Genome wide association study of plant height and tiller number in hulless barley.

Hulless barley (Hordeum vulgare L. var. nudum), also called naked barley, is a unique variety of cultivated barley. The genome-wide specific length amplified fragment sequencing (SLAF-seq) method is a rapid deep sequencing technology that is used for the selection and identification of genetic loci or markers. In this study, we collected 300 hulless barley accessions and used the SLAF-seq method to identify candidate genes involved in plant height (PH) and tiller number (TN). We obtained a total of 1407 M paired-end reads, and 228,227 SLAF tags were developed. After filtering using an integrity threshold of >0.8 and a minor allele frequency of >0.05, 14,504,892 single-nucleotide polymorphisms (SNP) loci were screened out. The remaining SNPs were used for the construction of a neighbour-joining phylogenetic tree, and the three subcluster members showed no obvious differentiation among regional varieties. We used a genome wide association study approach to identify 1006 and 113 SNPs associated with TN and PH, respectively. Based on best linear unbiased predictors (BLUP), 41 and 29 SNPs associated with TN and PH, respectively. Thus, several of genes, including Hd3a and CKX5, may be useful candidates for the future genetic breeding of hulless barley. Taken together, our results provide insight into the molecular mechanisms controlling barley architecture, which is important for breeding and yield.

Comparison of physicochemical properties of ß-glucans extracted from hull-less barley bran by different methods.

In this study, four extraction methods, including ultrasonic extraction (UE), hot water extraction (HWE), microwave extraction (ME), and microwave-assisted ultrasonic extraction (MUE) were utilized to extract ß-glucan from hull-less barley bran. Extraction yields and physicochemical properties of ß-glucans extracted by different methods were investigated. The MUE displayed a highest extraction yield (2.16%) within shorter extraction time. Besides, ß-glucans extracted by MUE (MUE-G) had higher number-average molecular weight (Mn) (3.415 × 105), whereas ß-glucans extracted by UE (UE-G) showed lower Mn (2.257 × 105) as compared to other methods. Accordingly, apparent viscosity of MUE-G was highest, while water solubility index of UE-G was highest (34.18-88.81%) at tested temperature ranges (25-95 °C). The MUE-G shower stronger foam stability and emulsifying properties and weaker foaming capability, while UE-G exhibited stronger foaming capability. The foaming capability and emulsifying properties of ß-glucan products were better in neutral solutions (pH = 7) than in the acidic (pH = 4) and alkaline (pH = 9).

Effects of hulless barley and exogenous beta-glucanase levels on ileal digesta soluble beta-glucan molecular weight, digestive tract characteristics, and performance of broiler chickens.

The reduced use of antibiotics in poultry feed has led to the investigation of alternatives to antibiotics, and one such substitution is fermentable carbohydrates. Exogenous ß-glucanase (BGase) is commonly used in poultry fed barley-based diets to reduce digesta viscosity. The effects of hulless barley (HB) and BGase levels on ileal digesta soluble ß-glucan molecular weight, digestive tract characteristics, and performance of broiler chickens were determined. A total of 360 day-old broilers were housed in battery cages (4 birds per cage) and fed graded levels of high ß-glucan HB (CDC Fibar; 0, 30, and 60% replacing wheat) and BGase (Econase GT 200 P; 0, 0.01, and 0.1%) in a 3 × 3 factorial arrangement. Beta-glucan peak molecular weight in the ileal digesta was lower with 30 and 60 than 0% HB, whereas the peak decreased with increasing BGase. The weight average molecular weight was lower at 0.1 than 0% BGase in wheat diets, whereas in HB diets, it was lower at 0.01 and 0.1 than 0% BGase. The maximum molecular weight was lower with 0.01 and 0.1 than 0% BGase regardless of the HB level. The maximum molecular weight was lower with HB than wheat at 0 or 0.01% BGase. Overall, empty weights and lengths of digestive tract sections increased with increasing HB, but there was no BGase effect. Hulless barley decreased the duodenum and jejunum contents, whereas increasing the gizzard (diets with BGase), ileum, and colon contents. The jejunum and small intestine contents decreased with increasing BGase. Ileal and colon pH increased with increasing HB, but there was no BGase effect. Treatment effects were minor on short-chain fatty acids levels and performance. In conclusion, exogenous BGase depolymerized the ileal digesta soluble ß-glucan in broiler chickens in a dose-dependent manner. Overall, feed efficiency was impaired by increasing HB levels. However, HB and BGase did not affect carbohydrate fermentation in the ileum and ceca, although BGase decreased ileal viscosity and improved feed efficiency at the 0.1% dietary level.

