Journal of Experimental Botany, Vol. 51, No. 342, pp. 9-17,
January 2000
© 2000 Oxford University Press
Wild barley: a source of genes for crop improvement in the 21st century?
Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
Received 25 February 1999; Accepted 13 October 1999
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Abstract |
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The development of new barleys tolerant of abiotic and biotic stresses is an essential part of the continued improvement of the crop. The domestication of barley, as in many crops, resulted in a marked truncation of the genetical variation present in wild populations. This process is significant to agronomists and scientists because a lack of allelic variation will prevent the development of adapted cultivars and hinder the investigation of the genetic mechanisms underlying performance. Wild barley would be a useful source of new genetic variation for abiotic stress tolerance if surveys identify appropriate genetic variation and the development of marker-assisted selection allows efficient manipulation in cultivar development. There are many wild barley collections from all areas of its natural distribution, but the largest are derived from the Mediterranean region. The results of a range of assays designed to explore abiotic stress tolerance in barley are reported in this paper. The assays included; sodium chloride uptake in wild barley and a mapping population, effects for
13C and plant dry weight in wheat aneuploids, effects of photoperiod and vernalization in wild barley, and measurements of root length in wild barley given drought and nitrogen starvation treatments in hydroponic culture. There are examples of the use of wild barley in breeding programmes, for example, as a source of new disease resistance genes, but the further exploration of the differences between wild barley and cultivars is hampered by the lack of good genetic maps. In parallel to the need for genetic studies there is also a need for the development of good physiological models of crop responses to the environment. Given these tools, wild barley offers the prospect of a ‘goldmine’ of untapped genetic reserves. Key words: Abiotic stress, genetic diversity, germplasm collections, SSR, barley
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Introduction |
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The improvement of abiotic stress tolerance in the barley crop (Robinson et al., 2000
) depends on understanding the range of genetic variation possessed by cultivated barley (Hordeum vulgare subsp. vulgare L.) and wild barley (H. vulgare subsp. spontaneum C. Koch.). In turn, the rate of progress depends on the occurrence of genetic variation desirable for crop development and the availability of precise methods of gene transfer and selection.
The development of dense chromosome maps, based on molecular markers, has permitted the detection of quantitative trait loci (QTL) (Hayes et al., 1997; Thomas et al., 1998) for a range of characters in cultivated barley. This gives potential for the study of genetic mechanisms underlying field performance and reveals the need for new genetic variation. Even in the relatively benign environments experienced in Scotland, where spring barley crops have higher yield potential than in southern England (Ellis and Kirby, 1980), periodic drought can depress yield (Russell and Ellis, 1988). While such cycles of yield depression in this type of situation may not cause famine it is still desirable to improve the abiotic stress tolerance of cultivars to enhance crop reliability. World-wide, environments are more extreme with drought and salinity causing widespread problems. In addition, the anticipated problems associated with human population increase and the lack of water available for agriculture mean that water-efficient crops are required. In particular situations the ability to use saline water for crop irrigation may be an advantage, requiring greater salt tolerance in crops.
Surveys of the genetic variation in wild barley and studies of the process of domestication show that cultivars represent only a part of the range of variation seen in wild populations. In particular, the loss of rare alleles (Saghai Maroof et al., 1990) may be particularly significant, as it has been reported that genetic diversity is greatest in populations from the most highly stressed environments (Nevo et al., 1997). A re-examination with simple sequence repeats (SSR), a more informative genetic assay than dominant markers (Powell et al., 1996), has shown that the actual situation is more serious than previously thought, as only some 40% of the alleles found in wild barley are present in cultivars (JR Russell, unpublished results).
Wild barley and Middle Eastern landraces have already proven to be a very fruitful source of genes for modern crop improvement. A notable example is the development of the mlo resistance to powdery mildew (reviewed by Thomas et al., 1998), which took place over a period of 40 years. There are fewer examples of useful genes for grain quality than disease resistance, probably because quantitative variation in endosperm composition confers few evolutionary advantages. However, it has been shown that desert populations consisted of slender plant types with thinner husk and lower grain milling energy (Ellis, et al., 1993) and the variation for ß-amylase has been analysed (Erkkila et al., 1998).
