Genetic Variability (genetic + variability)

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Genetic Variability

  • high genetic variability


  • Selected Abstracts


    THE EFFECTS OF MATING SYSTEM AND GENETIC VARIABILITY ON SUSCEPTIBILITY TO TREMATODE PARASITES IN A FRESHWATER SNAIL, LYMNAEA STAGNALIS

    EVOLUTION, Issue 12 2004
    Mikael Puurtinen
    Abstract The amount and distribution of genetic variability in host populations can have significant effects on the outcome of host-parasite interactions. We studied the effect of mating system and genetic variability on susceptibility of Lymnaea stagnalis snails to trematode parasites. Mating system of snails from eight populations differing in the amount of genetic variability was manipulated, and self- and cross-fertilized offspring were exposed to naturally occurring trematode parasites in a controlled lake experiment. Susceptibility of snails varied between populations, but mating-system treatment did not have a significant effect. Heterozygosity of snails was negatively correlated with the probability of trematode infection, however, suggesting that parasitic diseases may pose a serious threat to populations lacking genetic variability. [source]


    Morphological and Pathological Variability in Rice Isolates of Rhizoctonia solani and Molecular Analysis of their Genetic Variability

    JOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2007
    S. Guleria
    Abstract Nineteen isolates of Rhizoctonia solani collected from different rice varieties grown in various regions of Punjab were studied for their morphological and pathological characterization. Majority of the isolates were fast growing with raised and fluffy colonies and hyphal width of 9.6 ,m while four exhibited moderate growth rate. Colony colour in all except two isolates was light yellowish brown. While sclerotial number per 5.0 mm culture disc of the test isolates ranged between 2.1 and 11.2 mm, their size varied between 1.31 and 2.08 mm. Sclerotial colour in all except two isolates was dark brown and most of these were found scattered in the colony. There was no relationship between morphologically similar isolates and their pathogenic behaviour. Majority of the isolates produced lesion length between 45.6 and 58.2 mm on detached rice leaves (cv. PR116). Molecular characterization of genetic diversity in the test isolates was studied by using 10 inter simple sequence repeats (ISSR) and eight random amplified polymorphic DNA (RAPD) markers. The size of amplified DNA bands ranged from 0.25,3.0 to 0.5,4.0 kb with ISSR and RAPD markers, respectively. Combined data set of 155 DNA markers were analysed with UPGMA resulting five clusters with 49,89% genetic similarity. Most of the isolates showed grouping specific to the host variety. Out of these two types of DNA markers, RAPD markers were able to detect more genetic variability when compared to ISSR markers. [source]


    Genetic variability in a population of arbuscular mycorrhizal fungi causes variation in plant growth

    ECOLOGY LETTERS, Issue 2 2006
    Alexander M. Koch
    Abstract Different species of arbuscular mycorrhizal fungi (AMF) alter plant growth and affect plant coexistence and diversity. Effects of within-AMF species or within-population variation on plant growth have received less attention. High genetic variation exists within AMF populations. However, it is unknown whether genetic variation contributes to differences in plant growth. In our study, a population of AMF was cultivated under identical conditions for several generations prior to the experiments thus avoiding environmental maternal effects. We show that genetically different Glomus intraradices isolates from one AMF population significantly alter plant growth in an axenic system and in greenhouse experiments. Isolates increased or reduced plant growth meaning that plants potentially receive benefits or are subject to costs by forming associations with different individuals in the AMF population. This shows that genetic variability in AMF populations could affect host-plant fitness and should be considered in future research to understand these important soil organisms. [source]


    Genetic variability in environmental isolates of Legionella pneumophila from Comunidad Valenciana (Spain)

    ENVIRONMENTAL MICROBIOLOGY, Issue 6 2006
    Mireia Coscollá
    Summary Legionella pneumophila is associated to recurrent outbreaks in several Comunidad Valenciana (Spain) localities, especially in Alcoi, where social and climatic conditions seem to provide an excellent environment for bacterial growth. We have analysed the nucleotide sequences of three loci from 25 environmental isolates from Alcoi and nearby locations sampled over 3 years. The analysis of these isolates has revealed a substantial level of genetic variation, with consistent patterns of variability across loci, and comparable to that found in a large, European-wide sampling of clinical isolates. Among the tree loci studied, fliC showed the highest level of nucleotide diversity. The analysis of isolates sampled in different years revealed a clear differentiation, with samples from 2001 being significantly distinct from those obtained in 2002 and 2003. Furthermore, although linkage disequilibrium measures indicate a clonal nature for population structure in this sample, the presence of some recombination events cannot be ruled out. [source]


    Genetic variability of the ,bark canker resistance' character in several natural provenances of Cupressus sempervirens

