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.     

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.     

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’.     

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.     

Characterization of a set of common wheat–Hordeum chilense chromosome 7Hch introgression lines and its potential use in research on grain quality traits

Chromosome 7H^ch from Hordeum chilense has potential for improving seed carotenoid content in wheat as it carries a Phytoene synthase 1 (Psy1) gene, which has a major role in this trait. Structural changes in chromosome 7H^ch were obtained in common wheat background by crossing the wheat disomic substitution line 7H^ch(7D) with a disomic addition line carrying chromosome 2C^c from Aegilops cylindrica in common wheat cv. ‘Chinese Spring’. Rearranged 7H^ch chromosomes were cytologically characterized by FISH. A set of 24 molecular markers and the Psy1 gene were used to identify the H. chilense chromosome segments involved in the introgressions. Six structural rearrangements of chromosome 7H^ch were identified. They included three homozygous wheat–H. chilense centromeric translocations, one involving the 7H^chS arm (T‐7H^chS·A/B) and two involving the 7H^chL arm (T1‐7H^chL·A/B and T2‐7H^chL·A/B). In addition, one 7H^chS arm deletion, one 7H^chL·7H^chL isochromosome and one 7H^chS telosome were obtained in hemizygous condition. These genetic stocks will be useful for studying the effect of chromosome 7H^ch on wheat flour colour.     

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.     

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.     

Grain yield and other traits of tall and dwarf isolines of modern bread and durum wheats

Near-isogenic Rht lines of ten modern bread wheat (Triticumaestivum L.) and six durum wheat (T. turgidum L.) cultivars weredeveloped and evaluated in replicated trials under three soil moisturetreatments for two years in northwestern Mexico. The three soil moisturetreatments were created by providing one, two or six irrigations during eachcrop season. Grain yield and other traits were measured for each line ineach trial. Mean grain yields of short and tall T. aestivum or T.turgidum isolines were similar in the lowest yielding environment whenmean grain yields (0% grain moisture) of T. aestivum and T.turgidum were 2,232 and 1,870 kg ha^-1, respectively. Mean grainyield of dwarf T. aestivum was significantly higher than that of tallgenotypes in another five trials with moderate to high yields. Theperformance of dwarf and tall T. turgidum isolines was unpredictablein moderate yielding trials, and the dwarf isolines yielded significantly morein trials that received six irrigations. Given that the tall isolines producedsignificantly more straw than their shorter counterparts, cultivation of tallwheats may be beneficial in semiarid environments where farmers' yields areclose to 2.5 t ha^-1 or lower, and straw has value.     

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.     

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.     

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 of RAPD markers in tritordeum and addition lines of Hordeum chilense in Triticum aestivum

RAPD markers were developed for octoploid X Tritordeum (amphiploid Hordeum chilense × Triticum aestivum) and its parents. Two bread wheats, two H. chilense accessions and the two tritordeums synthesized with them were used. A total of 41 arbitrary decamer primers were tested, yielding 190 products that could be assigned to wheat, 185 to H. chilense and 108 that were nonspecific (present in wheat and barley). A total of 44 products were specific to one H. chilense line and 33 to the other 16 of the former were located on the chromosomes using a set of H. chilense in T. aestivum addition lines. The potential of RAPDs for developing addition lines or the detection of introgressions of H. chilense in bread wheat is discussed.     

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.     

Genetic Variability for Haploid Production in Crosses Between Tetraploid and Hexaploid Wheats with Maize

Crosses were made between 14 wheat genotypes (11 tetraploid, 3 hexaploid) and a single Fl hybrid of maize that was used as the male parent. The experimental design consisted of randomized blocks with three replications. Plants were grown under controlled greenhouse conditions (day length 16 h and temperature 25 °C/15 °C, day/night). To enhance embryo survival, 2, 4-D treatment (10 mg/1) was applied to spikes 24 h after pollination with maize. Embryos were recovered from all tetraploid and hexaploid wheats at a rate of 2.09 to 26.76 per 100 pollinated florets. Haploid and doubled haploid plants were obtained from all hexaploid genotypes (T. aestivum) and from 5 of 11 tetraploid genotypes (T. turgidum var.). The most important point of these experiments was the ability to produce haploid plants from tetraploid wheat for two reasons: firstly, anther culture cannot be applied in tetraploid wheat (T. turgidum var.) due to the inefficiency of embryo formation and the high proportion of albino plants. Secondly, to date, crosses between tetraploid wheat and maize have resulted in embryo formation, but not in haploid plants.     

The addition of Hordeum chilense chromosomes to Triticum turgidum conv. durum. biochemical,karyological and morphological characterization

Summary Biochemical, karyological and morphological characterization of Triticum turgidum conv. durum/Hordeum chilense addition forms was carried out. Nine H. chilense isozyme markers, belonging to ACPH, CPX, EST, PGM, 6-PGD, GOT and MDH enzymatic systems, were used to identify the chilense chromosomes in 50 monosonic or polysomic addition forms. Several morphological traits were associated with the presence of chilense chromosome in the complement. The transmission frequencies of addition chilense chromosomes were also investigated in the offspring of various crosses.     

Cytology, Fertility and Morphology of Amphiploids Hordeum chilense × Tetraploid Wheats (Tritordeum)

With the aim of widening the genetic variability of hexaploid tritorceum through the wheat parents, amphiploids between Hordeum chilense and Triticum turgidum ssp. dicoccoides, ssp. georgicum, and Cody, polonicum have been synthesized. The meiotic behaviour and the fertility were examined in these amphiploids. The morphology of the amphiploids in comparison to their wheat parents was described.     

Genetic distance between Triticum timopheevi Zhuk., T. aramticum Jakubz. and T. aestivum L.

The genetic distances between two cultivated wheat (Triticum aestivum L.) varieties (Martonvásári 9, Martonvásári 15), a Martonvásári 9 line possessing the crossability gene krl, and 21 accessions of T. timopheevi Zhuk. and T. araraticum Jakubz. were estimated, based on agro-morphological, physiological and biochemical analysis of data. Cluster analysis based on Mahalanobis' D² values was applied. All 21 accessions of T. timopheevi and T. araraticum could be classified into eight clusters. Clusters I and II consisted of all the T. timopheevi, while T. araraticum was located in six clusters. Discriminant analysis was applied to test significant differences between cluster pairs. The genetic distance (GD) based on the electrophoretic data of gliadins indicated two types of electrophoregrams in T. timopheevvi, distinguished as groups A and B. T. araraticum accessions were variable as regards the spectra. Mean, minimum and maximum GD were estimated within and between different wheat groups based on acid polyacrylamide gel electrophoresis.     

The Tolerance to Aluminum of Triticum N-Genome Amphiploids

Aluminum limits wheat (Triticum aestivum L.) yields on acid soils. An aluminum-tolerant, N-genome Triticum species was used to produce amphiploids, which were tested lor tolerance to 0.44 mM aluminum in solution, to assess the possibility of transferring tolerance to bread wheat. Two types of amphiploids, having the N-genomc (Triticum uniaristatum) in common, were produced by treating three different Triticum ventricosum (DDNN) ×Triticum turgidum (AABB) hybrids and a single Triticum ventricosun×Triticum timopheevii (AABB) hybrid with colchicine. It would appear that the N-genome amphiploids can be utilized to transfer tolerance to aluminum to cultivated Triticum species and to study the genetics of tolerance in the N genome.     

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.