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1.
Muhlenbergia torreyi occurs in the southwestern United States, northern Mexico, and northwestern Argentina. Allozyme data were used to evaluate genetic diversity within and among populations of this amphitropical disjunct species. Electrophoretic examination of 22 putative enzyme loci in 15 populations revealed high levels of genetic variation (P ranging from 64.7 to 82.4;H from 0.527 to 0.757) and high levels of genetic diversity (F ranging from −0.584 to −0.939). All populations possess high levels of heterogeneity (F 1S approaching −1, mean of −0.837) and exhibit lower levels of genetic fixation among populations (F ST mean of 0.127). A comparison of genetic identity values among populations from North and South America indicates that the genetic variation is slightly greater (I=0.93) in North America than in South America (I=0.96). A total of 51 alleles were shared among all populations, and four unique alleles were detected: two from North American populations and two from South America. It seems likely thatMuhlenbergia torreyi has dispersed to South America recently, because the populations there are less variable. Chromosome numbers, not determined by the authors, of 2n=20, 21 forM. torreyi and 2n=80, 82 forM. arenicola are reported.Muhlenbegia arenicola is first reported from South America.
Resumen   Muhlenbergia torreyi habita en el suroeste de Estados Unidos, norte de México, y noreste de Argentina. Mediante el análisis de alozimas se evaluó la diversidad genética dentro y entre poblaciones de esta especie, que es disjunctiva anfitropical. El exámen electroforético de 22 loci putativos enzimáticos en 15 poblaciones, reveló altos niveles de variación genética (P varía de 64.7 a 82.4;H varía de 0.527 a 0.757) y altos niveles de diversidad genética (F varía de −0.584 a −0.939). Todas las poblaciones poseen altos niveles de heterogeneidad dentro de las mismas poblaciones (F IS cerca −1, media de −0.837) y exhiben bajos niveles de fijación genética entre poblaciones (F ST media de 0.127). Una comparación de valores de identidad genética entre poblaciones de Norte y Sudamérica indican que la variación genética es un poco mayor (I=0.93) en Norte América que en Sudamérica (I=0.96). Las poblaciones poseían un total de 51 alelos en común y se detectaron cuatro alelos únicos; dos en las poblaciones norteamericanas y dos en las poblaciones sudamericanas. Probablemente,Muhlenbergia torreyi ha sido dispersada recientemente hacia Sudamérica porque esta poblacion es menos variable. El número de cromosomas, no determinado por los autores, de 2n=20, 21 paraM. torreyi and 2n=80, 82 paraM. arenicola son reportados.Muhlenbergia arenicola es reportada por primera vez en Sudamérica.
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2.
The influence of nitrate and ammonium assimilation on the flow of recently fixed carbon has been determined in intact Anacystis nidulans cells actively fixing CO2. Assimilation of nitrate or ammonium resulted in substantial increases in the incorporation of carbon into acid-soluble metabolites, the magnitude of the effect being dependent on the irradiance. The radiolabel in sugar phosphate was virtually unaffected by nitrogen assimilation, whereas that in organic acids and, in particular, in amino acids was markedly increased. Enhancement of carbon incorporation into amino acids induced by nitrogen assimilation was not accompanied by parallel increases in the size of the amino acid pools. This resulted in an appreciable increase of the specific radioactivity of most amino acids under conditions of nitrogen assimilation. The data indicate that nitrate and ammonium assimilation induce an enhancement of carbon flow through the glycolytic and the tricarboxylic-acid pathways to oxaloacetate and α-ketoglutarate, as well as a stimulation of amino-acid turnover. These effects were more pronounced at saturating irradiance. We thank the Dirección General de Investigación Científica y Técnica, Spain (research grant PB88-0019) and the Plan Andaluz de Investigación (grupo 3101) for financial support, and P. Pérez de León for excellent secretarial assistance.  相似文献   

