Genetic diversity in Hordeum agriocrithon E. Åberg, six-rowed barley with brittle rachis, from Tibet

Twenty-two accessions of H. agriocrithon from Tibet were investigated for morphological and physiological characters, and genotypes combined alleles at the tightly linked Est1, Est2 and Est4 complex locus encoding esterase isozymes. H. agriocrithon was similar in plant type to Tibetan cultivated barley, but different from H. spontaneum. The accessions of H. agriocrithon were classified by their spike-awn types into vars. eu-agriocrithon, dawoense and paradoxon, with one exceptional accession of the awnless naked type similar to var. nuditonsum of cultivated barley. They were characterized by spring growth habit, susceptibility to Japanese race I of powdery mildew, and either of the same three esterase genotypes as those of cultivated barley from Tibet, Bhutan and Ladakh. The similarity suggested that the esterase complex locus on chromosome 3H is closely linked with some QTL for adaptation to Tibetan conditions. On the origin of H. agriocrithon, it might be concluded that natural hybridization between H. spontaneum and six-rowed barley occurred in northern parts of Afghanistan, Pakistan or India, and seeds of their segregants mixed into barley or wheat were brought up to Tibet, resulting six-rowed barley with brittle rachis.     

Could early gene flow have created similar allozyme-gene frequencies in cultivated and wild barley?

The possible role of early gene flow between wild and cultivated barley in their similar esterase gene frequencies was tested in a simulation study. The hypothetical population consisted of 99.9% wild forms possessing three alleles of an esterase gene and 0.01% domesticated forms possessing one of these esterase alleles. Various rates of inbreeding, selection coefficients against the wild form and shifting cultivation methods were tested for their effect on the establishment of the domesticated form and the esterase gene flow between the two barley types. Of these factors, inbreeding rates, in the range of 90–99%, had the smallest effect on the establishment of the domesticated form under primitive cultivation. Via gene flow, the esterase allelic frequency in the domesticated form could be similar to that of the wild form under 90% outcrossing in the domesticated form for 115–230 years, an unrealistic situation for barley which normally exhibits about 1% outcrossing. It seems, therefore, that the similar esterase allelic frequencies in wild and cultivated barley is only partly due to gene flow, and it is more plausibly accounted for by multiple domestications.     

Natural diversity of inflorescence architecture traces cryptic domestication genes in barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.)

Many-grained mutants occurring spontaneously among their less well-endowed field mates may have appeared to early farmers as fortunate twists of fate foreboding wealth and abundance. In domesticated barley, the number of kernel rows in spike can be tripled by recessive mutant alleles at the Six-rowed spike 1 (vrs1) locus that abolish the suppression of lateral spikelet fertility. In another barley row-type, so called intermedium-spike (int), lateral floret size is often intermediate between six-and two-rowed types. Phenotypic and sequence analyses of our intermedium-spike collection revealed that other genes can increase the size of florets and even stimulate occasional grain setting in lateral spikelets. Here, we show that a complete six-rowed phenotype occurs in a diverse panel of intermedium-spike barley carrying wildtype Vrs1 in the presence of the Int-c.a allele of the intermedium spike-c (int-c) gene, previously considered only as a modifier of lateral spikelet fertility. Int-c.a-type alleles had arisen before domestication and are associated with the enlargement of lateral florets in wild barley, suggesting that natural selection/evolution acts towards reduced lateral floret size. Since Int-c.a cannot overcome the suppression of lateral florets in the genomic background of wild barleys, we infer the existence of other gene loci, at which novel alleles or allelic combinations were selected for after domestication, to increase grain number of barley independently of Vrs1.     