    FOREST PATHOLOGY, Issue 2 2000
    A. Santini
    Summary Several Aegean (Greece) and Anatolian (Turkey) cypress provenances were studied for resistance variability to bark canker, a disease caused by the fungal pathogen Seiridium cardinale. The investigation also examined whether the low disease rate within the natural area of cypress was due to genetic or geographic-climatic reasons. Results demonstrated strong variability for the ,bark canker resistance' character, in particular for trees within families. As trees from the provenances studied were not found to have genetic superiority for bark canker resistance, the above-mentioned low disease rate could be due to geographic-climatic barriers that inhibit the development of the fungus or its ability to infect the host. Several half-sib progenies exhibited high resistance, suggesting that this character is totally inherited through the maternal line. Should this finding be confirmed by further research, it would facilitate the task of genetic improvement for resistance, allowing progenies of resistant trees to be obtained. [source]


    Genetic variability in Irish populations of the invasive zebra mussel, Dreissena polymorpha: discordant estimates of population differentiation from allozymes and microsatellites

    FRESHWATER BIOLOGY, Issue 7 2008
    ELIZABETH GOSLING
    Summary 1. The recent arrival and explosive spread of the zebra mussel, Dreissena polymorpha (Pallas), in Ireland provided a rare opportunity to study the population genetics of an invasive species. 2. Eight polymorphic allozyme loci (ACO-1, ACO-2, EST-D, GPI, IDH-2, MDH, OPDH and PGM) were used to investigate genetic diversity and population structure in five Irish populations, and the results were compared with those from a previous microsatellite study on the same samples. 3. The mean number of alleles per locus (2.7 ± 0.1) was similar to the mean for the same loci in European populations, suggesting that Irish founder populations were large and/or multiple colonization events took place after foundation. A deficiency of heterozygotes was observed in all populations, but was uneven across loci. 4. Pairwise comparisons, using Fisher's exact tests and FST values, revealed significant genetic differentiation among populations. The overall multilocus FST estimate was 0.118 ± 0.045, which contrasted with an estimate of 0.015 ± 0.007 from five microsatellite loci on the same samples in a previous study. 5. Assuming that microsatellites can be used as a neutral baseline, the discordant results from allozymes and microsatellites suggest that selection may be acting on some allozyme loci, specifically ACO-1, ACO-2, IDH-2 and MDH, which contributed most to the significant differentiation between samples. [source]


    Genetic variability in the mitochondrial serine protease HTRA2 contributes to risk for Parkinson disease,

    HUMAN MUTATION, Issue 6 2008
    Veerle Bogaerts
    Abstract In one genetic study, the high temperature requirement A2 (HTRA2) mitochondrial protein has been associated with increased risk for sporadic Parkinson disease (PD). One missense mutation, p.Gly399Ser, in its C-terminal PDZ domain (from the initial letters of the postsynaptic density 95, PSD-95; discs large; and zonula occludens-1, ZO-1 proteins [Kennedy, 1995]) resulted in defective protease activation, and induced mitochondrial dysfunction when overexpressed in stably transfected cells. Here we examined the contribution of genetic variability in HTRA2 to PD risk in an extended series of 266 Belgian PD patients and 273 control individuals. Mutation analysis identified a novel p.Arg404Trp mutation within the PDZ domain predicted to freeze HTRA2 in an inactive form. Moreover, we identified six patient-specific variants in 5, and 3, regulatory regions that might affect HTRA2 expression as supported by data of luciferase reporter gene analyses. Our study confirms a role of the HTRA2 mitochondrial protein in PD susceptibility through mutations in its functional PDZ domain. In addition, it extends the HTRA2 mutation spectrum to functional variants possibly affecting transcriptional activity. The latter underpins a previously unrecognized role for altered HTRA2 expression as a risk factor relevant to parkinsonian neurodegeneration. Hum Mutat 29(6), 832,840, 2008. © 2008 Wiley-Liss, Inc. [source]


    Genetic variability, haplotypes, and htSNPs for exons 1 at the human UGT1A locus,,

    HUMAN MUTATION, Issue 7 2006
    Sushma S. Thomas
    Abstract UDP-Glucuronosyltransferases (UGTs) are a superfamily of enzymes responsible for glucuronidation of xenobiotics and endobiotics. Genetic polymorphisms have been identified in the promoter and exonic regions of several UGT genes. The UGT1As on chromosome 2q37 have unique exons 1 but share the remainder of their coding sequence. We screened exon 1 of each of the nine functional UGT1As in Asians (n=46) and Caucasians (n=92) with the aim of determining linkage disequilibrium (LD) and haplotypes across the entire locus in both populations. For polymorphisms in UGT 1A3, 1A4, 1A5, 1A7, and 1A8, we observed significant differences in the allele frequency between the two populations. The haplotype block structure across the UGT1A locus was constructed using all 83 polymorphisms and showed four and five haplotype blocks in Caucasians and Asians, respectively. There was long-distance LD between UGT pairs: 1A8 and 1A10; 1A1 and 1A3; 1A1 and 1A6; 1A6 and 1A7; and 1A7 and 1A9. Whereas both ethnic groups shared some haplotype-tagging SNPs (htSNPs), Caucasians and Asians also had unique htSNPs. This was partly due to the fact that rare variants (<5% allele frequency) were included in our analyses. Haplotypes with frequencies >5% represented only 60% of Caucasian and 65% of Asian UGT1A haplotypes. Differences in haplotype distribution patterns suggest individual and ethnic differences in glucuronidation capacity. Published 2006 Wiley-Liss, Inc. [source]


