Si amelioration of Al toxicity in barley (Hordeum vulgare L.) growing in two Andosols

The influence of silicon on aluminium toxicity in barley (Hordeum vulgare L. cv. Shunrai) was studied in two Andosols. Silicon sources were a solution of sodium metasilicate with pH adjusted to 5.0, silica gel, and an industrial waste, porous hydrated calcium silicate. The waste is produced in large amounts in the manufacturing processes of autoclaved light concrete, and has been used as a silicon source for rice plants. The addition of the waste increased the concentration of Si in the soil solution, soil pH and amelioration of aluminium toxicity was observed. The addition of silica gel and sodium metasilicate solution to both soils increased significantly (p<0.05) the Si concentration of the soil solutions, but no amelioration of aluminium toxicity was observed. An amelioration of aluminium toxicity by the waste porous hydrated calcium silicate was probably due to the increase in soil pH rather than to the increase of silicon concentration in the soil solution.     

Pre-germination effects on mechanically impeded root growth of barley (Hordeum vulgare L)

The effects of conditions pre-dating germination on growth rate of impeded barley cv. Harrington roots were measured using an agar-capillary tube technique. Seedling root tips were directed into glass capillary tubes twothirds filled with agar at eight concentrations ranging from 1.6 to 9.6%, equivalent to penetrometer resistances of 25 to 1240 kPa. The rate of unrestricted root elongation (growth in air) of seed stored for 13 months (old seed), and of seed grown for a second generation without subsequent storage (new seed) was compared with growth in agar over a 24-hour interval. Root elongation rate of old and new seed was identical in the absence of resistance. At low to intermediate agar concentrations, elongation was significantly slower in roots from old, compared with new seed. At high agar concentrations root growth of old and new seed was the same. In both old and new seed, root growth through agar was greater in seed that germinated after 24, compared with 48 h. Differences in impeded root growth between old and new seed were lost in progeny of the test seed. Environmental factors that pre-date germination are an important influence on the ability of seedling roots to elongate through soil.LRS Contribution no. 3879349LRS Contribution no. 3879349     

Aluminium/silicon interactions in barley (Hordeum vulgare L.) seedlings

The response of seedlings of the monocot Hordeum vulgare L. cv. Bronze to 0,25 and 50 M aluminium in factorial combination with 0, 1.4, 2.0 and 2.8 mM Si was tested in hydroponic culture at pH 4.5. Nutrient solution (500 M calcium nitrate) and Al/Si treatments were designed to avoid the precipitation of Al from solution. Silicon treatments gave significant amelioration of the toxic effects of Al on root and shoot growth and restored calcium levels in roots and shoots at harvest to levels approaching those of control plants. Aluminium uptake by roots was also significantly diminished in the presence of Si. Silicon alone gave a slight stimulation of growth, insufficient to explain its ameliorative effect on Al toxicity. The mechanism of the Si effect on Al toxicity in monocotyledons awaits further investigation.Abbreviations ICP inductively coupled plasma     

DNA restriction-fragment variation in the gene family encoding high molecular weight (HMW) glutenin subunits of wheat

Restriction enzyme digests of DNA from nullisomic-tetrasomic and intervarietal chromosome substitution lines of wheat were probed with a high molecular weight (HMW) glutenin cDNA. Three restriction endonucleases were used to investigate restriction-fragment differences among five wheat varieties. The results suggest that the hybridizing fragments contain single gene copies and permit the identification of the subunit encoded by each gene. Restriction-fragment variation associated with previously established allelic differences between varieties was observed. Also, there is a clear relationship between the electrophoretic mobility of a HMW subunit and the length of the central repetitive section of the gene encoding it. These results are discussed with reference to the evolution of the HMW glutenin gene family and the uses of restriction-fragment variation in plant breeding and genetics.N.P.H. was supported by a MRC Training Fellowship in Recombinant DNA Technology and a grant from the Perry Foundation. D.B. is supported by EEC Contract GBI-4-027-UK.     

Polymorphism of the cultivated barley (Hordeum vulgare L.) of South Arabia at hordein-coding loci

Electrophoresis in starch gel was used to study the polymorphism of hordeins controlled by loci Hrd A, Hrd B, and Hrd F in 89 samples of the local barleys from South Arabia (Yemen). Overall, 36 alleles were detected for locus Hrd A; 48 alleles, for Hrd B; and 5 alleles, for Hrd F. The existence of the blocks of hordein components controlled by loci Hrd A and Hrd B was demonstrated. Calculation of genetic distances allows us to conclude that the barley populations from Yemen and Ethiopia are more similar compared with the populations from Egypt. This confirms the hypothesis of Bakhteev on the origin of Ethiopian barleys.     

Structural homology of storage proteins coded by the Hor-1 locus of barley (Hordeum vulgare L.)

