A physical map of chromosome 4Hch from H. chilense containing SSR, STS and EST-SSR molecular markers

The construction of a physical map of chromosome 4H^ch from Hordeum chilense containing molecular markers capable of detecting segments of this chromosome in a wheat background would be very useful for marker-assisted introgression of 4H^ch chromatin into both durum and common wheat. With this aim, the applicability of 106 barley chromosome 4H primers (62 SSRs and 44 STSs) to amplify markers showing polymorphism between H. chilense and both common or bread and durum wheat was investigated. Twenty-five SSR (40.3%) and six STS (13.6%) barley primer pairs consistently amplified H. chilense products. Eight SSR (12.9%) and four STS (9.1%) barley primers were polymorphic between H. chilense and both common and durum wheat, 10 of them (6 SSRs and 4 STSs) were located on chromosome 4H^ch using both the addition line of chromosome 4H^ch in Chinese Spring wheat and a tritordeum line (an amphiploid between H. chilense and T. turgidum) nullisomic for chromosome 4H^ch. Additionally, 18 EST-SSR barley markers previously located on chromosome 4H^ch were screened for polymorphism; 15 were polymorphic between H. chilense and both durum and common wheat. For physical mapping we used a ditelosomic tritordeum line for the short arm of chromosome 4H^ch and a tritordeum line homozygous for a 70% terminal deletion of the long arm of 4H^ch. A total of 25 markers (6 SSRs, 4 STSs and 15 EST-SSRs) were mapped to chromosome 4H^ch. Eight markers were allocated on the 4H^chS, eight were mapped in the 30% proximal region of 4H^chL and nine were on the 70% distal region of 4H^chL, respectively. Arm location on barley chromosome 4H was also carried out using both 4HS and 4HL ditelosomic addition lines in wheat. All markers mapped may have a role in marker-assisted introgression of chromatin segments of chromosome 4H^ch in both durum and common wheat backgrounds. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Location of genes controlling resistance to greenbug (Schizaphis graminum Rond.) in Hordeum chilense

Wheat/Hordeum chilense disomic addition lines have been used to locate genes influencing resistance against greenbug (Schizaphis graminum Rond.) in specific chromosomes of H. chilense. H. chilense is a source of antixenosis, antibiosis and host tolerance to the greenbug, being resistant also to the Russian wheat aphid, the two key pests in wheat. For measuring antixenosis, the numbers of aphids per plant were recorded in a host free choice test; antibiotic resistance was determined by measuring the developmental time, the fecundity and the intrinsic rate of population increase of aphids reared on the different hosts, and host tolerance to aphids was evaluated by the leaf damage and the number of expanded leaves on the hosts after 3 weeks of infestation. The greenbugs belonged to a clone of biotype C. Plant genes with positive effects for antixenosis were located on chromosome 1H^ch. Genes with positive effects for antibiosis were located on three different chromosomes and those that prolonged aphid developmental time were located on chromosomes 5H^ch and 7H^ch while those that reduced the total fecundity were on 4Hch. Chromosome 7H^ch accounted for host tolerance to greenbug.     

Sub-arm location of prolamin and EST-SSR loci on chromosome 1H<Superscript>ch</Superscript> from <Emphasis Type="Italic">Hordeum chilense</Emphasis>

