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.     

Effects of Hordeum chilense cytoplasm on agronomic traits in common wheat

The genome of bread wheat, AABBDD, was substituted into the cytoplasm of Hordeum chilense by repeated backcrossing to produce alloplasmic lines. The aim of this work was to investigate the effect of H. chilense cytoplasm on agronomic traits in common wheat. Three cytolines were developed. The alloplasmic nature of these lines was confirmed using chloroplast simple‐sequence repeat markers. Each cytoline was compared with its respective euplasmic control for agronomic performance during 2 years of field trials. The interaction between H. chilense cytoplasm and common wheat genome greatly affected most of the traits evaluated. Among them, alloplasmic lines showed delayed anthesis date, lower yield and lower plant height. These effects are similar to those caused by Aegilops cytoplasm. The main conclusion of this work is that H. chilense cytoplasm is of limited value for wheat breeding.     

Use of ccSSR markers for the determination of the purity of alloplasmic wheat in different Hordeum cytoplasms

We tested three different consensus chloroplast simple sequence repeat (ccSSR) primers to identify amplified polymorphic products in Hordeum chilense, Hordeum vulgare and other Triticeae species with a double aim. First, to use chloroplast‐specific primers as an indirect method for the assessment of wheat cytoplasmic male sterile purity in seedlings during multiplication and in the development of alloplasmic lines. Second, to analyse cytoplasmic relationships among H. chilense accessions and between H. chilense and other members of the Triticeae tribe. The products from primer ccSSR‐4 were easily discriminated using agarose gel electrophoresis. Based on the lengths of amplification products, three groups were identified: the first included almost exclusively H. chilense accessions, the second contained H. vulgare accessions and the third comprised the wheat and the rest of the analysed accessions. Sequencing of PCR products revealed point mutations and insertions/deletions in addition to the expansion/contraction of the microsatellite repeat length. Data analyses of sequenced fragments revealed six groups of accessions among the material studied. No significant differences were found among H. chilense accessions.     

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.     

Screening for Greenbug Resistance in Hordeum chilense Roem et Schult.

Schizaphis graminum (Rondani) is a serious pest of cultivated wheat (Triticum aestivum L.) and resistance is only available in other related species such as Hordeum chilense. Amphiploids between H. chilense and Triticum spp. have been obtained, and addition lines of H. chilense in wheat have been developed. Thirty-five accessions of H. chilense were screened to identify greenbug antixenosis, antibiosis and tolerance. Antixenosis was determined in a conventional host free choice test; antibiosis was measured by aphid life cycle and fecundity rate, and tolerance was tested in a conventional infestation test of 4 weeks. Two commercial barley cultivars were used as susceptible and resistant controls. Eight H. chilense accessions showed higher degrees of antixenosis than the resistant check, 19 were similar and the rest were lower. All accessions were more resistant than the susceptible check. Measured by aphid life cycle, 22 H. chilense accessions showed higher antibiosis than the resistant cv., and all exhibited a higher antibiotic effect on fecundity rates than the control. A similar degree of tolerance to that of the resistant control was observed in six accessions, the remaining entries ranged between the controls. The presence of one mechanism did not exclude the existence of other mechanisms in the same entry and therefore, independence of the different mechanisms is proposed. Most of the accessions showed higher variability than both controls for the three mechanisms, and it appears to be genetic variability within entries for the three mechanisms.     

Resistance to Septoria tritici in Hordeum chilense×Triticum spp. Amphiploids

The reaction of tritordeum and its Hordeum chilense and Triticum spp. parents to Septoria tritici was studied in field and seedling experiments. All H. chilense lines were highly resistant to all the isolates and did not allow pycnidia development. The ‘durum wheat isolate’ developed pycnidia only on durum wheats. The ‘breed wheat isolate’ was very virulent on bread wheat but also on the wild tetra-ploid wheats. The other two isolates were compatible with durum and bread wheat. All hexaploid tritordeums were highly resistant both in the field and the seedling experiments. Some octoploid tritordeums allowed pycnidial development, but at much lower levels than their wheat parent. Resistance in tritordeum was not associated with plant stature and only in octoploid tritordeum was association of resistance with late maturity detected.     

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.     

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’.     

Short Communication Resistance to common bunt in Hordeum chilense X Triticum spp. Amphiploids

The reaction of tritordeum and its Hordeum chilense and Triticum spp. parents to common bunt incited by Tilletia tritici were determined in field experiments. H. chilense accessions were very resistant, and durum wheats exhibited high to moderate levels of resistance. Conversely, bread wheats were highly susceptible. Resistance from H. chilense was expressed in the amphiploids, although the level of resistance was partially diluted at higher ploidy levels. Hexaploid tritordeums were immune to the disease; some infection was observed among the octo-ploids but at much lower levels than in their respective wheat parents.     

