Genes for scald resistance from wild barley (Hordeum vulgare ssp spontaneum) and their linkage to isozyme markers

Summary Accessions of Hordeum vulgare ssp. spontaneum, the wild progenitor of barley, collected in Israel (70), Iran (15) and Turkey (6) were screened for seedling response to four isolates of Rhynchosporium secalis, the pathogen causing leaf scald in barley. Resistance was very common in the collection (77%) particularly among accessions from the more mesic sites (90%). The genetics of this resistance were investigated in fifteen backcross (BC₃) lines that contained an isozyme variant from H.v. ssp. spontaneum in a H.v. ssp. vulgare (cv. Clipper) background and were resistant to scald. Segregation in the BC₃F₂ families conformed with a single dominant resistance gene in 9 of the 15 lines. Scald resistance and the isozyme marker were closely linked in three of the BC₃-lines, loosely linked in four and unlinked in the remaining eight. Scald resistance genes were identified on barley chromosomes 1, 3, 4 and 6. Crosses between several of the scald resistant BC-lines together with the linkage data indicated that at least five genetically independent resistances are available for combining together for deployment in barley. The linkage of scald resistance in several BC₃-lines to the isozyme locus Acp2 is of special interest as this locus is highly polymorphic in wild barley.     

Salinity tolerance of wild barley Hordeum vulgare ssp. spontaneum

Salinity tolerance of 47 wild barley genotypes and six barley cultivars was evaluated under control and salinity stress (300 mM NaCl) conditions. Shoot and root dry weight (DW), plant height, membrane stability index (MSI), relative water content, survival rate, leaf malondialdehyde (MDA) and proline contents, root and leaf Na, K, Ca and K/Na ratio, and chlorophyll a fluorescence were measured. Salinity stress caused significant increase in the MDA, proline content, Na and Ca concentrations of the roots and leaves, but resulted in a decrease in the other traits. H. spontaneum genotypes were considerably less affected by the salinity than the genotypes of H. vulgare. Plant survivability was negatively correlated with the Na concentration (r =−.66) but positively correlated with the leaf K/Na ratio (r = .67) and MSI (r = .68). Tolerance mechanisms such as ion exclusion (Na) were likely to be present in the wild barley causing K/Na homeostasis as well as the much lower root and shoot Na, resulting in the higher survival rate.     

The grain yield of uniculm barley (Hordeum vulgare L.) in two contrasting environments

Summary Four six-rowed uniculm lines of spring barley were grown in two yield trials at different sowing densities. One trial was grown on light sandy soil in 1990. The second trial was grown on clay soil in 1991 and included the two-rowed, tillering cultivar Golf. In the trial on sandy soil, the grain yield of the uniculm lines approached that of Golf grown in an adjacent trial, but in 1991 when the growing conditions were more favourable, Golf yielded significantly more than the uniculm lines. Uniculm lines apparently perform relatively better under marginal growing conditions than in high yielding environments.The uniculm lines do not conform to the ideotype proposed for wheat by Donald (1968) but the results show that a drastic change in plant type need not to imply a large drop in grain yield.     

The effect of anther orientation on microspore-derived plant production in barley (Hordeum vulgare L.)

Summary The effect of anther orientation on culture response has been examined in a range of barley cultivars of agronomic importance. Anther orientation did not significantly affect the percentage of anthers responding. However, orientation of the anthers in the up position with one lobe in contact with the medium significantly increased the number of green plants produced when compared to anthers cultured in the flat position. Green plantlet production was observed directly from embryoids i.e. without an intermediate callus phase. Cytological examination of the regenerants indicated that the majority of the plantlets possessed the normal barley karyotype. The implications of these results for Barley breeding are discussed.     

Haploid barley from the intergeneric cross Hordeum vulgare x Psathyrostachys fragilis

Summary The intergeneric hybrid Hordeum vulgare x Psathyrostachys fragilis was fairly easily obtained. During each growing season the intermediate, perennial hybrid yielded haploid tillers of H. vulgare. Late in one season few, hybrid tillers headed. The morphology, cytology and enzymatic patterns of hybrid and haploid tillers were investigated.     

Resistance to Rhopalosiphum padi (Homoptera: Aphididae) in Hordeum vulgare subsp. spontaneum and in hybrids with H. vulgare subsp. vulgare

Summary Accessions of Hordeum vulgare subsp. spontaneum, the progenitor of cultivated barley, were screened in field and glasshouse trials for resistance to the aphid Rhopalosiphum padi. A few selected lines were furthermore hybridized with a modern barley variety and the resulting populations evaluated. High levels of resistance were found among some of the spontaneum accessions resulting in lower aphid growth rates (maximum reduction 57%). Segregation patterns among siblings in F2 populations were continuous, indicating the presence of several genes with possibly additive effects. The usefulness of H. vulgare subsp. spontaneum for breeding aphid resistant barley is discussed.     

