Chromosome 2H Research Articles

Fine mapping of qGL5H, a major grain length locus in barley (Hordeum vulgare L.).

A major grain length QTL on chromosome 5H was fine mapped from 180.5 to 1.7Mb. Quantitative trait loci (QTLs) mapping has been used extensively in barley to detect QTLs that underlie complex traits such as grain size. In the present study, we utilised 312 double haploid lines derived from a cross between two Australian malting varieties, Vlamingh and Buloke, to dissect the genetic control of a number of grain size characteristics. Digital image analysis was used to measure grain size characteristics including length, width, thickness and plumpness which are important traits influencing barley yield and grain physical quality. Using data from four independent environments and molecular marker genotype data, we identified 23 significant QTLs for these four traits, ten of which were consensus QTLs and identified in two or more environments. A QTL region on chromosome 5H designated qGL5H that was associated with grain size was fine mapped to a 1.7 Mb interval. qGL5H was able to explain 21.6% of phenotypic variation for grain length within the population. This major QTL is an appropriate candidate for further genetic dissection.

High intraspecific diversity of Restorer‐of‐fertility‐like genes in barley

SUMMARY Nuclear restorer of fertility (Rf) genes suppress the effects of mitochondrial genes causing cytoplasmic male sterility (CMS), a condition in which plants fail to produce viable pollen. Rf genes, many of which encode RNA‐binding pentatricopeptide repeat (PPR) proteins, are applied in hybrid breeding to overcome CMS used to block self‐pollination of the seed parent. Here, we characterise the repertoire of restorer‐of‐fertility‐like (RFL) PPR genes in barley (Hordeum vulgare). We found 26 RFL genes in the reference genome (‘Morex’) and an additional 51 putative orthogroups (POGs) in a re‐sequencing data set from 262 barley genotypes and landraces. Whereas the sequences of some POGs are highly conserved across hundreds of barley accessions, the sequences of others are much more variable. High sequence variation strongly correlates with genomic location – the most variable genes are found in a cluster on chromosome 1H. A much higher likelihood of diversifying selection was found for genes within this cluster than for genes present as singlets. This work includes a comprehensive analysis of the patterns of intraspecific variation of RFL genes. The RFL sequences characterised in this study will be useful for the development of new markers for fertility restoration loci.

Genetic basis of drought tolerance during seed germination in barley.

Drought is one of the harshest abiotic stresses hindering seed germination, plant growth, and crop productivity. A high rate and uniformity of germination under stressful conditions are vital for crop establishment and growth; thus, for productivity. A better understanding of the genetic architecture of seed germination under drought stress is a prerequisite for further increasing yield potential. Barley is considered one of the most abiotic stresses-tolerant cereals. Elucidating the drought tolerance of barley during seed germination would indeed pave the way towards improving the performance of all cereals. However, we still know relatively little about the genetic control of drought tolerance during the seed germination phase. In our study, 218 worldwide spring barley accessions were subjected to PEG-induced drought during seed germination. Induced drought stress "20% PEG" significantly reduced the seed germination parameters and seedling related traits. A genome-wide association scan (GWAS) was used to identify genomic regions associated with our trait of interest. In total, 338 single nucleotide polymorphisms (SNPs) were found to be associated with several traits distributed across seven barley chromosomes, of which 26 genomic regions were associated with candidate genes. The current study found some of the quantitative trait loci (QTL) that have previously been reported to be linked to seed germination-related traits under drought conditions, as well as some new associations. Noteworthy, the identified QTL colocalized with a number of genes (within interval ±0.5 Mbp) that are exclusively distributed on chromosomes 1H, 2H, and 5H. The annotation of these genes in barley shows their roles in drought tolerance through encoding different transcription factors. The function of the identified genes during seed germination was also confirmed by the annotation of their counterparts in Arabidopsis. The current analyses show the power of the GWAS both for identifying putative candidate genes and for improving plant adaptive traits in barley.

Genome-wide identification, characterization, and evolutionary analysis of NBS-encoding resistance genes in barley.