Cultivated barley and its wild relative have been considered by a number of authors to be both the same and different species (Bothmer et al., 1995). There is a range of flowering habit in cultivated barley from out-pollination to fully closed flowering (cleistogamy), particularly emphasized in the development of cultivars, for example, Proctor, resistant to loose smut (Ustilago nuda (Jens) Rostr). This taxonomic discussion is important in that it focuses on the utilization of the germplasm. While wild and cultivated barley are inter-fertile, introgression does not occur in the majority of cultivated crops. Hence, crossing programmes do not enrich wild populations and are only intended to transfer particular attributes into cultivars. The wide differences between wild and cultivated barley for a number of traits (Paterson et al., 1995) have meant that backcrossing has been the technique most widely used in cultivar improvement with wild barley germplasm.
Desert populations may be considered a source of valuable genes, for example, low milling energy (Ellis et al., 1993), but often physiological mechanisms interact with environments in a complex manner. It was expected that plants in desert populations would show ‘high water use efficiency’, but in fact they exploit sporadic rainfall and actually ‘squander’ water (Handley et al., 1994). This highlights the need to develop appropriate physiological models in parallel to exploring the genetic architecture of barley. The development of physiological models is, in turn, dependent on genetic variation. It was suggested that the model of genetical and environmental control of flowering in Arabidopsis (Weigel, 1995) can be applied to barley (Hay and Ellis, 1998). The model implies the interaction of some 30 known genes and so it is evident that wide allelic variation over such a large number of loci is important for their discovery.
Time of flowering is an important event in the life cycle because it defines the time at which grain growth begins. In temperate climates time of flowering effectively defines yield potential. Time of flowering is affected by genes controlling the response to vernalization, to differences in daylength and earliness per se (Hackett et al., 1992; Laurie et al., 1995; Bezant et al., 1996; Laurie, 1997). The genetic diversity of chromosome 4H has been explored in the light of previous reports (reviewed by Forster et al., 1997) of genes associated with 13C/12C discrimination (Handley et al., 1994; Ellis et al., 1997), drought tolerance (Chalmers et al., 1992) and sodium discrimination in wheat (Gorham et al., 1987). In this paper, consideration is given to the need for new genetic variation, its possible sources, methods of identification, and developments to facilitate gene transfer. In particular, the role of hydroponic experiments that provide flexible, rapid assays for the selection of genotypes with contrasting traits for subsequent testing in field trials are examined (Forster et al., 2000).
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Materials and methods |
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Plant material: hydroponic experiments
Experiment 1: reaction to sodium chloride, effects on sodium and chloride uptake, plant dry weight and
13C.Seed of 57 doubled haploids from the cross HS92xLina (HS92 is an accession of H. spontaneum from Canada Park, Israel), 30 wild barley genotypes, i.e. one genotype selected randomly per population (Pakniyat et al., 1997
), Chinese Spring (CS) wheat, Betzes barley, and wheat disomic addition lines for barley chromosome 4, i.e. 4H, 4Hch, 4HS, and 4HL were grown in the same experiment. Later, assay by AFLP indicated a number of duplicate genotypes in the HS92xLina doubled haploids that may have arisen in tissue culture so, after elimination of the duplicates, data were available for 53 doubled haploids. The disomic 4H is derived from cv. Betzes and 4Hch from Hordeum chilense and S and L denote the presence of the short and long arms, respectively of Betzes 4H. Seeds were germinated in Petri dishes and then transplanted into open-ended centrifuge tubes packed with dampened perlite.
The seedlings were established at laboratory temperatures for 7 d (coleoptile fully emerged), and then the tubes were transferred to a controlled environment maintained at 4 °C and lit by high-pressure sodium lamps at 300 µmol m-2 s-1 for an 18 h day. After vernalization for 6 weeks the tubes were put, on 11 September 1995 (day 1), into solution culture in a glasshouse maintained between 16–24 °C with natural daylight supplemented by high-pressure sodium lamps at 300 µmol m-2 s-1 for 16 h d-1. External air was supplied continuously by ventilation and an extractor fan to maintain source CO2 and its 13C constant.
The experimental design consisted of five replicates of a randomized block, arranged so that each replicate, consisting of a control and a salt treatment, was contained within six tubs. In each tub, 36 experimental plants were surrounded by 26 guard plants and the hydroponic solution was continuously and vigorously aerated (as in Robinson et al., 2000).
