Search

Background: Seedling characteristics play significant roles in the growth and development of barley (Hordeum vulgare L.), including stable stand establishment, water and nutrients uptake, biotic resistance and abiotic stresses, and can influence yield and quality. However, the genetic mechanisms underlying seedling characteristics in barley are largely unknown and little research has been done. In the present work, 21 seedling-related characteristics are assessed in a barley double haploid (DH) population, grown under hydroponic conditions. Of them, leaf age (LAG), shoot height (SH), maximum root length (MRL), main root number (MRN) and seedling fresh weight (SFW) were investigated at the 13th, 20th, 27th, and 34th day after germination. The objectives were to identify quantitative trait loci (QTLs) underlying these seedling characteristics using a high-density linkage map and to reveal the QTL expression pattern by comparing the QTLs among four different seedling growth stages. Results: A total of 70 QTLs were distributed over all chromosomes except 4H, and, individually, accounted for 5.01%-77. 78% of phenotypic variation. Out of the 70 detected QTLs, 23 showed a major effect on 14 seedling-related characteristics. Ten co-localized chromosomal regions on 2H (five regions), 3H (two regions) and 7H (three regions) involved 39 QTLs (55. 71%), each simultaneously influenced more than one trait. Meanwhile, 9 co-localized genomic regions involving 22 QTLs for five seedling characteristics (LAG, SH, MRL, MRN and SFW) at the 13th, 20th, 27th and 34th day-old seedling were common for two or more growth stages of seedling. QTL in the vicinity of Vrs1 locus on chromosome 2H with the favorable alleles from Huadamai 6 was found to have the largest main effects on multiple seedling-related traits. Conclusions: Six QTL cluster regions associated with 16 seedling-related characteristics were observed on chromosome 2H, 3H and 7H. The majority of the 29 regions identified for five seedling characteristics were selectively expressed at different developmental stages. The genetic effects of 9 consecutive expression regions displayed different developmental influences at different developmental stages. These findings enhanced our understanding of a genetic basis underlying seedling characteristics in barley. Some QTLs detected here could be used for marker-assisted selection (MAS) in barley breeding. [ABSTRACT FROM AUTHOR]

Background: Increasing the yield of barley (Hordeum vulgare L.) is a main breeding goal in developing barley cultivars. A high density genetic linkage map containing 1894 SNP and 68 SSR markers covering 1375.8 cM was constructed and used for mapping quantitative traits. A late-generation double haploid population (DH) derived from the Huaai 11 × Huadamai 6 cross was used to identify QTLs and QTL × environment interactions for ten traits affecting grain yield including length of main spike (MSL), spikelet number on main spike (SMS), spikelet number per plant (SLP), grain number per plant (GP), grain weight per plant (GWP), grain number per spike (GS), thousand grain weight (TGW), grain weight per spike (GWS), spike density (SPD) and spike number per plant (SP). Results: In single environment analysis using composite interval mapping (CIM), a total of 221 QTLs underlying the ten traits were detected in five consecutive years (2009-2013). The QTLs detected in each year were 50, 48, 41, 41 and 41 for the year 2009 to 2013. The QTLs associated with these traits were generally clustered on chromosome 2H, 4H and 7H. In multi-environment analysis, a total of 111 significant QTLs including 18 for MSL, 16 for SMS, 15 for SPD, 5 for SP, 4 for SLP, 14 for TGW, 5 for GP, 11 for GS, 8 for GWP, and 15 for GWS were detected in the five years. Most QTLs showed significant QTL × environment interactions (QEI), nine QTLs (qIMSL3-1, qIMSL4-1, qIMSL4-2, qIMSL6-1, qISMS7-1, qISPD2-7, qISPD7-1, qITGW3-1 and qIGWS4-3) were detected with minimal QEI effects and stable in different years. Among 111 QTLs,71 (63.40 %) QTLs were detected in both single and multiple environments. Conclusions: Three main QTL cluster regions associated with the 10 agronomic traits on chromosome 2H, 4H and 7H were detected. The QTLs for SMS, SLP, GP and GWP were located in the region near Vrs1 on chromosome 2H. The QTLs underlying SMS, SPD and SLP were clustered on chromosome 4H. On the terminal of chromosome 7H, there was a QTL cluster associated with TGW, SPD, GWP and GWS. The information will be useful for marker-assisted selection (MAS) in barley breeding. [ABSTRACT FROM AUTHOR]

