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PubMed2005

Diversity and selection in sorghum: simultaneous analyses using simple sequence repeats.

Although molecular markers and DNA sequence data are now available for many crop species, our ability to identify genetic variation associated with functional or adaptive diversity is still limited. In this study, our aim was to quantify and characterize diversity in a panel of cultivated and wild sorghums (Sorghum bicolor), establish genetic relationships, and, simultaneously, identify selection signals that might be associated with sorghum domestication. We assayed 98 simple sequence repeat (SSR) loci distributed throughout the genome in a panel of 104 accessions comprising 73 landraces (i.e., cultivated lines) and 31 wild sorghums. Evaluation of SSR polymorphisms indicated that landraces retained 86% of the diversity observed in the wild sorghums. The landraces and wilds were moderately differentiated (F st=0.13), but there was little evidence of population differentiation among racial groups of cultivated sorghums (F st=0.06). Neighbor-joining analysis showed that wild sorghums generally formed a distinct group, and about half the landraces tended to cluster by race. Overall, bootstrap support was low, indicating a history of gene flow among the various cultivated types or recent common ancestry. Statistical methods (Ewens-Watterson test for allele excess, lnRH, and F st) for identifying genomic regions with patterns of variation consistent with selection gave significant results for 11 loci (approx. 15% of the SSRs used in the final analysis). Interestingly, seven of these loci mapped in or near genomic regions associated with domestication-related QTLs (i.e., shattering, seed weight, and rhizomatousness). We anticipate that such population genetics-based statistical approaches will be useful for re-evaluating extant SSR data for mining interesting genomic regions from germplasm collections.

Cluster Analysis↗
PubMed2001

[Can disinfectants contribute to antibiotic resistance?].

BACKGROUND: Disinfectants are widely used in medicine, veterinary medicine, and the food processing industry. Increasingly, disinfectants are included in consumer products. Broad-scale use of antiseptics and disinfectants may have detrimental ecological consequences, for instance the development of antimicrobial resistance. MATERIAL AND METHODS: We give an overview of the correlation between the use of certain antiseptics and disinfectants, bacterial resistance to these agents, and antibiotic resistance. RESULTS: The mechanisms of antibiotic and biocide resistance share many common characteristics. There are links between disinfectant resistance and antibiotic resistance. Some biocides have the ability to select for antibiotic resistant mutants and vice versa. Resistance genes are often located on transferable genetic elements that facilitate horizontal gene transfer between microorganisms. Antibiotic resistance and disinfectant resistance may be stabilized and maintained even in the absence of a direct selective pressure. Higher incidence of bacteria resistant to certain disinfectants have been reported in environments where such agents are frequently used compared to environments where they are not in regular use. Increased domestic usage of non-antibiotic antimicrobial agents may select for antibiotic-resistant bacteria of clinical significance. INTERPRETATION: The use of antiseptics and disinfectants should be restricted to products and areas where they have an essential and documented effect.

Animals↗
PubMed2002

Feeding behavior of Lutzomyia pseudolongipalpis (Diptera: Psychodidae), a putative vector of visceral leishmaniasis in Venezuela.

Lutzomyia pseudolongipalpis Arrivillaga & Feliciangeli is the first new sand fly species in the L. longipalpis species complex that has been formally described since it was separated by genetic as well as by morphological characters. It is the putative vector of the American visceral leishmaniasis in La Rinconada, Curarigua, a restricted focus in central western Venezuela. We investigated the feeding behavior of this species. The blood meals from 210 of 429 (48.9%) engorged females caught by CDC light traps were identified by a dot enzyme-linked immuno-absorbent assay using antisera against humans and common domestic animals. We propose a new index, the host selectivity index, which is the number of sand flies fed on a given host relative to the available biomass of that host, as an indicator of the feeding behavior of this phlebotomine sand fly. The host selectivity index is compared with the forage ratio, which is the percentage of sand flies fed on a given host by the percentage which that host represented in the total census of available animals and humans. The most attractive animal for L. pseudolongipalpis in Curarigua was the dog, whereas humans were shown to be relatively unattractive. However, not only selectivity or biomass, but also the accessibility to this host may have influenced these results. The low population density of dogs and the low accessibility of L. pseudolongipalpis to humans in relation to domestic animals might help to explain the sporadic transmission of visceral leishmaniasis in this focus.