Overcoming barriers to the registration of new plant varieties under the DUS system.

Distinctness, Uniformity and Stability (DUS) is an intellectual property system introduced in 1961 by the International Union for the Protection of New Varieties of Plants (UPOV) for safeguarding the investment and rewarding innovation in developing new plant varieties. Despite the rapid advancement in our understanding of crop biology over the past 60 years, the DUS system has changed little and is still largely dependent upon a set of morphological traits for testing candidate varieties. As the demand for more plant varieties increases, the barriers to registration of new varieties become more acute and thus require urgent review to the system. To highlight the challenges and remedies in the current system, we evaluated a comprehensive panel of 805 UK barley varieties that span the entire history of DUS testing. Our findings reveal the system deficiencies such as inconsistencies in DUS traits across environments, limitations in DUS trait combinatorial space, and inadequacies in currently available DUS markers. We advocate the concept of genomic DUS and provide evidence for a shift towards a robust genomics-enabled registration system for new crop varieties.

Study on the origin traceability of Tibet highland barley (Hordeum vulgare L.) based on its nutrients and mineral elements.

The potential of traceability by nutrients and mineral elements in highland barley (Hordeum vulgare L.) from five cities in Tibet were investigated. The results showed that there were significant differences in nutrients and mineral elements in highland barley from different regions (P < 0.05). The original classification accuracy of linear discriminant analysis (LDA) was 78.3%, and the discrimination accuracy of training set samples based on partial least-squares discriminant analysis (PLS-DA) model was over 65%. The results of correlation analysis show that five elements (Fe, Zn, K, Mn and P) in highland barley are related to the concentration of elements in soil, while three elements (Ca, Cu and Mg) in highland barley have no obvious correlation with soil, because the special natural environment in Tibet affecting the growth of highland barley. This indicates that the origin traceability of highland barley can be achieved by measuring its nutrients and mineral elements.

Comparative assessment of effect of malt with different bud length on prolactin in hyperprolactinemia rat

Malt is the mature fruit of Hordeum vulgare L. after germination and drying and has been applied for treatment female abnormal galactorrhea. Previous studies have showed total alkaloids in malt have anti-HPRL effect. However, total alkaloids of malt change with the growth cycle, and the specified levels of total alkaloids in different bud length of malt have not been decided. To determine the definitive level of total alkaloids in different buds of malt and the most suitable bud length for clinical application by comparing effects on hyperprolactinemia rat. During the budding of malt, the content of total alkaloids first increased and then decreased, and it peaked at a bud length of 0.75 cm. Treated the HPRL model rats with different buds of malt, the PRL level was decreased, the number of PRLpositive cells and the mRNA expression level in the pituitary were significantly declined, and the number of dopamine D1 and D2 receptors in the hypothalamus was increased. The above changes were most significant in 0.75 cm bud. These results suggest that in terms of the content of effective substance and the effects on HPRL model rats, a malt bud length of 0.75 cm is optimal for clinical application.

The barley pan-genome reveals the hidden legacy of mutation breeding.