    Genetic variability of seven dog breeds based on microsatellite markers

    JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 2005
    C. Schelling
    Summary The present study, compared the genetic variability of seven dog breeds and a test sample from Switzerland by means of 26 microsatellite markers. Five loci were excluded from further analyses because one was monomorphic, one not in Hardy,Weinberg equilibrium in all breeds and three in linkage disequilibrium with linked loci. The proportion of shared alleles at the individual level of the remaining 21 microsatellite markers combined with the neighbour-joining method allowed for the clustering of the large majority of the individuals in accordance to their breed. The results were confirmed by analyses using a Bayesian approach for clustering and a Monte Carlo re-sampling method for individual assignment or exclusion to a given population. [source]


    Genetics, epigenetics and pharmaco-(epi)genomics in angiogenesis

    JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 6b 2008
    Ian Buysschaert
    ,,Introduction ,,Angiogenesis is genetically pre-determined ,,Mutations causing vascular anomalies -,Venous anomalies -,Haemangiomas -,The transforming growth factor-ß in vascular anomalies -,Cerebral cavernous malformations ,,Translocations reveal novel angiogenic genes ,,Single nucleotide polymorphisms shape the angio-genome -,SNPs in VEGF and their association with cancer -,SNPs in VEGF pathway genes associated with other diseases -,Genetic variability in VEGFR-2 -,Genetic variability in HIF-1, -,SNPs in VEGFR-1 integrate angiogenesis within the P53 pathway -,Variations in angiogenic genes are linked with neurodegeneration -,Angiogenic factors in genome-wide association studies ,,Copy number variability affects angiogenesis ,,Epigenetic regulation of angiogenesis -,Methylation of anti-angiogenic factors -,Methylation as a second hit event in cancer -,Histone modifications determine angiogenesis ,,Micromanagers of angiogenesis ,,Perspectives Abstract Angiogenesis is controlled by a balance between pro- and anti-angiogenic factors. Studies in mice and human beings have shown that this balance, as well as the general sensitivity of the endothelium to these factors, is genetically pre-determined. In an effort to dissect this genetic basis, different types of genetic variability have emerged: mutations and translocations in angiogenic factors have been linked to several vascular malformations and haemangiomas, whereas SNPs have been associated with complex genetic disorders, such as cancer, neurodegeneration and diabetes. In addition, copy number alterations of angiogenic factors have been reported in several tumours. More recently, epigenetic changes caused by aberrant DNA methylation or histone acetylation of anti-angiogenic molecules have been shown to determine angiogenesis as well. Initial studies also revealed a crucial role for microRNAs in stimulating or reducing angiogenesis. So far, most of these genetic studies have focused on tumour angiogenesis, but future research is expected to improve our understanding of how genetic variants determine angiogenesis in other diseases. Importantly, these genetic insights might also be of important clinical relevance for the use of anti-angiogenic strategies in cancer or macular degeneration. [source]


    Genetic evaluation of dairy cattle using a simple heritable genetic ground

    JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2010
    Josef Pribyl
    Abstract The evaluation of an animal is based on production records, adjusted for environmental effects, which gives a reliable estimation of its breeding value. Highly reliable daughter yield deviations are used as inputs for genetic marker evaluation. Genetic variability is explained by particular loci and background polygenes, both of which are described by the genomic breeding value selection index. Automated genotyping enables the determination of many single-nucleotide polymorphisms (SNPs) and can increase the reliability of evaluation of young animals (from 0.30 if only the pedigree value is used to 0.60 when the genomic breeding value is applied). However, the introduction of SNPs requires a mixed model with a large number of regressors, in turn requiring new algorithms for the best linear unbiased prediction and BayesB. Here, we discuss a method that uses a genomic relationship matrix to estimate the genomic breeding value of animals directly, without regressors. A one-step procedure evaluates both genotyped and ungenotyped animals at the same time, and produces one common ranking of all animals in a whole population. An augmented pedigree,genomic relationship matrix and the removal of prerequisites produce more accurate evaluations of all connected animals. Copyright © 2010 Society of Chemical Industry [source]


    Genetic variability and differentiation in red deer (Cervus elaphus) from Scotland and England

    JOURNAL OF ZOOLOGY, Issue 3 2006
    S. S. Hmwe
    Abstract Samples from 69 British red deer Cervus elaphus scoticus from seven populations in Scotland and England were analysed with respect to variability within and differentiation among stocks using 11 polymorphic microsatellite loci and 439 bp of the mitochondrial control region. The results clearly showed the effects of anthropogenic factors on British red deer. On the whole, variability values were within the species' reported range. The island population of Islay, Scotland, however, while showing average microsatellite variability, exhibited no mitochondrial variation at all. One microsatellite locus was monomorphic in three Scottish populations (Islay, Dunachton and Achnacarry). Overall and pairwise FST values indicate considerable differentiation among the populations studied, but Dunachton and Achnacarry, two adjacent populations free from recorded introductions, showed only a little differentiation and were paired in trees based on genetic distances. In terms of variability, no statistically significant differences were observed between island and mainland populations and the overall test of isolation by distance was negative. Possible reasons for the genetic patterns observed, such as differences in human impact on the populations, are discussed. [source]