In this study, a systematic analysis of Nucleotide-Binding Site (NBS) disease resistance (R) gene family in the barley, Hordeum vulgare L. cv. Bowman, genome was performed. Using multiple computational analyses, we could identify 96 regular NBS-encoding genes and characterize them on the bases of structural diversity, conserved protein signatures, genomic distribution, gene duplications, differential expression, selection pressure, codon usage, regulation by microRNAs and phylogenetic relationships. Depending on the presence or absence of CC and LRR domains; the identified NBS genes were assigned to four distinct groups; NBS-LRR (53.1%), CC-NBS-LRR (14.6%), NBS (26%), and CC-NBS (6.3%). NBS-associated domain analysis revealed the presence of signal peptides, zinc fingers, diverse kinases, and other structural features. Eighty-five of the identified NBS-encoding genes were mapped onto the seven barley chromosomes, revealing that 50% of them were located on chromosomes 7H, 2H, and 3H, with a tendency of NBS genes to be clustered in the distal telomeric regions of the barley chromosomes. Nine gene clusters, representing 22.35% of total mapped barley NBS-encoding genes, were found, suggesting that tandem duplication stands for an important mechanism in the expansion of this gene family in barley. Phylogenetic analysis determined 31 HvNBS orthologs from rice and Brachypodium. 87 out of 96 HvNBSs were supported by expression evidence, exhibiting various and quantitatively uneven expression patterns across distinct tissues, organs, and development stages. Fourteen potential miRNA-R gene target pairs were further identified, providing insight into the regulation of NBS genes expression. These findings offer candidate target genes to engineer disease-resistant barley genotypes, and promote our understanding of the evolution of NBS-encoding genes in Poaceae crops.

Marker-trait associations in two-rowed spring barley accessions from Kazakhstan and the USA

In this study, phenotyping and single nucleotide polymorphism (SNP) genotyping data of 272 accessions of two-rowed spring barley from the USA along with 94 accessions from Kazakhstan were assessed in field trials at six breeding organizations in Kazakhstan to evaluate the performance of the USA samples over three years (2009–2011). The average grain yield over the six locations was not significantly higher in Kazakh accessions in comparison to the USA samples. Twenty four samples from Montana, Washington, the USDA station in Aberdeen Idaho, and the Anheuser-Busch breeding programs showed heavier average yield than the local standard cultivar “Ubagan”. Principal Coordinate analysis based on two sets of SNP data suggested that Kazakh accessions were closest to the USA accessions among eight groups of samples from different parts of the World, and within five US barley origin groups the samples from Montana and Washington perfectly matched six groups of Kazakh breeding origins. A genome-wide association study (GWAS) using data from eighteen field trials allowed the identification of ninety one marker-trait associations (MTA) in two or more environments for nine traits, including key characters such as heading time (HT), number of kernels per spike (NKS), and thousand grain weight (TGW). Our GWAS allowed the identification of eight MTA for HT and NKS, and sixteen MTA for TGW, when those MTA were linked to mapped SNPs. Based on comparisons of chromosomal positions of MTA identified in this study, and positions of known genes and quantitative trait loci for HT, NKS and TGW, it was suggested that MTA for HT on chromosome 2H (at 158.2 cM, 11_21414), MTA for NKS on 5H (at 118.6 cM, 11_20298), and two MTA for TGW on chromosome 4H (at 94.7 cM, 12_30718, and at 129.3 cM, 11_20013) were potentially new associations in barley. GWAS suggested that six MTA for HT, including two on chromosome 1H, two on chromosome 3H, and one each on chromosomes 4H and 6H, had useful pleiotropic effects for improving barley spike traits.

Fine mapping of a dominant gene conferring resistance to spot blotch caused by a new pathotype of Bipolaris sorokiniana in barley.

We fine-mapped and physically anchored a dominant gene (Rbs7) conferring resistance to spot blotch caused by a new pathotype of Bipolaris sorokiniana in a genomic interval of 304kb on barley chromosome 6H. Spot blotch, caused by Bipolaris sorokiniana, is an economically important disease on barley in the Upper Midwest region of the USA and Prairie Provinces of Canada. A new pathotype (pathotype 7, represented by isolate ND4008) of B. sorokiniana has been identified, which is highly virulent on barley cultivars with resistance to other pathotypes of the fungus. In this study, we fine-mapped a dominant gene conferring resistance to pathotype 7 in the barley line PI 235186. Genetic analysis of the F1 and F2 plants from a cross between PI 356741 (highly susceptible to ND4008) and PI 235186 (highly resistant to ND4008) indicated that a single dominant gene (Rbs7) controls the resistance in PI 235186. This result was confirmed by genetic analysis of the F2:3 families and a recombinant inbred line (RIL) population derived from the same cross. Bulked segregant analysis using simple sequence repeat markers localized Rbs7 on the short arm of chromosome 6H. Additional DNA markers were developed from the 6H pseudomolecule sequence of barley cv. Morex and mapped to the genomic region carrying Rbs7 using the RIL population and F2 recombinants derived from the PI 356741 × PI 235186 cross. Rbs7 was fine-mapped between two markers (M13.06 and M13.37), which spans a physical distance of 304kb on Morex chromosome 6H. These results provide a foundation for future cloning of the resistance gene and development of user-friendly molecular markers that can be used for development of spot-blotch-resistant cultivars in barley breeding programs.

