Ecotypes and genetic divergence among sympatrically distributed populations of Hordeum vulgare and Hordeum spontaneum from the xeric region of Jordan

Summary The progeny of paired samples of Hordeum vulgare L. and Hordeum spontaneum C. Koch, collected from Jordan's xeric region was used in this study. Statistical analyses of seven easily measured morphometric traits were used to elucidate the relationships and distances between populations of both species, to detect any ecogeographical races, and to study the interrelationships and adjustments in the morphometric traits under study. Flag leaf area and plant height were the two most important discriminating variables which totally separated Hordeum vulgare from Hordeum spontaneum and accounted for 85.3% of total phenotypic variance in the collection. Cluster analysis indicated that the level of divergence among populations of both species was considerably different. Populations of Hordeum vulgare clustered at a maximum Euclidean distance of 2.08, while the maximum distance at which populations of Hordeum spontaneum clustered was 1.49. Three ecotypes each of Hordeum vulgare and Hordeum spontaneum were identified. These ecotypes corresponded to the environmental range of the collection sites. The interrelationships between the seven morphometric traits were adjusted in different ways as revealed by the principal components analysis. Sampling from the different clusters identified in this analysis is expected to increase the allelic diversity for selection and breeding purposes.     

Tolerance ofHolcus lanatus andAgrostis stolonifera to sodium chloride in soil solution and saline spray

Summary Inland and sea cliff populations of bothAgrostis stolonifera L. andHolcus lanatus L. were subjected to soil NaCl treatments, of 100 and 200 mol m⁻³ NaCl, and tolerance examined using plant dry weight data. A parallel experiment subjected them to salt spray treatments of 2.5%, 5% and 10% NaCl in distilled water, and tolerance assessed from leaf damage. Both populations of each species were equally sensitive to soil NaCl. When subjected to salt spray the sea cliff populations however showed marked resistance to leaf damage. Soil salinity resistance and salt spray resistance thus appear to be independent characteristics in these two species.     

Accumulation of selenium by different plant species grown under increasing sodium and calcium chloride salinity

High levels of naturally occurring selenium (Se) are often found in conjunction with different forms of salinity in central California. Plants considered for use in phytoremediation of high Se levels must therefore be salt tolerant. Selenium accumulation was evaluated for the following species under increasing salt (NaCl and CaCl) conditions:Brassica napus L. (canola),Hibiscus cannibinus L. (kenaf),Festuca arundinacea L. (tall fescue), andLotus tenuis L. (birdsfoot trefoil). The experimental design was a complete randomized block with four salt treatments of <1, 5, 10, and 20 dS m^-1, four plant species, three blocks, and six replicates per treatment. Ninety days after growing in the respective salt treated soil with a Se concentration of 2 mg Se kg^-1 soil, added as Na₂SeO₄, all plant species were completely harvested. Among the species tested, shoot and root dry matter yield of kenaf was most significantly (p<0.001) affected by the highest salt treatment and tall fescue and canola were the least affected species. Generally there was a decrease in tissue accumulation of Se with increasing salt levels, except that low levels of salinity stimulated Se accumulation in canola. Canola leaf and root tissue accumulated the highest concentrations of Se (315 and 80 mg Se kg^-1 DM) and tall fescue the least (35 and 7 mg Se kg^-1 DM). Total soil Se concentrations all harvest were significantly (p<0.05) lower for all species at all salt treatments. Removal of Se from soil was greatest by canola followed by birdsfoot trefoil, kenaf and tall fescue. Among the four species, canola was the best candidate for removing Se under the tested salinity conditions. Kenaf may be effective because of its large biomass production, while tall fescue and birdsfoot trefoil may be effective because they can be repeatedly clipped as perennial crops.     

Adaptation to salinity inHordeum jubatum L. populations studied using reciprocal transplants

Tillers and seedlings ofHordeum jubatum L. from three sites with contrasting salinity regimes in central Saskatchewan, Canada were reciprocally transplanted in order to examine the tolerance of populations of this species to salinity and related habitat factors. Survival, growth and fecundity of the three populations were controlled more by transplant site characteristics than by genetic differences, i.e. differences among populations at a site tended to be smaller than differences among sites. Survival, growth and reproduction of all three populations were best at the non-saline site. The population originating at the non-saline site showed the poorest growth in the two saline habitats, but still had substantial salt tolerance. Fecundity was greatest when the populations were grow at their site of origin.     