    Genetic variability and population structure of dorada (Brycon moorei sinuensis Dahl) in the Sinú River, Córdoba, Colombia

    LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2006
    Liliana López
    Abstract Six microsatellite loci, isolated for Piaractus mesopotamicus (Characidae, Serrasalminae) were used to evaluate the genetic variability of the dorada (Brycon moorei sinuensis, Characidae, Bryconinae) population in the Sinú River, Córdoba, Colombia, and to facilitate management recommendations for this species. The six loci were polymorphic, with an average of 9.25 alleles for dimeric loci (Pme2, Pme4, Pme5 and Pme20), and five alleles for trimeric loci. Tests for linkage disequilibrium were used to determine that the six loci had an independent distribution. The observed heterozygosities were lower than the expected ones for all loci, and the population was not in Hardy,Weinberg equilibrium because of heterozygote deficiency. F -statistics indicated inbreeding and a low population substructure. The homogeneity of the population was confirmed by high values of genetic flux and an agglomerated representation of the individuals, based on factor correspondence analysis. Recent bottlenecks were detected for three sample sites under the assumption of an infinite allele mutation model. Proposals for the management of the dorada population are made and validated with a genetic simulation. [source]


    Characterization of Aspergillus flavus strains from Brazilian Brazil nuts and cashew by RAPD and ribosomal DNA analysis

    LETTERS IN APPLIED MICROBIOLOGY, Issue 1 2008
    G.E.O. Midorikawa
    Abstract Aims:, The aim of this study was to determine the genetic variability in Aspergillus flavus populations from Brazil nut and cashew and develop a polymerase chain reaction (PCR) detection method. Methods and Results:, Chomatography analysis of 48 isolates identified 36 as aflatoxigenic (75%). One hundred and forty-one DNA bands were generated with 11 random amplified polymorphic DNA (RAPD) primers and analysed via unweighted pair group analysis, using arithmetic means (UPGMA). Isolates grouped according to host, with differentiation of those from A. occidentale also according to geographical origin. Aspergillus flavus -specific PCR primers ASPITSF2 and ASPITSR3 were designed from ribosomal DNA internal transcribed spacers (ITS 1 and 2), and an internal amplification control was developed, to prevent false negative results. Specificity to only A. flavus was confirmed against DNA from additional aspergilli and other fungi. Conclusions:, RAPD-based characterization differentiated isolates according to plant host. The PCR primer pair developed showed specificity to A. flavus, with a detection limit of 10 fg. Significance and Impact of the Study:, Genetic variability observed in A. flavus isolates from two Brazilian agroecosystems suggested reproductive isolation. The PCR detection method developed for A. flavus represents progress towards multiplex PCR detection of aflatoxigenic and nonaflatoxigenic strains in Hazard Analysis Critical Control Point systems. [source]


    Genetic variability of hepatitis C virus NS3 protein in human leukocyte antigen-A2 liver transplant recipients with recurrent hepatitis C

    LIVER TRANSPLANTATION, Issue 2 2004
    F. Xavier López-Labrador
    The association between the severity of chronic hepatitis C and the variability of the hepatitis C virus (HCV) genome remains controversial, but to our knowledge few data are available to date regarding T-cell epitope coding regions in transplant patients. In the current study, we identified 21 human leukocyte antigen (HLA)-A2-positive Spanish patients with chronic hepatitis C, 14 immunosuppressed liver transplant recipients, and 7 immunocompetent controls. Alanine aminotransferase, aspartate aminotransferase, viral load, and rate of fibrosis progression were determined. Genetic distances of HCV isolates and variations in epitopes of the HCV nonstructural 3 protein (NS3-1393 LIFCHSKKK and NS3-1406 KLVALGINAV) were compared between patients with slow or fast progression of fibrosis. Isolates from transplant patients with fast progression were found to be more divergent (P =.03), had a higher mean value of synonymous (dS) variations (P =.02), and some were differentiated in a phylogenetic tree, compared with isolates from patients with slow progression. The HLA-A2-restricted NS3-1406 epitope was found to be more variable (20 of 21 isolates differed from the prototype) compared with the A3-restricted NS3-1392 epitope (19% vs. 1.25% variation). A shift in the viral peptide was not detected in a subset of transplant patients, but was evident in two of three nontransplant patients with follow-up. There was no correlation noted between a particular amino acid variation and fibrosis progression (slow or fast) in either transplant or nontransplant patients. The results of the current study suggest that 1) there may be different HCV-1b strains in our geographic area, 2) immunosuppression appears to have little effect in amino acid variation at the HCV NS3-1406 epitope, and 3) variations over time might be more frequent in nonimmunosuppressed patients. (Liver Transpl 2004;10:217,227.) [source]