Background: Acid soil is a serious limitation to crop production all over the world. Toxic aluminium (Al) cations in acid soil inhibit root growth and reduce yield. Although a gene tolerant to acid soil has been identified, it has not been used in malting barley breeding, which is partly due to the acid soil tolerance gene being linked to unfavorable malting quality traits. Results: A Brazilian malting barley variety Br2 was identified as tolerant to acid soil. A doubled haploid (DH) population was developed from a cross between Br2 and the Australian acid-sensitive cultivar Hamelin. The DH population was tested for acid soil tolerance in native acid soil and a hydroponic system with pH 4.2, pH 4.2 + Al or pH 6.5, and genotyped using SSR, DArT and gene-specific markers. A single QTL was detected for all parameters related to acid soil tolerance. The QTL was mapped to the known HvMATE location on chromosome 4H. Sequence alignment of the HvMATE gene identified 13 INDELs and 87 SNPs, where one SNP coded for a single amino acid difference between the two varieties. A gene-specific marker was developed to detect the single nucleotide polymorphism between Hamelin and Br2. This marker co-segregated with aluminium tolerance and accounted for 79 % of phenotypic variation for acid soil tolerance. Conclusion: The present study identified a novel source of acid soil/Al tolerance from a Brazilian malting barley cultivar Br2. This variety tolerated Al toxicity but was sensitive to low pH which is similar to most other Al-tolerant varieties. A gene-specific marker Cit7 was developed based on the HvMATE gene sequence. Cit7 will improve the efficiency of molecular-assisted selection of new barley varieties with tolerance to acid soil. Multiple alleles exist for the acid soil tolerance gene on chromosome 4H, so a malting barley variety that tolerates acid soil could be developed by selecting suitable tolerant alleles. Tolerance to low pH may play an important role for barley to adapt to acid soils. [ABSTRACT FROM AUTHOR]

Background: Physiological and morphological traits of flag leaf play important roles in determining crop grain yield and biomass. In order to understand genetic basis controlling physiological and morphological traits of flag leaf, a double haploid (DH) population derived from the cross of Huaai 11 × Huadamai 6 was used to detect quantitative trait locus (QTL) underlying 7 physiological and 3 morphological traits at the pre-filling stage in year 2012 and 2013. Results: Total of 38 QTLs distributed on chromosome 1H, 2H, 3H, 4H, 6H and 7H were detected, and explained 6.53% - 31.29% phenotypic variation. The QTLs flanked by marker Bmag829 and GBM1218 on chromosome 2H were associated with net photosynthetic rate (Pn), stomatal conductance (Gs), flag leaf area (LA), flag leaf length (FLL), flag leaf width (FLW), relative chlorophyll content (SPD) and leaf nitrogen concentration (LNC). Conclusion: Two QTL cluster regions associated with physiological and morphological traits, one each on the chromosome 2H and 7H, were observed. The two markers (Bmag829 and GBM1218) may be useful for marker assisted selection (MAS) in barley breeding. [ABSTRACT FROM AUTHOR]

