Genetic variability evaluation in a Moroccan collection of barley, Hordeum vulgare L., by means of storage proteins and RAPDs

The genetic variation existing in a set of barley (Hordeum vulgare L.) landrace samples recently collected in Morocco was estimated. Two kinds of genetic markers, seed storage proteins (hordeins) and random amplified polymorphic DNA (RAPD), were used. Only six out of 31 landraces were subjected to RAPD analysis. Both kinds of markers, RAPD and storage proteins, yielded similar results, showing that the level of variation observed in Moroccan barley was high: all landraces showed variability; 808 different storage protein patterns (multilocus associations) were observed among 1897 individuals (2.32 seeds per association, on average) with an average of 43 multilocus associations per accession. In general, genetic variation within accessions was higher than between accessions. The 100 polymorphic RAPD bands generated by 21 effective primers were able to generate enough patterns to differentiate between uniform cultivars and even between individuals in variable accessions. One of the aims of this work was to compare the effectiveness of RAPD versus storage protein techniques in assessing the variability of genetic resource collections. On average hordeins were more polymorphic than RAPDs: they showed more alternatives per band on gels and a higher percentage of polymorphic bands, although RAPDs supply a higher number of bands. Although RAPD is an easy and standard technique, storage protein analysis is technically easier, cheaper and needs less sophisticated equipment. Thus, when resources are a limiting factor and considering the cost of consumables and work time, seed storage proteins must be the technique of choice for a first estimation of genetic variation in plant genetic resource collections.     

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.     

Resistance to powdery mildew in populations of barley landraces from Morocco

Forty-eight populations of barley landraces collected from Morocco were screened for resistance to powdery mildew and a number of different resistance genes were detected. Landraces originated from the collection of the International Center for Agricultural Research in the Dry Areas – ICARDA, Aleppo, Syria. Twenty populations of tested landraces (about 42%) showed resistance reactions and 46 single plant lines were selected. Fourteen of these lines were tested in the seedling stage with 17 and another 32 lines with 23 differential isolates of powdery mildew, respectively. The isolates were chosen according to their virulence spectra observed on the Pallas isolines differential set. Five lines originating from five populations of landraces showed resistance to all prevalent in Europe powdery mildew virulence genes. Thirty-five lines (76%) showed resistance reaction type 2. The distribution of reaction type scores indicated that about 81% of all reaction types observed were classified as powdery mildew resistance (scores 0, 1 and 2). In forty-one lines (89%) the presence of unknown genes alone or in combination with a specific one was detected. Four different resistance alleles (Mlat, Mla6, Mla14 and Mla22) were postulated to be present in the tested lines alone or in combination. Among specific resistance alleles the most common was allele Mlat (resistance Atlas). This allele was postulated to be present in twenty-three (50%) tested lines. The use of new identified sources of resistance to powdery mildew in barley breeding is discussed.     

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.     

Inferring seed exchange between farmers from population genetic structure of barley landrace Arabi Aswad from Northern Syria

Apart from their significance in genetic conservation, barley landraces are still favoured by local farmers in low-input farming systems. They often perform more predictably under adverse conditions than modern cultivars due to local adaptation. Increased seed exchange between farmers may put adaptation of local populations of barley landraces at risk. Isozyme markers were used to investigate differentiation and infer gene flow between local populations of barley landrace Arabi Aswad in Northern Syria. Inferred gene flow decreased exponentially with geographic distance and may imply that seed exchange between farmers is limited to a regional scale and diminishes over longer distance. Gene flow seems to be a suitable index for estimating seed exchange in highly inbreeding crop species such as barley. In the future, improved mobility of farmers and extension work may facilitate seed exchange over longer distances, and consequently jeopardise preservation of locally adapted landraces in barley.     