After a further 10 d growth in the glasshouse (day 11, when the seedlings had 2–3 fully emerged main stem leaves), NaCl was added to the salt treatments in equal increments every 2 d between 21 September and 3 October 1995 (day 23). The final concentration was 175 mol m-3 and this was maintained until harvest on 11 October 1995 (day 31), just after the control treatment started to show lodging (seedlings showed 5–8 fully emerged main-stem leaves). CaCl2 was added to maintain a Na+ to Ca2+ ratio of 20 : 1.
Whole shoots of the HS92xLina doubled haploids were oven-dried, milled in a ball mill and analysed for 13C (Handley et al., 1993). The wild barley genotypes and Chinese Spring (CS) wheat, Betzes barley, and wheat disomic addition lines were also milled and 10 mg of each sample was placed into an Eppendorf tube. 1 ml of deionized water was added, the mixture was mixed with a vortex mixer and left for at least 1 h to dissolve salts. Shoot Na+ and Cl- content was measured using Ion Sensing Electrodes (Lazar, ISM-146) and readings converted to mg of sodium and chloride g-1 DM.
Experiment 2: drought and nitrogen starvation effects on root length.
Seeds of 30 H. spontaneum genotypes from sites in the Middle East (Pakniyat et al., 1997) were germinated on 13 September 1996. Three days later, when roots were 5–6 mm long, seedlings were transplanted into open-ended centrifuge tubes filled with 0.8% agar containing 200 mg l-1 benzimidazole to suppress fungal pathogens and cultured in solution (Robinson et al., 2000). The length of roots, from the grain to the tip of the longest root, was measured for each plant on 20 September 1996 (day 16), when plants had 4–6 fully emerged leaves.
Time of flowering studies
Seeds of 39 wild barley lines (Pakniyat et al., 1997), i.e. one genotype selected randomly from each population, were germinated in Petri dishes and sown into pots of peat-based compost. Seedlings were vernalized at 4 °C for 6 weeks in 8 h day, lit by high-pressure sodium lamps at 300 µmol m-2 s-1. After vernalization, replicated layouts of the plants were grown in controlled environments with 10 h and 16 h day lengths. In addition, vernalized and unvernalized plants were grown in a glasshouse maintained between 16–24 °C with natural daylight supplemented by high-pressure sodium lamps at 300 µmol m-2 s-1 for 16 h d-1.
Time of flowering was observed as the time at which 1 cm of awn had emerged from the flag leaf sheath of the main stem. Plant height (cm) was also measured on the main stem, from the coleoptile node to the neck, ear length (mm) was taken from the neck to the base of the lemma awn of the uppermost grain and awn length (mm) measured from the base of the lemma awn of the uppermost grain tip to the tip of the longest awn.
Where appropriate, data from all the experiments were analysed first with the REsidual Maximum Likelihood (REML) procedure (Horgan and Hunter, 1993) to establish the absence of block effects and then by analysis of variance to investigate the significance of treatment effects.
SSR assays
DNA was isolated from the wild barley genotypes and was used to score four SSRs whose map locations were already known (Waugh et al., 1997). Primer sequences and amplification conditions for two of these markers, HVM3 and HVM 67, have been published previously (Lui et al., 1996). Two further markers HvOLE and Bmac0181were developed at the Scottish Crop Research Institute and primer sequences and amplification conditions are available over the Internet after registration by email with estew{at}scri.sari.ac.uk. The SSRs were scored by estimating the product size in relation to a standard marker.
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Results |
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Na/Cl uptake in H. vulgare s.l.
Wild barley accessions showed a significant genotype effect for sodium and chloride concentration (Table 1
). Sodium and chloride composition showed no significant relationship to each other, but genotypes sampled from Canada Park, Israel; Shahabad-e Gharb in Iran and the Turkish sites Gaziantep and Urfa showed lower sodium concentration than the average (Fig. 1). These genotypes contrast with plants from Mehran and Symarch, sites in Iran, in which sodium was most concentrated.
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Scores of sodium and chloride concentration in doubled haploids from the cross LinaxCanada Park showed significant genetic effects but only for chloride (Table 1). An attempt to locate QTLs for chloride and sodium concentration failed to find significant marker/trait associations for markers on chromosome 4H.
Dry weight and 13C
Chinese Spring (CS), Betzes and the barley chromosome 4H disomic additionlines showed significant treatment and genotype effects on plant weight and shoot 13C (Table 2). The largest plants in the Control were the 4HL and the Hordeum chilense 4Hch addition lines while the 4H and 4HS additions were similar to Betzes andChinese Spring, respectively. In the Salt treatment the 4HL and 4Hch addition lineswere also the heaviest and the remaining genotypes did not differ. These data imply the existenceof a factor concerned with seedling salt tolerance, expressed as dry weight, on chromosome 4HLbut do not indicate whether or not Na+/K+ discrimination is involved.