Identification of a large-effect QTL associated with kernel discoloration in barley

Three barley mapping populations sharing the parental line SusPtrit suffered from an unknown condition affecting grain quality and germination. Grains showed dark blotches or even whole-grain discoloration and shrivelling. Symptoms were similar to kernel discoloration as reported in wheat and barley. Some covered-seed lines affected by this quality condition produced grains that were either not covered at all or in which partial hull loss was observed, a phenotype that resembles that of grain skinning. No fungal or bacterial agent was identified as causal organism, and we demonstrate that the poor quality phenotype is not transmitted to the next generation – therefore unlikely due to a seed borne pathogen. A major effect QTL on chromosome 6H was mapped independently in all three populations, with the poor quality allele contributed by SusPtrit. A second, minor effect QTL, was mapped on chromosome 2H in the SusPtrit x Golden Promise population, with Golden Promise as the parent donor of the allele conferring poor quality. The grain quality disorder is not linked to the nud gene on chromosome 7H for the naked/covered seed trait.

A simple and effective ND-FISH probe design for identifying barley (Hordeum vulgare) chromosomes

Fluorescence in situ hybridization (FISH) has been widely used to analyze the physical mapping of chromosomes and study the chromosome rearrangements during evolution. The conventional FISH technique is time-consuming and labor-intensive as it involves many experimental steps including (1) PCR amplification of the target sequence, (2) recovery of the amplified product, (3) plasmid extraction, (4) fluorescence labeling, as well as (5) denaturing of chromosomes and probes. Here we report an effective method for the design of oligonucleotide probes and the development of a new oligonucleotide probe for non-denaturing FISH in barley. The probe Oligo-442A01 with 6133 copies in barley genome could be mapped to the subtelomeres of barley. However, there were significant differences in signal positions and strengths between Oligo-442A01 and the contrast probe Oligo-HvT01.1, especially on chromosome 3H. These oligonucleotide probes combinations (AGG)5 and Oligo-442A01, (CTT)5 and Oligo-HvT01.1 could effectively differentiate the barley chromosomes.

QTL Mapping of Fusarium Head Blight and Correlated Agromorphological Traits in an Elite Barley Cultivar Rasmusson.

Fusarium head blight (FHB) is an important fungal disease affecting the yield and quality of barley and other small grains. Developing and deploying resistant barley cultivars is an essential component of an integrated strategy for reducing the adverse effects of FHB. Genetic mapping studies have revealed that resistance to FHB and the accumulation of pathogen-produced mycotoxins are controlled by many quantitative trait loci (QTL) with minor effects and are highly influenced by plant morphological traits and environmental conditions. Some prior studies aimed at mapping FHB resistance have used populations derived from crossing a Swiss landrace Chevron with elite breeding lines/cultivars. Both Chevron and Peatland, a sib-line of Chevron, were used as founders in the University of Minnesota barley breeding program. To understand the native resistance that might be present in the Minnesota breeding materials, a cross of an elite cultivar with a susceptible unadapted genotype is required. Here, a mapping population of 93 recombinant inbred lines (RILs) was developed from a cross between a moderately susceptible elite cultivar ‘Rasmusson’ and a highly susceptible Japanese landrace PI 383933. This population was evaluated for FHB severity, deoxynivalenol (DON) accumulation and various agromorphological traits. Genotyping of the population was performed with the barley iSelect 9K SNP chip and 1,394 SNPs were used to develop a genetic map. FHB severity and DON accumulation were negatively correlated with plant height (HT) and spike length (SL), and positively correlated with spike density (SD). QTL analysis using composite interval mapping (CIM) identified the largest effect QTL associated with FHB and DON on the centromeric region of chromosome 7H, which was also associated with HT, SL, and SD. A minor FHB QTL and a minor DON QTL were detected on chromosome 6H and chromosome 3H, respectively, and the Rasmusson alleles contributed to resistance. The 3H DON QTL likely represents native resistance in elite germplasm as the marker haplotype of Rasmusson at this QTL is distinct from that of Chevron. This study highlights the relationship between FHB resistance/susceptibility and morphological traits and the need for breeders to account for morphology when developing FHB resistant genotypes.

