Associations between isozyme phenotypes and environment in the slender wild oat (Avena barbata) in Israel

Summary Collections from 31 populations of A. barbata from diverse habitats in Israel were assayed electrophoretically for seven enzyme systems. Phenotype frequencies were scored in nine enzyme zones, probably representing 27 loci, to determine isozyme variability within and among populations. Many different isozyme phenotypes were found in all of the populations; also the array of isozyme phenotypes found in each population differed distinctly from that found in each other population. Overlays of phenotypic frequencies on map locations showed that isozyme variability is distributed in mosaic patterns not related to geographical distance. Principal-component and multiple-regression analyses revealed that temperature and moisture-related variables are significantly correlated with particular isozyme phenotypes. Further, the mosaic patterns of isozyme variation were found to correspond closely to mosaic patterns of the habitat. This structuring of the genetic variability into multilocus combinations was attributed to the combined effects of directional and diversifying selection. Comparisons of patterns and extent of genetic variation in Israel and California led to the conclusion that the evolution of ecotypes, each adapted to a specific habitat and marked by a particular set of enzyme alleles, has proceeded further in Israel, where A. barbata is endemic, than in California, where it is a recent introduction.This study was supported in part by NSF Grant BMS-01113-A01. Seed collections were supported by a United States-Israel Binational Science Foundation Grant     

Analysis of genetic diversity of hordein in wild close relatives of barley from Tibet

We analyzed genetic diversity in the storage protein hordein encoded at Hor-1, Hor-2 and Hor-3 loci in seeds from 211 accessions of wild close relatives of barley, Hordeum vulgare ssp. agriocrithon and H. vulgare ssp. spontaneum. Altogether 32, 27 and 13 different phenotypes were found for Hor-1, Hor-2 and Hor-3, respectively. A comparison of our results with those of previous studies indicates that Tibetan samples reflect the highest diverse level of hordein phenotypes when compared to samples from Israel and Jordan. This high degree of polymorphism supports the hypothesis that Tibet is one of the original centers of H. vulgare L.Communicated by H.F. Linskens     

Genetic diversity among wild and cultivated barley as revealed by RFLP

Genetic variability of cultivated and wild barley, Hordeum vulgare ssp. vulgare and spontaneum, respectively, was assessed by RFLP analysis. The material consisted of 13 European varietes, single-plant offspring lines of eight land races from Ethiopia and Nepal, and five accessions of ssp. spontaneum from Israel, Iran and Turkey. Seventeen out of twenty-one studied cDNA and gDNA probes distributed across all seven barley chromosomes revealed polymorphism when DNA was digested with one of four restriction enzymes. A tree based on genetic distances using frequencies of RFLP banding patterns was estimated and the barley lines clustered into five groups reflecting geographical origin. The geographical groups of land-race lines showed less intragroup variation than the geographical groups of spontaneum lines. The group of European varieties, representing large variation in agronomic traits, showed an intermediate level. The proportion of gene diversity residing among geographical groups (F_ST) varied from 0.19 to 0.94 (average 0.54) per RFLP pattern, indicating large diversification between geographical groups.     

Polymorphism at rDNA loci in barley and its relation with climatic variables

The variation in length of the intergenic spacer (IGS) region of the ribosomal DNA repeat unit was examined in 63 accessions of wild barley, Hordeum spontaneum, and seven accessions of cultivated barley, Hordeum vulgare. The accessions of wild barley were collected from ecologically diverse climatic and edaphic microsites in Israel, and the barley cultivars were those grown in India. Sixteen spacer-length variants (slvs) observed in the present study presumably belonged to two known rDNA loci (Rrn1 and Rrn2). Each accession had one or more variants, which together represented the rDNA phenotype. The rDNA phenotypes of wild barley accessions were widely diverse and differed substantially from those of cultivated barley. The slv phenotypes and the corresponding alleles were shown to be largely correlated with different climatic, edaphic and ecogeographical microsites and niches (the ”Evolution Canyon” at Lower Nahal Oren, Mount Carmel; and Tabigha, Eastern Upper Galilee Mountains), so that a particular rDNA phenotype of an accession could be used to predict the climate and soil to which the accession belonged. This sharp microsite ecogeographic variation in ribosomal DNA appears adaptive in nature, and is presumably driven by climatic and edaphic natural selection. Received: 1 March 2001 / Accepted: 21 May 2001     