Genetic diversity in European accessions of the Barley Core Collection as detected by isozyme electrophoresis

Genetic diversity in 79 European accessions of the Barley Core Collections was surveyed using isozyme electrophoresis. A total of 26 alleles were observed at the ten isozyme loci. All loci were polymorphic except Pgd-1 which was monomorphic. The comparison of the results with those of previous studies indicates that most of the alleles occurring in the European Barley are also observed in this set of the European Barley Core Collections. Only five alleles (Est-1 Al; Est-5 Ag, Te; Pgi-1 C and Ndh-2 B) were absent. Nine of 26 alleles were rare alleles, which were detected only in one or two accessions. Moreover, most of rare alleles were detected in 6-rowed winter barley. It is very important to include rare alleles for maximising the genetic variations in core collections. In the set of European Barley Core Collection, 6-rowed barley contained larger diversity than 2-rowed barley; winter type contained larger diversity than spring type. The cluster analysis separated 79 accessions into three major groups. Group I is more complex and comprised 2-rowed spring, 2-rowed winter and 6-rowed winter barley. In this group, 18 accessions in the cluster A and 14 accessions in the cluster B possessed identical genotypes as judged from the ten isozyme data. Principal coordinate analysis could not clearly separate the spring cultivars from the winter barley lines, as well as not separate 2-rowed from 6-rowed barley.     

Microscale ecological stress causes RAPD molecular selection in wild barley, Neve Yaar microsite, Israel

Genetic micro-differentiation was studied in wild barley at the Neve Yaar microsite, Israel, an area of 3182 m², which includes a mosaic of sun-rock, sun-soil, shade-rock, and shade-soil microniches. Fifty-six genotypes were tested for ecological-genetic microniche correlates. Analysis of 75 RAPD loci revealed a significantly higher polymorphism and gene diversity (P _0.05 = 0.920; He = 0.411) on the more stressful sun-rock microniche, compared to the least stressful shade-soil microniche (P _0.05 = 0.653; He = 0.188). Fifty-six (74.7%) out of the 75 loci varied significantly in allele frequencies. On the average, of the 75 loci, 75.7% of the total genetic diversity exists within the four microniches, while 24.3% exists between the microniches. The highest genetic distance was between shade-soil and sun-rock (D = 0.220), which confirmed their sharp microecological contrasts. Gametic phase disequilibria (LD) differed significantly between sunny and shady microniches. The levels of correct classification of individual genotypes into their respective microniche, based on the presence/absence of bands of the 2, 3, 4, 5, and 7 best differentiating loci, obtained by stepwise discriminant analysis, were 79, 84, 89, 95, and 100%, respectively. We conclude that ecological contrasts at the Neve Yaar microsite cause molecular diversifying selection (presumably at both coding and noncoding genomic regions of wild barley) overriding gene flow.     

Characterization of Mexican Creole wheat landraces in relation to morphological characteristics and HMW glutenin subunit composition

One hundred lines derived from 14 wheat landraces collected in Mexico were characterized in relation to spike and grain morphology and HMW-glutenin subunit composition. Up to seven botanical varieties were identified among these materials based in four morphological traits. The remaining nine morphological traits showed wide variation. The allelic variation at the Glu-1 loci was wide, although showed a clear risk of genetic erosion due to the low frequency of some alleles. These genotypes could be used as genetic resources to improve important biotic and abiotic traits as well as to widen genetic diversity controlling the HMW glutenin subunit composition of common wheat.     

Genotypic variation in Fe concentration of barley grain

Abstract

Iron deficiency in humans is the most prevalent micronutrient deficiency worldwide. To screen for high Fe cultivar, genotypic variation in Fe concentration of barley grain was investigated in two collections of barley: 274 standard varieties selected at the Barley Germplasm Center of the Research Institute for Bioresources, Okayama University (SV) and 135 varieties from the Barley Core Collection of Americas (BCCAM). The Fe concentration of barley grain showed large variation, ranging from 24.6 to 63.3 mg kg^?1 in SV, from 21.0 to 83.0 mg kg^?1 in BCCAM barleys. The Fe concentration was not affected by the key characters of barley varieties, kernel row types, and hulled or hull-less. The Fe concentration was also not related to the place of origin of the barley variety. About 90% of total Fe was localized in the grain without hull. These results provide fundamental data for breeding Fe-rich cultivars and for studying the mechanisms involved in genotypic variation in Fe concentration.     