Evaluation of cultivated and wild barley for resistance to pathotypes ofPuccinia hordei with wide virulence

An isolate ofPuccinia hordei (ND89-3) originally collected in Morocco is virulent on most barley genotypes reported to possess resistance, except cultivar Estate (CI 3410), which possesses theRph3 gene and exhibits a low to intermediate level of resistance (infection type 12). Isolate ND89-3 possesses one of the widest virulence spectrums reported forP. hordei. Accessions ofHordeum vulgare (1,997 in total) andH. spontaneum (885 in total), mostly originating from the Mediterranean region and parts of North Africa, were evaluated with isolate ND89-3 at the seedling stage to identify new sources of leaf rust resistance. Fifty-eight accessions ofH. vulgare, and 222 accessions ofH. spontaneum exhibited low infection types to this isolate. Further evaluations of these resistant accessions with isolates ofP. hordei virulent forRph3,Rph7, andRph12 suggested that most of the resistantH. vulgare accessions possess theRph3 gene. Data suggested additional sources of effective resistance inH. vulgare are rather limited. FiveH. vulgare accessions and 167H. spontaneum accessions were identified as possible sources of new genes for leaf rust resistance. These accessions likely possess resistance genes that are different fromRph1 toRph12, or gene combinations thereof based on their reaction to four leaf rust isolates. Utilization of these accessions in barley breeding will broaden the germplasm resources available for genetic control ofP. hordei. North Dakota Agricultural Experiment Station Journal Series No. 2123. The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

Saprophytic soil microflora in relation to yield reductions in soil repeatedly cropped with barley (Hordeum vulgare L.)

Summary The yield-depressing effect due to repeated cropping (monoculture) of barley reported from long-term field experiments was observed as a reduction in plant growth in short-term pot experiments. The nature of the monoculture effect was investigated by mixing field soils with different cropping histories in different proportions in the greenhouse, while the influence of rhizosphere microflora from the monocultured and crop rotation soils on barley growth was studied in gnotobiotic experiments. Indigenous bacterial populations and the pH of the test soils were also measured. Significantly more bacteria were found in the crop rotation soil compared to the monocultured soil, but the two soils did not differ in pH. Greenhouse experiments showed that in the monocultured soil, seed germination was delayed and plant dry weight reduced, and that these effects had a biological origin. Attempts were also made to induce the monoculture effect in the crop rotation soil by inoculation with known harmful bacteria. The results from the experiments with mixed soils and with soil inoculation indicated that where crop rotation was practised the soil was more sensitive to bacterial effects than the monocultured soil. The rhizosphere microflora from the monocultured soil did not affect plant weights in short-term gnotobiotic experiments, but it significantly stimulated the number of lateral roots compared with the crop rotation microflora. This stimulation could not be related to differences in bacterial counts, pH, or ion concentrations in the plant-growing medium.     

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.     

Inter-simple sequence repeat (ISSR) and RAPD variation among wild barley (Hordeum. vulgare subsp. spontaneum) populations from west Turkey

Inter-Simple Sequence Repeat (ISSR) and Randomly Amplified Polymorphic DNA (RAPD) markers were used to analyze genetic distance among H. vulgare subsp. spontaneum populations from west Turkey. Fifty-five RAPD and 10 ISSR primers were used to detect variation among sample. A total of 55 polymorphic loci were found using 65 primers. Two distinct cluster groups were clearly established among populations. The minimum variation was detected between Pinarbasi and Bornova (GD = 0.192) populations and the maximum was found between Icmeler and Aydin populations (GD = 0.926). As two dominant markers, RAPD and ISSRs are effective and promising marker systems for detecting genetic variation.     

Variation of Agro-morphological Characters in Moroccan Barley Landraces Under Near Optimal and Drought Conditions

In many areas of North Africa, barley is often the only possible rainfed crop. In these regions water deficit is the primary constraint affecting crop production. Twenty barley landraces collected from different localities in south Morocco and four modern varieties were characterized in two field experiments, one under well-irrigated and one under limited-irrigated conditions. Nine agro-morphological characters were evaluated: Plant height, tiller number per plant, number of grains per spike, number of spikes per plant, spike weight, spike length, plant weight (PW), number of internodes of rachis (NIR), and length of the last internode of rachis. The correlation coefficients among characters were nearly the same in the well- and limited-irrigated experiment. Under limited-irrigated conditions, plant growth was significantly decreased as measured by all characters except NIR, which was unaffected. The percentage of reduction, ranging from 80.08% to 5.82%, was recorded on PW and NIR, respectively. The injury index ranging from 4.02 to 0.06 was recorded on PW and NIR, respectively. Using discriminant analysis the genotypes were arranged in three, clearly separated groups that varied in their tolerance to drought stress.     