Phenotypic landscapes: phenological patterns in wild and cultivated barley

Phenotypic variation in natural populations is the outcome of the joint effects of environmentally induced adaptations and neutral processes on the genetic architecture of quantitative traits. In this study, we examined the role of adaptation in shaping wild barley phenotypic variation along different environmental gradients. Detailed phenotyping of 164 wild barley (Hordeum spontaneum) accessions from Israel (of the Barley1K collection) and 18 cultivated barley (H. vulgare) varieties was conducted in common garden field trials. Cluster analysis based on phenotypic data indicated that wild barley in this region can be differentiated into three ecotypes in accordance with their ecogeographical distribution: north, coast and desert. Population differentiation (Q_ST) for each trait was estimated using a hierarchical Bayesian model and compared to neutral differentiation (F_ST) based on 42 microsatellite markers. This analysis indicated that the three clusters diverged in morphological but not in reproductive characteristics. To address the issue of phenotypic variation along environmental gradients, climatic and soil gradients were compared with each of the measured traits given the geographical distance between sampling sites using a partial Mantel test. Flowering time and plant growth were found to be differentially correlated with climatic and soil characteristic gradients, respectively. The H. vulgare varieties were superior to the H. spontaneum accessions in yield components, yet resembled the Mediterranean types in vegetative characteristics and flowering time, which may indicate the geographical origin of domesticated barley.     

Correlation between hordatine accumulation, environmental factors and genetic diversity in wild barley (Hordeum spontaneum C. Koch) accessions from the Near East Fertile Crescent

Wild barley shows a large morphological and phenotypic variation, which is associated with ecogeographical factors and correlates with genotypic differences. Diversity of defense related genes and their expression in wild barley has been recognized and has led to attempts to exploit genes from H. spontaneum in breeding programs. The aim of this study was to determine the variation in the accumulation of hordatines, which are Hordeum-specific preformed secondary metabolites with strong and broad antimicrobial activity in vitro, in 50 accessions of H. spontaneum from different habitats in Israel. Differences in the accumulation of hordatines in the seedling stage were significant between different H. spontaneum genotypes from different regional locations and micro-sites. Variation in the hordatine accumulation within genotypes was between 9% and 45%, between genotypes from the same location between 13% and 38%, and between genotypes from different locations up to 121%. Principal component analysis showed that water related factors explain 39%, temperature related factors explain 33% and edaphic factors account for 11% of the observed variation between the populations of H. spontaneum. Genetic analysis of the tested accessions with LP-PCR primers that are specific for genes involved in the biosynthetic pathway of hordatines showed tight correlations between hordatine abundance and genetic diversity of these markers. Multiple regression analyses indicated associations between genetic diversity of genes directly involved in hordatine biosynthesis, ecogeographical factors and the accumulation of hordatines.     

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.     

Ribosomal DNA repeat unit polymorphism in 25 Hordeum species

Summary Tandemly repeated DNA sequences containing structural genes encoding ribosomal RNA (rDNA) were investigated in 25 species of Hordeum using the wheat rDNA probe pTA71. The rDNA repeat unit lengths were shown to vary between 8.5 and 10.7 kb. The number of length classes (1–3) per accession generally corresponded to the number of nucleolar organizing regions (NORs). Intraspecific variation was found in H. parodii, H. spontaneum and H. leporinum, but not in H. bulbosum. Restriction analysis showed that the positions of EcoRI, SacI and certain BamHI cleavage sites in the rRNA structural genes were highly conserved, and that repeat unit length variation was generally attributable to the intergenic spacer region. Five rDNA BamHI restriction site maps corresponded to the following groups of species: Map A — H. murinum, H. glaucum, H. leporinum, H. bulbosum, H. marinum, H. geniculatum; Map B — H. leporinum; Map C — H. vulgare, H. spontaneum, H. agriocrithon; Map D — H. chilense, H. bogdanii; and Map E — remaining 14 Hordeum species. The repeat unit of H. bulbosum differed from all other species by the presence of a HindIII site. The closer relationship of H. bulbosum to H. leporinum, H. murinum and H. glaucum than to H. vulgare was indicated by their BamHI restriction maps.Contribution No. 1169, Plant Research Centre     

Genetic diversity and environmental associations of wild barley,Hordeum spontaneum (Poaceae), in Iran