Genetic diversity is key to crop improvement. Owing to pervasive genomic structural variation, a single reference genome assembly cannot capture the full complement of sequence diversity of a crop species (known as the 'pan-genome'1). Multiple high-quality sequence assemblies are an indispensable component of a pan-genome infrastructure. Barley (Hordeum vulgare L.) is an important cereal crop with a long history of cultivation that is adapted to a wide range of agro-climatic conditions2. Here we report the construction of chromosome-scale sequence assemblies for the genotypes of 20 varieties of barley-comprising landraces, cultivars and a wild barley-that were selected as representatives of global barley diversity. We catalogued genomic presence/absence variants and explored the use of structural variants for quantitative genetic analysis through whole-genome shotgun sequencing of 300 gene bank accessions. We discovered abundant large inversion polymorphisms and analysed in detail two inversions that are frequently found in current elite barley germplasm; one is probably the product of mutation breeding and the other is tightly linked to a locus that is involved in the expansion of geographical range. This first-generation barley pan-genome makes previously hidden genetic variation accessible to genetic studies and breeding.

Population structure and diversity assessment of barley (Hordeum vulgare L.) introduction from ICARDA.

This study was undertaken to measure the genetic diversity and population structure of 48 barley accessions introduced from ICARDA using 51 polymorphic simple sequence repeat (SSR) markers to select unique parents for breeding. The mean polymorphic information content was 0.491, suggesting high polymorphism for the selected SSR markers among the barley accessions. The population structure indicated a fine genetic base only with two major clusters. All accessions had 100% membership probability in their respective clusters. Analysis of molecular variance revealed that most (78%) of the variation was attributed between populations, while 22% was due to variation among individuals within populations. Neighbour-joining (NJ) tree was constructed using this distance matrix and two major clusters were observed in it. Cluster 1 had all hulled barley accessions and cluster 2 had all hulless barley accessions. Cluster 2 could be further divided into three subclusters. Principal coordinates analysis results were similar to the NJ tree, where the hulled and hulless barley accessions were grouped into separate clusters. This study established the existence of considerable genetic diversity among the 48 tested accessions. The selected genetic resources will be useful for barley breeding in India and other countries.

The chemical composition of barley grain (Hordeum vulgare L.) landraces from the Canary Islands.

The proximate composition, total phenolics, antioxidant activity, minerals, and trace elements were determined in 42 barley landraces in order to highlight their nutritional potential and promote their cultivation. Two-row barley landraces had a higher average content of starch, protein, total phenolic compounds, and iron, when compared with six-row ones that presented higher mean ash and fiber concentrations. Additionally, the six-row barley landraces with strongly pigmented grains had lower zinc and manganese and higher protein mean concentrations than the whitish or lightly pigmented barley landraces. Factor analysis and linear discriminant analysis were used to correctly differentiate samples according to type of barley (landrace or commercial) and number of rows. In general, all the parameters varied considerably among the barley landraces analyzed, but some barley landraces could be emphasized according to fiber, minerals, and phenolic antioxidants. There were important differences in the mean values in all the chemical parameters according to the island of origin of the barley grains. The application of linear discriminant analysis was also a useful tool to differentiate all the barley landraces with six rows according to the island of origin. PRACTICAL APPLICATION: Barley is a versatile cereal that can be used for human and animal feed, brewing, and as biodiesel. From the nutritional point of view, barley is rich in starch, protein, dietary fiber and minerals, as well as antioxidant compounds and vitamins. The landraces analyzed in this study have remained intact for the last 900 years, which gives opportunity to genome of these barley landraces to evolve some very specific traits. The physicochemical characterization of these local landraces carried out by us could be very useful as a source of new quality in breeding programs.

Characterization of ß-glucan gum for food applications as influenced by genotypic variations in three hulless barley varieties.