Assessing Genetic Diversity of Chinese Cultivated Barley by STS Markers

To assess the genetic diversity among China’s cultivated barley, sequence tagged site (STS) marker analysis was carried out to characterize 109 morphologically distinctive accessions originating from five Chinese eco-geographical zones. Fourteen polymorphic STS markers representing at least one in each chromosome were chosen for the analysis. The 14 STS markers revealed a total of 47 alleles, with an average of 3.36 alleles per locus (range 2–8). The proportion of polymorphic loci per population averaged 0.84 (range 0.71–1.00); the mean gene diversity averaged 0.39 (range 0.28–0.49). The means of P and H_e were highest in the Yangtze reaches and Southern zone (P = 1.00; H_e = 0.46) and lowest (P = 0.71 He = 0.28) in the Yellow river reaches zone. The STS diversity in different zones is quite different from the morphology diversity. The STS variation was partitioned into 17% among the zone and 83% within the zone. Both cluster and principal coordinate analyses clearly separated the accessions into a dispersed group (mostly two-rowed barley with a lower mean GS value) and a concentrated group (mostly six-rowed barley with a higher mean GS value) according to the spike characteristic with only a few exceptions. The accessions from the Qinghai-Tibet plateau formed a distinctive subgroup and can be distinguished from the concentrated group. The role of Tibet in the origin and evolution of cultivated barley has been discussed.     

Analysis of Genetic Diversity in the Brassica napus L. Gene Pool Using SSR Markers

Genetic diversity throughout the rapeseed (Brassica napus ssp. napus) primary gene pool was examined by obtaining detailed molecular genetic information at simple sequence repeat (SSR) loci for a broad range of winter and spring oilseed, fodder and leaf rape gene bank accessions. The plant material investigated was selected from a preliminary B. napus core collection developed from European gene bank material, and was intended to cover as broadly as possible the diversity present in the species, excluding swedes (B. napus ssp. napobrassica (L.) Hanelt). A set of 96 genotypes was characterised using publicly available mapped SSR markers spread over the B. napus genome. Allelic information from 30 SSR primer combinations amplifying 220 alleles at 51 polymorphic loci provided unique genetic fingerprints for all genotypes. UPGMA clustering enabled identification of four general groups with increasing genetic diversity as follows (1) spring oilseed and fodder; (2) winter oilseed; (3) winter fodder; (4) vegetable genotypes. The most extreme allelic variation was observed in a spring kale from the United Kingdom and a Japanese spring vegetable genotype, and two winter rape accessions from Korea and Japan, respectively. Unexpectedly the next most distinct genotypes were two old winter oilseed varieties from Germany and Ukraine, respectively. A number of other accessions were also found to be genetically distinct from the other material of the same type. The molecular genetic information gained enables the identification of untapped genetic variability for rapeseed breeding and is potentially interesting with respect to increasing heterosis in oilseed rape hybrids.     

Molecular analysis of the DNA polymorphism of wild barley (Hordeum spontaneum) germplasm using the polymerase chain reaction

Summary Hordeum spontaneum is the progenitor of cultivated barley (H. vulgare) and is an important source of genetic variation for barley breeding programs. The genetic diversity ofH. spontaneum in the Australian germplasm collection was investigated using the polymerase chain reaction with random and semi-random primers. This approach was found to be robust in respect of reaction conditions. Genetic dissimilarity values between genotypes were used to produce a phenogram of the relationships among the accessions using the unweighted pair group method with arithmetic mean. The largest divergence was observed among Israeli accessions, whereas the Turkish and Iranian samples clustered as distinct subsets, each apparently related to portion of the Israeli material. The results indicate that the genetic diversity of the wild barleys is broadly correlated with geographic distribution.     

Geographic patterns of Got1, Got2, Got3 and Est2 enzyme-encoding genes allelic variation in Aegilops tauschii Coss.

Geographic patterns of Got1, Got2, Got3 and Est2 enzyme-encoding genes allelic variation were investigated among 322 accessions of Aegilops tauschii Coss., 161 accessions of ssp. tauschii and 161 accessions of ssp. strangulata, representing all the species area. It was found that: (1) in the two ecologically different subspecies, ssp. tauschii and ssp. strangulata, the patterns of allelic variation of the four genes differ greatly; (2) the same allozymes have originated several times independently in different Ae. tauschii local populations; (3) allelic variation of Got1, Got3 and Est2 in ssp. strangulata corresponds to climatic conditions. The data obtained reflected that Ae. tauschii has been inhabiting its area from ancient times; and allelic variation patterns of Got1, Got2, Got3, Est2 loci were mostly formed by natural selection. Further investigations of these loci with molecular genetic methods are prospective for understanding the peculiarities of Ae. tauschii evolution.     

