• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 329
  • 164
  • 53
  • 10
  • 4
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 643
  • 643
  • 313
  • 285
  • 122
  • 101
  • 78
  • 71
  • 66
  • 65
  • 65
  • 65
  • 65
  • 64
  • 64
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Diversity of Low Chill Peaches (Prunus persica) from Asia, Brazil, Europe and the USA

Anderson, Natalie A. 2010 May 1900 (has links)
One hundred fifty-five peach (Prunus persica) cultivars, from Asia, Brazil, Europe, and the USA, were examined using eleven Simple Sequence Repeats (SSRs) to study the genetic relationships among low chill as compared to high chill peach germplasm. Data was analyzed by NTSYSpc to form a similarity matrix using Nei and Li’s Dice similarity coefficient. This similarity matrix was then subjected to a cluster analysis and a dendrogram was constructed using the UPGMA (Unweighted Pair-Group Method, Arithmetic Mean) method. A wide range of diversity was detected, from 0.33 coefficient of similarity amongst the Thai peaches to 0.97 between two Brazilian peaches. The most distant clusters were the low chill peaches from Thailand and Taiwan and the local cultivars (both fruit and ornamental types) from China. Among the improved germplasm, there were distinct clusters for the Chinese/Japanese cultivars, three clusters for the Brazilian cultivars and one for the cultivars from the USA and Europe. The Brazilian materials clustered according to breeding programs in São Paulo and Pelotas reflecting the different sets of local cultivars used in the breeding efforts. The largest group investigated was the European/USA peaches. This group subdivided into three distinct clusters, with a general clustering of the low chill germplasm. The low chill accessions from Asia were genetically distant from the improved low chill peaches from the USA or Brazil. The low chill peaches from the Americas were more closely related to the high chill peaches developed in the USA and China/Japan due to the introgression of this germplasm into a low chill background.
122

The Genetic Diversity of Taiwania cryptomerioides Hayata

Jui-Lin, Chang 18 February 2005 (has links)
The aim of this study was to obtain the molecular marker of Taiwania cryptomerioides Hayata based on DNA sequence data of PCR- sequencing and inter-simple sequence repeat (ISSR), and to evaluate the genetic diversity of populations of Taiwania cryptomerioides Hayata and molecular phylogeny of T. cryptomerioides and Taiwania flousiana Gaussen. The sequence data based on the internal transcribed spacer (ITS) of a total of 108 samples of T. cryptomerioides were determined. Eight different populations of T. cryptomerioides and 12 samples of T. flousiana from Yunnan, China were analyzed. The finding of the study showed that heterogeneity of ITS region within individuals of T. cryptomerioides was high by showing high nucleotide diversity among ITS sequences both in T. cryptomerioides ( £k = 0.18153) and T. flousiana ( £k = 0.19751). The findings fit in Tajima¡¦s D test of neutrality based on DNA sequence variation in the ITS region of T. cryptomerioides and T. flousiana. It is not obvious to incorporate into different population through clustering analysis based on data of the ITS region of T. cryptomerioides and T. flousiana. However, slightly genetic differentiation between T. cryptomerioides and T. flousiana was found, which figured of Fst (Fst = 0.0441~ 0.0856, an average value = 0.0611). On the other hand, the samples were studied by using ISSR markers. Of the 100 primers screened, 4 produced highly reproducible ISSR bands, and 24 discernible DNA fragments were generated with 17 being polymorphic. Based on cluster analysis of molecular data, the cluster is not clear among populations of T. cryptomerioides and T. flousiana. The analysis of AMOVA revealed that the variance component between species of T. cryptomerioides and T. flousiana was 38.54¢H (P < 0.001); however, the variance component within species is 61.46 (P < 0.001). The variation within population of T. cryptomerioides was 84.74¢H (P < 0.001) and the variance between populations is 15.26¢H (P < 0.001), indicating that the genetic diversity of individuals within population was high. The aforementioned data suggest that gene flow among different populations of T. cryptomerioides was high, indicating that the genetic diversity was high among individuals of T. cryptomerioides but was low between populations. Furthermore, it is concluded both species are genetically closer and could be grouped into the same species.
123