Three hulless barley varieties were grown under normal conditions during 2017/2018 and 2018/2019, to improve their agronomic yield, and to assess how the genotype influences ß-glucan contents, and its structural, thermal, rheological, and functional properties, as intended to be used in food applications. The extracted gums with hot water at 55 °C and pH 8.0, showed contents from 5.75% to 6.41% (w/w), and concentrations from 68.55% to 79.29% of ß-glucan, with some starch and protein impurities. The results of the agronomic trail indicated the highly significant (P ≤ 0.01) influence of the genotype on all studied characteristics, and on the ß-glucan contents (0.28** and 0.33** ) at both seasons. The morphology of the three gums was significantly different in the distribution and structure of networks. Peak intensities of the -OH and -CH groups and CH2 stretching were higher and wider in Giza129 and Giza131. ß-Glucan networks melt from 71.5 to 87.18 °C, and Giza131 exhibited the highest thermal stability. The aqueous dispersions (1%) of ß-glucan gums exhibited a non-Newtonian behavior, and Giza130 presented the highest significant (P ≤ 0.05) apparent viscosity (η) and foaming stability. Giza129 showed the highest significant water and fat binding capacities, whereas Giza131 showed the highest significant foaming capacity. ß-Glucan gums showed different potentials in food applications as fat replacers, stabilizers, thickeners, and foaming agents in food systems. This study suggests planting the proper barley variety in breeding and genetic improvement programs to supply the food industry with the expected ß-glucan content with consistent structural, thermal, rheological, and functional properties. PRACTICAL APPLICATION: ß-Glucans play an important technological role in processed foods. Little current information is available on ß-glucan contents, and its potentiality on food applications, as influenced by variability among hulless barley genotypes. Accordingly, knowledge of ß-glucan levels in barley varieties is a valuable attribute for both consumers and food processors, and it will create an opportunity for scientific cooperation between food technologist and breeders to identify the suitable barley varieties to be used in breeding programs, to obtain barley with required ß-glucan contents, targeted for specific end uses.

Genome-Wide Identification and Characterization of Drought Stress Responsive microRNAs in Tibetan Wild Barley.

Drought stress is a major obstacle to agricultural production. Tibetan wild barley with rich genetic diversity is useful for drought-tolerant improvement of cereals. MicroRNAs (miRNAs) play critical roles in controlling gene expression in response to various environment perturbations in plants. However, the genome-wide expression profiles of miRNAs and their targets in response to drought stress are largely unknown in wild barley. In this study, a polyethylene glycol (PEG) induced drought stress hydroponic experiment was performed, and the expression profiles of miRNAs from the roots of two contrasting Tibetan wild barley genotypes XZ5 (drought-tolerant) and XZ54 (drought-sensitive), and one cultivated barley Tadmor (drought-tolerant) generated by high-throughput sequencing were compared. There were 69 conserved miRNAs and 1574 novel miRNAs in the dataset of three genotypes under control and drought conditions. Among them, seven conserved miRNAs and 36 novel miRNAs showed significantly genotype-specific expression patterns in response to drought stress. And 12 miRNAs were further regarded as drought tolerant associated miRNAs in XZ5, which mostly participate in gene expression, metabolism, signaling and transportation, suggesting that they and their target genes play important roles in plant drought tolerance. This is the first comparation study on the miRNA transcriptome in the roots of two Tibetan wild barley genotypes differing in drought tolerance and one drought tolerant cultivar in response to PEG treatment. Further results revealed the candidate drought tolerant miRNAs and target genes in the miRNA regulation mechanism in wild barley under drought stress. Our findings provide valuable understandings for the functional characterization of miRNAs in drought tolerance.

Effects of Growth Conditions and Cultivar on the Content and Physiochemical Properties of Arabinoxylan in Barley.

The present study aims to evaluate the effect of the growth conditions and the cultivar on the total and water-extractable (W-E) arabinoxylan (AX) in barley. For this purpose, nine barley varieties from two different years were analyzed. The total AX content ranged from 5.97 to 8.98 wt % d.m., while the W-E AX ranged from 0.06 to 0.35 wt % d.m. The W-E AX molecular properties were characterized by high-pressure size exclusion chromatography (HPSEC)-triple detector array (TDA). The molecular weight was between 2.3 × 105 and 12.6 × 105 Da, the polydispersity was between moderate and broad (1.1 < Mw/Mn < 4.3), and the conformation was a stiff semiflexible coil (0.5 < α < 1.3). The results indicate that the year influences the content of total AX and W-E AX and some molecular characteristics of W-E AX, such as its polydispersity and its conformation. Finally, the results demonstrated that the W-E AX can be used as an index of the malting attitude of barley because it positively correlates with germinative energy and kernel dimension.

Diversity of a cytokinin dehydrogenase gene in wild and cultivated barley.