Genetic diversity and structure of populations of the wild progenitor of barleyHordeum spontaneum in Iran was studied by electrophoretically discernible allozymic variation in proteins encoded by 30 gene loci in 509 individuals representing 13 populations of wild barley. The results indicate that: a)Hordeum spontaneum in Iran is extremely rich genetically but, because of predominant self-pollination, the variation is carried primarily by different homozygotes in the population. Thus, genetic indices of polymorphismP-1% = 0.375, range = 0.267–0.500, and of genetic diversity,He = 0.134, range = 0.069–0.198, are very high. b) Genetic differentiation of populations includes clinal, regional and local patterns, sometimes displaying sharp geographic differentiation over short distances. The average relative differentiation among populations isGst = 0.28, range = 0.02–0.61. c) A substantial portion of the patterns of allozyme variation in the wild gene pool is significanctly correlated with the environment and is predictable ecologically, chiefly by combinations of temperature and humidity variables. d) The natural populations studied, on the average, are more variable than two composite crosses, and more variable than indigenous land races of cultivated barely,Hordeum vulgare, in Iran. — The spatial patterns and environmental correlates and predictors of genetic variation ofH. spontaneum in Iran indicate that genetic variation in wild barley populations is not only rich but also at least partly adaptive. Therefore, a much fuller exploitation of these genetic resources by breeding for disease resistance and economically important agronomic traits is warranted.     

Genetic variation ofHordeum spontaneum in Israel: Eco-geographical races,detected by trait measurements

Samples from 11 populations of wild barley,Hordeum spontaneum, from Israel, were examined for morphological variation in a common garden plot design. Earliness traits had the highest between population variation of all traits studied. No relationship was found between dimensions of leaves and size of seeds.—Using numerical taxonomy methods, four races were found, which correspond to the geographical and environmental range of the species in Israel. It is concluded thatH. spontaneum shows a well developed tendency toward formation of highly adaptive races rather than exhibiting clinical variation.     

Correlation of ecological factors and allozymic variations with resistance toErysiphe graminis hordei inHordeum spontaneum in Israel: Patterns and application

The association of ecological factors and allozymic markers of wild barley,Hordeum spontaneum, with genotypes varying in resistance to 3 cultures of the pathogenErysiphe graminis hordei, which incites the disease powdery mildew of barley, were explored theoretically and practically. The study involved 275 accessions comprising 16 populations largely representing the ecological range ofH. spontaneum in Israel. From earlier studies of allozymic variation and disease resistance it now becomes apparent that genetic polymorphisms for resistance toE. graminis hordei are structured geographically, and are predictable by climatic as well as allozymic variables. Three-variable combinations of temperature and water factors explain significantly 0.32 of the spatial variance in disease resistance between localities. Also, several allozyme genotypes, singly or in combination, are significantly associated with disease resistance. A high correlation was found between the standard deviation of infection types of the culture of the pathogen from Israel, and allozymic polymorphism,P (r_s = 0.86, p < 0.001). Consequently, the IsraelH. spontaneum populations, growing in the center of diversity of the species, contain large amounts of unexploited disease resistance polymorphism. These could be effectively screened and utilized for producing resistant barley varieties by using ecological factors and allozymic variants as guidelines.     

Genetic variation in small,isolated fern populations

Abstract. Differences in genetic variability of several small, isolated populations of four fern species in a restricted area in the Swiss lowlands reflect differences in breeding system, population size, the degree of population fragmentation, and ecological requirements. The investigated populations of Asplenium septentrionale show only little genetic variability (isozyme variation) without gene flow among populations (based on the banding pattern of multi-locus phenotypes), and they persist for long periods despite the small population sizes. In Asplenium ruta-muraria, genetic variability is correlated with age. Young populations show no genetic variation, while old populations show some. All individuals of Polypodium vulgare investigated, either epiphytic or epilithic, share exactly the same enzyme phenotype. The results for these three species can be related to predominance of inbreeding, lack of inbreeding depression, polyploidy, long-distance dispersal, production of large amounts of diaspores, single-spore colonization, and perennial life cycles. Genetic variability in these three species does not seem to be absolutely necessary for the maintenance of their populations. Ecological and demographic factors are considered to be more important. An isolated, glacial relict population of diploid Asplenium viride shows high variability in two out of eight enzyme systems, which may be due to prevailing outbreeding. We discuss aspects of the importance of genetics and life history for conservation biology.     