Animals↗
PubMed1982

Multiple avian influenza infection: selection of a non-avid virus by a heterologous avian host.

Experimental infection of domestic fowl, ducks and geese with an influenza A virus (H7N2) isolated from a domestic duck showed that this virus was apathogenic for these poultry. A second virus (H6N2), also apathogenic and more 'non-avid' than any such isolates previously recognised in surveillance of domestic poultry in Hong Kong, was isolated from one goose after H7N2 shedding had ceased. This goose, in effect, acted as a selective isolation system for the H6N2 virus whose presence in the field isolate could not be detected in spite of multiple passage in embryonated eggs.

Animals↗
PubMed1985

[Domestication and its sequelae].

The domestication of the dog took place in the late Glacial. Its earliest record comes from Oberkassel near Bonn and its age is some 14000 years B.C. On the other side the domestication of the farm animals began about 10000 years ago, during the so-called Neolithic Revolution, when man's way of life changed basicly from the hunter-and gatherer-culture to agriculture and animal husbandry. This change took place in the valleys and on the slopes of the mountains surrounding the basin of the Euphrat and Tigris rivers which is called the Fertile Crescent. Sheep and goat were succeeded by pig and cattle. Immediately after the transition to domestication with protection by human being taking the place of natural selection the livestock animals and the dog underwent a decrease in size. This reduction in size is one of the most important criteria for distinguishing prehistoric domestic livestock from their wild forms. In high developed cultures domestication resulted in a hardly imaginable morphological and physiological extension of variability, in a richness of forms not to be guessed by the whole potential of the corresponding ancestors. But all these rich appearing forms were due to intraspecific procedures. They don't create new species. By the way of the increasing influence of man and its domestic animals on the environment the procedure of domestication is more and more shifted in the foreground and increasingly intervenes with the interests of wild life.

Animals↗
PubMed2006

Genetic diversity at the hinge region of the unique immunoglobulin heavy gamma (IGHG) gene in leporids (Oryctolagus, Sylvilagus and Lepus).

Unlike other species, European rabbit (Oryctolagus cuniculus) possesses only one immunoglobulin gamma class. Allelic diversity at the Ig (immunoglobulin) gamma constant region encoded by the unique IGHG (immunoglobulin heavy gamma) gene is moreover much reduced. In the European rabbit, the genetic variation at IGGH hinge region is limited to a single nucleotide substitution, which causes a Met-Thr interchange at amino acid position 9 (IMGT hinge numbering). We have analysed the diversity at this region more in-depth by, (1) analysing the allelic variation in 11 breeds of domestic European rabbit (Oryctolagus cuniculus cuniculus), and (2) sequencing the gamma hinge exon in wild specimens of six species of rabbit (Oryctolagus and Sylvilagus) and hares (Lepus), including the two Oryctolagus subspecies (O. cuniculus cuniculus and O. cuniculus algirus). It appeared that among leporid species, amino acid changes occur exclusively at positions 8 and 9. However, while position 8 is occupied by either Pro or Ser residues, four different residues can occur at position 9 (Met, Thr, Pro and Leu). This variation concerns sites of potential O-glycosylation and/or proteolytic cleavage, suggesting that the underlying genetic diversity could be the outcome of selection. Preservation of the gamma hinge polymorphism in domestic stocks could therefore be important. We report here a polymerase chain reaction/restriction fragment length polymorphism protocol that has allowed the monitoring of the heterozygosity levels at the gamma hinge in 11 breeds of domestic European rabbit.

Alleles↗
PubMed1993

The effect of selection in sublines and crossing on genetic response and inbreeding.

More intense selection in a line gives greater genetic change but also gives a higher rate of inbreeding. Here, continuous selection in one line vs continuous selection in two or more sublines (for the same breeding objective and with the same total number of individuals tested) and crossing the sublines to reduce inbreeding, is studied by stochastic simulation using an infinitesimal model. On crossing, the inbreeding level in the cross, though zero, becomes equivalent to 1/n times that in the sublines, where n is the number of lines in the cross. In general, selecting in sublines and crossing gave less genetic response at the same level of inbreeding than selection in a single line. Use of the best subline generally gave less response than the whole line. It is concluded that selection response at the same level of inbreeding is greatest when all the test facilities and selection are concentrated in a single selection line.