The cytokinin dehydrogenase gene HvCKX2.1 is the regulatory target for the most abundant heterochromatic small RNAs in drought-stressed barley caryopses. We investigated the diversity of HvCKX2.1 in 228 barley landraces and 216 wild accessions and identified 14 haplotypes, five of these with ten or more members, coding for four different protein variants. The third largest haplotype was abundant in wild accessions (51 members), but absent from the landrace collection. Protein structure predictions indicated that the amino acid substitution specific to haplotype 3 could result in a change in the functional properties of the HvCKX2.1 protein. Haplotypes 1-3 have overlapping geographical distributions in the wild population, but the average rainfall amounts at the collection sites for haplotype 3 plants are significantly higher during November to February compared to the equivalent data for plants of haplotypes 1 and 2. We argue that the likelihood that haplotype 3 plants were excluded from landraces by sampling bias that occurred when the first wild barley plants were taken into cultivation is low, and that it is reasonable to suggest that plants with haplotype 3 are absent from the crop because these plants were less suited to the artificial conditions associated with cultivation. Although the cytokinin signalling pathway influences many aspects of plant development, the identified role of HvCKX2.1 in the drought response raises the possibility that the particular aspect of cultivation that mitigated against haplotype 3 relates in some way to water utilization. Our results therefore highlight the possibility that water utilization properties should be looked on as a possible component of the suite of physiological adaptations accompanying the domestication and subsequent evolution of cultivated barley.

Genome-wide identification, expression profiles and regulatory network of MAPK cascade gene family in barley.

BACKGROUND: Mitogen-activated protein kinase (MAPK) cascade is a conserved and universal signal transduction module in organisms. Although it has been well characterized in many plants, no systematic analysis has been conducted in barley. RESULTS: Here, we identified 20 MAPKs, 6 MAPKKs and 156 MAPKKKs in barley through a genome-wide search against the updated reference genome. Then, phylogenetic relationship, gene structure and conserved protein motifs organization of them were systematically analyzed and results supported the predictions. Gene duplication analysis revealed that segmental and tandem duplication events contributed to the expansion of barley MAPK cascade genes and the duplicated gene pairs were found to undergone strong purifying selection. Expression profiles of them were further investigated in different organs and under diverse abiotic stresses using the available 173 RNA-seq datasets, and then the tissue-specific and stress-responsive candidates were found. Finally, co-expression regulatory network of MAPK cascade genes was constructed by WGCNA tool, resulting in a complicated network composed of a total of 72 branches containing 46 HvMAPK cascade genes and 46 miRNAs. CONCLUSION: This study provides the targets for further functional study and also contribute to better understand the MAPK cascade regulatory network in barley and beyond.

An ancestral NB-LRR with duplicated 3'UTRs confers stripe rust resistance in wheat and barley.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a global threat to wheat production. Aegilops tauschii, one of the wheat progenitors, carries the YrAS2388 locus for resistance to Pst on chromosome 4DS. We reveal that YrAS2388 encodes a typical nucleotide oligomerization domain-like receptor (NLR). The Pst-resistant allele YrAS2388R has duplicated 3' untranslated regions and is characterized by alternative splicing in the nucleotide-binding domain. Mutation of the YrAS2388R allele disrupts its resistance to Pst in synthetic hexaploid wheat; transgenic plants with YrAS2388R show resistance to eleven Pst races in common wheat and one race of P. striiformis f. sp. hordei in barley. The YrAS2388R allele occurs only in Ae. tauschii and the Ae. tauschii-derived synthetic wheat; it is absent in 100% (n = 461) of common wheat lines tested. The cloning of YrAS2388R will facilitate breeding for stripe rust resistance in wheat and other Triticeae species.

Managing Fusarium Head Blight in Winter Barley With Cultivar Resistance and Fungicide.