Genetic Diversity Of Scald (rhynchosporium Secalis) Disease Resistant And Sensitive Turkish Barley Seed Sources As Determined With Simple Sequence Repeats

Dizkirici, Ayten 01 August 2006 (has links) (PDF)
Scald disease (Rhynchosporium secalis) is one of the major plant diseases causing considerable yield loss in barley (Hordeum vulgare) plantations in Turkey. To develop, scald resistant barley varieties, C.R.I.F.C. of Turkey has a large accumulated collection of barley seed sources in hand, but these samples are difficult to be followed and used in the breeding programs due to lack of genetic studies on them. Thus, the objective of this study was to characterize and fingerprint of eighty barley seed sources, and assess the magnitude and pattern of genetic diversity that could be used to have more efficient scald disease resistant breeding programs in the future. Forty scald disease resistant and 40 scald sensitive Turkish barley seed sources were screened using 6 simple sequence repeats (SSR) primers. Each of barley seed source were represented with four seeds, assuming they are genetically uniform since barley is a self-pollinated crop. Estimated genetic parameters indicated that scald disease resistant and sensitive barley seed sources still maintain large amount of genetic diversity. For example, expected heterozygosity was 0.62&plusmn / 0.01 and 0.64&plusmn / 0.01 for resistant and sensitive Turkish barley seed sources, respectively. Thirty-nine percent of total genetic variation was between populations for resistant and 46% for sensitive group, while 61% of total variation was within populations for resistant group and 54% for sensitive group. When overall Turkish barley seed sources were considered, genetic distances between scald sensitive seed source S18 and resistant R1 as well as between sensitive S28 and resistant R1 were large. Scald resistant and sensitive barley seed sources were generally located in different clusters in dendrogram. The presence of R25, R39 and S16 barley seed sources with high genetic diversity parameters among studied seed sources, suggests that this diversity could be important drive in future barley breeding program in Turkey. However, further study is needed to illustrate genetic divergence of Turkish barley seed sources with use of more molecular markers.
124

Determination And Comparison Of Genetic Variation In Honey Bee (apis Mellifera L.)populations Of Turkey By Random Amplified Polymorphic Dna And Microsatellite Analyses

Ivgin Tunca, Rahsan 01 February 2009 (has links) (PDF)
We analyzed a total of 760 worker bees, two samples per colony, 390 colonies in 26 provinces in Turkey to determine and compare the genetic variation of Turkish honey bee (Apis mellifera L.) populations using 10 primers for RAPD and 6 microsatellite loci. Mean gene diversity levels ranged from 0.035 (Sanliurfa) to 0.175 (Antalya) for RAPD and 0.449 (Mugla) to 0.739 (Artvin) for microsatellite markers. Private band patterns and alleles, pairwise FST values support that the Anatolian honey bees belong to C lineage except for Hatay and Sanliurfa populations illustrated from previous findings of mitochondrial DNA studies. Genetic differentiation (GST) from RAPD data ranged from 0.060 (Bilecik and Mugla) to 0.395 (G&ouml / k&ccedil / eada and Sanliurfa). The genetic diversity (FST) for microsatellites ranged from -0.068 (G&ouml / k&ccedil / eada and &amp / #272 / zmir) to 0.347 (Konya and Mugla). The results of the present research are in agreement to that of previous study in Turkish honey bee populations which used different microsatellite loci. That is the genetic variation was the highest in African, the lowest in European and intermediate in the Mediterranean honey bee populations. The data presented here indicate that in spite of extensive migratory beekeeping, there is still a large genetic differentiation among honey bee populations. These results should be considered in establishment of conservation plans particularly in moving of colonies between regions. The most importantly introduction of bees with foreign origin and distribution queen bees from one center to all over the country which will homogenize the gene pool of the populations should be prevented
125

Bioinformatic Analyses In Microsatellite-based Genetic Diversity Of Turkish Sheep Breeds