Background: Drought and salinity are two major abiotic stresses that severely limit barley production worldwide. Physiological and genetic complexity of these tolerance traits has significantly slowed the progress of developing stress-tolerant cultivars. Marker-assisted selection (MAS) may potentially overcome this problem. In the current research, seventy two double haploid (DH) lines from a cross between TX9425 (a Chinese landrace variety with superior drought and salinity tolerance) and a sensitive variety, Franklin were used to identify quantitative trait loci (QTL) for drought and salinity tolerance, based on a range of developmental and physiological traits. Results: Two QTL for drought tolerance (leaf wilting under drought stress) and one QTL for salinity tolerance (plant survival under salt stress) were identified from this population. The QTL on 2H for drought tolerance determined 42% of phenotypic variation, based on three independent experiments. This QTL was closely linked with a gene controlling ear emergency. The QTL on 5H for drought tolerance was less affected by agronomic traits and can be effectively used in breeding programs. A candidate gene for this QTL on 5H was identified based on the draft barley genome sequence. The QTL for proline accumulation, under both drought and salinity stresses, were located on different positions to those for drought and salinity tolerance, indicating no relationship with plant tolerance to either of these stresses. Conclusions: Using QTL mapping, the relationships between QTL for agronomic and physiological traits and plant drought and salinity tolerance were studied. A new QTL for drought tolerance which was not linked to any of the studied traits was identified. This QTL can be effectively used in breeding programs. It was also shown that proline accumulation under stresses was not necessarily linked with drought or salinity tolerance based on methods of phenotyping used in this experiment. The use of proline content in breeding programs can also be limited by the accuracy of phenotyping. [ABSTRACT FROM AUTHOR]

Background Lipoxygenases are a family of enzymes which catalyse the hydroperoxidation of polyunsaturated fatty acids with a cis, cis-1,4-pentadiene to form conjugated hydroperoxydienes. Lipoxygenase-1 (LOX-1) in barley worsens the flavour and foam stability of beer. It has become a major selection criteria for malting quality in the last few years. Results Lipoxygenase activity was investigated in 41 Australian barley cultivars and advanced breeding lines released since the 1950s; the cultivars differed markedly, ranging from 22.3 to 46.5 U/g. The structural gene and its promoter of lipoxygenase-1 were sequenced from the barley varieties representing different levels of LOX. Based on the analysis of nucleotide and deduced amino acid sequences, two major haplotypes were identified. Barley varieties with lower LOX were classified into three categories based on their pedigrees and sequence variations in the structural gene: (1) barley varieties derived from Canadian varieties with the pre-harvest sprouting susceptible allele, (2) Skiff and Hindmarsh with unique haplotype in the structural gene, and (3) Gairdner and Onslow with an unknown mechanism. Conclusion Lipoxygenase activity has been reduced in the malting barley cultivars in the last 60 years although it is only recognized as a malting quality trait recently. There are clear haplotypes of the lipoxygenase structual gene. The polymorphisms detected in the structural gene can be used to design molecular markers for selection of low LOX haplotype. Other mechanisms also existed for controlling lipoxygenase activity. The results suggest that it is possible to develop barley varieties with lower LOX by combination of low LOX-1 haplotype and other trans-regulation factors. [ABSTRACT FROM AUTHOR]

Background: Grain protein content (GPC) is an important quality determinant for barley used as malt, feed as well as food. It is controlled by a complex genetic system. GPC differs greatly among barley genotypes and is also variable across different environments. It is imperative to understand the genetic control of barley GPC and identify the genotypes with less variation under the different environments. Results: In this study, 59 cultivated and 99 Tibetan wild barley genotypes were used for a genome-wide association study (GWAS) and a multi-platform candidate gene-based association analysis, in order to identify the molecular markers associated with GPC. Tibetan wild barley had higher GPC than cultivated barley. The significant correlation between GPC and diastatic power (DP), and malt extract confirmed the importance of GPC in determining malt quality. Diversity arrays technology (DArT) markers associated with barley GPC were detected by GWAS. In addition, GWAS revealed two HvNAM genes as the candidate genes controlling GPC. No association was detected between HvNAM1 polymorphism and GPC, while a single nucleotide polymorphism (SNP) (798, P < 0.01), located within the second intron of HvNAM2, was associated with GPC. There was a significant correlation between haplotypes of HvNAM1, HvNAM2 and GPC in barley. Conclusions: The GWAS and candidate gene based-association study may be effectively used to determine the genetic variation of GPC in barley. The DArT markers and the polymorphism of HvNAM genes identified in this study are useful in developing high quality barley cultivars in the future. HvNAM genes could play a role in controlling barley GPC. [ABSTRACT FROM AUTHOR]