Although there has been research on managing Fusarium head blight (FHB) in spring barley, little has been published on cultivar resistance and optimal fungicide timing for FHB management in winter barley. A 3-year (2015 to 2017) field experiment was conducted to measure FHB resistance of winter barley varieties, gauge the potential benefit from a fungicide, and help determine the optimal timing for fungicide application. The split-plot experiment took place in a misted, inoculated nursery in Raleigh, North Carolina using main plots of four winter barley cultivars (Atlantic, Endeavor, Nomini, and Thoroughbred). Three fungicide treatments were applied to subplots: prothioconazole + tebuconazole at full spike emergence, the same fungicide 6 days later, or no fungicide. The late applications significantly reduced FHB index in each of 3 years and significantly reduced deoxynivalenol (DON) in harvested grain in 2 of the 3 years. Applications at full spike emergence also yielded significant benefit in 1 of the 3 years for each parameter. Neither disease symptoms nor DON gave reason to prefer one of the fungicide timings over the other. Across the 3 years, DON ranked the cultivars Endeavor < Nomini = Thoroughbred < Atlantic. Combining the moderate resistance of Endeavor with a fungicide application and averaging the two timings resulted in a 75% DON reduction compared with unsprayed Atlantic. Taken together, our results indicate that barley growers concerned about minimizing DON should both plant moderately resistant varieties and apply fungicide if there is scab risk. During the same period, 16 commercial winter barley cultivars were tested in from three to seven Virginia and North Carolina environments each, and the DON results were compared after standardization across environments. The winter two-row malting barley cultivars Endeavor and Calypso displayed superior and robust DON resistance across environments.

Root vacuolar Na+ sequestration but not exclusion from uptake correlates with barley salt tolerance.

Soil salinity is a major constraint for the global agricultural production. For many decades, Na+ exclusion from uptake has been the key trait targeted in breeding programs; yet, no major breakthrough in creating salt-tolerant germplasm was achieved. In this work, we have combined the microelectrode ion flux estimation (MIFE) technique for non-invasive ion flux measurements with confocal fluorescence dye imaging technique to screen 45 accessions of barley to reveal the relative contribution of Na+ exclusion from the cytosol to the apoplast and its vacuolar sequestration in the root apex, for the overall salinity stress tolerance. We show that Na+ /H+ antiporter-mediated Na+ extrusion from the root plays a minor role in the overall salt tolerance in barley. At the same time, a strong and positive correlation was found between root vacuolar Na+ sequestration ability and the overall salt tolerance. The inability of salt-sensitive genotypes to sequester Na+ in root vacuoles was in contrast to significantly higher expression levels of both HvNHX1 tonoplast Na+ /H+ antiporters and HvVP1 H+ -pumps compared with tolerant genotypes. These data are interpreted as a failure of sensitive varieties to prevent Na+ back-leak into the cytosol and existence of a futile Na+ cycle at the tonoplast. Taken together, our results demonstrated that root vacuolar Na+ sequestration but not exclusion from uptake played the main role in barley salinity tolerance, and suggested that the focus of the breeding programs should be shifted from targeting genes mediating Na+ exclusion from uptake by roots to more efficient root vacuolar Na+ sequestration.

Convergent Evolution of Effector Protease Recognition by Arabidopsis and Barley.

The Pseudomonas syringae cysteine protease AvrPphB activates the Arabidopsis resistance protein RPS5 by cleaving a second host protein, PBS1. AvrPphB induces defense responses in other plant species, but the genes and mechanisms mediating AvrPphB recognition in those species have not been defined. Here, we show that AvrPphB induces defense responses in diverse barley cultivars. We also show that barley contains two PBS1 orthologs, that their products are cleaved by AvrPphB, and that the barley AvrPphB response maps to a single locus containing a nucleotide-binding leucine-rich repeat (NLR) gene, which we termed AvrPphB Response 1 (Pbr1). Transient coexpression of PBR1 with wild-type AvrPphB but not with a protease inactive mutant triggered defense responses, indicating that PBR1 detects AvrPphB protease activity. Additionally, PBR1 coimmunoprecipitated with barley and Nicotiana benthamiana PBS1 proteins, suggesting mechanistic similarity to detection by RPS5. Lastly, we determined that wheat cultivars also recognize AvrPphB protease activity and contain two putative Pbr1 orthologs. Phylogenetic analyses showed, however, that Pbr1 is not orthologous to RPS5. Our results indicate that the ability to recognize AvrPphB evolved convergently and imply that selection to guard PBS1-like proteins occurs across species. Also, these results suggest that PBS1-based decoys may be used to engineer protease effector recognition-based resistance in barley and wheat.

