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.     

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.     

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.     

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.     

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.     

Genetic variability in antibiotic resistance to the greenbug Schizaphis graminum in Hordeum chilense

Hordeum chilense (Roem. et Schult), a native grass of South America, is a source of antixenotic and antibiotic resistance to the greenbug Schizaphis graminum Rondani. The genetic and environmental components of the variability in antibiotic resistance shown by H. chilense were determined by measuring the developmental time, the length of adult life, fecundity and intrinsic rate of population increase of green-bugs reared on this host. The aphids belonged to a clone of biotype C. Plants were cloned to reduce the incidence of environmental variability. Different plant characters appeared to prolong aphid developmental time and reduce the length of adult life and total fecundity. The broad sense heritability and the genetic variability of these plant characters were different. The plant character that affected aphid development appears to differ from that affecting fecundity.     

Resistance to Karnal bunt in Hordeum chilense and its amphiploids with Triticum species

Reactions of Hordeum chilense accessions H1 and H7 and their amphiploids, HT8, HT9 and HT28 (named as tritordeum) alongwith wheat lines, T22, T24 and T59 used in their synthesis, were studied for resistance to the Karnal bunt pathogen (Tilletia indica) of wheat. Both the accessions of H. chilense and one tritordeum line, HT8, were rated as highly resistant with zero co-efficient of infection, whereas the other two tritordeum lines HT28 and HT9 were rated as moderately susceptible and susceptible with 5.2 and 10.5 co-efficients of infection, respectively, compared to reaction of the wheat lines involved in their synthesis. Karnal bunt infection was maximum on the susceptible wheat cultivar WL-711 with 24.3 co-efficient of infection. All the wheat lines involved in the synthesis of amphiploids were susceptible to Karnal bunt except, T59 (Triticum sphaerococcum) (6X), which showed a moderate level of resistance. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

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.     

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.     

Characteristics of the Incomplete Resistance of Hordeum chilense to the Root-Knot Nematode Meloidogyne naasi Franklin — Description of a Newly Conceived Test to Detect the Resistance

We are able to describe, due to some assays conducted under field conditions, the different ways the root-knot nematode of cereals was affected in some amphiploid plants carrying the resistance of a wild Hordeum sp. This resistance arises in one of three ways: (i) a reduction in the establishment of the infective juvenile stages in the root, (ii) a delay and/or a cessation of development of the parasite occurring at the J2 or swelling-J2 stage, (iii) an altered fecundity of the females. These three actions efficiently control the multiplication of the nematode, resulting in few females at the end of growing period of the crop. A new test was developed for early screening of the resistance under controlled conditions. Based on the analysis of the gall rating and the contents of five young galls from each plant, the response of a line can be seen within 16 days, while preserving the viability of the plants to continue their growth.     

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.     

Identification for H. villosa chromatin in wheat lines using genomic in situ hybridization, C-banding and gliadin electrophoresis techniques

Detection of H. villosa chromosomes in telosomic addition and translocation lines of common wheat was undertaken using genomic in situ hybridization (GISH), C-banding techniques and polyacrylamide gels electrophoresis. The result of GISH on mitotic metaphase cells of the addition line `95039' indicated that the added telochromosomes originated from H. villosa, and it was probably 6VS or 7Vs of H. villosa according to the C-banding pattern. Furthermore, the analysis of gliadin profiles demonstrated that the telochromosome was 6VS. A pair of 1RS/1BL translocation chromosome was also found in `95039'. In addition, mitotic GISH analysis showed that the 6VS/6AL translocation chromosome remained unchanged after being transferred into new wheat background. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

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.     

Karyotype analysis and physical mapping of 45S rRNA genes in Hydrangea species by fluorescence in situ hybridization

Detailed karyotypes of Hydrangea macrophylla, Hydrangea paniculata and Hydrangea quercifolia were constructed on the basis of arm lengths and centromeric index, together with 45S rDNA fluorescence in situ hybridization. Although the chromosomes were small, they were well distinguishable for all species. Chromosome morphology and karyotypes were different for the three species. H. macrophylla had six metacentric (M), eight submetacentric (SM) and four subtelocentric (ST) chromosomes. The karyotype of H. paniculata contained seven M, 10 SM and one ST chromosomes and H. quercifolia had six M, 10 SM and two ST chromosomes. The variability among three species also was expressed by 45S rDNA signals. H. macrophylla had a nucleolar organizing region on chromosome 2, H. paniculata had 45S rDNA signals on chromosomes 2, 5 and 11 and H. quercifolia on chromosomes 3 and 8. Hybridization signal always was distally on the short arm but the strength of the signals was different for the three species. The chromosome portraits made in this study will be used to trace chromosome behaviour in interspecific hybrids resulting from breeding work between the three species.