Three C hordein fractions were prepared by ion-exchange chromatography of a total hordein preparation on carboxymethyl cellulose at pH 4.6 Polyacrylamide gel electrophoresis at pH 3.2 and sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) at pH 8.9 showed that each fraction contained a single major band. The apparent molecular weights of these were determined by SDS-PAGE as 58, 57, and 54,000. When compared by isoelectric focusing, however, the 58 and 57,000 components each separated into two major bands and the 54,000 component into four. Amino acid analysis showed that although the three fractions had similar compositions with high glutamate+glutamine (38–39%), proline (30–32%) and phenylalanine (8–9%) contents, some differences were present, notably in the relative content of lysine. The three fractions had identical amino acid sequences for the first ten residues at the N-terminal end. They also had identical sequences for the first five residues at the C-terminal end, with the exception that a mixture of two amino acids were released from position 4 of the 58,000 fraction only. Peptide mapping with three enzymes (trypsin, chymotrypsin and V8 protease) indicated that the 58 and 57,000 fractions were more closely related to each other than to the 54,000 fraction. It is suggested that the 57 and 58,000 fractions and the 54,000 fraction constitute two families of closely related polypeptides which are coded by genes derived from the duplication and divergence of a single ancestral gene.     

Construction of a barley (Hordeum vulgare L.) YAC library and isolation of a Hor1-specific clone

We have constructed an EcoRI-based YAC (yeast artificial chromosome) library from barley (Hordeum vulgare L. cv. Franka) using the vector pYAC4. The library consists of approximately 18 000 recombinant YACs with insert sizes ranging between 100 and 1000 kb (average of 160 kb) corresponding to 50% of the barley genome. Size fractionation after ligation resulted in an increased average insert size (av. 370 kb) but also in a substantial decrease in cloning efficiency. Less than 1% of the colonies showed homology to a plastome-specific probe; approximately 50% of the colonies displayed a signal with a dispersed, highly repetitive barley-specific probe. Using a primer combination deduced from the sequence of a member of the small Hor1 gene family coding for the C-hordein storage proteins, the library was screened by polymerase chain reaction and subsequently by the colony hybridization technique. A single YAC, designated Y66C11, with a 120 kb insert was isolated. This DNA fragment represents a coherent stretch from the terminal part of the Hor1 gene region as judged from the correspondence of the restriction patterns between Y66C11 DNA and barley DNA after hybridization with the Hor1-specific probe. Restriction with the isoschizomeric enzymes HpaII/MspI suggests a high degree of methylation of the Hor1 region in mesophyll cells but not in YAC-derived (yeast) DNA.     

Hordein locus polymorphism of cultivated barley (Hordeum vulgare L.) in Turkey

Starch gel electrophoresis has been used to study the polymorphism of hordeins encoded by the Hrd A, Hrd B, and Hrd F loci in 93 landrace specimens of barley assigned to 17 ancient provinces located in modem Turkey. Forty-five alleles of Hrd A with frequencies of 0.11-29.34%, 51 alleles of Hrd B with frequencies of 0.11-8.07%, and 5 alleles of Hrd F with frequencies of 0.75-41.29% have been detected. Cluster analysis of the matrix of allele frequencies has demonstrated that barley populations from different old provinces of Turkey are similar to one another. Cluster structure of local barley populations has been found, most populations (82%) falling into three clusters. The first cluster comprises barley populations from six provinces (Thracia, Bithynia, Pontus, Lydia, Cappadocia, and Armenia); the second cluster, populations from five provinces (Paphlagonia, Galatia, Lycaonia, Cilicia, and Mesopotamia); and the third one, populations from three provinces (Phrygia, Karia, and Lycia). Barley populations from Mysia, Pamphlya, and Syria do not fall in any cluster.     

Phosphorus concentration in barley (Hordeum vulgare L.) seed: Influence on seedling growth and dry matter production

The effect of phosphorus (P) concentration in barley seed on seedling growth has not been much investigated. Consequently, two experiments were conducted in the greenhouse to determine the effect of P concentration in barley seed (Hordeum vulgare L., cv. Empress) on the seedlings grown in sand-filled boxes receiving a culture solution without P. Seeds were selected with three P concentrations: high-P (113.0 mmol P kg⁻¹), medium-P (80.7 mmol P kg⁻¹) and low-P (54.9 mmol P kg⁻¹). At 21 days after sowing, the shoot and root yield or shoot height was the least with seedlings from low-P seed. In the other experiment, high-P and low-P seeds were wetted with distilled water or with a solution of 25.8 cmol L⁻¹ of NaH₂PO₄ for 24 h, and then grown for 31 days. Solution P had been imbibed by seeds whether low or high in native P, but only the imbibed P held by low native P seed benefited seedling dry matter accumulation and shoot elongation. The lack of benefit from seed-imbibed P on seedlings grown from high-P barley seed was associated with low recovery of the imbibed P in those seedlings.     