Mapping adult plant stem rust resistance in barley accessions Hietpas-5 and GAW-79.

Key message Major stem rust resistance QTLs proposed to be Rpg2 from Hietpas-5 and Rpg3 from GAW-79 were identified in chromosomes 2H and 5H, respectively, and will enhance the diversity of stem rust resistance in barley improvement programs. Stem rust is a devastating disease of cereal crops worldwide. In barley (Hordeum vulgaressp. vulgare), the disease is caused by two pathogens: Puccinia graminis f. sp. secalis (Pgs) and Puccinia graminis f. sp. tritici (Pgt). In North America, the stem rust resistance gene Rpg1 has protected barley from serious losses for more than 60years; however, widely virulent Pgt races from Africa in the Ug99 group threaten the crop. The accessions Hietpas-5 (CIho 7124) and GAW-79 (PI 382313) both possess moderate-to-high levels of adult plant resistance to stem rust and are the sources of the resistance genes Rpg2 and Rpg3, respectively. To identify quantitative trait loci (QTL) for stem rust resistance in Hietpas-5 and GAW-79, two biparental populations were developed with Hiproly (PI 60693), a stem rust-susceptible accession. Both populations were phenotyped to the North American Pgt races of MCCFC, QCCJB, and HKHJC in St. Paul, Minnesota, and to African Pgt races (predominately TTKSKin the Ug99 group) in Njoro, Kenya. In the Hietpas-5/Hiproly population, a major effect QTL was identified in chromosome 2H, which is proposed as the location for Rpg2. In the GAW-79/Hiproly population, a major effect QTL was identified in chromosome 5H and is the proposed location for Rpg3. These QTLs will enhance the diversity of stem rust resistance in barley improvement programs.

Root architectural traits and yield: exploring the relationship in barley breeding trials

Root system architecture is fundamental to resource capture and productivity of cereal crops. Understanding the genetics modulating root development will empower plant breeders to design cultivars with optimal root systems for the target environment. Here, we investigate the genetic association between seminal root traits and yield in elite barley (Hordeum vulgare L.) germplasm. A panel of 216 breeding lines from the Northern Region Barley Breeding program in Australia, genotyped with Diversity Arrays Technology markers, were characterised for seminal root angle and number. A high degree of phenotypic variation was evident in the population, ranging from 12.0° to 89.4° and 4.8 to 6.1 for root angle and number, respectively. A quantitative trait locus for root angle (qRA-5) was detected on chromosome 5H and co-located with the previously described RAQ2. The genetic relationship between seminal root traits and yield for the panel was investigated using root phenotypes and yield data from 20 field trials. Genetic correlations with yield ranged from − 0.21 to 0.36 for root angle and from − 0.20 to 0.25 for root number. The direction and magnitude of the correlations for both root traits varied across the environments, but overall root angle was deemed more strongly associated with yield. Here we provide insight into the root phenotypes of breeding lines and deliver a first look at the genetic relationship between root architectural traits and yield in barley breeding trials.

A locus on barley chromosome 5H affects adult plant resistance to powdery mildew

Adult plant resistance against plant pathogens is of interest as a means to achieve durable resistance. Prior to this research, the barley lines CLE210 (from Uruguay) and Denar (from the Czech Republic) had been reported to exhibit adult-plant resistance against powdery mildew. Here, populations of doubled haploid lines from crosses of these lines with the susceptible cultivar Baudin were evaluated for powdery mildew resistance in field experiments. Using linkage maps constructed from genotyping-by-sequencing (GBS) data, it was determined that differences in resistance were largely attributable to a region on the long arm of chromosome 5H (5HL). Therefore, KASP™ assays were developed based on GBS tag sequences mapped on that chromosome, providing more reliable genetic maps. In each population, a large-effect QTL was mapped on 5HL. As no sequence variation was detected between CLE210 and Denar in this region of 5HL, the two sources of resistance may be identical by descent in the QTL region and carry the same resistance gene. Marker assays from the QTL region were evaluated on a panel of barley lines, providing information that breeders could use to select assays for use in marker-assisted selection.