A barley RFLP map: alignment of three barley maps and comparisons to Gramineae species

Several gene linkage maps have been produced for cultivated barley. We have produced a new linkage map for barley, based on a cross between Hordeum vulgare subsp. spontaneum and Hordeum vulgare subsp. vulgare (Hvs x Hvv), having a higher level of polymorphism than most of the previous barley crosses used for RFLP mapping. Of 133 markers mapped in the Hvs x Hvv F₂ population, 69 were previously mapped on other barley maps, and 26 were mapped in rice, maize, or wheat. Two known gene clones were mapped as well as two morphological markers. The distributions of previously mapped markers were compared with their respective barley maps to align the different maps into one consensus map. The distributions of common markers among barley, wheat, rice and maize were also compared, indicating colinear linkage groups among these species.To be considered dual first authorsPublished with the approval of the Director of the Colorado State University/Agricultural Experiment Station.     

Vegetative salt tolerance of barnyard grass mutants selected for salt tolerant germination

Improving salt tolerance of economically important plants is imperative to cope with the increasing soil salinity in many parts of the world. Mutation breeding has been widely used to improve plant performance under salinity stress. In this study, we have mutagenized Echinochloa crusgalli L. with sodium azide and three selected mutants (designated fows A) with salt tolerant germination. Their vegetative growth was compared to that of the wild type after short-term and long-term salt stress. The germination of the three fows A mutants in the presence of inhibitory concentrations of NaCl, KCL, and mannitol was better than that of the wild type. Early growth of the mutants in the presence of 200 mM NaCl was also better than that of the wild type perhaps due to improved K⁺ uptake and enhanced accumulation of sugars particularly sucrose at least in two mutants. But the three mutants and the wild type responded similarly to long-term salt stress. The tolerance mechanisms during short-term and long-term salt stress are discussed.     

Diversity within and between populations of two sympatrically distributed Hordeum species in Jordan

Summary The diversity of two sympatrically distributed barley species (Hordeum vulgare L. and Hordeum spontaneum C. Koch.) has been assessed for 7 morphometric and 13 qualitative traits. Phenotypically, Hordeum vulgare was more stable than Hordeum spontaneum for all morphometric traits; this is a reflection of domestication and selection. The overall diversity indexes were 0.546±0.125 and 0.502±0.113 for Hordeum vulgare and Hordeum spontaneum, respectively (P=0.095). However, Hordeum spontaneum expressed a higher level of diversity for most qualitative traits. The observed similarity for a number of diversity indexes is probably due to gene flow between the two species.     

Mechanisms of salt tolerance and interactive effects of <Emphasis Type="Italic">Azospirillum brasilense</Emphasis> inoculation on maize cultivars grown under salt stress conditions

The present work has been performed to study the growth and metabolic activities of two maize cultivars (cv. 323 and cv. 324) which are shown to have different tolerances to salt stress and to determine the effects of inoculation with Azospirillum spp. Along with identifying the mechanisms of maize salt tolerance and the role of Azospirillum (growth promoting rhizobacteria) in elevating salinity stress conditions is examined Maize cv. 323 was the most sensitive to salinity, while cultivar 324 was the most resistant of the 12 maize cultivars tested. Cultivars differences were apparent with certain growth criteria as well as related metabolic activities. The lack of a negative response to increasing NaCl concentration for water content, dry matter yield and leaf area of cv. 324 up to a concentration of – 0.6 MPa indicated salt tolerance. While for cv. 323 there was a marked inhibitory effect of salinity on growth. In the tolerant cv. 324, soluble and total saccharides, soluble protein in shoots and total protein in roots increased with salinity stress. The sensitivity of cv. 323 however was associated with depletion in saccharides and proteins. Proline accumulation was higher and detected earlier at a lower salinity concentration in the salt sensitive cv. 323 comapred to the salt tolerant cv. 324. When salt stressed maize was inoculated with Azospirillum, proline concentration declined significantly. The present study showed, in general, that the concentration of most amino acid increased on exposure to NaCl as well as when inoculated with Azospirillum. The relatively high salt tolerance of cv. 324, compared with cv. 323 was associated with a significantly high K⁺/Na⁺ ratio. Azospirillum inoculation markedly altered the selectivity of Na⁺, K⁺ and Ca⁺⁺ especially in the salt sensitive cultivar cv. 323. Azospirillum restricted Na⁺ uptake and enhanced the uptake of K⁺ and Ca⁺⁺ in cv. 323. A sharp reduction in the activity of nitrate reductase and nitrogenase in shoots and roots of both cultivars was induced by salinity stress. This reduction in NR and NA activity was highly significant at all salinity concentrations. Azospirillum inoculation stimulated NR and nitrogenase activity in both shoots and roots of both cultivars. The differential effect of Azospirillum inoculation on maize cv. 323 and cv. 324 illustrates the different sensitivity of these two cultivars to stress, but still does not provide any clues as to the key events leading to this difference.     