Genetic diversity of ICARDA’s worldwide barley landrace collection

Twenty genic- and genomic SSR markers were used to study genetic diversity and geographical differentiation of barley from 29 countries through analysis of a worldwide collection of 304 ICARDA’s barley landraces. Of these, 19 loci were highly polymorphic in the material studied. Based on Nei-distance matrix, Principal Component Analysis (PCoA) and cluster analysis using UPGMA associated with AMOVA the data revealed countries’ grouping within regions. Three distinct germplasm pools were identified in the landraces. The first of these was from Eastern Africa (Eritrea and Ethiopia) and South America (Ecuador, Peru and Chile) suggesting that barley introduced to South America might have originated specifically from East Africa or that they share a common genetic basis for adaptation. The second was the Caucasus (Armenia and Georgia) and the third included the remaining regions of Central Asia, Near East, Northern Africa and Eastern Asia. Genetic diversity of barley subspecies (Six-rowed barley, Two-rowed barley, H. spontaneum C. Koch and H. agriocrithon Åberg) also discriminates them into three groups: cultivated barleys (Six-rowed barley and Two-rowed barley), wild barley H. spontaneum and subspecies H. agriocrithon. These results associated with parsimony analysis demonstrate that H. agriocrithon and H. spontaneum might be distinct and do not support a hybrid origin for H. agriocrithon suggesting further investigation of the basis of more intense sampling of the two subspecies H. spontaneum and H. agriocrithon.     

Variation in gluten strength and yellow pigment in Ethiopian tetraploid wheat germplasm

Ten released varieties and one hundred and eleven tetraploid (2n = 4x = 28, AABB) wheat accessions collected from different major wheat producing regions, consisting of totally 2904 entries were characterized for content of yellow pigment, gluten strength, thousand kernel weights, grain yield, percent of yellow berry, glumes color, awn color, seed color, beak shape and spike density. The objectives were to assess variation with respect to regions of origin, species and altitudinal classes and to study the interrelationships of the qualitative traits used for the study. The accessions and/or released varieties showed significant regional variation for all the traits used in the study, but clinal variation among altitudinal classes and species were significant (P ≤ 0.01) in 6 (60%) and 9 (90%) of the studied traits, respectively. The accessions revealed consistent variation (P ≤ 0.001) within both regions and altitudinal classes for all the traits used in the study. The sedimentation volume was positively correlated with content of yellow pigment, percent of yellow berry, thousand kernel weights, glumes color, awn color, beak shape, seed color and grain yield. The contents of yellow pigment was positively correlated with awn color, beak shape and grain yield, but negatively correlated with seed color and spike density. Generally wide variation was found in the germplasm. Particularly variation was high for the content of the yellow pigment as well as the gluten strength, which provides opportunities to be utilized for genetic improvement.     

Free and Bound Phenolic Acids and Total Phenolics in Black,Blue, and Yellow Barley and Their Contribution to Free Radical Scavenging Capacity

Barley is considered a healthy food because of its high content of β‐glucan and phenolic antioxidants. In the current study, 28 black, blue, and yellow barleys were investigated in terms of their composition of free and bound phenolic acids and 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging capacity. Free phenolics were based on aqueous methanol extraction, whereas bound phenolics were extracted following alkaline hydrolysis. Phenolics were then separated and quantified by liquid chromatography and the Folin–Ciocalteu method. Significant differences were observed between the three barley color groups, and within each color group a wide range of phenolics concentrations existed. Ferulic acid was the predominant phenolic acid in free and bound extracts, followed by p‐coumaric acid in all the barleys investigated. Total phenols content and individual phenolic acids strongly correlated with free radical scavenging capacity of barley. Black and blue barley were found to be related and distinct from yellow barley. The results showed significant variations in phenolics among barleys, with a potential for the development of barley grains with high content of phenolic compounds as antioxidant potential.     