    Genetic variability in CRTH2 polymorphism increases eotaxin-2 levels in patients with aspirin exacerbated respiratory disease

    ALLERGY, Issue 3 2010
    N. S. Palikhe
    To cite this article: Palikhe NS, Kim S-H, Cho B-Y, Ye Y-M, Choi G-S, Park H-S. Genetic variability in CRTH2 polymorphism increases eotaxin-2 levels in patients with aspirin exacerbated respiratory disease. Allergy 2010; 65: 338,346. Abstract Introduction:, CRTH2 is expressed on the surface of eosinophils and has been shown to mediate PGD2-induced eosinophil migration in vitro. Eosinophilic infiltration in the upper and lower airways is the key feature of asthma. Considering the fact that eosinophil infiltration is prominent in the upper and lower airways of aspirin exacerbated respiratory disease (AERD) compared to aspirin-tolerant asthma (ATA) patients, we hypothesized that activation of eosinophils via dysregulation of the CRTH2 gene may play an important role and be an important marker for AERD. Methods:, The three study groups , 107 with AERD, 115 with ATA and 133 normal healthy controls (NC) , were recruited from Ajou University Hospital, South Korea. Two polymorphisms of the CRTH2 gene at -466T>C and -129C>A were genotyped using primer extension methods. Results:, AERD patients had significantly higher serum eotaxin-2 levels than did those with ATA (P = 0.034). A significant difference in the genotype frequencies of CRTH2 -466T>C was detected between AERD and ATA patients (P < 0.05). The serum eotaxin-2 level was significantly higher in AERD patients carrying the TT genotype of CRTH2 -466T>C than those with the CT and CC (P < 0.05). In vitro functional study demonstrated that the -466T allele had lower luciferase activity (P < 0.001) and lower mRNA expression with higher production of eotaxin-2 (P = 0.003) in human lung epithelial cells. EMSA showed that CRTH2 -466T produced a specific band with a higher affinity than CRTH2 -466C had. Conclusion:, The CRTH2 -466T>C polymorphism increases serum and cellular eotaxin-2 production through lowered CRTH2 expression, leading to eosinophilic infiltration in AERD patients. [source]


    Genetic variability: The key problem in the prevention and therapy of RNA-based virus infections

    MEDICINAL RESEARCH REVIEWS, Issue 4 2003
    Magdalena Figlerowicz
    Abstract Despite extraordinary progress that has recently been made in biomedical sciences, viral infectious diseases still remain one of the most serious world health problems. Among the different types of viruses, those using RNA as their genetic material (RNA viruses and retroviruses) are especially dangerous. At present there is no medicine allowing an effective treatment of RNA-based virus infections. Many RNA viruses and retroviruses need only a few weeks to escape immune response or to produce drug-resistant mutants. This seems to be the obvious consequence of the unusual genetic variability of RNA-based viruses. An individual virus does not form a homogenous population but rather a set of similar but not identical variants. In consequence, RNA-based viruses can easily adapt to environmental changes, also those resulting from immune system response or therapy. The modifications identified within viral genes can be divided into two groups: point mutations and complex genome rearrangements. The former arises mainly during error-prone replication, whereas RNA recombination and generic reassortment are responsible for the latter. This article shortly describes major strategies used to control virus infections. Then, it presents the various mechanisms generating the genetic diversity of RNA-based viruses, which are most probably the main cause of clinical problems. © 2003 Wiley Periodicals, Inc. Med Res Rev, 23, No. 4, 488,518, 2003 [source]


    Genetic variability is unrelated to growth and parasite infestation in natural populations of the European eel (Anguilla anguilla)

    MOLECULAR ECOLOGY, Issue 22 2009
    J. M. PUJOLAR
    Abstract Positive correlations between individual genetic heterozygosity and fitness-related traits (HFCs) have been observed in organisms as diverse as plants, marine bivalves, fish or mammals. HFCs are not universal and the strength and stability of HFCs seem to be variable across species, populations and ages. We analysed the relationship between individual genetic variability and two different estimators of fitness in natural samples of European eel, growth rate (using back-calculated length-at-age 1, 2 and 3) and parasite infestation by the swimbladder nematode Anguillicola crassus. Despite using a large data set of 22 expressed sequence tags-derived microsatellite loci and a large sample size of 346 individuals, no heterozygote advantage was observed in terms of growth rate or parasite load. The lack of association was evidenced by (i) nonsignificant global HFCs, (ii) a Multivariate General Linear Model showing no effect of heterozygosity on fitness components, (iii) single-locus analysis showing a lower number of significant tests than the expected false discovery rate, (iv) sign tests showing only a significant departure from expectations at one component, and, (v) a random distribution of significant single-locus HFCs that was not consistent across fitness components or sampling sites. This contrasts with the positive association observed in farmed eels in a previous study using allozymes, which can be explained by the nature of the markers used, with the allozyme study including many loci involved in metabolic energy pathways, while the expressed sequence tags-linked microsatellites might be located in genes or in the proximity of genes uncoupled with metabolism/growth. [source]