Hordeum chilense Roem. et Schult. is a diploid wild South American barley that contains genes of interest for cereal breeding, many of them located on chromosome 1H^ch. In the current study, two H. chilense-wheat addition lines with deletions in the 1H^ch chromosome were used for sub-arm localization of five prolamin (glutenin and gliadin) loci and 33 EST-SSR marker loci on chromosome 1H^ch. The two sets of markers were distributed across five sub-arm chromosome regions. Three glutenin loci (Glu-H ^ch 2, Glu-H ^ch 3, Glu-H ^ch 4) together with the gliadin locus Gli-H ^ch 1 were located on the distal 20% of the 1H^chS arm, whereas the glutenin locus Glu-H ^ch 1 was on the proximal 88% region of 1H^chL. Among 33 EST-SSR marker loci, 7 (21.2%) were on the 1H^chS arm and, of them, 3 (9.1%) were on the distal 20% end and 4 (12.1%) on the proximal 80% region. The 26 loci (78.8%) on 1H^chL were distributed across three different regions: 18 (78.8%) in the proximal 88%, 3 (9.1%) in the distal 12% and 5 (15.2%) in a region less than 12% from the distal end. The deletions in the 1H^ch chromosome added to the common wheat background were thus shown to be useful for determining the sub-arm location of EST-SSR and prolamin loci. This could facilitate the identification of molecular markers linked to genes of agronomic interest and the isolation of such genes for use in common wheat improvement.     

Nearly Total Absence of Homoeologous Pairing in a Hybrid between Tetraploid Hordeum chilense and Triticum aestivum

A hybrid between an induced tetraploid of Hordeum chilense (2n = 28 = H^chH^chH^chH^ch) and Triticum aestivum var. ‘Chinese Spring’ (2n = 42 = AABBDD) has been produced to test gene effects of this wild barley on homoeologous pairing in wheat. Cytological investigations in metaphase I have shown that the hybrid, which is perennial like H. chilense but morphologically more similar to the wheat parent, possesses the expected genome composition H^chH^ch ABD and a stable euploid chromosome number of 2n = 35. Pairing among the homologous H. chilense chromosomes was almost complete. The level of non-homologous chromosome association proved to be lower than the range of pairing known from euhaploids of ‘Chinese Spring’.     

Chromosomal localization of genes for carotenoid pigments using addition lines of Hordeum chilense in wheat

×Tritordeum sp. (Ascherson et Graebner) is the amphiploid obtained after chromosome doubling of hybrids between Hordeum chilense (Roem. et Schult.) and diploid, tetraploid or hexaploid wheats. Tritordeums have consistently higher carotenoid pigment contents than durum or bread wheat. Two distinct H. chilense accessions (used for the synthesis of tritordeum) were analysed for this trait. The chromosomal localization of the genes coding the ability of H. chilense to increase the carotene content of wheat were carried out using two sets of wheat- H. chilense addition lines. The a arm of chromosome 7H^ch is proposed to be responsible for the high carotene content in tritordeum. The implication of this finding in wheat breeding is discussed.     

Application of C-banding and fluorescence in situ hybridization for the identification of the trisomics of Hordeum chilense

Hordeum chilense is a wild barley species that has a high degree of genetic variability and significant potential for use in plant breeding. To establish a series of trisomics in H. chilense (2n = 14), plants with 2n + 1 chromosome numbers were isolated from the progenies of selfed triploid plants. Based on both fluorescent in situ hybridization with pAs1 and pTa71 repetitive DNA probes and C-banding patterns, seven different trisomics were tentatively identified. Primary trisomic plants were for chromosomes 1H^ch, 4H^ch, 5H^ch, 6H^ch and 7H^ch. A secondary trisomic carrying a 5H^chS-5H^chS isochromosome as the extra chromosome and a trisomic for chromosome 3H^ch heterozygous for the 3H^chS-4H^chL and 4H^chS–3H^chL interchange were identified. The trisomic for chromosome 1H^ch cannot be phenotypically distinguished from the diploid. The rest of the trisomic types were distinguishable from the diploid by their morphological characteristics (relatively poor vigour, decreased size and shorter spikes) but they were morphologically indistinguishable from each other. The frequencies of trisomics among the progenies derived from self-fertilization of these aneuploids ranged from 10.7% to 37.5%, with an average frequency of 26.1%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genome discrimination and chromosome pairing in the Hordeum chilense × Aegilops tauschii amphiploid