Identification,characterization, and comparison of RNA-degrading enzymes of wheat and barley

RNA-degrading enzymes play an important role in regulating gene expression, and sequence analyses have revealed significant homology among several plant RNA-degrading enzymes. In this study we surveyed crude extracts of the above-ground part of the common wheat (Triticum aestivum L.) and the cultivated barley (Hordeum vulgare L.) for major RNA-degrading enzymes using a substrate-based SDS-PAGE assay. Fifteen wheat and fourteen barley RNA-degrading enzymes, with apparent molecular masses ranging from 16.3 to 40.1 kD, were identified. These RNA-degrading enzymes were characterized by their response to pH changes and addition of EDTA and ZnCl₂ to the preincubation or incubation buffers. The 33.2- to 40.1-kD wheat and barley, 31.7-kD wheat, and 32.0-kD barley enzyme activities were inhibited by both zinc and EDTA and were relatively tolerant to alkaline environment. The 22.7- to 28.2-kD enzymes were inhibited by zinc but stimulated by EDTA. The 18.8-kD enzyme exists in both wheat and barley. It was active in an acid environment, was inhibited by zinc, but was not affected by EDTA. Two enzyme activities (31.0 and 32.0 kD) are unique to the common wheat. Contribution from Agriculture Research Division, University of Nebraska, Journal Series No. 9895.     

Salinity induced differences in growth,ion distribution and partitioning in barley between the cultivar Maythorpe and its derived mutant Golden Promise

Dry matter changes and ion partitioning in two near isogenic barley cultivars Maythorpe (relatively salt sensitive) and Golden Promise (relatively salt tolerant) were studied in response to increasing salinity. Although the growth of both cultivars was significantly reduced by exposure to NaCl, the effect was greater in Maythorpe, whilst Golden Promise maintained an increased ratio of young to old leaf blade. Golden Promise maintained significantly lower Na⁺ concentrations in young expanding tissues compared with Maythorpe. Partitioning of Cl^– was evident in that both varieties maintained lower Cl^– concentrations in mesophyll than in epidermal cells. Golden Promise maintained higher K⁺/Na⁺ and Ca²⁺/Na⁺ ratios in young leaf blade and young sheath tissues than Maythorpe when exposed to salt. Differences in ion partitioning and the maintenance of higher K⁺ and Ca²⁺ to Na⁺ ratios, especially in young growing and recently expanded tissues, would appear to be important mechanisms contributing to the improved salt tolerance of Golden Promise.     

Fast growth responses of barley and durum wheat plants to NaCl- and PEG-treatment: resolving the relative contributions of water deficiency and ion toxicity

Effects of adding osmotically comparable concentrations of PEG and NaCl to nutrient solution were studied in 1-week-old durum wheat (Triticum durum Desf., salt-sensitive) and barley (Hordeum vulgare L., more salt tolerant). Both treatments arrested leaf extension immediately, followed by partial recovery within 40–60 min. Similarities and differences were observed between the responses of the two species and between the two treatments. Typically, PEG-treatment increased leaf extensibility of both barley and wheat as measured by changes in leaf extension rate monitored by an electromechanical sensor to which a stretching counter-weight was added. In barley, NaCl-treatment increased extensibility in a similar way to PEG, but in wheat, extensibility did not change within 40 min of NaCl-treatment. The contrasting fast responses of wheat plants to NaCl and PEG treatments suggests that, unlike barley, wheat leaf extension was sensitive not only to osmotic effects of salinity, but also to ion toxicity. Thus, separate PEG- and NaCl-treatments enabled us to distinguish between ionic and osmotic effects and to show, for the first time, that ionic effects of salinity on leaf extension can commence after only short-term exposure (<1 h) in the case of a salt-sensitive species such as durum wheat.     