Genetic characterization of wild barley populations (Hordeum vulgare ssp. spontaneum) from Kazakhstan based on genome wide SNP analysis

The wild ancestral form of barley, Hordeum vulgare ssp. spontaneum, is a valuable source for gene enrichment of cultivated barley. The purpose of this work was to study the area of distribution as well as the extent and structure of genetic variation of wild barley populations grown in Kazakhstan. It was found that distribution of wild barley populations in Kazakhstan is restricted to the most southern province. A genome wide single nucleotide polymorphism (SNP) analysis was performed in order to study the level of the genetic diversity in 96 accessions representing 14 wild barley populations from Kazakhstan and 25 accessions from the Middle East which is the center of diversity of this subspecies. The oligonucleotide pooled assay was used to genotype 384 SNPs distributed throughout the genome. In total 233 polymorphic SNPs were selected for further statistical analysis. The level of genetic diversity of wild barley populations from Kazakhstan was predictably narrower (He = 0.19 ± 0.01) in comparison with wild barley samples from the Middle East (He = 0.29 ± 0.01). The results suggested that H. vulgare ssp. spontaneum populations in Kazakhstan probably represent a recent spread of a limited number of plants from the primary distribution area and might be well adapted to winter low temperature.     

Cytogenetic variation in somatic tissue cultures and regenerated plants of barley (Hordeum vulgare L.)

Summary Chromosome number of morphogenic and non-morphogenic calli and regenerated plants of barley were determined. Cultures were obtained from two kinds of explants, immature embryos and seedling leaves from three cultivars, Ingrid, Dissa and Golden Promise. Callus chromosome analyses were carried out during a 12 month period in a medium containing 2 mg/l of 2,4-D. Diploid cells were predominant in all cases; although in leaf-derived cultures, retraploid cells (2n=4x=28) showed a tendency to increase as time in culture increased and after more than six months in culture, diploid cells decreased to percentages of almost 70%. Aneuploid cells were generally infrequent in all cases. The source of explant has been more important than the genotype (cultivar) and the type of callus (morphogenic vs. non-morphogenic) in the chromosomal stability of cultures as time increases. From short term cultures, only 1.85% of the regenerated plants were tetraploid, the remaining were diploids. The ability of morphogenic calli to regenerate plants decreased before any significant reduction of diploid cells were observed.     

Genetic diversity among elite Bulgarian barley varieties evaluated by RFLP and RAPD markers

Genetic variation among five elite winter barley cultivars (H. vulgare L.) currently grown in Bulgaria was assessed at the molecular level using restriction fragment length polymorphism (RFLP) and randomly amplified polymorphic DNA (RAPD) markers. The present study sampled RFLPs in four well characterized multigene families in barley: the seed storage protein loci; the 18S, 5.8S and 26S ribosomal DNA loci; the loci coding for 5S ribosomal RNA and the loci coding subunit α of ATP-A complex in the mitochondrial genome. RFLPs were detected in three out of five investigated chromosomal loci in the barley cultivars studied. RAPD assay using arbitrary 10-base primers was applied to generate amplified length polymorphic markers in barley. Overall a total of 15 polymorphic phenotypes were found among the studied barley cultivars by using 11 out of 25 tested primers. All RAPDs were considered as dominant genetic markers except for two, where PCR and Southern blot analysis indicated the presence of codominant amplification products. Five RAPD polymorphisms in F₁ and F₂ progenies of the cross between Alpha and Obzor were inherited in Mendelian fashion. The determined values for the genetic variation proved a high genetic similarity among the tested cultivars. Genetic similarity (GS) calculated from RFLP and RAPD data ranged from 0.888 to 0.997 with a mean GS – 0.933. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation in developmental patterns of wild barley (Hordeum spontaneum L.) and cultivated barley (H. vulgare L.)

Summary Six wild barley (Hordeum spontaneum) accessions, from a diverse range of habitats, and two spring-cultivated barleys, were examined for variation in durations of development phases. The durations of the leaf initiation and spikelet initiation phases were longer and spikelet growth phases shorter, in wild than in cultivated barley. Across all wild and cultivated barleys the rate and duration of spikelet initiation were negatively correlated, but neither was related to the number of spikelets per spike. The number of spikelets was positively correlated with the number of leaves and the ratio of the number of spikelets to the number of leaves declined with increasing time to anthesis, indicating that each successive leaf was associated with a diminishing increase in the number of spikelets. The duration of culm elongation and final culm length were shorter in accessions of cultivated barley compared with wild barley. This paper also discusses the feasibility for increasing the number of spikelets per spike through breeding for genetic changes in lengths of pre-anthesis phases of development.Abbreviations ANOVA Analysis of variance - HV Hordeum vulgare - CE Culm elongation - DR Double ridge - HS Hordeum spontaneu - ° Cd Degree days     