Tritordeum (X Tritordeum Ascherson et Graebner) is a synthetic amphiploid belonging to the Triticeae tribe, which resulted from crosses between Hordeum chilense and wheat. It presents useful agronomic traits that could be transferred to wheat, widening its genetic basis. In situ hybridisation with total genomic DNA from H. chilense and cloned, repetitive DNA sequences (pTa71 and pAs1) probes were used to discriminate the parental origin of all chromosomes, to analyse the chromosome pairing and to identify the chromosomes in pollen mother cells (PMCs) at metaphase I of the tritordeum line HT251 (H^chH^chDD, 2n = 4x = 28). The H. chilense total genomic DNA and the ribosomal sequence pTa71 probes, allowed the unequivocal discrimination of the 14 chromosomes of H^ch genome-origin and the 14 chromosomes of D genome-origin. Chromosome pairing analysis revealed meiotic irregularities such as reduced percentage of PMCs with complete homologous pairing, high frequency of univalents, most of H. chilense-origin and a reduced frequency of intragenomic multivalents from both genomes. The H. chilense genome revealed high meiotic instability. After individual chromosome identification at metaphase I with the pAs1 probe, we found the occurrence of pairing between chromosomes of different homoeology groups. The possible interest of the tetraploid tritordeum in the improvement of other Triticeae species is also discussed.     

Analysis of D-prolamins synthesized by the Hordeum chilense genome and their effects on gluten strength in hexaploid tritordeum

Hexaploid tritordeum is the amphiploid derived from the cross between Hordeum chilense and durum wheat. The storage proteins synthesized in the H^ch genome influence the gluten strength of this amphiploid. The D‐prolamins of H. chilense have been analysed by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis with and without urea. A new locus named Glu‐H^ch3 has been detected. The effects of allelic variation at this locus on gluten strength, as measured the sodium dodecyl sulphate sedimentation test, were determined using seeds of 92 lines from a cross of two hexaploid tritordeum lines. Two allelic variants have been detected for this locus, which have shown different effects on gluten strength.     

Development and cytogenetic characterisation of a double goat grass-barley chromosome substitution in tritordeum

×Tritordeum (Ascherson et Graebner, an amphiploid between Triticum turgidum conv. durum and Hordeum chilense), and chromosome substitution lines of tritordeum where chromosomes 2 H ^ch or 3 H ^ch H. chilense were replaced with chromosome 2 D of T. aestivum or 3 H ^v chromosome of H. vulgare, respectively, were used to assess the effect of specific chromosomes on the rachis. ×Tritordeum has brittle rachis while the 2 D(2 H ^ch) and 3 H ^v (3 H ^ch) substitution lines have non-brittle rachis. Both lines also have compact spikes, a character highly desirable for the improvement of tritordeum threshability. Different combinations of 2 D and 3 H ^v translocations were developed in tritordeum. In this article we present information on the identification and characterisation of all these introgression lines by the fluorescent in situ hybridisation.     

Bread-making quality in hexaploid tritordeum with substitutions involving chromosome 1D

Hexaploid tritordeum, the amphiploid Hordeum chilense×Triticum turgidum, has potential for bread making. In order to estimate the potential of bread wheat chromosome 1D for improving the bread‐making quality of tritordeum, and the processing properties and agronomic performance of euploid tritordeum, (1H^ch)1D and (1A)1D substitution lines have been evaluated in field trials. No significant differences for agronomical traits were observed between the two substitution lines and the sister euploid tritordeum, except for the kernel weight of the (1H^ch)1D tritordeum substitution, which was lower than that of euploid tritordeum. Gluten strength, estimated by alveograph deformation energy (W), and loaf volume were substantially higher in both substitution lines than in the euploid tritordeum.     

