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Uniparental chromosome elimination occurs in several interspecific hybrids of plants. We studied the mechanism underlying selective elimination of the paternal chromosomes during the early development of Hordeum vulgare x Hordeum bulbosum embryos. The following conclusions regarding the role of the centromere-specific histone H3 variant (CENH3) in the process of chromosome elimination were drawn: (i) centromere inactivity of H. bulbosum chromosomes triggers the mitosis-dependent process of uniparental chromosome elimination in unstable H. vulgare x H. bulbosum hybrids; (ii) centromeric loss of CENH3 protein rather than uniparental silencing of CENH3 genes causes centromere inactivity; (iii) in stable species combinations, cross-species incorporation of CENH3 occurs despite centromere-sequence differences, and not all CENH3 variants get incorporated into centromeres if multiple CENH3s are present in species combinations; and (iv) diploid barley species encode two CENH3 variants, the proteins of which are intermingled within centromeres throughout mitosis and meiosis.

Three Hordeum spontaneum -derived resistances (referred to as 145L2, 41T1 and 40Y5) have demonstrated long-term effectiveness against barley scald, caused by Rhynchosporium commune , in western Canada. Genetic mapping of these resistances in three populations, and the use of five barley genome assemblies, revealed they co-located to a narrowly defined 0.58–1.2 Mbp region of chromosome 6HS containing the Rrs13 scald resistance gene. Differential disease reactions among the three resistances and a Rrs13 carrier (AB6) to a panel of 24 scald isolates indicated that the four resistances were unique from one another. A marker created to target the 6HS scald locus was screened across a panel of barley germplasm that included H. vulgare , H. spontaneum and H. bulbosum lines. The marker showed specificity to H. vulgare lines known to carry the 6HS scald resistances and to two H. spontaneum lines that trace their origins to Jordan. Within the 0.58–1.2 Mbp region were 2–7 tandemly repeated leucine-rich repeat receptor-like proteins (LRR-RLP) and one lectin receptor-like kinase (Lec-RLK) genes with abundant sequence variation between them. The well-defined role that RLP and RLK genes play in plant defense responses make them logical candidate resistance genes, with one possible hypothesis being that each unique scald resistance may be encoded by a different RLP that interacts with a common RLK. It is suggested the three scald resistances be temporarily named Rrs13 145L2 , Rrs13 41T1 and Rrs13 40Y5 to recognize their co-location to the Rrs13 locus until it is determined whether these resistances represent unique genes or alleles of the same gene.

Molecular research was carried out on a group of wild barley species ( Hordeum spontaneum, H. bulbosum ) from four governorates (Damascus, Damascus Countryside, Tartous, Hama (Salamiyah)) and cultivated barley (Arabi Aswad, Arabi Abiad, Furat 3, Furat 6, Furat 7, Furat 9). Additionally, genotypes of cultivated barley were gathered fromTartous and Hama (Salamiyah) to be genetically compared with those indicated previously. The objective of this research was to determine the allelic patterns of dehydrin genes among various Syrian barley genotypes including wild species. The polymerase chain reaction (PCR) final results of dehydrin genes patterns showed not only variation among the genotypes in the molecular weight but also showed one monomorphic pattern (A) in all genotypes. The PCR results also showed that the genes Dhn3 and  Dhn7 had the largest the number of monomorphic patterns (14 in all genotypes), while the gene Dhn 5 had the minimum number of patterns (only 2). In addition, the results showed that two genotypes (Furat 7 and Salamiyah H. spontaneum ) were superior according to their number of genetic patterns, which were 10 and 9, respectively, while Tartous H. bulbosum and Arabi Abiad had the lowest number of patterns (5).

Key messageThe quantitative barley leaf rust resistance gene, Rph26, was fine mapped within a H. bulbosum introgression on barley chromosome 1HL. This provides the tools for pyramiding with other resistance genes.A novel quantitative resistance gene, Rph26, effective against barley leaf rust (Puccinia hordei) was introgressed from Hordeum bulbosum into the barley (Hordeum vulgare) cultivar ‘Emir’. The effect of Rph26 was to reduce the observed symptoms of leaf rust infection (uredinium number and infection type). In addition, this resistance also increased the fungal latency period and reduced the fungal biomass within infected leaves. The resulting introgression line 200A12, containing Rph26, was backcrossed to its barley parental cultivar ‘Emir’ to create an F2 population focused on detecting interspecific recombination within the introgressed segment. A total of 1368 individuals from this F2 population were genotyped with flanking markers at either end of the 1HL introgression, resulting in the identification of 19 genotypes, which had undergone interspecific recombination within the original introgression. F3 seeds that were homozygous for the introgressions of reduced size were selected from each F2 recombinant and were used for subsequent genotyping and phenotyping. Rph26 was genetically mapped to the proximal end of the introgressed segment located at the distal end of chromosome 1HL. Molecular markers closely linked to Rph26 were identified and will enable this disease resistance gene to be combined with other sources of quantitative resistance to maximize the effectiveness and durability of leaf rust resistance in barley breeding. Heterozygous genotypes containing a single copy of Rph26 had an intermediate phenotype when compared with the homozygous resistant and susceptible genotypes, indicating an incompletely dominant inheritance.