Response of Barley Lines with Structural Rearrangements in Chromosomes 5, 6 and 7 to Limited Nitrogen Nutrition

The responses of barley (Hordeum vulgare L.) lines with rebuilt chromosomes 5, 6 and 7 to reduced nitrogen nutrition were evaluated in juvenile growth stages. The material included two series of duplications (D) produced in the short arm of chromosome 6 and of chromosome 7, and in the long arm of chromosome 5 and of chromosome 6; their parental translocation lines (T) - from which analyzed duplications were derived and a standard karyotype cv. Bonus as a control. The translocation lines have break points located in 6_S and 7_S, or 5_L and 6_L. Only the lines with duplicated segments of the short arms of satellited (6 and 7) chromosomes exhibited an improved tolerance to reduced nitrogen supply. No changes relative to cv. Bonus were observed in the T-lines. More tolerant D-lines showed lower stimulation of the root development. Obtained results suggests that the adaptability factors for the low N tolerance at the vegetative growth stage of barley are located in the short arms of 6 and 7 chromosomes. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of competition and edaphic conditions on the establishment of halophytes on brine effected soils

In order to test the feasibility of using native halophytes to reclaim brinecontaminated soil, seedlings of five inland halophytes, Atriplexprostrata, Hordeum jubatum, Salicornia europaea, Spergularia marina, and Suaeda calceoliformis, were planted at threedensities on a site near Athens, Ohio which had been contaminated by oilwell brine water. Ten replicates of each density treatment weretransplanted on two distinct areas of high and low salinity in May of 1993. Seedling survivorship, soil moisture, and soil salinity were monitored weeklythroughout the growing season. Biomass production and ion uptake weredetermined for each plant surviving until harvest. Soil analyses wereperformed prior to planting and after harvest to determine overall changesin soil chemistry and to determine the amount of Na⁺ reductionfrom the soil due to leaching by precipitation during the course of theexperiment. Survival was determined to be density independent for all ofthe species with the exception of S. marina where survival wasfacilitated at high density. Increased salinity negatively affected the survivaland yield of A. prostrata. The remaining species had greater survivalunder high salinity conditions, and density appeared to be the key factorinfluencing yield. Sodium and chloride ions were accumulated in planttissues in much greater amounts than K⁺, Ca⁺²or Mg⁺². Salicornia europaea plants grown in high densityon the high salinity site accumulated the highest amount of Na⁺ andH. jubatum grown in low density on the high salinity site accumulatedthe lowest amount of Na⁺. Soil salinities measured directly from theroot zone were significantly reduced (p<0.05) at the end of thegrowing season when compared to their controls. Atriplex prostrata(high density/low salinity) plots produced the greatest reduction in soilsalinity (15.8%) and S. marina (high density/high salinity) plots hadthe least reduction (1.2%).     

Foliar and root absorption of Na+ and Cl− in maize and barley: Implications for salt tolerance screening and the use of saline sprinkler irrigation