A regulator of early flowering in barley (Hordeum vulgare L.).

Heading date (HD) of cereals is an important trait for adaptation to diverse environments and is critical for determining yield and quality and the number of genes and gene combinations that confer earliness in barley under short days is limited. In our study, a QTL for early flowering was identified from the cross between an Australian malting barley cultivar and a Chinese landrace. Four sets of near isogenic lines (NILs) were developed with a QTL located on chromosome 5H at the interval of 122.0–129.0 cM. Further experiments were conducted to investigate how this gene was regulated by photoperiod using the NILs with three sowing dates from autumn to summer. The NILs carrying the earliness allele were significantly earlier than the late genotype at all sowing dates. This gene was different from previously reported vernalisation genes that are located at a similar position as no vernalisation was required for all the NILs. The difference between this gene and Eam5 (HvPHYC) locus which also located between two co-segregated markers (3398516S5, 122.5 cM, and 4014046D5, 126.1 cM), is that with the existence of Ppd-H1 (Eam1), Eam5 has no effect on ear emergence under long days while the gene from TX9425 still reduced the time to ear emergency. The locus showed no pleiotropic effects on grain pasting properties and agronomic traits except for spike length and number of spikelets per spike, and thus can be effectively used in breeding programs. The array of early heading dates caused by interactions of Eam5 gene with other maturity genes provides an opportunity to better fine tune heading dates with production environments, which can be critical factor in barley breeding.

Semi-dwarf barley (Hordeum vulgare L.) brh2 and ari-l mutants are deficient in a U-box E3 ubiquitin ligase

Lodging is the process where crop plants fall over and lie on the ground due to strong winds and heavy precipitation. This problem reduces yield and increases the risk of fungal infections and pre-harvest germination. In order to avoid lodging, plant breeders utilize short-culm mutants, which often have a robust culm that can support the weight of a heavy spike. In barley (Hordeum vulgare L.), thousands of short-culm mutants have been isolated in breeding programs around the world. Our long-term goal is to reveal the genetic network underlying culm length, with the objective to provide an enlarged repertoire of genes and alleles suitable for future breeding of lodging resistant barley. In the present work we studied a group of allelic brh2 and ari-l mutants, which have a relatively strong semi-dwarf phenotype and are phenotypically similar to previously identified mutants deficient in brassinosteroid signalling or metabolism. The Brh2 gene is located in the centromeric region of chromosome 4H and we applied a candidate gene approach to identify the gene. Brh2 is orthologous to TUD1 in rice (Orysa sativa L.), which encodes a U-box E3 ubiquitin ligase. We identified one missense mutation, one nonsense mutation and four deletions of the complete Brh2 gene. The mutants could respond to exogenously applied brassinolide, which suggests that the apparent brassinosteroid deficient phenotype of barley brh2 and ari-l mutants is related to brassinosteroid metabolism rather than signalling.

Genome-Wide Association Study for Spot Blotch Resistance in Hard Winter Wheat.

Spot blotch (SB) caused by Cochliobolus sativus (anamorph: Bipolaris sorokiniana) is an economically important disease of wheat worldwide. Under a severe epidemic condition, the disease can cause yield losses up to 70%. Previous approaches like bi-parental mapping for identifying SB resistant genes/QTLs exploited only a limited portion of the available genetic diversity with a lower capacity to detect polygenic traits, and had a lower marker density. In this study, we performed genome-wide association study (GWAS) for SB resistance in hard winter wheat association mapping panel (HWWAMP) of 294 genotypes. The HWWAMP was evaluated for response to B. sorokiniana (isolate SD40), and a range of reactions was observed with 10 resistant, 38 moderately resistant, 120 moderately resistant- moderately susceptible, 111 moderately susceptible, and 15 susceptible genotypes. GWAS using 15,590 high-quality SNPs and 294 genotypes we identified six QTLs (p = <0.001) on chromosomes 2D, 3A, 4A, 4B, 5A, and 7B that collectively explained 30% of the total variation for SB resistance. Highly associated SNPs were identified for all six QTLs, QSb.sdsu-2D.1 (SNP: Kukri_c31121_1460, R2 = 4%), QSb.sdsu-3A.1 (SNP: Excalibur_c46082_440, R2 = 4%), QSb.sdsu-4A.1 (SNP: IWA8475, R2 = 5.5%), QSb.sdsu-4B.1 (SNP: Excalibur_rep_c79414_306, R2 = 4%), QSb.sdsu-5A.1 (SNP: Kukri_rep_c104877_2166, R2 = 6%), and QSb.sdsu-7B.1 (SNP: TA005844-0160, R2 = 6%). Our study not only validates three (2D, 5A, and 7B) genomic regions identified in previous studies but also provides highly associated SNP markers for marker assisted selection. In addition, we identified three novel QTLs (QSb.sdsu-3A.1, QSb.sdsu-4A.1, and QSb.sdsu-4B.1) for SB resistance in wheat. Gene annotation analysis of the candidate regions identified nine NBS-LRR and 38 other plant defense-related protein families across multiple QTLs, and these could be used for fine mapping and further characterization of SB resistance in wheat. Comparative analysis with barley indicated the SB resistance locus on wheat chromosomes 2D, 3A, 5A, and 7B identified in our study are syntenic to the previously identified SB resistance locus on chromosomes 2H, 3H, 5H, and 7H in barley. The 10 highly resistant genotypes and SNP markers identified in our study could be very useful resources for breeding of SB resistance in wheat.