Animals↗
PubMed2000

Role of the serotoninergic system in the acceleration of sexual maturation in wild Norway rats selected for reduced aggressiveness toward humans.

The role of the serotoninergic system in acceleration of the sexual development of domesticated rats (Rattus norvegicus) was assessed. The onset of age-related changes in hypothalamic serotonin during prepubertal period occurred earlier in domesticated than in aggressive male rats. Blockade of the serotoninergic system after p-chlorophenylalanine (PCPA) administration on days 40 and 44 delayed the development of the reproductive system in both aggressive and domesticated males. In 60-day-old rats treated with PCPA, levels of testosterone in plasma and the number of mature spermatozoa in epididymis were decreased compared to controls. At the same time, the administration of PCPA on days 30 and 34 did not modify basal testosterone secretion and other parameters in 60-day-old aggressive rats and produced a decrease similar to PCPA injections on days 40 and 44, although less pronounced, in the weights of testes in domesticated animals. Administration of 5-hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, on days 30, 32, 34, 36 and 38 increased plasma testosterone levels and weights of the sex organs in 60-day-old domesticated males, but did not significantly affect the development of reproductive system in aggressive animals. These data indicate that serotonin stimulates sexual development of males during prepubertal period and this activating effect of serotonin occurs earlier in domesticated than in aggressive males. They also suggest that the acceleration in sexual maturation of domesticated rats could result from changes in the ontogenetic dynamic of hypothalamic serotonin induced by a selection for low aggressiveness towards man.

5-Hydroxytryptophan↗
PubMed2006

Genetic diversity and gene flow among pearl millet crop/weed complex: a case study.

Weedy plants with intermediate (domesticated x wild) phenotypes occur in most pearl millet fields in West Africa, even in the absence of wild populations. They are usually found, in high numbers, both inside and outside of drills. Questions pertaining to the evolutionary dynamics of diversity within the pearl millet complex (domesticated-weedy-wild forms) were addressed in this study. The diversity of the different components of this complex sampled in two pearl millet fields in two villages of southwestern Niger was assessed at both molecular (AFLP) and morphological levels. Results show that, in both fields, weedy plants found outside of drills are morphologically distinct from weedy plants found inside drills, despite their close similarity at AFLP markers. The data suggest some introgression from the wild to the weedy population but nevertheless that the gene flow between the parapatric wild and domesticated populations is very low. This challenges the traditional view that regular hybridization between domesticated and wild pearl millets explains the abundance of these weedy plants despite farmers' seed selection. The level of genetic differentiation between fields from the two villages was low when considering domesticated and weedy plants. This could be explained by high gene flow resulting from substantial seed exchanges between farmers. The fact that it is very difficult for farmers to keep their own selected seeds, and the consequent substantial seed exchanges between them, is probably the main factor accounting for the maintenance and dispersal of weedy pearl millets in the region, even in areas where no wild forms have been observed.

Evolution, Molecular↗
PubMed1995

Comparison of evaluation-selection systems for maximizing genetic response at the same level of inbreeding.

Use of improved methods of genetic evaluation and intense selection lead to higher rates of genetic change but also lead to higher rates of inbreeding. A number of methods have been proposed to attain high rates of genetic response with moderate or low inbreeding (i.e., restrict the number of close relatives selected, use false high heritability in the genetic evaluation, use assortative mating, adjust estimated breeding values for the relationship with those already selected, avoid matings of related individuals, and increase the number of parents selected). These various methods were compared here using stochastic simulation of an infinitesimal genetic model. The results were studied graphically plotting response against inbreeding, so allowing comparison of the methods at each of a range of inbreeding levels. None of the methods was best over all conditions. At high rates of inbreeding and with a fixed number of sires, several of the methods gave large decreases in inbreeding for small losses in response. However, these were matched by simply increasing the number of sires selected. There is an optimum response-inbreeding "front" attained by several methods, and this front seems hard to breach. Characterization of the front would be useful in designing selection programs.

Algorithms↗
PubMed1986

Mapping genes in domesticated animals.