Above-canopy sprinkler irrigation with saline water favours the absorption of salts by wetted leaves and this can cause a yield reduction additional to that which occurs in salt-affected soils. Outdoor pot experiments with both sprinkler and drip irrigation systems were conducted to determine foliar ion accumulation and performance of maize and barley plants exposed to four treatments: nonsaline control (C), salt applied only to the soil (S), salt applied only to the foliage (F) and salt applied to both the soil and to the foliage (F+S). The EC of the saline solution employed for maize in 1993 was 4.2 dS m^–1 (30 mM NaCl and 2.8 mM CaCl₂) and for barley in 1994, 9.6 dS m^–1 (47 mM NaCl and 23.5 mM CaCl₂). The soil surface of all pots was covered so that in the F treatment the soil was not salinized by the saline sprinkling and drip irrigation supplied nutrients in either fresh (treatments C and F) or saline water (treatments S and F+S).Saline sprinkling increased leaf sap Na⁺ concentrations much more than did soil salinity, especially in maize, even though the saline sprinkling was given only two or three times per week for 30 min, whereas the roots of plants grown in saline soil were continuously exposed to salinity. By contrast, leaf sap Cl^– concentrations were increased similarly by saline sprinkling and soil salinity in maize, and more by saline sprinkling than saline soil in barley. It is concluded that barley leaves, and to a greater extent maize leaves, lack the ability to selectively exclude Na⁺ when sprinkler irrigated with saline water. Moreover, maize leaves selectively absorbed Na⁺ over Cl^– whereas barley leaves showed no selectivity. When foliar and root absorption processes were operating together (F+S treatment) maize and barley leaves accumulated 11–14% less Na⁺ and Cl^– than the sum of individual absorption processes (treatment F plus treatment S) indicating a slight interaction between the absorption processes. Vegetative biomass at maturity and cumulative plant water use were significantly reduced by saline sprinkling. In maize, reductions in biomass and plant water use relative to the control were of similar magnitude for plants exposed only to saline sprinkling, or only to soil salinity; whereas in barley, saline sprinkling was more detrimental than was soil salinity. We suggest that crops that are salt tolerant because they possess root systems which efficiently restrict Na⁺ and Cl^– transport to the shoot, may not exhibit the same tolerance in sprinkler systems which wet the foliage with saline water. ei]T J Flowers     

The transfer of a powdery mildew resistance gene from Hordeum bulbosum L to barley (H. vulgare L.) chromosome 2 (2I)

Hordeum bulbosum L. is a source of disease resistance genes that would be worthwhile transferring to barley (H. vulgare L.). To achieve this objective, selfed seed from a tetraploid H. vulgare x H. bulbosum hybrid was irradiated. Subsequently, a powdery mildew-resistant selection of barley phenotype (81882/83) was identified among field-grown progeny. Using molecular analyses, we have established that the H. bulbosum DNA containing the powdery mildew resistance gene had been introgressed into 81882/83 and is located on chromosome 2 (2I). Resistant plants have been backcrossed to barley to remove the adverse effects of a linked factor conditioning triploid seed formation, but there remains an association between powdery mildew resistance and non-pathogenic necrotic leaf blotching. The dominant resistance gene is allelic to a gene transferred from H. bulbosum by co-workers in Germany, but non-allelic to all other known powdery mildew resistance genes in barley. We propose Mlhb as a gene symbol for this resistance.     

Growth and mineral nutrition of six rapid-cycling Brassica species in response to seawater salinity

The growth of six rapid-cycling lines of Brassica species, B. napus, B. campestris, B. nigra, B. juncea, B. oleracea and B. carinata was inhibited by seawater salinity. Based on the change in dry matter reduction relative to the control at varying concentrations of salts (4, 8 and 12 dS m^-1), the relative salt tolerance of these species was evaluated. B. napus and B. carinata were the most tolerant and most sensitive species, respectively, while the other four species were moderately tolerant. The influence of seawater on the concentrations of 12 elements including macronutrients and micronutrients in the shoots of these Brassica plants was characterized to determine the relationship between nutritional disturbance and relative salt tolerance. It was found that seawater salinity had a significant effect on the concentrations of Ca, Mg, K, Cl, Na and total N in the shoots of these plants but only the change in Ca concentration was significantly related to the relative salt tolerance of these six rapid-cycling Brassica species according to a rank analysis of the data. This finding indicates that Ca may play a regulatory role in the responses of Brassica species to saline conditions.     

Ion measurements by X-ray microanalysis in unfixed,frozen, hydrated plant cells of species differing in salt tolerance

A technique is described for X-ray microanalysis of unfixed, frozen, hydrated higher plant cells using a scanning electron microscope in conjunction with a cryostage. Freezing in liquid N₂ is the only preparative step required. Using this method, ion distribution was compared in the roots of Zea mays L. (termed a salt excluder) and Hordeum vulgare L. (which is rather more tolerant), both grown in the presence of NaCl. Distinct differences were observed between the two species in Na, K and Cl distribution. Evidence is presented to support the hypothesis that reabsorption of Na from the xylem sap in the mature regions of the root may occur in salt-sensitive glycophytes such as Z. mays.     