3.
We determined the nine-locus isozyme genotype of 267 landrace accessions of Avena sativa from 31 provinces of Spain. Our results establish that level of genetic variability is usually high both within and among accessions of this heavily self-fertilizing hexaploid grass and that multilocus genetic structure differs in various ecogeographical regions of Spain. We concluded that selection favoring different multilocus genotypes in different environments was the main integrating force that shaped the internal genetic structure of local populations as well as the overall adaptive landscape of A. sativa in Spain. Implications in genetic resource conservation and utilization are discussed.  相似文献   

4.
In vitro culture of explants were used to apply genetic or cell engineering techniques to the sexually incompatible potato relative Solanum commersonii (2n=2x=24) Three accessions of S. commersonii were tested for regeneration from leaf explants using six different protocols. A two step-regeneration procedure gave the best results. Genetic variability for regeneration ability was found between accessions, and between clones within accessions. The accession PI 472834 regenerated at highest frequency. Clones with high regeneration ability were selected. Approximately 60% of regenerated plants were diploids and 40% were tetraploids. A very low frequency of chimeras was found. Leaf shape and chloroplast counts in guard cells were shown to be quick and reliable methods for estimating ploidy levels. Use of the diploid and tetraploid regenerants obtained for potato breeding is discussed.Abbreviations BAP 6-benzylaminopurine - EBN Endosperm Balance Number - GA3 gibberellic acid - IAA indole-3-acetic acid - MS Murashige and Skoog - NAA 1-naphthalene-acetic acid - ZEA zeatin  相似文献   

5.
Theobroma grandiflorum (cupuassu) is an important fruit tree native to the Brazilian Amazon. Establishing the genetic diversity and structure of populations is critical to define long-term strategies for cupuassu conservation presently threatened by rapid deforestation. Three natural populations collected at the putative center of diversity, three groups of accessions established at a germplasm collection, and one derived from commercial plantings were analyzed. The genetic diversity was assessed using 21 polymorphic microsatellite loci originally developed for Theobroma cacao, disclosing a total of 113 alleles. The estimated genetic diversity parameters averaged over cupuassu populations (A = 3.53 alleles per locus; H e = 0.426; H o = 0.346) were lower than the values reported for other Neotropical tree species. The three natural populations presented a positive and significant fixation index (f), ranging from 0.133 to 0.234. Cupuassu apparently adhered to a general pattern of genetic diversity structure of some Neotropical tree species occurring at low densities, with a low intrapopulation genetic diversity and important levels of endogamy, possibly due to biparental inbreeding derived from the presence of spatial genetic structure in the populations. A high level of genetic divergence was detected among the natural populations (θ p = 0.301), a strong differentiation caused by limited gene flow, and suggesting that human interference in spreading and/or stimulating plantings might have had a smaller effect than expected. The approximate location of the T. grandiflorum center of diversity could not be confirmed by analyzing natural populations from the putative region.  相似文献   

6.
We studied the genetic diversity of great bustards (Otis tarda) in Iberia and Morocco, the main stronghold of this globally endangered species. Samples were collected from 327 individuals covering most of the distribution range within the study area. Sequence variation in a 657 bp fragment of the mtDNA control region revealed 20 variable sites defining 22 haplotypes, two of them exclusive to Morocco. Genetic diversity showed marked regional differences (π = 0–0.53, h = 0–0.89). Multidimensional scaling analysis based on F ST values showed a clear division between Morocco and the Iberian Peninsula, with no evidence of current gene flow between them. Our results suggest that Morocco, where few matrilines have persisted to present, was colonized from Iberia thousands of years ago. Last century reports suggest dispersal through Gibraltar, when the species was more abundant at both sides of the Strait but later population declines and the Strait’s barrier effect have favoured current genetic isolation. Within Iberia, only the most peripheral populations (Navarra, Aragón and Andalusia) differed significantly from the main ones in central Spain. The first two showed extremely low genetic diversity and are probably threatened by inbreeding depression. Diversity was higher in Andalusia, where three exclusive haplotypes were found, suggesting some degree of isolation from other populations. Andalusia and Morocco could be regarded as separate management units which hold a significant proportion of the current genetic diversity and thus deserve urgent conservation measures.  相似文献   