RAPD Analysis of the Genome in Species of the Genus Hordeum

Random amplification of polymorphic DNA (RAPD) was used to analyze six species, three populations, and seven regional cultivars of barley. A unique pattern of amplified DNA products was obtained for each species of the genus Hordeum.High polymorphism of barley species was revealed. Specific fragments were found in most RAPD patterns; the fragments can be used as molecular markers of corresponding species and subspecies. Several other DNA fragments were shown to serve as molecular markers of the H genome. Specific RAPD patterns were obtained for each population and each cultivar of H. vulgaresensu lato. In total, variation between the populations and between the cultivars was substantially lower than between species. Cluster analysis (UPGMA) was used to estimate genetic distances between theHordeumspecies, between the H. spontaneumpopulations, and between regional H. vulgarecultivars and a dendrogram was constructed.     

Structure and inheritance of ribosomal DNA variants in cultivated and wild hop, Humulus lupulus L.

Genetic variation was assessed among cultivated and wild hop, Humulus lupulus, by restriction fragment length polymorphisms (RFLPs) of the ribosomal RNA genes (rDNA). Two rDNA length variants of 10.3 and 9.3 kbp represented by three phenotypes designated A, B and C were detected with XhoI. Restriction-site mapping showed that hop rDNA is structurally similar to those of most higher plants. A high level of homogeneity existed in rDNA repeat lengths among the diverse hop genotypes. Generally, phenotype A was predominant in wild and cultivated European and Asian genotypes; phenotype B in North American cultivars; while phenotype C was present only in native North American hop, providing a potential molecular marker for the identification of this germ plasm. The rDNA data provided genetic evidence for the separation of native and cultivated American genotypes and supports the hypothesis that North American hop cultivars are of hybrid origin from European and native American genotypes. The segregation of rDNA phenotypes in four F₁ families suggests that a single locus with two co-dominant alleles controls genetic variability for rDNA variants in hop.     

Genetic resources of wild barley in the Near East: structure, evolution and application in breeding

Genetic diversity and structure of populations of the wild progenitor of barley, Hordeum spontaneum, from three countries, Israel, Turkey and Iran, in the Near East Fertile Crescent, are compared and contrasted. The analysis is based on electrophoretically discernible allozymic variation in proteins encoded by 27 shared loci in 2125 individuals representing 52 populations of wild barley. The results indicate that: (a) H. spontaneum in the Near East Fertile Crescent is very variable genetically; (b) genetic differentiation of populations includes some clinal but primarily regional and local patterns often displaying sharp geographic differentiation over short distances; (c) the average relative genetic differentiation (G_st) was 54% within populations, 39% among populations, and 8% between the three countries; (d) allele distribution is characterized by a high proportion of unique alleles (51%), and a high proportion of common alleles that are distributed either locally or sporadically; (e) discriminant analysis by allele frequencies successfully clustered wild barley of each of the three countries (96% correct classification); (f) a substantial portion of the patterns of allozyme variation in the wild gene pool is significantly correlated with the environment and is predictable ecologically, chiefly by a combination of humidity and temperature variables; (g) natural populations of wild barley are, on the average, more variable than two composite crosses and land races of cultivated barley. The spatial patterns and environmental correlates and predictors of genetic variation of H, spontaneum in the Fertile Crescent indicate that genetic variation in wild barley populations is not only rich but at least partly adaptive and predictable by ecology and allozyme markers. Consequently, conservation and utilization programmes should optimize sampling strategies by following the ecological-genetic factors and allozyme markers as effectively predictive guidelines.     

Estimating the outcrossing rate of barley landraces and wild barley populations collected from ecologically different regions of Jordan

The results of previous studies conducted at the University of Hohenheim and the International Center for Agricultural Research in the Dry Areas (ICARDA) indicated that the yielding ability and stability of barley (Hordeum vulgare L.) could be improved in environments with drought stress by increasing the level of heterozygosity. This would require increasing the outbreeding rate of locally adapted breeding materials. As a first step, we estimated the outcrossing rate of 12 barley landraces (Hordeum vulgare ssp. vulgare, in short H. vulgare) and 13 sympatrically occurring populations of its wild progenitor [Hordeum vulgare ssp. spontaneum (C. Koch), in short H. spontaneum] collected from semi-arid localities in Jordan during the 1999/2000 growing season. In each H. vulgare or H. spontaneum population 28–48 spikes were sampled, and up to six offspring (seeds) per spike (called a family) were used for PCR analyses. Collection sites covered high–low transects for rainfall and altitude in order to detect possible environmental effects on the outcrossing rate. Four microsatellite markers located on different chromosomes were used to genotype the samples for estimating the outcrossing rate. Low season-specific multilocus outcrossing rates (t_m) were found in both cultivated and wild barley, ranging among populations from 0–1.8% with a mean of 0.34%. Outcrossing rates based on inbreeding equilibrium (t_e), indicating outcrossing averaged across years, were two- to threefold higher than the season-specific estimates. Under high rainfall conditions somewhat higher—though not significantly higher—outcrossing rates were observed in H. spontaneum than in H. vulgare. The season-specific outcrossing rate in H. spontaneum was positively correlated (r=0.67, P=0.01) with average annual precipitation and negatively correlated (r=0.59, P=0.05) with monthly average temperature during flowering. The results suggest that outcrossing may vary considerably among seasons and that high precipitation and cool temperatures during flowering tend to enhance outcrossing. The rather low levels of outcrossing detected indicate that increased vigour due to heterozygosity has not been a major fitness advantage in the evolution and domestication of H. spontaneum and H. vulgare, respectively. Stable seed production to secure survival under extreme heat and drought stress may have been more important. Cleistogamy may be considered as an effective mechanism to warrant pollination even in drought-stunted plants with non-extruding spikes.     

