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.     

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.     

Variation in vegetative parameters related to the nitrogen economy of wild barley,Hordeum spontaneum,in Israel

Summary Hordeum spontaneum, the wild progenitor of cultivated barley, has previously been examined in various studies as a germplasm resource in breeding for grain protein content and related nutritional traits.The nitrogen content and dry weight of leaf and stem (stem plus sheath) at anthesis, and the final grain size and grain protein content were measured in 33 H. spontaneum and two H. vulgare genotypes. H. spontaneum was generally higher in nitrogen content of leaves and stems, but lower in dry weight at anthesis. Consistent with previous reports, the H. spontaneum genotypes were considerably higher in grain protein than the cultivars. There was wide variation between and within populations of H. spontaneum suggesting that for breeding purposes lines combining high vegetative nitrogen content, dry weight and grain protein content can be selected.Incumbent of the Seagram Chair for Plant Science     

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.     

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.     

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.     

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.     

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.     

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.     

Environmental, phenotypic and genetic variation of wild barley (Hordeum spontaneum) from Israel

Wild relatives of crop plants offer an attractive gene pool for cultivar improvement. We evaluated genetic and phenotypic variation for a set of 72 Israeli accessions of wild barley from 21 populations. These populations were grouped further into four ecotypes. In addition, environmental variables describing the local conditions for the populations were used to infer the environmental divergence. Genetic, phenotypic and environmental distances were estimated from the data and UPGMA dendrograms constructed. The results showed that genetic variation was larger between populations than within them, whereas for phenotypic measurements variation was larger within populations than between them. No significant correlation was found between genetic and phenotypic similarities, or between phenotypic and environmental similarities, whereas a weak correlation between genetic and environmental similarities was detected. Twenty-three AFLP-markers were identified to be ecotype specific. Chromosomal location was known for five of these markers. Four of the five ecotype specific markers were correlated with both phenotypic traits and environmental variables.     

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.     

Genetic resources of wild cereals in Israel and vicinity. II. Phenotypic variation within and between populations of wild barley,Hordeum spontaneum

Summary Populations of wild barley, Hordeum spontaneum, in Israel, originating from diverse habitats, and tested earlier for allozyme (Nevo et al., 1979a) and disease resistance polymorphisms (Moseman et al., 1984; Nevo et al., 1984a), were compared and contrasted for performance in agronomically important phenotypic traits. The traits compared involved 10 variables comparing germination, earliness, numerical and weight variables of biomass and yield. The field experiments were conducted in 1980, 1981 and 1982 in two relatively standardized and contrasting environments: mesic (Mount Carmel, Haifa) and xeric Avedat farm, and Sede Boqer (both in the northen Negev desert). The experimental design involved 26 population quadrangles at Avedat farm (1980), and rows of randomized plants of 11 populations in both Haifa and Sede Boqer (1981 and 1982).The results indicate that the characters studied are partly genetically determined. Striking genetic variation was found between and within populations in each site, whereas remarkable environmental variation including genetic environmental interaction was found between the mesic and the xeric sites, as well as between populations and years. We conclude that natural populations of wild barley in Israel vary not only in genetic polymorphisms of allozymes and disease resistance, but also in quantitative traits of agronomie importance. These traits are economically significant and should be conserved and utilized in barley crop improvement.     

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.     

Endosperm protein accumulation in wild and cultivated barley and their cross grown in spike culture

Summary The high protein wild relatives of cultivated cereals have proven difficult to utilize in plant breeding by direct selection for high grain protein percentage, and hence alternative selection criteria are needed. In this study, a spike culture method was used to measure differences in protein accumulation between wild and cultivated barley, and their cross, at different levels of nitrogen supply. Three genotypes, barley cultivar Hordeum vulgare L. cv. Clipper, a wild barley accession H. spontaneum Koch line 363, and a high protein F₅ line (38.4) derived from their cross, were grown from 8 to 27 days after flowering in in vitro spike culture. Nitrogen supply in the culture medium was either 0.4 g/l or 2.0 g/l of N supplied as NH₄NO₃. Spikes were harvested at approximately 3 day intervals during grain development, and salt soluble and hordein protein fractions were measured. Lines 363 and 38.4 differed from Clipper in having extremely high initial rates of protein accumulation, even at 0.4 g/l N. In high nitrogen conditions all three genotypes reached similar salt soluble plus hordein protein levels. Hordein-1 and hordein-2 fractions were measured separately; the percent of hordein-1 was higher in lines 363 and 38.4 than in Clipper at 0.4 g/l N. For all parameters measured, pot-grown spikes of matching age were harvested and were shown to be similar to the 0.4 g/l N treatment. The possible utilization of spike culture for identification of critical protein accumulation parameters is discussed, in relation to their possible utilization in breeding.     

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.     

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.     

Conservation of diversity in bulk populations of barley (hordeum vulgare L.)

Summary A series of experiments was conducted to investigate the effectiveness of mass propagated heterogeneous populations (bulk populations) in preserving genetic and phenotypic diversity. Five genetically broad-based bulk populations of cultivated barley (Hordeum vulgare L.) were employed. All of them were produced originally through mass hybridization that was facilitated by male sterility. Four of these populations had a common origin, but were subsequently propagated in different North American locations. Comparisons between early and advanced generations of these bulk populations revealed loss of variability in all populations for morphological and agronomic characters and very little to none for eight isozyme characters. Populations propagated in different locations differed in levels of residual diversity. The bulk populations were less variable than a random sample of parental accessions. The rapid loss of diversity in bulk populations was considered detrimental to genetic conservation.     

RAPD characterization of Brazilian barley (Hordeum vulgare ssp. vulgare) varieties

Thirteen varieties of Brazilian barley selected for malting qualities were analysed by RAPD (Random Amplified Polymorphic DNA). Amplification with 18 random primers generated 221 reproducible bands, of which 206 bands were polymorphic (93%):of this number, 137 fragments (62%) detected diversity among varieties and 56 bands (25.34%) allowed the distinction of varieties or groups of them. Variation was detected in all Brazilian varieties studied. Within-variety similarities estimated by Jaccard Similarity Coefficient ranged from 0.28 to 0.94, with averages ranging from 0.57 to 0.83, and an overall average of 0.72. Nevertheless, in the cluster analysis representatives of the same variety always fell into the same group and only later joined the other varieties. The average intervarietal similarities estimated by Jaccard Similarity Coefficient ranged from 0.45 to 0.62, with an overall average of 0.52. Many bands or combinations of bands which were responsible for the differentiation of all varieties were detected. Nevertheless, the majority of these bands cannot be considered as diagnostic markers because a great number of them did not occur in many representatives of the variety or had low intensity or even because they were not easily identified in the total pattern of bands.     

Embryo development in two barley genotypes after self pollination and pollination with Hordeum bulbosum L.

Summary Embryo development in vivo was compared in the two barley genotypes VK 16032 and Vogelsanger Gold after self pollination and after pollination with H. bulbosum. Embryo growth in VK 16032 after crossing with H. bulbosum showed a similar growth pattern to that of the self pollinated embryos, although the size increase was smaller. The hybrid embryos continued to grow until day 18 after pollination. The embryos from the cross between Vogelsanger Gold and H. bulbosum ceased to grow 8 days after pollination. Arrested embryo growth with subsequent abortion in Vogelsanger Gold was associated with a very early depletion and break down of the endosperm. Use of barley genotypes less sensitive to the genomic disturbances after crossing with H. bulbosum in combination with genotypes like Vogelsanger Gold is recommended in haploid breeding work.