7.
The population biology ofAquilaria malaccensis, one source of gharu, and Cinnamomum mollissimum, one source of wild cinnamon, was studied in a 50 ha permanent plot of primary rain forest in Malaysia. Median diameter growth rates of 0.22 cm yr-1 and 0.1 cm yr-1 should not be prohibitive of economic exploitation, and suggest that the trees could be grown commercially. However, the natural densities were between 2 and 3 trees over 1 cm d.b.h. per ha, which is roughly the median for all trees in the plot, would preclude economic exploitation of these natural populations. The economics of harvesting natural populations is considered in a preliminary fashion by allowing favorable assumptions of quantity and quality of production. The price likely to be fetched from either a first time extraction (on the order of US$10.00 per ha) or from sustained production (on the order of USThe population biology ofAquilaria malaccensis, one source of gharu, and Cinnamomum mollissimum, one source of wild cinnamon, was studied in a 50 ha permanent plot of primary rain forest in Malaysia. Median diameter growth rates of 0.22 cm yr-1 and 0.1 cm yr-1 should not be prohibitive of economic exploitation, and suggest that the trees could be grown commercially. However, the natural densities were between 2 and 3 trees over 1 cm d.b.h. per ha, which is roughly the median for all trees in the plot, would preclude economic exploitation of these natural populations. The economics of harvesting natural populations is considered in a preliminary fashion by allowing favorable assumptions of quantity and quality of production. The price likely to be fetched from either a first time extraction (on the order of US10.00 per ha) or from sustained production (on the order of US10.00 per ha) or from sustained production (on the order of US0.10 per ha per yr), are too small to be of interest as single-product schemes, and are negligible compared to the extraction of multi-species crops of timber. However, it is possible that by combining multiple products under a “High Diversity Forestry” scheme, one could increase the density of harvestable products, reduce the unit cost of labor and improve the economic portrait. La poblacion dinamica de algunos arboles tropicales. La población biológica deAquilaria malaccensis, un original de gharu, yCinnamomum mollissimum, un original del cinnamon salvage, ha sido estudiado en 50 ha en un terreno primario permanente de lluvia tropical en. Con un índice de crecimiento de medio dimetro 0.22 cm yr-1 0.1 cm yr-1 no deberia prohibirse la explotación económica, y se segiuere que los árboles pueden ser cultivados comercialmente. De cualquier manera, la densidad natural siendo aproximadamente entre 2 y 3 árboles per encima de 1 cm dbh per ha, lo cúal es un promedio de todos los árboles en el terreno, esto representa un impedimento a la explotacion económica de la población natural. La economía de la población natural de recolección de la cosecha está considerada como una moad preliminar por permitirse favorablemente la supuesta cantidad y calidad de productión. Los precios problemente alcanzen, bien sea, la primera vex de su extracción sobre el pedido de US10.00 per ha o desde una continua productión ininterrumpida, (sobre un pedido US10.00 per ha o desde una continua productión ininterrumpida, (sobre un pedido US0.10 per ha per yr), siendo demassiado peque?o para ser de interés tal proyecto comoproducto-unico, y son insignificantes comparados con la extracción de multiples especies de semillas de madera. De caulquier manera esposible que sepueda combinar los multiple productos en el proyecto de “Alta Diversidad Forestal,” uno puede la un puede incrementar la densidad de la productión de la cosecha, reduciendo el costo de mano de obra por unidad y mejorando la imagen económica.  相似文献   

8.
Anin vitro core collection of African coffee germplasm, structured in 32 diploid diversity groups, was established and conserved under slow growth for 3 years (6 subcultures). The initial objective was to store twenty accessions per group, with four replicates per accession. A statistical model was developed to analyse observations of survival rates within each diversity group. The goodness of fit of the model was shown. Survival analysis indicated a broad variability of the accessions in their response to the storage conditions and confirmed the importance of structuring the coffee complex down to the intraspecific level. Intra- and inter-group differences had consequences on the genetic representativity of thein vitro core collection. For practical purposes, conservation was carried on when the intra-group genetic drift was less than 50%.Abbreviations BA 6-benzyladenine - CAR Central African Republic - CIRAD Centre de Coopération Internationale en Recherche Agronomique pour le Développement - FAO Food and Agriculture Organization - IBPGR International Board for Plant Genetic Resources - IDEFOR-DCC Institut Des Fôrets - Département Café Cacao - ORSTOM Institut français de recherche scientifique pour le développement en coopération  相似文献   