Identification of proteins associated with ion homeostasis and salt tolerance in barley

Identification and characterization of proteins involved in salt tolerance are imperative for revealing its genetic mechanisms. In this study, ionic and proteomic responses of a Tibetan wild barley XZ16 and a well‐known salt‐tolerant barley cv. CM72 were analyzed using inductively coupled plasma‐optical emission spectrometer, 2DE, and MALDI‐TOF/TOF MS techniques to determine salt‐induced differences in element and protein profiles between the two genotypes. In total, 41 differentially expressed proteins were identified in roots and leaves, and they were associated with ion homeostasis, cell redox homeostasis, metabolic process, and photosynthesis. Under salinity stress, calmodulin, Na/K transporters, and H⁺‐ATPases were involved in establishment of ion homeostasis for barley plants. Moreover, ribulose‐1,5‐bisphosphate carboxylase/oxygenase activase and oxygen‐evolving enhancer proteins were significantly upregulated under salinity stress, indicating the great impact of salinity on photosynthesis. In comparison with CM72, XZ16 had greater relative dry weight and lower Na accumulation in the shoots under salinity stress. A higher expression of HvNHX1 in the roots, and some specific proteins responsible for ion homeostasis and cell redox homeostasis, was also found in XZ16 exposed to salt stress. The current results showed that Tibetan wild barley XZ16 and cultivated barley cultivar CM72 differ in the mechanism of salt tolerance.     

Characterisation of progeny from backcrosses of triploid hybrids between Hordeum vulgare L. (2x) and H. bulbosum L (4x) to H. vulgare

Interspecific hybridisations between Hordeum vulgare L. (cultivated barley) and H. bulbosum L. (bulbous barley grass) have been carried out to transfer desirable traits, such as disease resistance, from the wild species into barley. In this paper we report the results of an extensive backcrossing programme of triploid hybrids (H. vulgare 2x x H. bulbosum 4x) to two cultivars of H. vulgare. Progenies were characterised cytologically and by restriction fragment length polymorphism analysis and comprised (1) haploid and diploid H. vulgare plants, (2) hybrids and aneuploids, (3) single and double monosomic substitutions of H. bulbosum chromosomes into H. vulgare and (4) chromosomal rearrangements and recombinants. Five out of the seven possible single monosomic chromosome substitutions have now been identified amongst backcross progeny and will be valuable for directed gene introgression and genome homoeology studies. The presence amongst progeny of 1 plant with an H. vulgare-H. bulbosum translocated chromosome and one recombinant indicates the value of fertile triploid hybrids for interspecific gene introgression.     

Response of barley grains to the interactive e.ect of salinity and salicylic acid

Effect of grain soaking presowing in 1 mM salicylic acid (SA) and NaCl (0, 50, 100, 150 and 200 mM) on barley (Hordeum vulgare cv Gerbel) was studied. Increasing of NaCl level reduced the germination percentage, the growth parameters (fresh and dry weight), potassium, calcium, phosphorus and insoluble sugars content in both shoots and roots of 15-day old seedlings. Leaf relative water content (RWC) and the photosynthetic pigments (Chl a, b and carotenoids) contents also decreased with increasing NaCl concentration. On the other hand, Na, soluble sugars, soluble proteins, free amino acids including proline content and lipid peroxidation level and peroxidase activity were increased in the two plant organs with increasing of NaCl level. Electrolyte leakage from plant leaves was found to increase with salinity level. SA-pretreatment increased the RWC, fresh and dry weights, water, photosynthetic pigments, insolube saccharides, phosphorus content and peroxidase activity in the stressed seedlings. On the contrary, Na⁺, soluble proteins content, lipid peroxidation level, electrolyte leakage were markedly reduced under salt stress with SA than without. Under stress conditions, SA-pretreated plants exhibited less Ca²⁺ and more accumulation of K⁺, and soluble sugars in roots at the expense of these contents in the plant shoots. Exogenous application (Grain soaking presowing) of SA appeared to induce preadaptive response to salt stress leading to promoting protective reactions to the photosynthetic pigments and maintain the membranes integrity in barley plants, which reflected in improving the plant growth.