changed. Moreover, obvious difference could be detected among the three genotypes in the damage of cell ultrastructure under salt stress, with XZ16 and Gairdner being least and most affected, respectively. It may be concluded that high salt tolerance in XZ16 is attributed to less Na accumulation and K reduction in leaves, more slight damage in cell ultrastructure, which in turn caused less influence on chloroplast function and photosynthesis. [ABSTRACT FROM AUTHOR]

Limit dextrinase (LD) is a unique de-branching enzyme involved in starch mobilization of barley grains during malting, and closely related to malt quality. Genotypic variation of LD activity is controlled by genetic factors and also affected by environmental conditions. Correlation analysis between LD activity and four malt quality parameters showed that LD activity was positively correlated with diastatic power, Kolbach index and the quality of malt extract, while negatively correlated with viscosity. The structure-based association analysis demonstrated that HvLDI, a gene encoding limit dextrinase inhibitor, was a major determinant of LD activity and malt quality. The single nucleotide polymorphisms associated with LD activity could be used in early generation selection for barley breeding. [ABSTRACT FROM AUTHOR]

The genetic associations and differences of four protein fractions were investigated in Tibetan wild barley. Albumin, globulin and hordein contents were under genetic control probably via multiple genes/quantitative trait loci. A correlation analysis showed that globulin was significantly associated with albumin, glutelin and hordein, while hordein was closely correlated with glutelin. Forty-nine diversity array technology (DArT) markers, which were distributed over seven chromosomes, were associated with the protein fraction contents. Those DArT markers associated with hordein were the same as those associated with globulin and glutelin. Only five markers associated with hordein, globulin and glutelin were also associated with albumin. Most of the protein fraction contents are therefore controlled by same genes which may contribute to total protein content. The discovery of new markers associated with specific protein fractions could be used to detect genes controlling protein content in the barley germplasm. [ABSTRACT FROM AUTHOR]

The terminal region of barley chromosome 5HL controls malt extract, diastatic power, free amino acid nitrogen, alpha-amylase activity, seed dormancy and pre-harvest sprouting. Comparative analysis of the barley and rice maps has established that the terminal region of barley chromosome 5HL is syntenic to rice chromosome 3L near the telomere end. The rice BAC (Bacterial Artificial Chromosome) sequences covering the region of chromosome 3L were used to search barley expressed sequenced tags database. Thirty-three genes were amplified by PCR (polymerase chain reaction) with the primers designed from barley ESTs (expressed sequence tag). Comparison of the sequences of the PCR generated DNA fragments revealed polymorphisms including single nucleotide polymorphism (SNP), insertions or deletions between the barley varieties. Seven new PCR based molecular markers were developed and mapped within 10 cM in three doubled haploid barley populations (Stirling × Harrington, Baudin × AC Metcalfe and Chebec × Harrington). The mapped genes maintain the micro-syntenic relationship between barley and rice. These gene specific markers provide simple and efficient tools for germplasm characterization and marker-assisted selection for barley malting quality, and ultimately lead to isolation and identification of the major gene(s) controlling multiple quality traits on barley chromosome 5HL. [ABSTRACT FROM AUTHOR]

Wild barley germplasms are a treasure trove of useful genes and provide rich sources of genetic variation for crop improvement. We carried out a hydroponic and pot evaluation of diverse germplasms in response to drought stress using 47 Tibet annual wild barley genotypes. Our results from the hydroponic experiment showed that SPAD (soil-plant analyses development analyses, based on chlorophyll meter readings), plant height, and biomass of shoot/root were significantly reduced in plants exposed to drought stress (exposure of plant roots to air for 6 h daily for a period of 7 days) compared with control plants. There were significant differences among the 47 wild barley genotypes in terms of the reduction in these growth parameters, with variation coefficients and diversity indexes ranging from 23.2 to 49.1% and 1.46 to 1.62, respectively, suggesting a rich genetic diversity among the tested accessions. Genotypes XZ5 and XZ150 showed the least reduction, indicating their high tolerance to drought stress, while genotypes XZ54 and XZ147 showed the greatest reduction, and drought stress symptoms appeared rapidly and severely in these latter genotypes. The trends in the different responses of these genotypes to drought stress were fairly consistent in both the hydroponic and the two pot selection experiments, with XZ5 and XZ150 screened as drought-resistant genotypes and XZ54, XZ147 as drought-sensitive ones. Significant genotypic differences in leaf soluble sugar content and water use efficiency in response to drought stress were also observed in pot experiment two, with the drought-tolerant genotype XZ5 showing a markedly higher recovery and the two drought-sensitive genotypes XZ54 and XZ147 showing a markedly lower recovery than the control plants. [ABSTRACT FROM AUTHOR]

The experiment was conducted to investigate the formation of oxidative stress and the development of anti-oxidative enzymes in two barley genotypes differing in anoxia tolerance. Waterlogging led to significant reduction in root and shoot weight, green leaf area and tillers per plant, but tolerant Xiumai 3 was much less reduced than sensitive Gerdner. Malondialdehyde (MDA) content, an indicator of membrane lipid peroxidation, significantly increased in Gerdner when the plants were subjected to waterlogging, but remained little changed in Xiumai 3. Superoxide dismutase (SOD) activity was increased with waterlogging treatment and the sensitive cultivar had higher activity than the tolerant one during the experimental duration. At early stage of waterlogging treatment, both peroxidase (POD) and catalase (CAT) activities significantly increased in Xuimai 3, while obviously decreased in Gerdner. Moreover, both cultivars showed substantial increase in both POD and CAT with the progress of waterlogging exposure. Glutathione reductase (GR) activity was increased in both tolerant- and sensitive cultivars under waterlogging. It may be assumed from the current results that SOD activity appears to be not a constraining factor limiting the scavenging of ROS, and it is the change of POD and CAT activity under waterlogging that determine the status of oxidative stress. The difference between genotypes in waterlogging tolerance could be distinguished from the changed patterns of these enzymatic activities. [ABSTRACT FROM AUTHOR]

Heading date (HD) is an important agronomic trait that influences plant adaptability to varying environment and, ultimately, grain yield. In this study, two doubled haploid (DH) populations were used to identify new QTL for HD. One of the DH populations is originated from a cross between an Australian malting barley cv. Franklin and a wild barley accession TAM407227 and the other one is from the cross between a Syrian wild barley SYR01 and an Australian malting barley cv. Gairdner. Using three times of sowing (TOS) differing in daylength and temperature, we investigated quantitative trait loci (QTL) controlling HD from both populations. Fourteen QTL were identified for HD from different populations and sowing dates. The expression of HD related genes varied with the TOS, suggesting a significant QTL × environment interaction. By comparing the positions of previously mapped HD genes and those of QTL detected in this population, we found that eleven of the fourteen QTL identified in this study were located at similar positions to those reported genes for HD. Among the three new potential QTL, one was located at 73.5 cM on chromosome 2H, explaining 19.2% and 4.6% HD of DH lines in spring and summer growing, respectively. The wild barley parent TAM407227 contributed the early maturity allele. HORVU2Hr1G088460 within the interval of QTL could be the candidate gene. The second new QTL was identified on chromosome 3H from a summer sowing trial and the third one on chromosome 4H affected HD of DH lines only under spring sowing condition. These new QTL identified will provide alternative genetic resources for plant breeders developing barley varieties with improved HD adaptability to varying environments. [ABSTRACT FROM AUTHOR]