9.
The genetic identity of eight wheat (Triticum aestivum L.) accessions maintained in the Gatersleben genebank and regenerated up to 24 times was studied by using wheat microsatellite markers (WMS). It was demonstrated that WMS can be used to analyze bulks of seeds stored more than 50 years in a seed reference collection at room temperature. No contamination due to foreign pollen or incorrect handling during the multiplication cycles was discovered. For one accession (TRI 4599) genetic drift was observed, whereas for TRI 249 a heterogenous situation for two markers was maintained over the years. We were able to show that microsatellites can be used as a simple and reliable marker system for the verification of the integrity and genetic stability of genebank accessions. Received: 29 March 1999 / Accepted: 22 June 1999  相似文献   

10.
 A collection of 66 Malus×domestica Borkh. accessions from the USDA-ARS Plant Genetic Resources Unit’s core collection was screened with a set of eight SSR (simple sequence repeat) primers developed at the PGRU in order to determine genetic identities, estimate genetic diversity, and to identify genetic relationships among these accessions. All eight primer pairs generated multiple fragments when used in amplification reactions with DNA from these accessions. High levels of variation were detected with a mean of 12.1 alleles per locus and a mean heterozygosity across all eight loci of 0.693. The eight primer pairs utilized in this study unambiguously differentiated all but seven pairs of accessions in this collection of 66 M.×domestica Borkh. genotypes. The probability of matching any two genotypes at all eight loci in this study was approximately 1 in 1 billion. The markers detected two misnamed accessions in the collection. Genetic-identity data produced a genetic-relatedness phenogram which was concordant with geographic origins and/or known pedigree information. These SSR markers show great promise as tools for managing Malus ex situ germplasm collections as well as for collection and preservation strategies concerning wild Malus populations in situ. Received: 28 March 1998 / Accepted: 29 April 1998  相似文献   

11.
Lupu A  Nevo E  Zamorzaeva I  Korol A 《Genetica》2006,127(1-3):121-132
Regulation of genetic variation in natural populations is a problem of primary importance to evolutionary biology. In the reported study, the repair efficiency of double strand DNA breaks was compared in six wild barley accessions from Israeli natural populations of H. spontaneum: three from mesic populations (one from Maalot and two from Mount Meron, Upper Galilee) and three from xeric populations (one from Wadi Quilt in the Judean Desert and two from Sede Boqer, in the northern Negev Desert). Pulsed field gel electrophoresis was used to score double-strand breaks of DNA (DSBs) caused by methyl methanesulphonate (MMS) treatment. All six accessions were also tested for heat tolerance: four of these, three xeric and one mesic (from Maalot population), were scored as heat tolerant whereas both accessions from Mount Meron population displayed heat sensitivity. MMS caused a significant increase in the level of DSBs relative to the control in all accessions. The major questions were whether and how the efficiency of DNA repair after mutagenic treatment is affected by the environmental conditions and accession’s adaptation to these conditions. Differences were found among the accessions in the repair pattern. Plants of two out of the four heat tolerant accessions did not manage to repair DNA neither at 25°C nor at 37°C. The remaining two heat tolerant accessions significantly repaired the breaks at 37°C, but not at 25°C. By contrast, plants of the two heat susceptible accessions significantly lowered the level of DSBs at 25°C but not at 37°C. Therefore, the accessions that proved capable to repair the induced damages in DNA at one of the two temperatures displayed a pattern that may imply the existence of a negative feedback mechanism in regulation of genetic variation. Such a dependence of DNA integrity on environment and genotype may serve an important factor for maintaining relatively high level of mutability without increasing the genetic load.  相似文献   