Virus diseases are causing high yield losses in crops worldwide. The Barley yellow dwarf virus (BYDV) complex is responsible for one of the most widespread and economically important viral diseases of cereals. While no complete resistance gene has been uncovered in the primary genepool of barley, sources of resistance were identified in the wild relative Hordeum bulbosum, representing the secondary genepool of barley. One such locus, Ryd4Hb, has been previously introgressed into barley, and was allocated to chromosome 3H, but is tightly linked to a sublethality factor that prevents the incorporation and utilization of Ryd4Hb in barley varieties. To solve this problem, we fine-mapped Ryd4Hb and separated it from this negative factor. We narrowed the Ryd4Hb locus to a 66.5 kbp physical interval in the barley 'Morex' reference genome. The region comprises one complete and one partial gene from the nucleotide-binding and leucine-rich repeat immune receptor family, typical of dominant virus resistance genes. The closest homolog to these two Ryd4Hb candidate genes is the wheat Sr35 stem rust resistance gene. In addition to the fine mapping, we reduced the sublethality factor interval to 600 kbp in barley. Aphid feeding experiments demonstrated that Ryd4Hb provides a direct resistance to BYDV rather than a resistance to its vector. The presented results, including the high-throughput molecular markers, will permit a more targeted selection of the resistance in breeding, enabling the use of Ryd4Hb in barley varieties.

Hordeum bulbosum L. (Poaceae) is considered to be sources of useful alleles which can be used in cereal improvement. Thirty two native Iranian H. bulbosum were collected from different localities and were studied by karyotype analysis. We assessed the karyotype asymmetry of the Iranian bulbous barley populations and analyzed the data to look for their geographic distribution correlations. All of the studied populations were tetraploid (2n=4x=28) and the analysed parameters of karyotype of H. bulbosum support the autopolyploidy origin of the species with nearly symmetric karyotype. The results showed the most asymmetric karyotypes within northeast (Golestan) and northwest (Gardane-e Heiran) populations and the most symmetric karyotyps in populations from the west of Iran. Therefore, it can be assumed that the oldest populations are in the slopes of Zagros Mountains and the youngest germplasms occur in the northeast of this country. It can be concluded that the species originated from the west of Iran and distributed towards east and northeast.

Powdery mildew caused by the airborne ascomycete fungus Blumeria graminis f. sp. hordei (Bgh) is one of most common diseases of barley (Hordeum vulgare). This, as with many other plant pathogens, can be efficiently controlled by inexpensive and environmentally-friendly genetic resistance. General requirements for resistance to the pathogens are effectiveness and durability. Resistance of barley to Bgh has been studied intensively, and this review describes recent research and summarizes the specific resistance genes found in barley varieties since the last conspectus. Bgh is extraordinarily adaptable, and some commonly recommended strategies for using genetic resistance, including pyramiding of specific genes, may not be effective because they can only contribute to a limited extent to obtain sufficient resistance durability of widely-grown cultivars. In spring barley, breeding the nonspecific mlo gene is a valuable source of durable resistance. Pyramiding of nonspecific quantitative resistance genes or using introgressions derived from bulbous barley (Hordeum bulbosum) are promising ways for breeding future winter barley cultivars. The utilization of a wide spectrum of nonhost resistances can also be adopted once practical methods have been developed.

Key messageWe mapped the Rym14Hb resistance locus to barley yellow mosaic disease in a 2Mbp interval. The co-segregating markers will be instrumental for marker-assisted selection in barley breeding.Barley yellow mosaic disease is caused by Barley yellow mosaic virus and Barley mild mosaic virus and leads to severe yield losses in barley (Hordeum vulgare) in Central Europe and East-Asia. Several resistance loci are used in barley breeding. However, cases of resistance-breaking viral strains are known, raising concerns about the durability of those genes. Rym14Hb is a dominant major resistance gene on chromosome 6HS, originating from barley’s secondary genepool wild relative Hordeum bulbosum. As such, the resistance mechanism may represent a case of non-host resistance, which could enhance its durability. A susceptible barley variety and a resistant H. bulbosum introgression line were crossed to produce a large F2 mapping population (n = 7500), to compensate for a ten-fold reduction in recombination rate compared to intraspecific barley crosses. After high-throughput genotyping, the Rym14Hb locus was assigned to a 2Mbp telomeric interval on chromosome 6HS. The co-segregating markers developed in this study can be used for marker-assisted introgression of this locus into barley elite germplasm with a minimum of linkage drag.