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In the case of 13C/12C discrimination the data show a significantly different pattern. In the Salt treatment the 4H and 4HL addition lines showed a morenegative
13C than Chinese Spring or Betzes, but the 4Hch addition was only slightly more tolerant than Chinese Spring. In the Control Betzes, Chinese Spring and the 4HS and 4Hch disomic addition lines showed similar 13C values while 13C for the 4HL addition and 4H additions was more negative than Chinese Spring. The reaction of the 4H disomic addition line indicates that the stomata of this genotypewere more often open and that water conduction through the plant was greater than in Chinese Spring or Betzes. The reason for this response is unknown; it may indicate ‘tolerance’ of waterculture and further explanation requires a more precise definition of the genotype of the addition line.
Flowering time, plant morphology and root length
Flowering under controlled conditions was variable (Table 3) with highly significant effects of 10 h and 16 h photoperiods and vernalization treatments. The shortest time to flowering was seen in the vernalized plants while, in contrast, the longest time to flowering was found in the plants grown in 10 h days.
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Photoperiod differences resulted in significant effects on plant morphology (Table 3a) as ear length and plant height were greater in long days, but awn length was reduced. Vernalization treatments also had morphological consequences (Table 3b), possibly more significant in situ than photoperiod effects, with early flowering after vernalization associated with longer ears and awns but shorter plants.
The analysis of variance for root length in wild barley genotypes,given a series of treatments, in solution culture, showed highly significant treatment and genotype effects (Table 4).In addition, the analysis detected significant genotype with treatment interaction. Root length, relative to the control, was reduced (to about 50%) by the Drought treatment but increased (to125%) by the Nitrogen starvation treatment. This does not mean that the greatest total root length or biomass (Robinson et al., 2000) occurred in the Nitrogen starvation treatment since,while being longer overall, roots of the Nitrogen starvation treatment had fewer laterals.
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Root length may have biological importance in allowing the exploitation of soil water and mineral nutrients. No assays of the uptake of mineral nutrients are reported, as this study is a survey of genetic differences that depend on unknown mechanisms. Root length was shortest inthe Canada Park sample (mean 14.9 cm) and longest in the sample from Urfa (mean44.4 cm). There was no obvious relationship between mean root length and theenvironmental data reported (Pakniyat et al., 1997
), for example,both Canada Park and Urfa tend to the driest extremes of the sites reported. In contrast, the sample from the wettest site, Mt. Hermon, ranked eight with a mean root length of36.7 cm, i.e. close to the driest site, Mehran, that, with a mean root length of33.1 cm, ranked tenth. It may be more appropriate to assess response relative to the Control treatment rather than the absolute responses. The smallest relative response to the Drought treatment was seen in the Bitlis (20) and Gawdar (6) samples and the largest in Canada Park (39). For the Nitrogen starvation treatment the smallest response was in the Nahal Oren (36)sample and the largest in both the Gaziantep samples (11, 12). While it may be difficult to relate the differences reported to simple environmental measures, it is hypothesized that the underlying genetic differences are related to environmental responses, and this hypothesis is testable insubsequent studies.
Significant negative correlations were found between flowering time and root length (Table 5), particularly for plants given avernalization treatment and grown in the glasshouse (VGH). The time from germination to flowering delimits the period for growth and differentiation at the stem apex and, by analogy, the corelations reported may indicate a similar regulatory effect for root growth. In the context of theuse of germplasm for cultivar improvement the correlations that were found imply significant problems in the manipulation of phenotypic characters. Marker assisted selection procedures offer the optimum solution.
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SSR
Variation in SSR on chromosome 4H is summarized in Table 6.Two of the loci assayed on chromosome 4H, i.e. HVM3, in the Rubisco activase gene, and Bmac0181 had more alleles than HvOLE and HVM67. The driest and wettest environments tested (Pakniyat et al., 1997) were Mehran and Mt. Hermon, which show contrasting alleles at all the loci assayed. Similarly, environmental extremes of temperature and moisture were associated with wide genetic diversity. The alleles in the wild barley lines can be contrasted with those in the cultivar Blenheim in which the HVM3 allele was of the same size as that found in the wild barley growing at the driest site and the HVM67 allele was not represented in the wild barley samples. The SSR HVM3 in the gene coding for Rubiscoactivase has a wide range of alleles and provides an extreme example of the effects of domestication as in 50 wild barley accessions there were 17 alleles while in 101 cultivars there were nine (JR Russell, unpublished data).