Acar, Hande 01 September 2010 (has links) (PDF)
In the present study, within and among breed genetic diversity in thirteen Turkish sheep breeds (Sakiz, Karag&uuml / l, Hemsin, &Ccedil / ine &Ccedil / apari, Norduz, Herik, Akkaraman, Dagli&ccedil / , G&ouml / k&ccedil / eada, Ivesi, Karayaka, Kivircik and Morkaraman / in total represented by 628 individuals) were analyzed based on 20 microsatellite loci. Loci were amplified by Polymerase Chain Reactions and products were electronically recorded and converted into [628 x 20] matrix representing genotypes of individuals. Reliability of the genotyping and genetic diversity analyses were done by means of various bioinformatics tools. For the analyses, various statistical methods (Fisher&#039 / s Exact Test, Neighbor-Joining tree construction, Factorial Correspondence Analysis (FCA), Analysis of Molecular Variation, Structure Analysis and Delaunay Analysis) were used. Since, inputs of some software were not compatible with the outputs of other software some Java classes were written whenever necessary. Analyses revealed that among the major breeds Dagli&ccedil / , Karayaka and Morkaraman breeds are highly admixed but Kivircik, Akkaraman and Ivesi are relatively distinct. Among the minor breeds, distinctness of Hemsin, Sakiz, &Ccedil / ine &Ccedil / apari, G&ouml / k&ccedil / eada and Karag&uuml / l are more pronounced compared to all of the examined breeds. Since highly admixed individuals can be identified by Structure and FCA tests, results of the present study, which is part of a national project with the acronym TURKHAYGEN-I (www.turkhaygen.gov.tr), were found to be promising in establishing and managing relatively pure conservation flocks for the Turkish native sheep breeds which are believed to be the reservoirs of genetic variability.
126

Population Genetic Methods and Applications to Human Genomes

Gattepaille, Lucie January 2015 (has links)
Population Genetics has led to countless numbers of fruitful studies of evolution, due to its abilities for prediction and description of the most important evolutionary processes such as mutation, genetic drift and selection. The field is still growing today, with new methods and models being developed to answer questions of evolutionary relevance and to lift the veil on the past of all life forms. In this thesis, I present a modest contribution to the growth of population genetics. I investigate different questions related to the dynamics of populations, with particular focus on studying human evolution. I derive an upper bound and a lower bound for FST, a classical measure of population differentiation, as functions of the homozygosity in each of the two studied populations, and apply the result to discuss observed differentiation levels between human populations. I introduce a new criterion, the Gain of Informativeness for Assignment, to help us decide whether two genetic markers should be combined into a haplotype marker and improve the assignment of individuals to a panel of reference populations. Applying the method on SNP data for French, German and Swiss individuals, I show how haplotypes can lead to better assignment results when they are supervised by GIA. I also derive the population size over time as a function of the densities of cumulative coalescent times, show the robustness of this result to the number of loci as well as the sample size, and together with a simple algorithm of gene-genealogy inference, apply the method on low recombining regions of the human genome for four worldwide populations. I recover previously observed population size shapes, as well as uncover an early divergence of the Yoruba population from the non-African populations, suggesting ancient population structure on the African continent prior to the Out-of-Africa event. Finally, I present a case study of human adaptation to an arsenic-rich environment.
127