12.
Glucosinolates (GSL) present in cultivated and feral accessions of mashua (Tropaeolum tuberosum í & Pavón) were identified and quantfied by High Performance Liquid Chromatography (HPLC) analysis. The nwin glucosinolates detected were aromatic: 4—Hydroxybenzyl GSL (OHB, Glucosinalbin), Benzyl GSL (B, Glucotropaeolin), and m—Methoxybenzyl GSL (MOB, Glucolimnathin). The total amount of GSL observed ranged from 0.27 to 50.74 micromols per gram (μMol/g) of dried tuber tissue. Most of the low-content GSL accessions are distributed within the cultivated population with a total GSL concentration lower than 5.00 μMol/g of dried tuber tissue. The highest total and specific GSL (OHB, B, and MOB) contents (more than 25.00 μMol/g of dried tuber tissue) were observed in the feral population with few exceptions. in addition, only six different GSL profiles were found: Only MOB; only B; OHB and B; OHB and MOB; B and MOB; and OHB, B and MOB.
Contenido de Glucosinolatos en mashuas (Tropaeolum tuberosum Ruiz & Pavon) cultivadas y silvestres de la region del Cusco, Peru
Se identifico y cuantificó mediante “High Performance Liquid Chromatograph” los glucosinolatos (GSL) presentes en mashua cultivada (Tropaeolum tuberosum Ruíz & Pavón) y sus parientes silvestres. Los compuestos principales descubiertos fueron los siguentes glucosinolatos aromáticos: 4—Hydroxybenzyl GSL (OHB, Glucosinalbin), Benzyl GSL (B, Glucotropaeolin) y m—Methoxybenzyl GSL (MOB, Glucolimnathin). El contenido total de GSLfluctuó entre 0.27 a 50.74 μMol/g de tejido del tubérculo seco. La mayorIa de las accesiones con bajo contenido de GSL estuvieron distribuidos dentro de la población cultivada con una concentración total de GSL menor a 5.00 μMol/g de tejido del tubérculo seco, mientras que el mas alto contenido total (mds de 25.00 μMol/g de tejido del tubérculo seco) y la mas alta concentración de GSL individuales (OHB, B y MOB) se observó en Ia población silvestre con pocas excepciones. Además, seis fenotipos de GSL diferentesfueron determinados: Sólo MOB; sólo B; OHB y B; OHB y MO; B y MOB; y OHB, B y MOB.
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13.
Fragmentation represents a serious threat to biodiversity worldwide, however its effects on epiphytic organisms is still poorly understood. We study the effect of habitat fragmentation on the genetic population structure and diversity of the red-listed epiphytic lichen, Lobaria pulmonaria, in a Mediterranean forest landscape. We tested the relative importance of forest patch quality, matrix surrounding fragments and connectivity on the genetic variation within populations and the differentiation among them. A total of 855 thalli were sampled in 44 plots (400 m2) of 31 suitable forest fragments (beeches and oaks), in the Sierra de Ayllón in central Spain. Variables related to landscape attributes of the remnant forest patches such as size and connectivity and also the nature of the matrix or tree species had no significant effects on the genetic diversity of L. pulmonaria. Values of genetic diversity (Nei’s) were only affected by habitat quality estimated as the age patches. Most of the variation (76%) in all populations was observed at the smallest sampled unit (plots). Using multiple regression analysis, we found that habitat quality is more important in explaining the genetic structure of the L. pulmonaria populations than spatial distance. The relatively high level of genetic diversity of the species in old forest patches regardless of patch size indicates that habitat quality in a highly structured forest stand determines the population size and distribution pattern of this species and its associated lichen community. Thus, conservation programmes of Mediterranean mountain forests have to prioritize area and habitat quality of old forest patches.  相似文献   