    Genetic variation and structure in six Rhododendron species (Ericaceae) with contrasting local distribution patterns in Hong Kong, China

    MOLECULAR ECOLOGY, Issue 7 2000
    Sai-Chit Ng
    Abstract Genetic variability of six rhododendrons with contrasting local distribution patterns in Hong Kong was assessed by starch gel electrophoresis. Rhododendron championiae, R. hongkongense and R. simiarum are locally rare with disjunct distributions, R. moulmainense is restricted and R. farrerae and R. simsii are common. For each species, 13,18 allozyme loci representing 12,16 enzyme systems were scored. The six species showed similar levels of genetic variations (HT ranged from 0.209 to 0.386 and AT ranged from 2.4 to 4.1) which are high compared to plants with similar life history traits. Genetic structure, in contrast, varied greatly between species, with FST ranging from 0.056 to 0.393. The three rarest species had high genetic differentiation (FST and FPT) and distinct geographical patterns, while the other three had low differentiation and little or no geographical structure. These differences are attributed to both present distributions and historical changes following deforestation within the last 1000 years. The conservation implications of these results are discussed. [source]


    Unravelling the genetic diversity of the three main viruses involved in Sweet Potato Virus Disease (SPVD), and its practical implications

    MOLECULAR PLANT PATHOLOGY, Issue 2 2005
    FRED TAIRO
    SUMMARY Sweetpotato (Ipomoea batatas) is a widely grown food crop, in which the most important diseases are caused by viruses. Genetic variability of three widely distributed sweetpotato viruses was analysed using data from 46 isolates of Sweet potato feathery mottle virus (SPFMV), 16 isolates of Sweet potato mild mottle virus (SPMMV) and 25 isolates of Sweet potato chlorotic stunt virus (SPCSV), of which 19, seven and six isolates, respectively, are newly characterized. Division of SPFMV into four genetic groups (strains) according to phylogenetic analysis of coat protein (CP) encoding sequences revealed that strain EA contained the East African isolates of SPFMV but none from elsewhere. In contrast, strain RC contained ten isolates from Australia, Africa, Asia and North America. Strain O contained six heterogeneous isolates from Africa, Asia and South America. The seven strain C isolates from Australia, Africa, Asia, and North and South America formed a group that was genetically distant from the other SPFMV strains. SPMMV isolates showed a high level of variability with no discrete strain groupings. SPCSV isolates from East Africa were phylogenetically distant to SPCSV isolates from elsewhere. Only from East Africa were adequate data available for different isolates of the three viruses to estimate the genetic variability of their local populations. The implications of the current sequence information and the need for more such information from most sweetpotato-growing regions of the world are discussed in relation to virus diagnostics and breeding for virus resistance. [source]


    Genetic variability in the myostatin gene does not explain the muscle hypertrophy and clinical penetrance in myotonia congenita

    MUSCLE AND NERVE, Issue 3 2010
    Viviane P. Muniz MS
    No abstract is available for this article. [source]


    Comparative evaluation of exotic and adapted germplasm of spring wheat for floral characteristics in the Indo-Gangetic Plains of northern India

    PLANT BREEDING, Issue 6 2007
    S. K. Singh
    Abstract Four hundred spring wheat genotypes, comprising exotic and indigenous germplasm and adapted cultivars for commercial cultivation, were investigated during four crop seasons for six floral characteristics related to outcrossing behaviour. Genetic variability and heritability were investigated along with phenotypic correlation coefficients among these characteristics. A significant quantitative variation existed among the characteristics in all three groups. High heritability for stigma length, openness of florets, anther extrusion and duration of floral opening indicated that selection for these characteristics may be effective. The adapted cultivars were found more promising than the exotic and indigenous germplasm. Most of the characteristics showed significantly positive correlation with each other and high correlation was observed between anther and stigma length, and anther extrusion and duration of floral opening. Superiority of varietal mixtures and segregating generations (F3 and F4) of two crosses over parental lines suggested that heterozygosity and heterogeneity can provide yield advantages. Germplasm lines possessing superior expression of floral characteristics may be used to improve yielding ability through enhanced heterozygosity or the development of hybrids. [source]


    Plasticity to soil water deficit in Arabidopsis thaliana: dissection of leaf development into underlying growth dynamic and cellular variables reveals invisible phenotypes