Background In this study, a multi-parent population of barley cultivars was grown in the field for two consecutive years and then straw saccharification (sugar release by enzymes) was subsequently analysed in the laboratory to identify the cultivars with the highest consistent sugar yield. This experiment was used to assess the benefit of accounting for both the multiphase and multi-environment aspects of large-scale phenotyping experiments with field-grown germplasm through sound statistical design and analysis. Results Complementary designs at both the field and laboratory phases of the experiment ensured that non-genetic sources of variation could be separated from the genetic variation of cultivars, which was the main target of the study. The field phase included biological replication and plot randomisation. The laboratory phase employed re-randomisation and technical replication of samples within a batch, with a subset of cultivars chosen as duplicates that were randomly allocated across batches. The resulting data was analysed using a linear mixed model that incorporated field and laboratory variation and a cultivar by trial interaction, and ensured that the cultivar means were more accurately represented than if the non-genetic variation was ignored. The heritability detected was more than doubled in each year of the trial by accounting for the non-genetic variation in the analysis, clearly showing the benefit of this design and approach. Conclusions The importance of accounting for both field and laboratory variation, as well as the cultivar by trial interaction, by fitting a single statistical model (multi-environment trial, MET, model), was evidenced by the changes in list of the top 40 cultivars showing the highest sugar yields. Failure to account for this interaction resulted in only eight cultivars that were consistently in the top 40 in different years. The correspondence between the rankings of cultivars was much higher at 25 in the MET model. This approach is suited to any multiphase and multi-environment population-based genetic experiment. [ABSTRACT FROM AUTHOR]

A total of 199 germplasm accessions collected from 10 administrative regions of Ethiopia and four released cultivars, which were used for estimating of error variance, of barley in Ethiopia were field evaluated for nine agronomic traits at Holetta and Bekoji Agricultural Research Centers of Ethiopia during the 2006 main cropping season using non-replicated augmented design plots consisting of four incomplete blocks. The objectives were to assess the extent and pattern of morphological variation in the barley accessions with respect to regions and altitude of collection, to classify the genotypes tested into relatively homogenous groups and to identify the major traits contributing to the overall observed diversity in the germplasm. Genotype variance estimate of regions and altitudes indicated wide variation among accessions depending on the traits involved. The presence of high morphological variation within regions and altitudes particularly above 2000 m a.s.l. indicated the potential of each region and high altitude zones for barley improvement and conservation in the country. The clustering of accessions did not show grouping on the basis of regions of origin. Traits like thousand kernel weight, plant height, days to head and days to maturity accounted for most of the gross variance among the barley accessions and played role in differentiating accessions collected from different regions and altitude classes into principal components. In general because of environmental factors on the observed morphological variation future germplasm collection should consider to explore wide geographical and climatic differences within the country. [ABSTRACT FROM AUTHOR]

In water-limited areas of Tunisia, more than 30% of subsurface water used for irrigation is saline water, leading to a long-term salinization and degradation processes. To prevent the problems and to minimize the negative impact of using saline water, selection of proper germplasm as well as integrated soil and water management are essential. Understanding the diversity for salt tolerance in barley ( Hordeum vulgare L.) genotypes will facilitate their use in genetic improvement. Our objectives were to evaluate, in green, house-salt tolerance for 14 barley cultivars under three different salinity levels: (tap water with an Ec = 0.73 dSm−1, tap water with 102 mM of NaCl, Ec = 10.76 dSm−1 and tap water with 151 mM of NaCl, Ec = 15.38 dSm−1), and quantify genetic variation based on salt tolerance index, morphological traits, molecular and factorial analysis of correspondence (FAC). The study was conducted in a randomized complete block design arranged as a split plot. The results indicate a great genetic variability to salt tolerance among used barley genotypes. Consequently, it is possible to identify superior cultivars, and evaluate the genotypic performance under salinities conditions. In addition, results obtained were confirmed by clustering made by SSR tool on the base of DNA analysis, which is compatible with the arrangement obtained with statistical method. [ABSTRACT FROM AUTHOR]