Sources of powdery mildew resistance in a wild barley collection

A total of 1,383 accessions of wild barley (Hordeum vulgare ssp. spontaneum) held in the USDA-National Small Grains Collection, Aberdeen were screened for resistance to powdery mildew (Blumeria graminis f. sp. hordei) in the Czech Republic. They were subsequently tested at the seedling stage for reaction to selected powdery mildew pathotypes and simultaneously for their adult plant resistance in the field. One hundred and twenty-three accessions exhibited resistance to 22 pathotypes in the greenhouse tests (reaction type 2–3 or lower) as well as resistance to the natural population of this pathogen in the field in the Czech Republic during at least 2-year testing. These accessions represent large amount of promising sources in breeding barley for resistance to powdery mildew.     

The bioprotective effect of AM root colonization against the soil-borne fungal pathogen Gaeumannomyces graminis var. tritici in barley depends on the barley variety

The systemic effect of root colonization by the arbuscular mycorrhizal fungus (AMF) Glomus mosseae on the susceptibility of old and modern barley varieties to the soil-borne fungal pathogen Gaeumannomyces graminis var. tritici (Ggt) was studied in a split-root system. Plants were precolonized on one side of the split-root system with the AMF and thereafter the other side of the split-root system was inoculated with the pathogen. At the end of the experiment the level of bioprotection was estimated by quantifying lesioned roots and the determination of the root fresh weight. AM root colonization provided protection in some of the barley genotypes tested, but not in others. This protective effect seemed to vary in the oldest and the most modern barley variety tested.     

Genetic variation in barley landraces from Bhutan

Summary In Bhutan, barley is usually grown in mountainous regions over 2,000 m elevation. The barleys investigated were six-rowed naked, and classified into three groups by spike and awn characters; lax spike and long awn, dense spike and long awn, and dense spike and elevated hood. They also varied in spike color; yellow, purple and black. For isozymes, there was no variation at Aat2 and Aat3 loci for aspartate aminotransferase in the Bhutanese barley.However, allelic variations at Est1, Est2 and Est4 loci for esterase were detected, and three genotypes consisting of their allelic combinations were found. Most of the collections were heterogeneous for these features. Combinations between spike-awn types and esterase genotypes were not at random, indicating that genetic diversities resulted from mechanical mixtures of different types. These types were distributed with geographical regularity in Bhutan. In comparing the spike-awn type and esterase genotype in barley collections from other regions of the Himalayas, the Bhutanese barleys were s-imilar to the Tibetan ones, but were much different from the Nepalese barleys. This suggests that the Bhutanese barleys had been introduced from Tibet.     

Agronomic traits of exotic barley germplasms resistant to soil-borne mosaic-inducing viruses

Summary In order to obtain information on agronomic performance and potential use of yellow mosaic virus resistant barley germplasms (Hordeum vulgare L.) in breeding programmes, twenty-six varieties were tested for agronomic traits in two years trials. The varieties tested differ in their reaction to the soil-borne mosaic-inducing viruses (BaMMV, BaYMV, BaYMV-2) and their genetic base of BaMMV-resistance. All of the exotic varieties tested are of inferior agronomic performance as compared to resistant German cultivars. Grain yield ranged from 77% to 33% in comparison to the highest yielding German winter barley cultivar Franka. Furthermore, a large variation was also observed in thousand grain weight, number of grains per spike, height, lodging, winterkilling and susceptibility to scald (Rhynchosporium secalis (Oudem) Davis).     

Molecular marker-mediated validation of morphologically defined landraces of Pejibaye (<Emphasis Type="Italic">Bactris gasipaes</Emphasis>) and their phylogenetic relationships