Use of Microsatellite Polymorphisms to Develop an Identification Key for Tunisian Apricots

Microsatellite polymorphisms in 54 apricot landrace cultivars were identified by using 26 Prunus microsatellite primers. Samples of apricot cultivars were collected in eight growing regions in Tunisia ranging from the north to the south of the country and from the sub-humid to the saharian areas. The primers revealed 103 alleles and 155 different genotypes among the 54 apricot accessions. The most polymorphic microsatellite loci were used to develop an identification key. Five microsatellite primers and the 28 resulting alleles were sufficient to discriminate among all 54 cultivars. These results are discussed in the context of cultivar nomenclature, geographic origins, and the comprehensive fingerprinting of Tunisian apricot collections.     

The Spanish barley core collection

Spanish barleys constitute a germplasm group of particular interest for breeding purposes, as Spain has been proposed as a possible centre of origin of the crop. The Spanish National Germplasm Bank (Banco Nacional de Germoplasma, BNG), holds a collection of about 2000 barley accessions, mostly landraces collected in Spain prior to extensive introduction of modern varieties. The objective of this work is to create a core collection of barleys representative of old barley genotypes grown in Spain. The core collection will be constituted by three groups of germplasm: successful old varieties (15); entries in common with previously existing barley core collections (15); and 2-row (8) and 6-row (122) entries from the BNG, for a total of 160 entries. Entries were allocated by stratified sampling in agro-ecological uniform zones of barley cultivation in Spain. Classification of agro-ecological regions for barley was based on historical yield records for Spanish provinces. The number of entries for each region was determined in proportion to the logarithm of historical barley acreage. Final choice of accessions within provinces tried to maximize the diversity and avoid duplications by looking at passport data, and to agronomic evaluation data available for a group of about 900 accessions.     

Assessment of genetic diversity in Egyptian barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.) genotypes using SSR and SNP markers

A barley core collection can be studied extensively and the derived information can be used to identify loci/genes for the genetic improvement of quantitative and qualitative traits. To assess genetic diversity, allelic variation and population structure of Egyptian barley, 134 barley genotypes collected from a different region along with 19 cultivated genotypes obtained from of the Egyptian Agricultural Research Center. All genotypes were analyzed with 261 polymorphic SSR and SNP alleles. The mean number of alleles per locus was 4 and PIC was 0.49, while the level of genetic diversity was 0.55 ranging from 0.03 to 0.82. The genotypes were assigned to three subpopulations that were consistent with their origins. The genetic variation within population was higher (51%) than among population at the molecular levels (F_ST =?0.491 when P?<?0.10). The level of polymorphic variation was highest in subpopulations-II, due to collected from different regions with different ear-types thus, expected to contain more diversity than local genotypes in subpopulations-I and subpopulations-III. The structured study found that the 153 barley genotypes are in harmony with clustering approaches using the SSR and SNP genotypic data in a neighbor-joining tree and principal components analysis, which identified three subpopulations. These results demonstrated genetic diversity among the Egyptian barley genotypes can be applied to suggest approaches, such as association analysis, classical mapping population development, and parental line selection in breeding programs. Therefore, it is necessary to use the exotic genotypes as the genetic resources for developing new barley cultivars in Egypt.     

Aegilops tauschii: Genetic Variation in Iran

All the 79 Aegilops tauschii Coss. accessions of Iranian origin from Prof. Kihara’s collection were analyzed electrophoretically. Of 23 enzyme-encoding loci studied, 11 were polymorphic. In Iran Ae. tauschii is presented by ssp. tauschii and ssp. strangulata which distinctly differ genetically, morphologically and ecologically. Variation patterns of low polymorphic locus Aco2 and highly polymorphic Ep are similar in both subspecies. In contrast, variation of Acph1, Ak, Est2, Est5, Got1, Got2, Got3 and Lap is a set of diverse patterns which markedly differ between subspecies and natural regions also, implying that natural selection is involved.