Barley ( Hordeum vulgare L.) plants of two commercial cultivars were transformed with sense and antisense constructs of a chitinase class II gene in order to develop a transformation system for this gene in barley. Transformation of embryos with the two antisense constructs resulted in ten regenerated plants, while no plants could be obtained using the sense construct. The presence of the inserted construct could be confirmed for six of the plants by PCR analysis. This system was used to study the role of class II chitinase in the regulation of mycorrhizal symbiosis. The colonization of two of the antisense transformants by the arbuscular mycorrhizal fungus Glomus intraradices was investigated microscopically and by use of signature fatty acids. The arbuscular incidence increased in transformed barley, and one transformant supported higher extraradical mycelium biomass. It is concluded that antisense transformation of barley could be a useful tool in investigations on the symbiosis between barley and mycorrhizal fungi. [ABSTRACT FROM AUTHOR]

Background: Colored hulless barley are more suitable in food processing compared to normal (yellow) varieties because it is rich in bioactive compounds and produces higher extraction pearling fractions. Therefore, seed coat color is an important agronomic trait for the breeding and study of hulless barley. Results: Genotyping-by-sequencing single-nucleotide polymorphism (GBS-SNP) analysis of a doubled haploid (DH) mapping population (Nierumuzha × Kunlun10) was conducted to map the purple seed coat color genes (Psc). A high-density genetic map of hulless barley was constructed, which contains 3662 efficient SNP markers with 1129 bin markers. Seven linkage groups were resolved, which had a total length of 645.56 cM. Chromosome length ranged from 60.21 cM to 127.21 cM, with average marker density of 0.57 cM. A total of five loci accounting for 3.79% to 23.86% of the observed phenotypic variation for Psc were detected using this high-density map. Five structural candidate genes (F3'M, HID, UF3GT, UFGT and 5MAT) and one regulatory factor (Ant1) related to flavonoid or anthocyanin biosynthesis were identified.. Conclusions: Five structural candidate genes and one regulatory factor related to flavonoid or anthocyanin biosynthesis have been identified using a high-density genetic map of hulless barley. This study lays the foundation for map-based cloning of Psc but provides a valuable tool for studying marker-trait associations and its application to marker-assisted breeding of hulless barley. [ABSTRACT FROM AUTHOR]

Background: Phenotyping is a bottleneck for the development of new plant cultivars. This study introduces a new hyperspectral phenotyping system, which combines the high throughput of canopy scale measurements with the advantages of high spatial resolution and a controlled measurement environment. Furthermore, the measured barley canopies were grown in large containers (called Mini-Plots), which allow plants to develop field-like phenotypes in greenhouse experiments, without being hindered by pot size. Results: Six barley cultivars have been investigated via hyperspectral imaging up to 30 days after inoculation with powdery mildew. With a high spatial resolution and stable measurement conditions, it was possible to automatically quantify powdery mildew symptoms through a combination of Simplex Volume Maximization and Support Vector Machines. Detection was feasible as soon as the first symptoms were visible for the human eye during manual rating. An accurate assessment of the disease severity for all cultivars at each measurement day over the course of the experiment was realized. Furthermore, powdery mildew resistance based necrosis of one cultivar was detected as well. Conclusion: The hyperspectral phenotyping system combines the advantages of field based canopy level measurement systems (high throughput, automatization, low manual workload) with those of laboratory based leaf level measurement systems (high spatial resolution, controlled environment, stable conditions for time series measurements). This allows an accurate and objective disease severity assessment without the need for trained experts, who perform visual rating, as well as detection of disease symptoms in early stages. Therefore, it is a promising tool for plant resistance breeding. [ABSTRACT FROM AUTHOR]