Demography and Polyploidy in Capsella

St.Onge, Kate January 2010 (has links)
Studies of demography and population structure give insight into important evolutionary processes such as speciation and diversification. In the present work I perform such studies in the genus Capsella, which has three species: C. grandiflora, an outcrossing diploid, C. rubella a selfing diploid, and C. bursa-pastoris a selfing tetraploid. These three species make a good model system for evolutionary studies because they encompass two major plant evolutionary processes: mating system shifts and polyploidization. To conduct my studies I have gathered a large number of samples across the distributions of each species and scored them both phenotypically and genotypically: more specifically we measured flowering time and collected DNA sequence data. In the tetraploid C. bursa-pastoris we applied an association mapping approach which takes population structure into account to search for genetic variation associated with variation in flowering time. Flowering time is an important and highly adaptive trait which is frequently subject to natural selection. We found evidence of association between flowering time and several single nucleotide polymorphisms (SNPs) within the flowering locus C (FLC) and cryptochrome 1 (CRY1). In the case of FLC these SNPs code for nonconsensus splice site variation in one of the two copies of the gene. The SNPs could potentially have functional consequences and our results imply that non-functionalization of duplicate genes could be an important source of phenotypic variation. Using a novel coalescent based approach, we investigated the polyploid origin of C. bursa-pastoris and find evidence supporting a recent autopolyploid origin of this species. In the two diploid species, I use sequence data to investigate population structure and demographic history and to assess the effects of selfing on C. rubella. Observed patterns of population structure and genetic diversity in C. rubella can be explained by a combination of both demographic history and mating system. Observed patterns in C. grandiflora suggest that the investigated populations do not deviate strongly from the SNM, which has rarely been found in modern demographic studies. Finally, we investigate the effect of sampling strategy on demographic inference. Extensive sampling both within and across our populations allow us to empirically test the effect of sampling strategy on demographic inference. We complement the empirical analysis with simulations and conclude that the effect of sampling strategy is in many cases weak compared with that of demographic events. Nevertheless, these effects are real and have the potential to lead to false inference and therefore sampling strategy should be carefully considered in demographic studies. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 725
128

Lenkinio maumedžio ( Larix polonica Racib. ) regeneracijos in vitro ir genetinės įvairovės įvertinimas / The assessment of in vitro regeneration and genetic variety of Polish larch (Larix polonica Racib.)

Gregeris, Algimantas 21 June 2010 (has links)
Magistro darbe tiriama in vitro sąlygų įtaka lenkinio maumedžio regeneracijai ir genetinė įvairovė. Darbo objektas – Lenkiniai maumedžiai (Larix polonica Racib.) iš Degsnės sėklinės maumedžių palantacijos ir europinis maumedis (Larix decidua Mill.) iš Girionių parko. Darbo tikslas – Nustatyti sąlygas maumedžio palikuonių regeneracijai gemalų kultūroje ir įvertinti genetinę įvairovę ankstyvose vystymosi stadijose. Darbo metodai – Regeneravusių mikroūglių įvertinimas, DNR nustatymas. Darbo rezultatai: Atlikus maumedžių regeneracijos tyrimus in vitro nustatyta: sterilinimo procedūrą papildžius aseptiku “ACE” pavyko ženkliai padidinti sterilių eksplantų skaičių. Po sterilinimo dauginamąją medžiagą savaitę palaikius tamsoje 3◦C temperatūroje ir tik po to pasodinus į sterilią terpę sulauktas didesnis sudygusių gemalų skaičius. Terpės pH limituojantis eksplantų vystymąsi veiksnys. Citokininas N–izopentenilaminopurinas (2–iP) WPM terpėje tinkamiausias lenkinio maumedžio kultivavimui audinių kultūroje. Oligonukleotidiniai pradmenys A 03, R370 03, R370 04, R370 10 informatyvūs maumedžių polimorfizmo tyrimams, o oligonukleotidinis pradmuo R170 01 neinformatyvus. / Master thesis in vitro conditions on polish larch regeneration and genetic diversity. Object of study – Polish larch (Larix polonica Racib) from Degsnės larch seed plantation and European larch (Larix decidua Mill.) from the park Girionys. Goal of study – Establish conditions for the regeneration of larch seed embryo culture and assessment of genetic diversity in the early stages of development. Methods of study – Regenerate shoot evaluation, DNA identification. Results of study: After larch regeneration studies in vitro set: steriling procedure for adding an antiseptic “Ace” was able to significantly increase the number of aseptic explants. After a week sterile propagating material in the dark brew 3◦C, and only then seated in a sterile environment attracted larger number of germ sprouted. PH factor limit explants development. Cytokinin 2-iP in WPM medium appropriate polish larch cultivation in tissue culture. Oligonucleotidic primers A 03, R370 03 R370 04 R370 10 informative for larch polymorphism analysis, and oligonucleotidic primer R170 01 noninterpretable.
129