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Discussion |
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The dilemma faced by gene bank curators has always been that evaluation of the accessions is necessary before they can be routinely used in breeding programmes. Alternately, the use of exotic material in a breeding programme often necessitates a ‘pre-breeding programme’ to move useful genes into an adapted background. While there are outstanding examples of success in the transfer of disease resistance from exotic sources into modern cultivars (Thomas et al., 1998
), there are also examples of complex disease resistances leading to problems with malting quality.
Studies of canopy development and dry weight accumulation show that modern cultivars are vulnerable to reduced rainfall in the early summer even in the UK (Russell and Ellis, 1988). Careful analysis of the adaptation of barley to harsh Mediterranean environments has illuminated the role of plantmorphology, apical development and, particularly, drought avoidance by appropriate time of flowering (van Oosterom and Acevedo, 1992a, b, c). The time of flowering in wild populations depends on the profundity of post-harvest dormancy (Guttermann and Gozlan, 1999) and seedling responses to temperature and light (Kirby and Ellis, 1980). As profound dormancy is not a useful trait in malting barley the present study concentrated on day length and vernalization responses.
Some of the contrasts in environmental stresses that exist in wild barley populations and cultivars can be usefully enumerated in Table 7.
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The environmental contrasts between the Mediterranean Region and north-west Europe are an essential reason for much of the loss of genetic variability in the production of cultivars. They may not be the most important reasons for the loss of variability asselection for heading date, ear and seed traits are of greater importance (Paterson et al., 1995
).
The genetic heterogeneity of wild populations has long been recognized as an important mechanism of adaptation to the environment (Nevo et al., 1997). Commercial pressures in crop production ensure the greatest possible morphological and developmental uniformity in crops but with the consequence of vulnerability to biotic and abiotic stresses. The application of contemporary genetical techniquesto barley breeding will allow the better definition of traits determining stress tolerance and realize the potential for the construction of appropriate cultivar mixtures.
There is as yet no demonstration of successful transfer of greater drought tolerance into European cultivars. This is not surprising in view of the complexity of the possible mechanisms that underlie droughttolerance (van Oosterom and Acevedo, 1992a, b, c). In breeding programmes it is not possible to manipulate such complex characteristics with the sole use of conventional phenotypic assays.The assessment of characters such as rate of apex differentiation, harvest index, stem soluble carbohydrate content or yield in drought is often too complex to be justified. Appropriate marker/trait associations are needed to define drought responses at the level of the plant cell andorgan. These markers can then be used in the selection of the appropriate alleles in breeding programmes. It is suggested that the development of methods to test seedlings in controlled environments is a useful step (see Table 5; Robinson et al., 2000) in examining such marker/trait associations. For example, unpublished data from this laboratory indicate that the effects of dwarfing genes observed in the field are mimicked in solution culture. This hypothesis has been examined by identifying extreme genotypes in solution culture, backcrossing them with local cultivars and the SSR genotyped recombinants tested at Mediterranean sites in northern Africa (Forster et al., 2000).
Germplasm collections can be made systematically by exploiting potential genoclines associated with known ecoclines. The success of this non-random sampling of genetic diversity depends on a number of factors. For example,the innate genetic diversity of the species, the flowering habit, the nature of migration and the extent of selection by environmental components. This work is a further illustration that theFertile Crescent contains considerable variation between populations. These genetic differences are reflected in physiological characteristics and now the challenge is to devise marker assisted selection techniques to make this variation available for crop improvement. This survey provides a starting point for detailed studies of genetic variation in barley for economically importanttraits. Crosses between cultivars and Hordeum vulgare subsp. spontaneumgenotypes that contrast for physiological traits and the creation of mapping populations will permit more detailed genetic analysis. The identification of QTL and in special cases, genecloning, are steps in the process of building a programme for the genetic manipulation of abiotic stress tolerance (Forster et al., 2000) without using transformation.