Gene maps are constructed by the synthesis of data obtained by different methods which include family analyses, somatic cell hybridization, direct mapping of DNA segments by Southern blot analysis, and in situ hybridization to fixed metaphase chromosomes. Gene mapping has already contributed significantly to a better understanding of the mammalian genome, in particular the human genome, but the gene maps of economically important domestic species are not well-characterized. The application of somatic cell genetics and recombinant DNA methodologies now allows rapid progress to be made in the construction of detailed gene maps for domestic animals. Such gene maps will serve as tools for selection in applied animal breeding and for the analysis of polygenic traits.

Animals↗
PubMed2006

Multilevel selection 2: Estimating the genetic parameters determining inheritance and response to selection.

Interactions among individuals are universal, both in animals and in plants and in natural as well as domestic populations. Understanding the consequences of these interactions for the evolution of populations by either natural or artificial selection requires knowledge of the heritable components underlying them. Here we present statistical methodology to estimate the genetic parameters determining response to multilevel selection of traits affected by interactions among individuals in general populations. We apply these methods to obtain estimates of genetic parameters for survival days in a population of layer chickens with high mortality due to pecking behavior. We find that heritable variation is threefold greater than that obtained from classical analyses, meaning that two-thirds of the full heritable variation is hidden to classical analysis due to social interactions. As a consequence, predicted responses to multilevel selection applied to this population are threefold greater than classical predictions. This work, combined with the quantitative genetic theory for response to multilevel selection presented in an accompanying article in this issue, enables the design of selection programs to effectively reduce competitive interactions in livestock and plants and the prediction of the effects of social interactions on evolution in natural populations undergoing multilevel selection.

Models, Genetic↗
PubMed1999

Seroepidemiology of Helicobacter pylori infection in a Jamaican community.

We researched epidemiologic associations between environmental and demographic factors and prevalence of Helicobacter pylori infection in a suburban Jamaican community. Using a clustered sampling technique, 22 domestic yards enclosing 60 separate households were randomly selected from a local community. All household members (n = 346) were invited to participate following informed consent; the overall compliance rate was 58.9%. A commercial enzyme immunoassay (HMáCAP) was used to detect IgG antibodies raised against H. pylori. Environmental and demographic information was obtained by questionnaire. The seroprevalence of H. pylori was 69.9% (n = 202). Analysis of the independent variables revealed three major components: Component 1 described, collectively, good personal hygiene and sanitation, indoor water supply and absence of straying animals in the peridomestic area; Component 2 included older age, good personal hygiene and large yard size; Component 3 the presence of domestic animals (cats and dogs) and, again, large yard size. These three complexes explained 42.2% of the variability in the data set. Logistic regression showed that Components 2 and 3 were independently associated with H. pylori seropositivity, indicating that a combination of demographic, environmental and zoonotic factors is involved in the spread of H. pylori infections at the tropical community level.

Adolescent↗
PubMed1992

Spatial memory and adaptive specialization of the hippocampus.

The hippocampus plays an important role in spatial memory and spatial cognition in birds and mammals. Natural selection, sexual selection and artificial selection have resulted in an increase in the size of the hippocampus in a remarkably diverse group of animals that rely on spatial abilities to solve ecologically important problems. Food-storing birds remember the locations of large numbers of scattered caches. Polygynous male voles traverse large home ranges in search of mates. Kangaroo rats both cache food and exhibit a sex difference in home range size. In all of these species, an increase in the size of the hippocampus is associated with superior spatial ability. Artificial selection for homing ability has produced a comparable increase in the size of the hippocampus in homing pigeons, compared with other strains of domestic pigeon. Despite differences among these animals in their histories of selection and the genetic backgrounds on which selection has acted, there is a common relationship between relative hippocampal size and spatial ability.

Adaptation, Physiological↗
PubMed2000

Genetic resistance to experimental infection with Mycobacterium bovis in red deer (Cervus elaphus).