Association and genome analyses to propose putative candidate genes for malt quality traits.

BACKGROUND: We studied the genetics of nine malt quality traits using association genetics in a panel of North Dakota, ICARDA, and Ethiopian barley lines. Grain samples harvested from Bekoji in 2011 and 2012 were used. RESULTS: The mapping panel revealed strong population structure explained by inflorescence-type, geographic origin, and breeding history. North Dakota germplasm were superior in malt quality traits and they can be donors to improve malt quality properties. We identified 106 marker-trait associations (MTAs) for the nine traits, representing 81 genomic regions across all barley chromosomes. Chromosomes 3H, 5H, and 7H contained most of the MTAs (58.5%). Nearly 18.5% of these genomic regions contained two to three malt quality traits. Within ±250 kb of 81 genomic regions, we recovered 348 barley genes, with some potential impacting malt quality. These include invertase, ß-fructofuranosidase, α-glucosidase, serine carboxypeptidase, and bidirectional sugar transporter SWEET14-like protein. Eighteen of these genes were also previously reported in the Hordeum Toolbox, and 17 of them highly expressed during the germination process. CONCLUSION: The results from this study invite further follow-up functional characterization experiments to relate the genes with individual malt quality traits with higher confidence. It also provides germplasm resources for malt barley improvement. © 2018 Society of Chemical Industry.

Influence of malt source on beer chemistry, flavor, and flavor stability.

Beverage quality in the brewing industry is heavily influenced by ingredient properties. The contribution of raw ingredients such as yeast and hops to beer flavor is well understood. However, the influence of barley genotype and/or environment on flavor (the malt 'source') is largely unexplored. Here, a study was performed to determine (i) if there are metabolite differences among six commercial malt sources, (ii) if differences in malt chemistry are reflected in the chemistry of the beer, and (iii) if the differences in the beer chemistry impact sensory attributes of beer, through flavor and flavor stability. Six distinct sources of malts (six varieties from three maltsters) were brewed into six beers using a recipe designed to evaluate differences in flavor. Metabolomics and ionomics was used to characterize chemical variation among the six malts and beers using UHPLC- and HILIC-MS (non-volatile metabolites), HS-SPME/GC-MS (beer volatiles), and ICP-MS (malt metals). These analyses detected a total of 5042 compounds in malt, of which 217 were annotated and included amines, amino acids, fatty acids/lipids/fatty acyls, saccharides/glucosides/sugar acids/sugar alcohols, carboxylic acid derivatives, organic acids, phenolics/benzenoids, purines, pyrimidines/pyridines, terpenes, and organosulfurs. A total of 4568 compounds were detected in beer, of which 246 were annotated and included esters, aldehydes, and alcohols. Statistical analysis revealed chemical variation among the six malts (50/217 malt metabolites varied) and beers (150/246). The six beers were evaluated for flavor using a modified descriptive analysis for 45 sensory traits at 0, 4, and 8 weeks of storage at 4 °C. Principal component analysis of the sensory data revealed flavor differences among the six beers at 8 weeks, and the malt-type Full Pint was described as fruity and Meredith as corn chip. The metabolite and sensory data were integrated and revealed associations between flavor profiles in beer and the annotated malt and beer. The fruity or corn chip flavor profiles in beer were associated beer purines/pyrimidines, volatile ketones, amines, and phenolics, and malt lipids, saccharides, phenols, amines, and alkaloids. Taken together, these data support a role of malt source in beer flavor and flavor stability. As a raw ingredient, malting barley genotypes can be evaluated for a contribution to flavor, and this may be a future target for plant breeding, agronomy, and malting efforts to selectively improve flavor, flavor stability, and quality in beer.