The reaction of x Tritordeum and its Triticum spp. and Hordeum chilense parents to rust diseases

Summary Hexaploid and octoploid tritordeums and their parents Hordeum chilense and Triticum spp. were screened for resistance to isolates of wheat and barley yellow and brown rusts. All H. chilense lines were highly resistant to both wheat and barley brown rust, few lines were susceptible to wheat yellow rust while susceptibility to barley yellow rust was common. In general the resistance of tritordeum is predominantly contributed by the wheat parent and apparently the genes for resistance in H. chilense are inhibited in their expression by the presence of the wheat genome.Abbreviations WYR wheat yellow rust - WBR wheat brown rust - BYR barley yellow rust - BBR barley brown rust     

Genetics of Hordeum chilense– Current Status

Hordeum chilense, a South-American wild barley, is being used in cereal breeding because of its good crossability with both wild and cultivated Triticeae species. Amphiploids and chromosome addition lines of H. chilense in common and durum wheats have been obtained as a means to transfer desirable agronomic characters from wild barley to wheat. No allosyndetic pairing has been detected in diverse hybrids involving H. chilense. Several biochemical markers have been associated with the seven chilense chromosome pairs. New approaches are necessary to transfer genes from H. chilense to cereals.     

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.     

Chromosomal location of resistance to Septoria tritici in Hordeum chilense determined by the study of chromosomal addition and substitution lines in `Chinese Spring' wheat

Hordeum chilense exhibits resistance to Septoria tritici. Addition and substitution lines of H. chilensein wheat were utilized in growth chamber and field experiments to determine which H. chilense chromosomes carry resistance genes. Resistance is conferred by gene(s) on chromosome 4 and, to a minor extent, by genes on chromosomes 5, 6 and 7. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Genetic variation for carotenoid pigment content in the amphiploid Hordeum chilense × Triticum turgidum conv. durum

Hexaploid tritordeum, the amphiploid Hordeum chilense x Triticum turgidum conv. durum has a higher grain carotene content than durum wheat. In order to decide strategies for introgressing this character into durum wheat, the effect on the carotene content of tritordeum synthesized with H. chilense and durum wheat differing in carotene content was analysed. Carotene content was evaluated in 35 primary tritordeum lines and their parents, 27 H. chilense accessions and 19 durum wheat cultivars. Some amphiploids have either one barley or wheat parent in common. In general, the influence of H. chilense is more important than that of wheat in the amphiploid carotene content. Nevertheless, the interactions between both parents on the amphiploid carotene content are also important.     

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.     

The introduction into bread wheat of a major gene for resistance to powdery mildew from wild emmer wheat

Summary A new source of resistance to wheat powdery mildew caused by Erysiphe graminis has been transferred to hexaploid bread wheat, Triticum aestivum, from the wild tetraploid wheat, Triticum dicoccoides. The donor was crossed to bread wheat and the pentaploid progeny was then self-pollinated. Plants having a near stable hexaploid chromosome complement were selected in the F₃ progeny and topcrossing and backcrossing of these to a second wheat cultivar to improve the phenotype was undertaken. Monosomic analysis of early backcross lines showed the transferred gene to be located on chromosome 4A. The gene has been designated Pm16.     

Reaction of tritordeum to Fusarium culmorum and Septoria nodorum

Summary Hordeum chilense is a wild barley extensively used in wide crosses in the Triticeae. It could be a valuable source of resistance to Fusarium culmorum and Septoria nodorum. Some H. chilense x Triticum spp. amphiploids, named tritordeums, were more resistant than the parental wheat line to these diseases, others were not. Average contents of ergosterol and deoxynivalenol (DON) suggested that resistance to colonization by Fusarium was the highest for Hordeum chilense, followed by tritordeum and wheat in decreasing order. In particular, the H. chilense genotypes H7 and H17 enhanced the wheat resistance to F. culmorum in its tritordeum offsprings. Resistance to S. nodorum in tritordeum was not associated with tall plant height. There is sufficient genetic variation for resistance to F. culmorum and S. nodorum among tritordeum to allow the breeding of lines combining short straw and resistance to both diseases.     

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.     

Genealogical Identification of Hexaploid Tritordeum by Electrophoretic Separation of Endosperm Storage Proteins

Hexaploid Tritordeum (×Tritordeum Ascherson et Graebner) has been analyzed by SDS-PAGE, to test the efficiency of the method for confirming the parents of different lines, and for unequivocally discriminating between the lines. The results clearly show that endosperm storage proteins from both parents (durum wheat ——Triticum turgidum conv. durum Desf. em. M.K. —— and Hordeum chilense Roem. et Schulz.) are expressed in the endosperm of the amphiploid between them. Although the spectra of proteins from the parental species overlap on the gel, there are sufficient number of bands with distinct electrophoretic mobilities to identify unambiguously their parental origin. Furthermore, in the six lines of tritordeum analyzed, obtained from crosses between three accessions of H. chilense and four cultivars or lines of wheat, there was sufficient polymorphism amongst the parents, particularly amongst the H. chilense accessions, to enable both aims of the project to be met, that is, to confirm the genealogy of each tritordeum, and to discriminate between different lines. This study provides the basis of future investigation on the relationship between bread-making quality in tritordeum and the allelic composition of storage proteins.