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Acknowledgments |
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The Scottish Crop Research Institute receives grant in aid from The Scottish Executive Rural Affairs Department. We thank E Nevo, University of Haifa, for the gift of the seed and S Holdus for technical assistance. We thank the anonymous referees for very helpful and constructive comments.
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1 To whom correspondence should be sent. Fax: +44 1382 568507. E-mail: ellis@scri.sari.ac.uk
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References |
|---|
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Bezant J,Laurie D, Pratchett N, Chojecki J, Kearsey M. 1996. Marker regression mapping of QTL controlling flowering time and plant height in a spring barley cross (Hordeumvulgare L.). Heredity 77, 64–73.
Bothmer R von, Jacobsen N,Baden C, Jorgensen RB, Linde-Laursen I. 1995. An ecogeographical study ofthe genus Hordeum. Systematic and ecogeographical studies on crop genepools, 7, 2nd edn. Rome: IPGRI.
Chalmers KJ, Waugh R, Watters J, Forster BP, Nevo E, Abbott RJ,Powell W. 1992. Grain isozyme and ribosomal DNA variability in Hordeumspontaneum populations from Israel. Theoretical and Applied Genetics 84, 313–322.
Ellis RP, Forster BP, Waugh R, Bonar N, Handley LL, Robinson D, Gordon D, Powell W. 1997. Mapping physiological traits in barley. New Phytologist 137, 149–157.
Ellis RP, Kirby EJM. 1980. A comparison of spring barley grown in England and Scotland. 2. Yield and its components. Journal of Agricultural Science, Cambridge 95, 111–115.
Ellis RP,Nevo E, Beiles A. 1993. Milling energy polymorphism on Hordeumspontaneum C. Koch in Israel and its potential utilization in breeding for malting quality. Plant Breeding 111, 78–81.
Erkkila MJ, Leah R, AhokasH, Cameron Mills V. 1998. Allele-dependent barley grain beta-amylase activity. Plant Physiology 117, 679–685.
Forster BP, Russell JR, Ellis RP, Handley LL, Robinson D, Hackett CA, Nevo E, Waugh R, Gordon DC, Keith R, Powell W. 1997. Locating genotypes and genes for abiotic stress tolerance in barley, astrategy using maps, markers and species. New Phytologist. 137, 141–147.
Forster BP, Ellis RP, Thomas WTB, Newton AC, Tuberosa R, This D, El-Enein RA,Bahri MH, Ben Salem M. 2000. The development and application of molecular markers for abiotic stress tolerance in barley. Journal of Experimental Botany 51, 000–000.
Gorham J, Hardy C, Wyn Jones RG, Joppa LR, Law CN. 1987. Chromosomal location of a K/Na discrimination character in the D genome of wheat. Theoretical and Applied Genetics 74, 584–588.
GuttermanY, Gozlan S. 1999. After ripening, amounts of rain for germination and seedling drought tolerance of local and edaphic geno-ecotypes of Hordeum spontaneum C. Koch.From Israel. In: Wasser SP, ed. Evolutionary theory and processes: modern perspectives. Dordrecht: Kluwer Academic Press.
Hackett CA, Ellis RP, Forster BP, McNicol JW, Macaulay M. 1992.Statistical analysis of a linkage experiment in barley involving quantitative trait loci for height and ear-emergence time and two genetic markers on chromosome 4. Theoretical and Applied Genetics 85, 120–126.
Handley LL, Daft J, Scrimgeour CM, Ingleby K, Sattar MA. 1993. Effects of the ecto- and VA-mycorrhizal fungi Hydnagium carneum and Glomus clarum on the 15N and 13C values of Eucalyptus globus and Ricinus communis. Plant, Cell and Environment 16, 375–382.
Handley LL, Nevo E, RavenJA, Martinez-Carrasco R, Scimgeour CM, Pakniyat H, Forster BP. 1994.Chromosome 4 controls potential water use efficiency (13C) in barley. Journal of Experimental Botany 45, 1661–1663.
Hay RKM, Ellis RP. 1998. The control of flowering in wheat and barley: what recent advances inmolecular genetics can reveal. Annals of Botany 82, 541–554.
Hayes PM, Cerono J, Witsenboer H, et al. 1997.Characterizing and exploiting genetic diversity and quantitative traits in barley (Hordeumvulgare) using AFLP markers. Journal of Quantitative Trait Loc 3, 1–15. http//probe.nalusda.gov.8000/otherdocs/jqtl
Horgan GW, Hunter EA. 1993.Introduction to REML for scientists. BioSS, Edinburgh: University of Edinburgh.