A Pathogen-Responsive Leucine Rich Receptor Like Kinase Contributes to Fusarium Resistance in Cereals.

Receptor-like kinases form the largest family of receptors in plants and play an important role in recognizing pathogen-associated molecular patterns and modulating the plant immune responses to invasive fungi, including cereal defenses against fungal diseases. But hitherto, none have been shown to modulate the wheat response to the economically important Fusarium head blight (FHB) disease of small-grain cereals. Homologous genes were identified on barley chromosome 6H (HvLRRK-6H) and wheat chromosome 6DL (TaLRRK-6D), which encode the characteristic domains of surface-localized receptor like kinases. Gene expression studies validated that the wheat TaLRRK-6D is highly induced in heads as an early response to both the causal pathogen of FHB disease, Fusarium graminearum, and its’ mycotoxic virulence factor deoxynivalenol. The transcription of other wheat homeologs of this gene, located on chromosomes 6A and 6B, was also up-regulated in response to F. graminearum. Virus-induced gene silencing (VIGS) of the barley HvLRRK-6H compromised leaf defense against F. graminearum. VIGS of TaLRRK-6D in two wheat cultivars, CM82036 (resistant to FHB disease) and cv. Remus (susceptible to FHB), confirmed that TaLRRK-6D contributes to basal resistance to FHB disease in both genotypes. Although the effect of VIGS did not generally reduce grain losses due to FHB, this experiment did reveal that TaLRRK-6D positively contributes to grain development. Further gene expression studies in wheat cv. Remus indicated that VIGS of TaLRRK-6D suppressed the expression of genes involved in salicylic acid signaling, which is a key hormonal pathway involved in defense. Thus, this study provides the first evidence of receptor like kinases as an important component of cereal defense against Fusarium and highlights this gene as a target for enhancing cereal resistance to FHB disease.

Molecular cytogenetic and morphological characterization of two wheat-barley translocation lines.

Barley chromosome 5H, carrying important QTLs for plant adaptation and tolerance to abiotic stresses, is extremely instable in the wheat genetic background and is eliminated in the early generations of wheat-barley crosses. A spontaneous wheat-barley 5HS-7DS.7DL translocation was previously obtained among the progenies of the Mv9kr1 x Igri hybrid. The present work reports on the transfer of the 5HS-7DS.7DL translocation into a modern wheat cultivar, Mv Bodri, in order to use it in the wheat breeding program. The comparison of the hybridization bands of DNA repeats HvT01, pTa71, (GAA)n and the barley centromere-specific (AGGGAG)n in Igri barley and the 5HS-7DS.7DL translocation, together with the visualization of the barley chromatin made it possible to determine the size of the introgressed barley segment, which was approximately 74% of the whole 5HS. Of the 29 newly developed PCR markers, whose source ESTs were selected from the Genome Zipper of barley chromosome 5H, 23 were mapped in the introgressed 1–0.26 FL 5HS bin, three were located in the missing C-0.26 FL region, while three markers were specific for 5HL. The translocation breakpoint was flanked by markers Hv7502 and Hv3949. A comparison of the parental wheat cultivars and the wheat-barley introgression lines indicated that the presence of the translocation improved tillering ability in the Mv9kr1 and Mv Bodri genetic background. The similar or better yield components under high- or low-input cultivation environments, respectively, indicated that the 5HS-7DS.7DL translocation had little or no negative effect on yield components, making it a promising genotype to improve wheat genetic diversity. These results promise to accelerate functional genomic studies on barley chromosome 5H and to support pre-breeding and breeding research on wheat.