Discovery and assay of single-nucleotide polymorphisms in barley (Hordeum vulgare)

The least ambiguous genetic markers are those based on completely characterized DNA sequence polymorphisms. Unfortunately, assaying allele states by allele sequencing is slow and cumbersome. The most desirable type of genetic marker would be unambiguous, inexpensive to assay and would be assayable singly or in parallel with hundreds of other markers (multiplexable). In this report we sequenced alleles at 54 barley (Hordeum vulgare ssp. vulgare) loci, 38 of which contained single-nucleotide polymorphisms (SNPs). Many of these 38 loci contained multiple polymorphisms, and a total of 112 polymorphisms were scored in five barley genotypes. The polymorphism data set was analyzed both by using the individual mutations as cladistic characters and by reducing data for each locus to haplotypes. We compared the informativeness of these two approaches by consensus tree construction and bootstrap analysis. Both approaches provided similar results. Since some of the loci sequenced contained insertion/deletion events and multiple point mutations, we thought that these multiple-mutated loci might represent old alleles that predated the divergence of barley from H. spontaneum. We evaluated sequences from a sample of H. spontaneum accessions from the Eastern Mediterranean, and observed similar alleles present in both cultivated barley and H. spontaneum, suggesting either multiple domestication events or multiple transfers of genes between barley and its wild ancestor.     

Boron toxicity in barley (Hordeum vulgare L.) seedlings in relation to soil temperature

Boron (B) is an essential micronutrient in crop growth but its sufficiency range is narrow. Boron toxicity is a widespread problem in arid and semi-arid areas with cold weather. We investigated the effect of soil temperature (5, 10 and 15°C) on development of symptoms of B toxicity, plant growth and plant development, and on content and concentration of B in tissue of seedlings of four barley lines grown in soil with high level of available B (12 mg kg^–1). Visual symptoms of toxicity were first observed in the high B soil concentration treatment at 5 °C at 12 days after emergence. Concentration of B in tissue decreased with increasing soil-temperatures. There was no effect of soil temperature on B content or B concentration in plant tissue at the final sample (17 days after emergence). High soil B reduced seedling and leaf emergence rates, although the final seedling emergence and number of leaves were unaffected. Barley lines differed in concentration of B in tissues and visual toxicity symptom development. Adaptation to high B was either through maintaining low tissue B concentration or through tolerance to high tissue B concentration. While the investigated range of temperature does influence B toxicity in barley seedlings, it remains to be determined whether it affects crop yield.     

Polymorphism of hordein-coding loci in cultivated barley (Hordeum vulgare L.) in Afghanistan

Polymorphism of hordeins encoded by the HrdA, Hrd B, and Hrd Floci was analyzed in 84 accessions of local barley (Hordeum vulgare L.) varieties from major agricultural regions of Afghanistan using starch gel electrophoresis. Forty alleles of the Hrd A locus with the frequencies from 0.12 to 32.73%, 62 alleles of the Hrd B locus with the frequencies from 0.12 to 14.29%, and five alleles of the Hrd Flocus with the frequencies from 0.59 to 32.15% have been identified. The conclusion about genetic similarity of barley populations from different regions of Afghanistan is made on the basis of cluster analysis of the matrix of allele frequencies in barley populations from 31 localities. The local barley populations form four unequal clusters. The largest cluster I includes populations from 14 localities of Afghanistan. The second largest cluster IV consists of populations from ten localities, and clusters II and III comprise populations from four and three localities, respectively. Each of the four clusters includes populations from different regions of northern and southern Afghanistan. Based on our results, we conclude that the diversity of hordein-coding loci and the distribution of their alleles among different regions of Afghanistan are the consequences of introduction of barley landraces and their distribution over trade routes.     

Salt tolerance of barley (Hordeum vulgare L.) cultivars at the germination stage: Analysis of the response functions

Two models, initially proposed by Van Genuchten (1983) for evaluating salinity-yield response curves at the adult stage, were applied to study the salinity response of 24 barley cultivars at the germination stage. According to the calculated salinity threshold, EC_t (the solution electrical conductivity, EC, at which germination starts to decrease), and EC₅₀ (the solution EC at which germination is reduced by 50%) parameters, both models give similar results, although model 2, a sigmoid-form curve, fits the observed data slightly better than model 1, a piecewise response function. Also, the results suggest that, for model 1, EC_t seems to be the most reliable parameter for screening barley germplasm because it clearly discriminates the relative salt-tolerance of the studied cultivars and, furthermore, it basically determines their salinity response for the 100 to 50% germination interval. On the other hand, the model 1 s parameter — percent germination decrease per unit salinity increase bove EC_t—is less relevant because of its smaller variation interval and lack of correlation with EC₅₀, indicating that the salinity response of the studied cultivars for the 50% germination value is independent of this parameter.     