Tuberculosis (Tb) caused by Mycobacterium bovis is a worldwide threat to livestock and humans. One control strategy is to breed livestock that are more resistant to Mycobacterium bovis. In a 3-year heritability study 6 farmed red deer stags were selected from 39 on the basis of their differing responses to experimental challenge via the tonsillar sac with approximately 500 CFU of M. bovis. Two stags remained uninfected, two were moderately affected, and two developed serious spreading Tb. Seventy offspring, bred from these six stags by artificial insemination using stored semen, were similarly challenged with M. bovis. The offspring showed patterns of response to M. bovis challenge similar to those of their sires, providing evidence for a strong genetic basis to resistance to Tb, with an estimated heritability of 0.48 (standard error, 0.096; P < 0. 01). This is the first time the heritability of Tb resistance in domestic livestock has been measured. The breeding of selection lines of resistant and susceptible deer will provide an ideal model to study the mechanisms of Tb resistance in a ruminant and could provide an additional strategy for reducing the number and severity of outbreaks of Tb in farmed deer herds. Laboratory studies to identify genetic and immunological markers for resistance to Tb are under way. Preliminary studies showed no associations between NRAMP or DRB genes and resistance to Tb in deer. Patterns of immune responses seen in resistant animals suggest that both innate and acquired pathways of immunity are necessary to produce the resistant phenotype.

Animals↗
PubMed2002

Sperm mobility: mechanisms of fertilizing efficiency, genetic variation and phenotypic relationship with male status in the domestic fowl, Gallus gallus domesticus.

When females are sexually promiscuous, sexual selection continues after insemination through sperm competition and cryptic female choice, and male traits conveying an advantage in competitive fertilization are selected for. Although individual male and ejaculate traits are known to influence paternity in a competitive scenario, multiple mechanisms co-occur and interact to determine paternity. The way in which different traits interact with each other and the mechanisms through which their heritability is maintained despite selection remain unresolved. In the promiscuous fowl, paternity is determined by the number of sperm inseminated into a female, which is mediated by male social dominance, and by the quality of the sperm inseminated, measured as sperm mobility. Here we show that: (i) the number of sperm inseminated determines how many sperm reach the female sperm-storage sites, and that sperm mobility mediates the fertilizing efficiency of inseminated sperm, mainly by determining the rate at which sperm are released from the female storage sites, (ii) like social status, sperm mobility is heritable, and (iii) subdominant males are significantly more likely to have higher sperm mobility than dominant males. This study indicates that although the functions of social status and sperm mobility are highly interdependent, the lack of phenotypic integration of these traits may maintain the variability of male fitness and heritability of fertilizing efficiency.

Animals↗
PubMed2000

Current state in biotechnology in canine and feline reproduction.

Biotechnology has proceeded much further in cats than in canines, although the pregnancy rate after in vitro maturation (IVM), IVC and embryo transfer (ET) is still relatively low. The use of AI with frozen-thawed semen as a breeding tool to overcome breeding incompatibility or to preserve male genetic material has been limited in felines in contrast to the situation in domestic dogs and foxes. In many research scenarios and endangered felid species programs, the in vitro production of feline embryos with subsequent transfer has complemented the use of AI. Improvement of IVM, in vitro fertilization (IVF) and embryo culture coupled with ovarian tissue grafting, cryobanking of follicles, oocytes, semen, or embryos, with subsequent ET into surrogate females, may render this technology feasible for use in endangered wild felids. In canines, reliable systems for in vitro production of embryos, embryo cryopreservation and transfer are yet to be developed. The refinement of invasive fertilization techniques, such as intracytoplasmic sperm injection (ICSI), may eventually provide a tool for removal of recipient oocyte nuclei and transfer of selected embryonic or somatic cell donor nuclei into domestic cat ooplasm, thereby providing a tool for genetic modification, or for preservation of valuable genetic material.

Animals↗
PubMed2006

Preservation of plant genetic resources in the biotechnology era.

Thousands of years ago humans began domesticating crops as a food source. Among the wild germplasm available, they selected those that were best adapted for cultivation and utilization. Although wild ancestors have continued to persist in regions where domestication took place, there is a permanent risk of loss of the genetic variability of cultivated plants and their wild relatives in response to changing environmental conditions and cultural practices. Recognizing this danger, plant ex situ genebank collections were created since the beginning of the last century. World-wide, more than 6 million accessions have been accumulated including the German ex situ genebank in Gatersleben, one of the four largest global collections, housing 150,000 accessions belonging to 890 genera and 3032 species. This review summarizes the ex situ plant genetic resources conservation behavior with a special emphasis on German activities. Strategies for maintenance and management of germplasm collections are reviewed, considering modern biotechnologies (in vitro and cryo preservation). General aspects on genetic diversity and integrity are discussed.

Biological Specimen Banks↗