Somatic Embryogenesis and Plant Regeneration from Tritordeum

Regeneration of plants by somatic embryogenesis from immature embryos of hexaploid tritordeum (AABBH^chH^ch, amphiploid Hordeum chilense×Triticum turgidum conv. durum) and durum wheat (Triticum tergidum) was induced on MS medium supplemented with different 2.4-D concentrations. Well-defined embryoids were formed with a high frequency on the scutellar callus from 1 or 2 weeks onwards and plantlets were developed from them. In the best cases from one single explant more than 100 plants could be obtained. Plants were also regenerated by somatic embryogenesis from inflorescences of Hordeum chilense×Triticum turgiditm conv. durum hybrid and its respective hexa-amphiploid. With regard to callus induction and regenerative ability, evident differences between hexa- and octoploid (H. chilense×T. aestivum) tritordeum were found, the latter showing a very low response.     

Effects of Hordeum chilense and Triticum Cytoplasms on Agronomical Traits in Hexaploid Tritordeum

The genome of Tritordeum, AABBH^chH^ch, was substituted into the cytoplasms of Triticum aestivum, T. turgidum and Hordeum chilense by repeated back-crossing to produce alloplasmic lines. This substitution did not greatly affect the characters studied, except yield per plot and fertile ears per plant, which were lower on T. turgidum cytoplasm. Cytoplasm from either H. chilense or T. aestivum could be used for breeding tritordeum.     

Development and characterization of two new <Emphasis Type="Italic">Triticum aestivum</Emphasis>–<Emphasis Type="Italic">Dasypyrum</Emphasis><Emphasis Type="Italic">villosum</Emphasis> Robertsonian translocation lines T1DS·1V#3L and T1DL·1V#3S and their effect on grain quality

Dasypyrum villosum (L.) Candargy is a diploid, wild relative of bread wheat (Triticum aestivum L.). Previous studies showed that D. villosum chromosome 1V has genes that encode seed storage proteins that may be used to enhance the grain quality of bread wheat. As a first step in genetic transfer, the present study was initiated to develop compensating Robertsonian translocations involving wheat chromosome 1D and D. villosum chromosome 1V and to analyze their effects on grain quality. A monosomic 1D stock was crossed with the disomic addition stock DA1V#3 and the double monosomic plants (20″ + 1D′ + 1V#3′) were self pollinated. Two co-dominant STS markers (BE499250 and BE591682) polymorphic for the short arm of 1V#3S and two dominant STS markers (BE518358 and BE585781) polymorphic for the long arm of 1V#3L were developed to screen a large number of progeny to identify plants that had only the 1V#3S or 1V#3L arms. Five compensating Robertsonian heterozygous translocations, two (plants #56 and #83) for the short arm (T1DL·1V#3S) and three (plants #7, #123, and #208) for the long arm (T1DS·1V#3L) were identified from 282 F₂ plants and confirmed by genomic in situ hybridization and C-banding analyses. Two homozygous translocations T1DL·1V#3S (plants #14 and #39) were identified from 52 F₃ plants derived from F₂ plant #83. Four homozygous translocations T1DS·1V#3L (plants #3, #22, #29, and #30) were identified from 68 F₃ plants derived from F₂ plant #208. The homozygous translocation T1DL·1V#3S had a significantly higher (37.4 ml) and T1DS·1V#3L had significantly lower (10 ml) Zeleny sedimentation values compared to Chinese Spring wheat (30.7 ml). Our results showed that 1V#3S increased gluten strength and enhanced wheat quality, but 1V#3L decreased gluten strength and did not enhance wheat quality.     