Adaptation of barley (Hordeum vulgare L.) to harsh Mediterranean environments

Summary Differences in development of the apex may be the reason for cultivar differences in adaptation of barley to terminal drought in Mediterranean environments. The present study was conducted to identify apical development patterns of barley adapted to terminal drought stressed Mediterranean environments and to determine plant characteristics which can be used as criteria to select for an adapted development. Thirty-five two-rowed barley (Hordeum vulgare L.) entries were grown at two sites in northern Syria (Tel Hadya and Breda) in 1988/89. Four apical development patterns were observed: a slow or fast vegetative development, depending on the vernalization requirement, combined with a slow or fast generative development, depending on the daylength response of the crop. Early heading was related to fast generative development. Leaf appearance rates on the main shoot were constant during a major part of the pre-anthesis period, but significant differences were observed among development patterns. Genotypic differences in main shoot tiller number were associated with differences in the onset of tiller appearance and not with differences in tiller appearance rate or final leaf number on the main shoot. Since vernalization requirements and daylength responses are largely independent of terminal drought stress, selection for an adapted phenology can be done in favourable environments. Morphological traits related to these responses (winter growth habit, cold tolerance, plant colour, growth vigour, heading date) can be used as criteria for selection for adaptation to low-rainfall Mediterranean environments.     

Aluminum tolerance in barley: Methods for screening and genetic analysis

Aluminum (Al) tolerance in roots of two cultivars of barley was studied using hematoxylin staining and root re-growth procedures. This study was performed in two F₂ segregating populations originated from crosses between the tolerant FM-404 and sensitive Harrington cultivars. The F₂ progeny analysed with hematoxylin staining revealed a segregation ratio of 3 tolerant: 1 sensitive, showing that the Al tolerance is controlled by a single gene with complete dominance for tolerance. The root re-growth measures do not confirm the 3:1 ratio. This last result can be explained due to the occurrence of genes that affect root growth rate or to the difficulties found in the evaluation of root re-growth. Barley has a complex root system, which makes it difficult to measure root re-growth after an extended period in nutrient solution. Due to the simplicity, reliability and better precision, the hematoxylin staining is the best procedure to determine the Al tolerance and its inheritance in barley. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diallel analysis of partial resistance to powdery mildew caused by Erysiphe graminis f. sp. hordei in spring barley (Hordeum vulgare L.)

Summary Six spring barley genotypes with growth stage dependent expression of partial resistance to powdery mildew were crossed following a half diallel scheme. Data for percentage infected leaf area at different growth stages from the F1 and F2 generation and the F2 offspring were analyzed. The absence of a contrast between parents and offspring indicated that dominance effects were not important at the young growth stages. Diallel analysis showed that general combining ability effects (GCA) were important at all growth stages. Although significant, specific combining ability effects were of minor importance. The cross between the most resistant parents with the largest, negative GCA resulted in the most resistant progeny.     

The influence of genotype and environment on seed and embryo development in barley (Hordeum vulgare L.) after crossing with Hordeum bulbosum L.

Summary Seed and embryo development was studied in crosses between H. bulbosum and the barley genotypes VK 16032, Vada and Vogelsanger Gold and subsequently the F₁ and F₂ progenies from VK 16032 x Vada and VK 16032 x Vogelsanger Gold. Both seed and embryo development are strongly influenced by the barley genotype. Favourable environmental conditions can promote seed and embryo development in genotypes with existing good characters. Dominant inheritance for good seed development and incomplete dominance for large embryos is evident. Linkage between small embryo size and winter habit exists in Vogelsanger Gold.     

Long-term callus cultures of diploid barley (Hordeum vulgare). II. Effect of auxins on chromosomal status of cultures and regeneration of plants

Summary Chromosomal abnormalities increased with time on the relatively high concentrations (2.0mg/l or more) of 2,4-D. Prolonged exposures of cell cultures to high concentrations of 2,4-D significantly increased the percent polyploid mitoses and were also associated with increased abnormalities of the spindle apparatus. Cultures maintained in the presence of NAA had a large number of cells with structural alterations of the chromosomes. The best embryogenic callus production (those maintained on 0.1 and 1.0 mg/l 2.4-D) occurred in cultures with least detectable genetic variation. Plants could not be regenerated from cultures that had been on the maintenance media for seven months or more. The loss of regeneration potential was uniform across the concentrations and auxins tested, and only correlated with time. This loss could not be associated directly with detectable genetic variation.     

Attempts to overcome partial incompatibility between Hordeum vulgare L. and H. bulbosum L.