Fine mapping and chromosome walking towards the Ror1 locus in barley (Hordeum vulgare L.)

Key message

The Ror1 gene was fine-mapped to the pericentric region of barley chromosome 1HL.

Abstract

Recessively inherited loss-of-function alleles of the barley (Hordeum vulgare) Mildew resistance locus o (Mlo) gene confer durable broad-spectrum disease resistance against the obligate biotrophic fungal powdery mildew pathogen Blumeria graminis f.sp. hordei. Previous genetic analyses revealed two barley genes, Ror1 and Ror2, that are Required for mlo-specified resistance and basal defence. While Ror2 was cloned and shown to encode a t-SNARE protein (syntaxin), the molecular nature or Ror1 remained elusive. Ror1 was previously mapped to the centromeric region of the long arm of barley chromosome 1H. Here, we narrowed the barley Ror1 interval to 0.18 cM and initiated a chromosome walk using barley yeast artificial chromosome (YAC) clones, next-generation DNA sequencing and fluorescence in situ hybridization. Two non-overlapping YAC contigs containing Ror1 flanking genes were identified. Despite a high degree of synteny observed between barley and the sequenced genomes of the grasses rice (Oryza sativa), Brachypodium distachyon and Sorghum bicolor across the wider chromosomal area, the genes in the YAC contigs showed extensive interspecific rearrangements in orientation and order. Consequently, the position of a Ror1 homolog in these species could not be precisely predicted, nor was a barley gene co-segregating with Ror1 identified. These factors have prevented the molecular identification of the Ror1 gene for the time being.     

Ring chromosomes in barley (Hordeum vulgare L.)

A plant with 2n = 14 + 1 ring chromosomes was obtained in the progeny of a primary trisomie for chromosome 7 of a two-rowed cultivar, Shin Ebisu 16. The morphological characteristics of the trisomic plants with an extra ring chromosome were similar to the primary trisomic for chromosome 7 (Semierect), which suggests that it originated from this chromosome. The ring chromosomes were not completely stable in mitotic cells because of abnormal behavior. Chromosome complements varied in different plants and in different roots within a plant. Root tip cells and spikes with 2n = 14 and 14 + 2 ring chromosomes were observed on plants with 14 + 1 ring chromosomes. Breakage-fusion-bridge cycle was inferred. The ring chromosome was associated with two normal homologues forming a trivalent in 17.6% sporocytes at metaphase I. The transmission of the extra ring chromosome was 23.1% in the progeny of the plant with 14 + 1 ring chromosomes. Trivalent formation may have been much higher at early prophase stages which were difficult to analyze in barley; only 4 of 120 sporocytes analyzed showed an isolated ring at pachytene. The ring chromosome moved to one pole without separation in 24.7% of the sporocytes at AI, and divided in 27.1% sporocytes giving rise to 8-8 separation. Only 10% of the sporocytes showed bridge formation at AI.     

Effect of anther orientation on microspore-callus production in barley (Hordeum vulgare L.)

Barley anthers from cold pretreated spikes produced no or few calluses when plated with both loculi in contact with the medium (flat). When anthers were plated with only one loculus in contact with the medium (up), a high proportion of the anthers produced calluses. The top loculus of the up anthers was most productive. Flat anthers, when compared with up anthers, were not only slower to produce multicellular pollen grains (MCPs) and microcalluses, but also produced fewer of them and ceased production earlier. The MCPs and microcalluses in flat anthers grew more slowly and few developed beyond the 30 cell stage. These results establish the importance of anther orientation for barley anther culture.     

Effects of UV-B radiation on Chl fluorescence of greening barley (Hordeum vulgare L.) seedling

Effects of UV-B radiation on the developing chloroplast of barley (Hordeum vulgare L.) seedling during greening were determined by Chl contents, Fo, Fv and fluorescence quenching coefficients. In greening of etiolated barley seedling, the value of Fo was greatly increased after the initiation of greening. However Fv and Fv/Fo were gradually increased. In greening with the additional irradiation of UV-B radiation, the value of Fo was strikingly decreased than that of the control after the initiation of greening, but Fv was gradually decreased from than that of the control during the greening period. These results suggest that the function of light-harvesting Chl are more sensitive than photosynthetic electron transport system by UV-B. Chl contents, Fv/Fo, qP and qNP, were decreased from than that of the control during the 72 h greening, especially, qR was strikingly decreased, but qE was slightly decreased by UV-B. These suggest that the sites of inhibition by UV-B are PSII and all sites of photosynthetic electron transport system. But PQ pool seems to be slightly inhibited by UV-B.