RAPD markers were used to evaluate the genetic variability and structure of seven morphologically defined landraces of pejibaye (Bactris gasipaes Kunth, Palmae) to determine their validity and phylogenetic relationships. Two hundred and twenty plants of four Amazonian and three Central American landraces of var.gasipaes (the domesticate) and 30 plants of var.chichagui (H. Karsten) Henderson (the crop ancestor) maintained at the National Research Institute for Amazonia, Manaus, Amazonas, Brazil, were utilized. Eight RAPD primers yielded 113 markers, with good reproducibility, of which 97 were polymorphic. The four Amazonian landraces had an average heterozygosity of 0.30, with 86% polymorphism, greater than the Central American landraces (0.25; 74.3%) and var.chichagui (0.27; 80%). Among landrace genetic diversity (G_ST) was 15%, while within (Hs) was 85%, essentially equivalent to the AMOVA within (82.2%) and among (17.8%) variances. The Jaccard similarities, PCA, gene flow coefficients and Exact tests suggested that only one landrace exists in Central America, called Utilis after the first taxon described there, and that the Solimões landrace is part of the Putumayo landrace, rather than a separate entity. The Pará and Pampa Hermosa landraces were validated in accordance with their morphometric interpretations. The dendrogram of Neis genetic distances among valid landraces and var.chichagui supported the hypothesis of a single origin for pejibaye in southwestern Amazonia, with two migration routes: one to the northeast, becoming the Pará landrace, and another to the northwest along the Andes, spreading into western Amazonia (Pampa Hermosa and Putumayo landraces) and across the Andes, reaching Central America (Utilis landrace).     

Molecular size distribution and enzymatic degradation of organic phosphorus in root exudates of spring barley

Seeds from two varieties of spring barley (Prisma and Camorgue) were grown axenically in water. After 14 days, the culture solutions contained organic P substances (about 4 g P per plant) derived from root exudation, representing about 3% of the total P found in the seed. Gel filtration, separated the organic P into two well defined peaks, one with a high molecular weight (>45000 daltons) and the other with a low molecular weight (<500 daltons). The bioavailability of the soluble organic P released was assessed enzymatically and chemically. At the optimum pH of 5.0, phytase and acid phosphatase hydrolysed about 80% and 65%, respectively of the organic P in the exudate after 24 h whereas at the optimum pH of 9.8, alkaline phosphatase hydrolysed up to 40% P after the same length of time. In a pH 5.0 buffer, up to 10% of the organic P was hydrolysed compared with up to 45% in a pH 9.8 buffer. The high molecular weight organic P fraction recovered from the G-75 Sephadex behaved similarly.     

Diversity between some Ethiopian farmer's varieties of barley and within these varieties among seed sources

Barley is one of Ethiopia's major crops. Cultivation is mostly by traditional varieties that are chosen by farmers for their suitability for end-use or their adaptation to specific farming systems. A collection of 155 barley lines was grouped in 13 varieties, according to the name given by the farmers. The collection was evaluated for simple agronomic traits and resistance to barley scald disease. A large level of diversity was found, mainly between varieties, but also within varieties between farms from which the samples originated. In spite of a certain degree of overlapping, these traditional farmer's varieties showed coherence for the characters measured. Earlier maturing varieties were found to be more susceptible to scald, but a number of accessions combined earliness with scald resistance. It is suggested that the traditional variety name be included, next to the physical characters of the collection site, as a parameter to explain the degree of diversity in Ethiopian barley germplasm evaluation. The cultivated area of a number of traditional barley varieties is declining rapidly and special collection missions are needed to preserve this germplasm.     

Genetic diversity in cowpea [Vigna unguiculata (L.) Walp.] as revealed by RAPD markers

The present study, using RAPD analysis, was undertaken to characterize genetic variation in domesticated cowpea and its wild progenitor, as well as their relationships. The materials used consisted of 26 domesticated accessions, including accessions from each of the five cultivar-group, and 30 wild/weedy accessions, including accessions from West, East and southern Africa. A total of 28 primers generated 202 RAPD bands. One hundred and eight bands were polymorphic among the domesticated compared to 181 among wild/weedy cowpea accessions. Wild accessions were more diverse in East Africa, which is the likely area of origin of V. unguiculata var. spontanea. Var. spontanea is supposed to have spread westward and southward, with a loss of variability, loss counterbalanceed in southern Africa by introgressions with local perennial subspecies. Although the variabilty of domesticated cowpea was the highest ever recorded, cultivar-groups were poorly resolved, and several results obtained with isozyme data were not confirmed here. However primitive cultivars were more diverse than evolved cultivars, which still suggests two consecutive bottlenecks within domesticated cowpea evolution. As isozymes and AFLP markers, although with a larger number of markers, RAPD data confirmed the single domestication hypothesis, the gap between wild and domesticated cowpea, and the widespread introgression phenomena between wild and domesticated cowpea.     

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.