    PLANT CELL & ENVIRONMENT, Issue 12 2006
    LUIS AGUIRREZABAL
    ABSTRACT Genetic variability in the plasticity of leaf area expansion in response to water deficit has been reported in Arabidopsis thaliana. Here, the objective was to identify the underlying dynamic and cellular processes involved in this variability. Twenty-five accessions were subjected to identical soil water deficit treatments. In all accessions, the plasticity of leaf production was low compared with that of individual leaf expansion. A subset of accessions was selected for further dissection of individual leaf expansion into its underlying variables: the rate and duration of leaf expansion and epidermal cell number and area. In all accessions, water deficit had opposite effects on the rate and duration of leaf expansion. The accumulation of these effects was reflected in changes in final leaf area. At the cellular level, moderate water deficits had opposite effects on cell number and cell size, but more severe ones reduced both variables. The importance of these opposing effects is highlighted by the behaviour of the accession An-1, for which the compensation between the decrease in leaf expansion rate and the increase in the duration of expansion is total. This dynamic plasticity in response to water deficit is not detectable when only final measurements are done. [source]


    Genetic diversity, presence of the syrB gene, host preference and virulence of Pseudomonas syringae pv. syringae strains from woody and herbaceous host plants

    PLANT PATHOLOGY, Issue 3 2003
    M. Scortichini
    A total of 101 Pseudomonas syringae pv. syringae strains, obtained from international culture collections or isolated from diseased tissues of herbaceous and woody plant species, were assessed by repetitive PCR using the BOX primer, and for the presence of the syrB gene. Representative strains were also tested for pathogenicity to lilac, pear, peach, corn and bean, as well as for virulence to lemon and zucchini fruits. The unweighted pair-group method using arithmethic averages analysis (UPGMA) of genomic fingerprints revealed 17 different patterns which grouped into three major clusters, A, B and C. Most of the strains (52·4%) were included in patterns 1,4 of group A. These patterns comprised strains obtained from either herbaceous or woody species, and showed four fragments of similar mobility. Genetic variability was ascertained for strains isolated from apple, pear, apricot, Citrus spp. and cereals. No clear relationship was observed between host plant and bacterial genomic fingerprint. Variability was also observed in pathogenicity and virulence tests. The inoculation of pear leaves discriminated strains isolated from pear as well as the very aggressive strains, whereas inoculation of lilac, peach and corn did not discriminate the host plant from which the strains were originally isolated. Lemon fruit inoculation proved very effective for P. syringae pv. syringae virulence assessment. The syrB gene was present in almost all strains. [source]


    Detection of the Dinozoans Pfiesteria piscicida and P. shumwayae: A Review of Detection Methods and Geographic Distribution,

    THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005
    PARKE A. RUBLEE
    Abstract. Molecular methods, including conventional PCR, real-time PCR, denaturing gradient gel electrophoresis, fluorescent fragment detection PCR, and fluorescent in situ hybridization, have all been developed for use in identifying and studying the distribution of the toxic dinoflagellates Pfiesteria piscicida and P. shumwayae. Application of the methods has demonstrated a worldwide distribution of both species and provided insight into their environmental tolerance range and temporal changes in distribution. Genetic variability among geographic locations generally appears low in rDNA genes, and detection of the organisms in ballast water is consistent with rapid dispersal or high gene flow among populations, but additional sequence data are needed to verify this hypothesis. The rapid development and application of these tools serves as a model for study of other microbial taxa and provides a basis for future development of tools that can simultaneously detect multiple targets. [source]


    Objectives, criteria and methods for using molecular genetic data in priority setting for conservation of animal genetic resources

    ANIMAL GENETICS, Issue 2010
    P. J. Boettcher
    Summary The genetic diversity of the world's livestock populations is decreasing, both within and across breeds. A wide variety of factors has contributed to the loss, replacement or genetic dilution of many local breeds. Genetic variability within the more common commercial breeds has been greatly decreased by selectively intense breeding programmes. Conservation of livestock genetic variability is thus important, especially when considering possible future changes in production environments. The world has more than 7500 livestock breeds and conservation of all of them is not feasible. Therefore, prioritization is needed. The objective of this article is to review the state of the art in approaches for prioritization of breeds for conservation, particularly those approaches that consider molecular genetic information, and to identify any shortcomings that may restrict their application. The Weitzman method was among the first and most well-known approaches for utilization of molecular genetic information in conservation prioritization. This approach balances diversity and extinction probability to yield an objective measure of conservation potential. However, this approach was designed for decision making across species and measures diversity as distinctiveness. For livestock, prioritization will most commonly be performed among breeds within species, so alternatives that measure diversity as co-ancestry (i.e. also within-breed variability) have been proposed. Although these methods are technically sound, their application has generally been limited to research studies; most existing conservation programmes have effectively primarily based decisions on extinction risk. The development of user-friendly software incorporating these approaches may increase their rate of utilization. [source]


    Molecular structure in peripheral dog breeds: Portuguese native breeds as a case study