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.     

Invasion of <Emphasis Type="Italic">Rhynchosporium commune</Emphasis> onto wild barley in the Middle East

Rhynchosporium commune was recently introduced into the Middle East, presumably with the cultivated host barley (Hordeum vulgare). Middle Eastern populations of R. commune on cultivated barley and wild barley (H. spontaneum) were genetically undifferentiated and shared a high proportion of multilocus haplotypes. This suggests that there has been little selection for host specialization on H. spontaneum, a host population often used as a source of resistance genes introduced into its domesticated counterpart, H. vulgare. Low levels of pathogen genetic diversity on H. vulgare as well as on H. spontaneum, indicate that the pathogen was introduced recently into the Middle East, perhaps through immigration on infected cultivated barley seeds, and then invaded the wild barley population. Although it has not been documented, the introduction of the pathogen into the Middle East may have a negative influence on the biodiversity of native Hordeum species.     

Phenotypic plasticity and gene diversity in Pistacia lentiscus L. along environmental gradients in Israel

The Mediterranean common shrub Pistacia lentiscus is distributed in a wide range of habitats along the climatic gradient in Israel. We studied the factors that may shape its morphological, physiological, and genetic differentiation. We examined the phenotypic and molecular genetic variability among and within the six Israeli populations as correlated with the local environmental conditions. The genetic structure of the shrub on the island of Cyprus was also examined. Plant morphological parameters correlated significantly with the local environmental conditions, especially with the annual precipitation and temperature. Gene diversity did not differ significantly among locations, and, hence, no differentiation among Israeli populations or between populations in Israel and Cyprus was found. The major part of the molecular variance (69%) was found within the populations, 22% of the variance was found between Israel and Cyprus and 9% among the populations within the region. Gene flow estimates among all the tested populations were high with no indication for the isolation by distance. We did not find any pattern of ecologically related genetic differentiation; hence, the morphological and physiological differences are probably due to phenotypic plasticity. It seems that the ability of P. lentiscus to express the different phenotypes in response to the varying conditions in the Mediterranean region is an adaptive trait in a species that is characterized by intensive gene flow.     

Genetic diversity and environmental associations of wild barley,Hordeum spontaneum,in Turkey

Genetic variability within and between populations of the wild progenitor of barley was studied electrophoretically. Thirty enzyme loci were assayed in 437 individuals representing 11 populations ofH. spontaneum in Turkey. The results indicated that: (a)H. spontaneum in Turkey is genetically rich in allozyme variation, but because of predominant self-pollination the variation is maintained as different homozygotes in the population; (b) genetic differentiation of populations includes clinal, regional, and local patterns, sometimes displaying sharp geographic differentiation over short distances; (c) overall indices of allozymic diversity and some allele frequencies of wild barley are significantly correlated with the environment and are predictable ecologically, chiefly by combinations of temperature and humidity variables; (d) a high percentage of alleles (66%) occur in local areas or are distributed sporadically rather than widespread; (e) Wright Fixation index was very high, F=0.995; (f) genetic distance was high (D=0.11, ranging from 0.031 to 0.288) between populations, and (g) average relative genetic differentiation was high among populations (Gst=0.47, ranging from 0.02 to 0.66). The spatial patterns and environmental correlates and predictors of genetic variation ofH. spontaneum in Turkey, indicated that genetic variation in wild barley populations is not only common, but also at least partly, adaptive. Therefore, a much fuller exploitation of these genetic resources by breeding is warranted.