Fourier-transform infrared (FTIR) spectroscopy enables the chemical characterization and identification of pollen samples, leading to a wide range of applications, such as paleoecology and allergology. This is of particular interest in the identification of grass (Poaceae) species since they have pollen grains of very similar morphology. Unfortunately, the correct identification of FTIR microspectroscopy spectra of single pollen grains is hindered by strong spectral contributions from Mie scattering. Embedding of pollen samples in paraffin helps to retrieve infrared spectra without scattering artifacts. In this study, pollen samples from 10 different populations of five grass species (Anthoxanthum odoratum, Bromus inermis, Hordeum bulbosum, Lolium perenne, and Poa alpina) were embedded in paraffin, and their single grain spectra were obtained by FTIR microspectroscopy. Spectra were subjected to different preprocessing in order to suppress paraffin influence on spectral classification. It is shown that decomposition by non-negative matrix factorization (NMF) and extended multiplicative signal correction (EMSC) that utilizes a paraffin constituent spectrum, respectively, leads to good success rates for the classification of spectra with respect to species by a partial least square discriminant analysis (PLS-DA) model in full cross-validation for several species. PLS-DA, artificial neural network, and random forest classifiers were applied on the EMSC-corrected spectra using an independent validation to assign spectra from unknown populations to the species. Variation within and between species, together with the differences in classification results, is in agreement with the systematics within the Poaceae family. The results illustrate the great potential of FTIR microspectroscopy for automated classification and identification of grass pollen, possibly together with other, complementary methods for single pollen chemical characterization.

Winter barley (Hordeum vulgare) production areas in the middle and lower reaches of the Yangtze River are severely threatened by barley yellow mosaic disease, which is caused by Barley yellow mosaic virus and Barley mild mosaic virus. Improving barley disease resistance in breeding programs requires knowledge of genetic loci in germplasm resources. In this study, bulked segregant analysis (BSA) identified a novel major quantitative trait loci (QTL) QRym.ZN1‐7H for barley yellow mosaic disease resistance in an F2 population derived from the cross between “Nongke 1–6” (H. vulgare) and “Zaoshu 3” (H. vulgare). This QTL, originating from bulbous barley (Hordeum bulbosum), demonstrated stability and was further validated in another F2 population derived from the cross between “Nongke 2–6” (H. vulgare) and “Supi 1” (H. vulgare). QRym.ZN1‐7H accounted for 10.61%–19.34% of the phenotypic variance. The QTL was further fine mapped to the 14‐ to 39‐Mb interval on barley chromosome 7H. Transcriptome analysis identified 53 and 35 differentially expressed genes in roots and leaves (at QRym.ZN1‐7H locus), respectively, with nine genes differentially expressing in both tissues. HORVU.MOREX.r3.7HG0650990, a member of the disease resistance protein family (NBS‐LRR class), is the most likely candidate gene for QRym.ZN1‐7H. Enrichment analysis indicated that QRym.ZN1‐7H may be involved in signal transduction in plant innate immune response. This study laid a foundation for barley disease resistance breeding. Core Ideas A novel quantitative trait loci (QTL) (QRym.ZN1‐7H) for barley yellow mosaic disease resistance was identified from bulbous barley. QRym.ZN1‐7H was fine mapped to the 14‐ to 39‐Mb interval on chromosome 7H. Transcriptome analysis identified nine differentially expressed genes both in roots and leaves (at QRym.ZN1‐7H). QRym.ZN1‐7H may be involved in signal transduction in plant innate immune response. Plain Language Summary Barley yellow mosaic disease affects the yield and quality of barley. Breeding for resistant varieties is the most effective way of overcoming the problem, which relies on the available resistant germplasm resources and the identification of resistant loci or genes. However, relatively few resistance loci/genes have been identified for barley yellow mosaic disease, despite the numerous and constantly evolving virus strains. Therefore, ongoing discovery of novel resistance loci specific to certain strains or exhibiting broad‐spectrum resistance, combined with the use of molecular markers in marker‐assisted breeding, is vital for improving resistance to barley yellow mosaic disease.