    ANIMAL GENETICS, Issue 4 2009
    A. E. Pires
    Summary Genetic variability in purebred dogs is known to be highly structured, with differences among breeds accounting for ,30% of the genetic variation. However, analysis of the genetic structure in non-cosmopolitan breeds and local populations is still limited. Nine Portuguese native dog breeds, and other peripheral dog populations (five) with regional affinities, were characterized using 16 microsatellites and 225 amplified fragment length polymorphism (AFLP) markers, and the pattern of genetic differentiation was investigated. Although the level of breed differentiation detected is below that of other dog breeds, there is in most cases a correlation between breed affiliation and molecular structure. AFLP markers and Bayesian clustering methods allowed an average of 73.1% of individuals to be correctly assigned to source populations, providing robust genotypic assessment of breed affiliation. A geographical genetic structure was also detected, which suggests a limited influence of African dogs on the Iberian breeds. The sampling effect on the estimation of population structure was evaluated and there was a 2.2% decrease in genetic differentiation among breeds when working animals were included. Genetic diversity of stray dogs was also assessed and there is no evidence that they pose a threat to the preservation of the gene pool of native dog breeds. [source]


    Genetic variability of Old Portuguese bread wheat cultivars assayed by IRAP and REMAP markers

    ANNALS OF APPLIED BIOLOGY, Issue 3 2010
    A. Carvalho
    Retrotransposons (RTNs) constitute informative molecular markers for plant species as a result of their ability of integrating into a multitude of loci throughout the genome and thereby generating insertional polymorphisms between individuals. Inter-retrotransposon amplified polymorphisms (IRAPs) and the retrotransposon-microsatellite amplified polymorphisms (REMAPs) are marker systems based on long terminal repeats (LTRs) RTNs, developed for plants, that have been widely used for evolution, genetic diversity, DNA fingerprinting of cultivars and varieties, genetic mapping linkage and for detection of genetic rearrangements induced by polyploidisation. In the present study, we aimed to analyse the genetic variability among 48 Old Portuguese bread wheat cultivars using both IRAP and REMAP markers. Five IRAP and six REMAP primer combinations were used. IRAP produced 103 polymorphic fragments in a total of 113 bands. On average, 22.6 bands were amplified per IRAP primer combination. The bands ranged in size from 250 to 5000 bp. The REMAP primer combinations allowed the amplification of 53 bands, 51 of them polymorphic. An average of 8.8 REMAP bands was scored per primer combination. The REMAP bands ranged from 250 to 3000 bp. Both marker systems presented high percentages of polymorphism. However, IRAP markers were suitable for detecting genetic variability at the individual level and did not differentiate higher taxa. The REMAP maker system allowed the clustering by botanical variety and identified most of the homonym bread wheat cultivars. [source]


    Genetic variability of Tomato spotted wilt virus in Australia and validation of real time RT-PCR for its detection in single and bulked leaf samples

    ANNALS OF APPLIED BIOLOGY, Issue 4 2005
    R G DIETZGEN
    Summary The potential for large-scale use of a sensitive real time reverse transcription polymerase chain reaction (RT-PCR) assay was evaluated for the detection of Tomato spotted wilt virus (TSWV) in single and bulked leaf samples by comparing its sensitivity with that of DAS-ELISA. Using total RNA extracted with RNeasy® or leaf soak methods, real time RT-PCR detected TSWV in all infected samples collected from 16 horticultural crop species (including flowers, herbs and vegetables), two arable crop species, and four weed species by both assays. In samples in which DAS-ELISA had previously detected TSWV, real time RT-PCR was effective at detecting it in leaf tissues of all 22 plant species tested at a wide range of concentrations. Bulk samples required more robust and extensive extraction methods with real time RT-PCR, but it generally detected one infected sample in 1000 uninfected ones. By contrast, ELISA was less sensitive when used to test bulked samples, once detecting up to 1 infected in 800 samples with pepper but never detecting more than 1 infected in 200 samples in tomato and lettuce. It was also less reliable than real time RT-PCR when used to test samples from parts of the leaf where the virus concentration was low. The genetic variability among Australian isolates of TSWV was small. Direct sequencing of a 587 bp region of the nucleoprotein gene (S RNA) of 29 isolates from diverse crops and geographical locations yielded a maximum of only 4.3% nucleotide sequence difference. Phylogenetic analysis revealed no obvious groupings of isolates according to geographic origin or host species. TSWV isolates, that break TSWV resistance genes in tomato or pepper did not differ significantly in the N gene region studied, indicating that a different region of the virus genome is responsible for this trait. [source]


    ,-Synuclein promoter confers susceptibility to Parkinson's disease

    ANNALS OF NEUROLOGY, Issue 4 2004
    Philippe Pals MD
    Familial Parkinson's disease (PD) has been linked to missense and genomic multiplication mutations of the ,-synuclein gene (SNCA). Genetic variability within SNCA has been implicated in idiopathic PD in many populations. We now confirm and extend these findings, within a Belgian sample, using a high-resolution map of genetic markers across the SNCA locus. Our study implicates the SNCA promoter in susceptibility to PD, and more specifically defines a minimum promoter haplotype, spanning approximately 15.3kb of sequence, which is overrepresented in patients. Our findings represent a biomarker for PD and may have implications for patient diagnosis, longitudinal evaluation, and treatment. Ann Neurol 2004;56:591,595 [source]