Introgression of useful genes from Thinopyrum intermedium to wheat for improvement of bread‐making quality

To study the influence of genes from Thinopyrum intermedium on traits affecting the bread‐making quality of wheat, two derivatives from a putative disomic addition line in cultivar ‘Vilmorin 27’ were used in cytological, biochemical and molecular characterization. Cytological analysis suggested that one of the derivatives (Line‐1) had a terminal deletion involving the long arm of chromosome 1D (2n = 42, Del‐1DL”), and the other (Line‐2) was a conventional addition line, but also carried the same deletion on chromosome 1D (2n = 44, Thi”+Del‐1DL”). Amplification and sequencing of high‐molecular‐weight glutenin subunit (HMW‐GS) genes coded by the Th. intermedium chromosome in Line‐2 indicated the presence of one x‐type with an extra cysteine and four (rather than one) unique y‐type genes. Rheological studies of Line‐1 showed significantly lower dough strength compared to ‘Vilmorin 27’, confirming the recognized role of Glu‐1D coded HMW‐GSs. Line‐2 showed significantly higher dough strength compared to the background cultivar, indicating a significant potential of Th. intermedium for improvement of bread‐making quality in wheat.     

Chromosomal location of genes for carotenoid pigments in Hordeum chilense

In wheat, carotenoids are very important for end‐use quality in noodle production. Hexaploid tritordeums are the amphiploids derived from the cross between a wild diploid barley (Hordeum chilense) and durum wheat. Hexaploid tritordeums exhibit a higher carotenoid content than their respective wheat parents. The cross between H1 and H7 lines of H. chilense was used in order to map quantitative trait loci (QTL) for carotenoid content. Multiple interval mapping identified one QTL mapped on chromosome 2. This knowledge is helpful to transfer this favourable trait to other cereal genomes because of the high crossability of H. chilense with other members of the tribe Triticeae.     

Development and molecular cytogenetic identification of a new wheat–Leymus mollis Lm#6Ns disomic addition line

We developed a new disomic addition line M11028‐1‐1‐5 (2n = 44 = 21” + 1”) from a cross between wheat cv. ‘7182’ and octoploid Tritileymus M47 (2n = 8x = 56, AABBDDN sNs ). Cytological observations demonstrated that M11028‐1‐1‐5 contained 44 chromosomes and formed 22 bivalents during meiotic metaphase I. The genomic in situ hybridization (GISH) investigations showed this line contained 42 wheat chromosomes and a pair of L. mollis chromosomes. SSR, EST and PCR‐based landmark unique gene (PLUG) markers were screened to determine the homoeologous relationships of the introduced L. mollis chromosomes in wheat background. Nine markers, i.e. Xwmc256, Xgpw312, Swes123, CD452568, BF483643, BQ169205, TNAC1748, TNAC1751 and TNAC1752, all of which were located on the homoeologous group 6 chromosomes of common wheat, amplified bands unique to L. mollis in M11028‐1‐1‐5. Gliadin analysis also confirmed that the added chromosomes in M11028‐1‐1‐5 were correlated with the sixth group chromosome. This indicated that M11028‐1‐1‐5 contained a pair of introduced L. mollis chromosome belonging to homoeologous group 6, which we designated it as Lm#6 Ns disomic addition line. This is the first report of a common wheat–L. mollis disomic addition line.     

A Robertsonian translocation from Thinopyrum bessarabicum into bread wheat confers high iron and zinc contents

Development of wheat–alien translocation lines has facilitated practical utilization of alien species in wheat improvement. The production of a compensating Triticum aestivum–Thinopyrum bessarabicum whole‐arm Robertsonian translocation (RobT) involving chromosomes 6D of wheat and 6E^b of Th. bessarabicum (2n = 2x = 14, E^bE^b) through the mechanism of centric breakage–fusion is reported here. An F₂ population was derived from plants double‐monosomic for chromosome 6D and 6E^b from crosses between a DS6E^b(6D) substitution line and bread wheat cultivar ‘Roushan’ (2n = 6x = 42, AABBDD) as female parent. Eighty F₂ genotypes (L1–L80) were screened for chromosome composition. Three PCR‐based Landmark Unique Gene (PLUG) markers specific to chromosomes 6D and 6E^b were used for screening the F₂ plants. One plant with a T6E^bS.6DL centric fusion (RobT) was identified. A homozygous translocation line with full fertility was recovered among F₃ families and verified with genomic in situ hybridization (GISH). Grain micronutrient analysis showed that the DS6E^b(6D) substitution line and T6E^bS.6DL stock have higher Fe and Zn contents than the recipient wheat cultivar ‘Roushan’.     