Kirby EJM, Ellis RP. 1980. A comparison of spring barley grown in England and Scotland. 1. Shoot apex development. Journal of Agricultural Science, Cambridge 95, 101–110.
Laurie DA. 1997.Comparative genetics of flowering time. Plant Molecular Biology 35, 167–177.[Web of Science][Medline]
Laurie, DA, Pratchett, N, Bezant, JH, Snape JW. 1995. RFLP mapping of five major genes and eight QTL controlling flowering time in a winterxspring barley (Hordeum vulgare L.) cross. Genome 38, 575–585.
Lui ZW, Biyashev RM, Saghai Maroof MA. 1996. Development of simple sequence repeat DNA markers and their integration into a barley linkage map. Theoretical and Applied Genetics 93, 869–876.
Nevo E, Apelbaum-Elkaher I, Garty J, Beiles A. 1997. Natural selection causes microscale allozyme diversity in wild barley and a lichen at ‘Evolution Canyon’ Mt. CarmelIsrael. Heredity 78, 373–382.
Pakniyat H, Powell W,Baird E, Handley LL, Robinson D, Scrimgeour CM, Nevo E, Hackett CA, Caligari PDS, Forster BP. 1997. AFLP variation in wild barley (Hordeum spontaneum C.Koch) with reference to salt tolerance and associated ecogeography. Genome 40, 332–341.
Paterson AH, Lin Y-R, Li Z, Schertz KF, Doebley JF, PinsonSRM, Liu S-C, Stansel JW, Irvine JE. 1995. Convergent evolution of cereal cropsby independent mutations at corresponding genetic loci. Science 269, 1714–1718.
Powell W, Morgante M, Doyle JJ, McNicol JW, Tingey SV, RafalskiJA. 1996. Genepool variation in Genus Glycine subgenus Sojarevealed by polymorphic nuclear and chloroplast microsatellites. Genetics144, 793–803.
Robinson D, Handley LL, Scrimgeour CM, Gordon DC, Forster BP, Ellis RP. 2000. Using stable isotope natural abundances (15N and 13C) to integrate the stress responses of wild barley (Hordeum spontaneum C. Koch.)genotypes. Journal of Experimental Botany 51, 000–000.
Russell G, Ellis RP. 1988. The relationship between leafcanopy development and yield of barley. Annals of Applied Biology 113, 357–374.
Saghai Maroof, MA, Allard, RW, Zhang, Q. 1990. Genetic diversity and ecogeographical differentiation among ribosomal alleles in wild and cultivated barley. Proceedings of the National Academy of Sciences, USA 87, 8486–8490.
Thomas WTB, Baird E, Fuller J, Lawrence P, Young GR, Russell JR,Ramsay L, Waugh R, Powell W. 1998. Identification of a QTL decreasing yield in barley linked to Mlo powdery mildew resistance. Molecular Breeding 4, 381–93.
van Oosterom EJ, Acevedo E. 1992a. Adaptation of barley (Hordeum vulgare L) to harsh Mediterranean environments. I. Morphological traits. Euphytica 62, 1–14.
van Oosterom EJ, AcevedoE. 1992b. Adaptation of barley (Hordeum vulgare L) to harshMediterranean environments. II. Apical development, leaf and tiller appearance. Euphytica 62, 15–27.
van Oosterom EJ, Acevedo E. 1992c. Adaptation of barley (Hordeum vulgare L) to harsh Mediterranean environments. III. Plant ideotype and grain yield. Euphytica 62, 29–38.
Waugh R, Macaulay M, McLean K, Fuller J, Bonar N, Ramsay L, Powell W. 1997. Development of a simple sequence repeat-based linkage map in barley. In: Annual Report of the Scottish Crop Research Institute for 1996/7, 82–84.
Weigel D. 1995. The genetics of flower development: from floral induction to ovule morphogenesis. Annual Review of Plant Physiology and Plant Molecular Biology 29, 19–39.
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 V. Ivandic, C.A. Hackett, Z.J. Zhang, J.E. Staub, E. Nevo, W.T.B. Thomas, and B.P. Forster Phenotypic responses of wild barley to experimentally imposed water stress J. Exp. Bot., December 1, 2000; 51(353): 2021 - 2029. [Abstract] [Full Text] [PDF]
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