Summary Partial incompatibility has already been reported between Hordeum vulgare and H. bulbosum during the course of doubled haploid production, and in this paper attempts to overcome the breeding barrier are described. The methods which seem to offer most success are those of environmental adjustments and the adoption of new genotypes of H. bulbosum. Further cultivars of H. vulgare exhibiting this phenomenon are also noted.     

The effect of pedicel length on lateral kernel weight in two-six rowed near isogenic lines of barley (Hordeum vulgare L.)

Summary Fifteen backcross derived, six-rowed isogenic barley (Hordeum vulgare L.) lines with the genotype vvii, nine in a six-rowed background, and six in a two-rowed background, were evaluated over 3 years for pedicel length and lateral and central kernel weight.Within the six-rowed and two-rowed backgrounds there were significant differences between isolines for all three characteristics studied. The lateral kernel weights of the six-rowed isolines were approximately half of their central kernel weights. Isolines with club heads had signicantly longer pedicels and significantly lower lateral and central kernel weight than lax headed types. A significant negative correlation was found between pedicel length and lateral kernel weight for the 15 isolines and within the six-rowed background, indicating that as pedicel length increases, lateral kernel weight tends to decrease.We recommend that breeders making selections of six-rowed segregates from two x six-rowed crosses should select against pedicellate (vvii) laterals.Cooperative investigations of the Mont. Agric. Exp. Stn. and ARS, USDA. Published with the approval of the Director of the Mont. Agric. Exp. Stn. as Journal Series No. 1463.     

The production and behaviour of hexaploid hybrids between Hordeum vulgare and H. Bulbosum

Summary To produce hexaploid (or other polyploid) hybrids, diploid or tetraploid Hordeum vulgare was crossed with hexaploid or octoploid H. bulbosum, and perennial triploid hybrids between the two species were treated with colchicine. The crosses did not yield viable plants: seedset was low, the seed aborted and embryo culture was unsuccessful. The colchicine treatments geve rise to plants in which hexaploid chromosome numbers were observed. At the hexaploid level chromosomal instability occurred, resulting in chromosome elimination.The colchicine-treated triploid hybrids showed in the first years after the treatment better fertility after open flowering than untreated plants, but the level of fertility remained very low. The offspring consisted of haploid, diploid and approximately triploid plants like H. vulgare, tetraploid and approximately tetraploid plants like H. bulbosum, and plants with hybrid morphology and unstable chromosome number, which were highly sterile. Thus the crossing barrier between H. vulgare and H. bulbosum could not be broken down at higher ploidy level.     

A skeletal linkage map of Hordeum bulbosum L. and comparative mapping with barley (H. vulgare L.)

A restriction fragment length polymorphism (RFLP) based linkage map of a cross between two diploid Hordeum bulbosum (2n = 2x = 14) clones, PB1 and PB11, was constructed from 46 recombinant progeny clones. Since both parents are heterozygous, separate and combined parental maps were constructed. All of the RFLP markers screened had previously been mapped in barley (H. vulgare L.) so that comparative maps could be produced. The PB1 linkage map consists of 20 RFLP marker loci assigned to four linkage groups covering 94.3 cM. The PB11 linkage map consists of 27 RFLP marker loci assigned to six linkage groups covering 149.1 cM. Thirteen markers polymorphic in both parents were used as ‘anchors’ to create a combined linkage map consisting of 38 loci assigned to six linkage groups and covering a genetic distance of 198 cM. Marker order was highly conserved in a comparison with the linkage map of H. vulgare (Laurie etal., 1995). However, in contrast, the genetic distances for the same markers were very different being 649 cM and 198 cM respectively, a genetic distance ratio of 1: 3.3. Thus although the map was short, it can be presumed to cover half the genome of H. bulbosum. This study provides further confirmation of the close relationship between the two species and gives a basis for the development of marker mediated introgression through interspecific hybridisation between the two species. This revised version was published online in July 2006 with corrections to the Cover Date.     

The relation between grain yield and some related traits of spring barley (Hordeum vulgare L.) and their usefulness in a breeding program

Summary The objective of this study was to evaluate traits which can facilitate and improve selection for grain yield of spring barley. Five experiments were conducted in different environments to measure grain yield and yield related traits of breeding lines and exotic varieties. Differences for rate of canopy expansion were significant and offer the opportunity to select for a high weed suppressing potential but there was no relation to grain yield. Dry matter yield/m² at anthesis and its water-soluble-carbohydrate content were not correlated with grain yield/m² and number of grains/m². Variation in biomass among breeding lines with a similar development and plant height was small. Biomass standardized for plant height was stable across environments and showed a good correlation with number of grains and grain yield. The contribution of pre-anthesis assimilation to grain yield was only important under low yielding experimental conditions, but the differences among the genotypes for this trait were inconsistent. It may be difficult to select genotypes with a high potential contribution of pre-anthesis assimilation to grain yield.