14.
This study is part of the Restoration Program of the animal populations from the Guadiamar River basin. The main objective is to evaluate the current state of populations of the most representative groups of edaphic coleoptera in the Guadiamar River basin. In 1998, a breach in the Aznalcóllar mines retaining wall (Southern Iberian Peninsula) led to toxic sludge pouring out into this area. Systematic samples were taken from monitoring plots, scattered throughout the affected area. In order to provide an overall assessment of the fauna collected from this area in relation to adjacent areas, ecological indices were applied, and temporal course and biogeographical comparisons were also made. The results indicate that, overall, the edaphic fauna has not been significantly affected by the spillage; however, a faunistic poverty was also detected, which becomes increasingly evident closer to the accident site. Moreover, temporal evolution analysis suggests that the most affected areas are undergoing a re-colonization process, although this varies widely between species and higher taxa. This research has been financed by the Project ‘Caracterización, restauración y conservación de las comunidades animales de la cuenca del río Guadiamar’ (Characterization, Re-establishment and Conservation of the animal communities from the Guadiamar River basin). Consejería de Medio Ambiente. Junta de Andalucía (Spain).  相似文献   

15.
Astragalus mario-sousae is described from the central part of state of Nuevo León, Mexico. It differs fromAstragalus esperanzae by its habit, peduncles, pedicels, and fruits.
Resumen   Astragalus mario-sousae (Fabaceae: Galegeae), a new species from northeastern Mexico. Brittonia 57: 314–319. 2005.—Astragalus mario-sousae es propuesta como especie nueva. Se conoce solo de la porción central del estado mexicano de Nuevo León. Se presentan una descripción e ilustración. Difiere deAstragalus esperanzae por su hábito erecto, pedúnculos, pedicelos y frutos más cortos.
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16.
The genetic integrity of six accessions represented by 14 sub-populations of the open-pollinating species rye (Secale cereale L.) was investigated. Seeds available from a herbarium collection (first regeneration) and from the cold store (most recent regeneration) were multiplied two to fourteen times and fingerprinted using microsatellite markers. Four accessions had significantly different allele frequencies. These were multiplied seven to thirteen times. Nearly 50% of the alleles discovered in the original samples were not found in the material present in the cold store. However alleles were detected in the most recently propagated sub-populations, that were not observed in the investigated plants of the original one. The change in allele frequencies is a continuous process. Reasons for the occurrence of genetic changes and consequences for managing open pollinating species maintained in ex situ genebanks are discussed.Communicated by G. Wenzel  相似文献   

17.
Three important phytopathogenic spores which cause serious fungal diseases on vines (Botrytis, Uncinula andPlasmopara) were monitored from June 2, 1994 to September 21, 1994, in vineyards belonging to ‘Estación de Enoloxía e Viticultura’ of Ponte San Clodio-Leiro (Ourense), one of the most important vine growing areas of northwest of Spain. The concentrations for each of the genera were correlated with rainfall, humidity, maximum, minimum and average temperatures. These meteorological parameters are currently used to determine chemical sprays to be applied to the vines. The aim was to establish the behaviour of airborne concentrations of spores of these taxa during the period from the flowering to harvest because these are the periods of greatest susceptibility to attack by these pathogens.  相似文献   

18.
19.
A genetic analysis of freshwater pearl mussel Margaritifera margaritifera populations from NW Spain, a peripheral area of its European distribution, was carried out using microsatellite markers. These populations were formerly reported as genetically differentiated on the basis of growth and longevity studies. Ten loci previously characterized in populations from central Europe were used to comparatively analyze the genetic variability at the southern edge of the species’ range. Iberian pearl mussel populations showed very low genetic variability and significant high genetic differentiation. Half of the total genetic diversity observed appeared to be distributed between populations, which suggested a highly structured adaptive potential in pearl mussel at the southern peripheral distribution of the species. Population distinctiveness was evidenced by assignment tests, which revealed a high accuracy of individual assignments to their population of origin. All data suggested low effective population size and major effects of genetic drift on population genetic structure. In order to avoid further loss of genetic variation in biologically distinctive populations from NW Spain, prioritization of genetic resources of this species is required for conservation and management.  相似文献   

20.
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