A Genetic Characterization of the Hays Converter

Fleming, Allison 03 April 2013 (has links)
This thesis gives a genetic overview of the Hays Converter, a beef breed developed in Canada in the 1950s. Pedigree records were examined to determine genetic diversity and inbreeding. A positive rate of inbreeding and a decrease in the amount of genetic diversity was found. Single trait and bivariate animal models were used to determine genetic parameters and trends for growth, ultrasound, and carcass traits. An increasing genetic trend was found for growth traits which the breed was selected for. The accuracy of imputation from 6k to 50k marker panels using a reference group of 100 animals was determined. Imputation was performed with a high accuracy (>0.93) for pure Hays Converter animals, but was found to be unsuccessful when individuals had large contributions from additional breeds. This work forms the foundation for future management and advance of the breed while outlining its history and progress. / Daniel P. Hays
130

Skirtingų paprastosios pušies (Pinus Sylvestris L.) lajos dalių sėklinių palikuonių genetinės įvairovės palyginimas / The comparison of genetic diversity of seedling progenies from different part of scots pine’s (Pinus sylvestris L.) crown

Kerpauskaitė, Vilma 20 June 2012 (has links)
Magistro darbe lyginama vieno paprastosios pušies (Pinus sylvestris L.) klono skirtingų lajos dalių sėklinių palikuonių, augančių Višakio Rūdos bandomuosiuose želdiniuose, genetinė įvairovė remiantis DNR žymenimis ir kokybiniais bei kiekybiniais požymiais. Darbo objektas – paprastosios pušies (Pinus sylvestris L.) sėklinių palikuonių želdiniai iš skirtingų lajos dalies sėklų (viršutinės, vidurinės, apatinės). Darbo metodai – genetinė įvairovė tirta atliekant želdinių kiekybinių ir kokybinių požymių analizę bei jų DNR polimorfizmo tyrimą. Darbo rezultatai. Fenotipinių požymių tyrimai parodė, kad 24 m amžiuje, viršutinės lajos dalies sėkliniai palikuonys pasižymi ženkliai didesniu išlikimu, bet esminiai nesiskiria savo kiekybinių ir kokybinių požymių įvairove nuo apatinės lajos dalies palikuonių. Gali būti, kad fenotipinių požymių įvairovei atsiskleisti trukdo nevienodas medžių išlikimas, kur esant mažesniam išlikimui, susidaro nevienodi tarpai tarp medžių, galėję įtakoti didesnę erdvinę įvairovę radialiniam prieaugiui. 6 chloroplasto DNR(cpSSR) lokusų DNR polimorfizmo tyrimai parodė, kad viršutinės lajos dalies sėklinių palikuonių genetinė įvairovė yra ženkliai didesnė nei vidurines ir apatinės lajos dalių sėklinių palikuonių. Iš 30 skirtingų cpSSR tipų (tėvinių genotipų) 18 buvo aptikti viršutinės lajos dalies palikuonyse, tuo tarpu vidurinėje dalyje – 8, o apatinėje - 10 .Visi 5 proc. savidulkinių individų aptikti tarp apatinės ir centrinės lajos dalies palikuonių (18 vnt.)... [toliau žr. visą tekstą] / The genetic diversity of the progeny from different parts of Scots pine crown of a single clone by quantitative and qualitative traits and DNA polymorphism was investigated in the work of master science. Object of the work - 24 years old progeny from different parts of Scots pine crown of a single clone. The aim of the study - to compare the diversity of quantitative and qualitative traits and DNA polymorphism of24 years old progeny from different parts of Scots pine crown of a single clone by using cpSSR DNA markers. Methods of the work - Survival, stem diameter, stem straightness, flowering, cone yield, barktype,condition,the beginning of activegrowth and other parameters of the seedling progenies were evaluated. The genetic diversity was assessed at six cpDNA loci by the aid of cpSSRs. Study results. The results showed, that the survival of the progeny from the middle and the bottom of the crown was much lower than from the top. However, there were not any significant differences nor in the other traits neither between the variances of the progeny from the different parts of the crown. A reason could be that owing to low survival of the bottom and middle progeny, the remaining trees grew in a wider spacing and this uneven spacing between the treatments disturbed the comparison. cpSSR markers revealed much greater haplotype and allele diversity of the progeny from the top of the crown. Selfing rate was 5; background pollination 50; as much as 28 of the progeny from the... [to full text]

Page generated in 0.0538 seconds