Chromosome and chromosomal arm locations of genes for resistance to Septoria glume blotch in wheat cultivar Cotipora

Summary Septoria glume blotch, caused by Stagonospora nodorum, is an important disease of wheat (Triticum aestivum). Separate genetic mechanisms were found to control flag leaf and spike resistance. Genes for resistance to S. nodorum were located on different chromosomes in the few wheat cultivars studied. These studies only partially agree on the chromosome locations of gene in wheat for resistance to S. nodorum, and chromosomal arm locations of such genes are not known. The objectives of this study were to determine the chromosome and chromosomal arm locations of genes that significantly influence resistance to S. nodorum in wheat cultivar Cotipora. Monosomic analysis showed that flag leaf resistance was controlled by genes on chromosomes 3A, 4A, and 3B whereas the spike resistance was controlled by genes on chromosomes 3A, 4A, 7A, and 3B (P=0.01). Additionally, genes on chromosomes 6B and 5A influenced the susceptibility of the flag leaf and spike reactions, respectively (P=0.01). Telocentric analysis showed that genes on both arms of chromosome 3A, and the long arms of chromosomes 4A and 3B were involved in the flag leaf resistance whereas genes on both arms of chromosome 4A, the short arm of chromosome 3A, and the long arm of chromosome 3B conferred spike resistance.     

Molecular mapping of an aluminum tolerance locus on chromosome 4D of Chinese Spring wheat

Summary The tolerance of aluminum (Al) of disomic substitution lines having the chromosomes of the D genome of Triticum aestivum L. cv. Chinese Spring individually substituted for their homoeologues in T. turgidum L. cv. Langdon was investigated by the hematoxylin method. The disomic substitution lines involving chromosome 4D were more Al tolerant than Langdon. The tolerance was found to be controlled by a single dominant gene, designated Alt2, that is in the proximal region of the long arm of chromosome 4D. The locus was mapped relative to molecular markers utilizing a population of recombinant chromosomes from homoeologous recombination between Chinese Spring chromosome 4D and T. turgidum chromosome 4B. Comparison of the location of Alt2 in this map with a consensus map of chromosomes 4B and 4D based on homologous recombination indicated that Alt2 is in a vicinity of a 4 cM interval delineated by markers Xpsr914 and Xpsr1051. The Alt2 locus is distal to marker Xpsr39 and proximal to XksuC2. The Altw locus is also proximal to the Knal locus on chromosome 4D that controls K⁺/Na⁺ selectivity and salt tolerance. In two lines, Alt 2 and Knal were transferred on a single 4D segment into the long arm of T. turgidum chromosome 4B.     

Genetic analysis of falling number in three bi‐parental common winter wheat populations

The objective of the present study was to analyse the genetic basis of falling number in three winter wheat populations. Samples for falling number determination for each population originated from at least three test environments that were free from the occurrence of preharvest sprouting at harvest time. Quantitative trait locus (QTL) analysis employing falling number values from single environments identified eight, five and three QTL in the populations Dream/Lynx, Bussard/W332‐84 and BAUB469511/Format, respectively. A major QTL common to all three populations and consistently detected in each environment mapped to the long arm of chromosome 7B. The QTL was located to a similar genomic region as the previously described major QTL for high‐isoelectric point α‐amylase content. The T1BL.1RS wheat‐rye translocation and the dwarfing gene Rht‐D1 segregating in Dream/Lynx and BAUB469511/Format were found to be important factors of falling number variation. In both populations, the presence of Rht‐D1b or the absence of T1BL.1RS increased falling number. The results indicate that late maturity α‐amylase, responsible for low falling numbers, has now been documented in German wheat germplasm.