Identification of QTL hot spots for malting quality in two elite breeding lines with distinct tolerance to abiotic stress

BackgroundBarley (Hordeum vulgare) is an important crop cultivated across the world. Drought is a major abiotic factor compromising barley yield worldwide, therefore in modern spring barley cultivars superior seed and malting quality characteristics should be combined with reasonable level of drought tolerance. Previously we have identified a number of barley lines demonstrating the superior yield performance under drought conditions. The aim of this work was to perform a QTL analysis of malting quality traits in a doubled haploid (DH) mapping population of two elite barley lines that differ in their reaction pattern to drought stress.ResultsA population of DH lines was developed by crossing two drought-tolerant elite breeding lines, Victoriana and Sofiara, exploiting distinct mechanism of drought tolerance, sustaining assimilation vs remobilization. The mapping population was assayed under field conditions at four distinct locations that differed in precipitation rate. DH lines were genotyped with the Illumina 9 K iSelect assay, and linkage map including 1782 polymorphic markers and covering a total map length of 1140 cM was constructed. The result of quantitative trait loci (QTL) analysis showed that majority of the traits were affected by several main effect QTL and/or QTL x environment (QE) interactions. In total, 57, 41, and 5 QTL were associated with yield-related traits, malting quality traits and seed quality traits, respectively. 11 and 29 of mapped QTL explained more than 10 and 5% of phenotypic variation, respectively. In several chromosomal regions co-localization between QTL for various traits were observed. The largest clusters were detected on chromosomes 3H and 4H.ConclusionsOur QTL mapping results revealed several novel consistent genomic regions controlling malting quality which could be exploited in marker assisted selection. In this context, the complex QTL region on chromosome 3H seems of particular interest, as it harbors several large effect QTL.

Identification of genes associated with drought tolerance in barley

Mapping of quantitative trait genes (QTGs) associated with drought related traits is essential for improving drought tolerance in crop species. In silico identification of candidate genes relies on annotation of critical QTGs to a variety of web resource-based datasets. The barley reference sequence was employed to map QTGs significantly associated with the proline accumulation and osmotic potential. Annotation of the critical QTGs contigs to the NCBI protein database identified 72 gene orthologs located on chromosomes 1H, 2H, and 7H, from which seven genes were identified as candidates. Expression analysis of all seven candidate genes revealed differential expression pattern between plants grown under well-watered conditions and drought-stress. The results represent a successful and highly powerful implementation of genome-wide scanning approach based on in silico mapping of QTGs to identify gene clusters having a common transcript pattern with similar function.

Genome Wide Association Mapping of Seedling and Adult Plant Resistance to Barley Stripe Rust (Puccinia striiformis f. sp. hordei) in India.

Barley stripe rust is caused by Puccinia striiformis f.sp. hordei, (Psh), occurs worldwide, and is a major disease in South Asia. The aim of this work was to identify and estimate effects of loci underlying quantitative resistance to rust at seedling and adult plant stages. HI-AM panel of 261 barley genotypes consisting of released cultivars from North and South America, Europe, Australia, advanced breeding lines, and local landraces from ICARDA barley program were screened at seedling and adult plant stages for resistance to Psh. Seedling resistance was evaluated with the five prevalent Psh races in India. Screening for the adult plant stage resistance was also performed in two different locations by inoculating with a mixture of the five races used for seedling screeing. The panel was genotyped using DaRT-Seq high-throughput genotyping platform. The genome-wide association mapping (GWAM) showed a total of 45 QTL located across the seven barley chromosomes for seedling resistance to the five races and 18 QTL for adult plant stage resistance. Common QTL for different races at seedling stage were found on all chromosomes except on chromosome 1H. Four common QTL associated with seedling and adult plant stage resistance were found on chromosomes 2, 5, and 6H. Moreover, one of the QTL located on the long arm of chromosome 5H showed stable effects across environments for adult plant stage resistance. Several QTL identified in this study were also reported before in bi-parental and association mapping populations studies validating current GWAM. However 15 new QTL were found at adult plant stage on all chromosomes except the 4H, explaining up to 36.79% of the variance. The promising QTL detected at both stages, once validated, can be used for MAS in Psh resistance breeding program globally.