scholarly journals Inference of Population Genetic Structure and High Linkage Disequilibrium Among Alternaria spp. Collected from Tomato and Potato Using Genotyping by Sequencing

2019 ◽  
Author(s):  
Tika B. Adhikari ◽  
Brian J. Knaus ◽  
Niklaus J. Grünwald ◽  
Dennis Halterman ◽  
Frank J. Louws
Keyword(s):  
Population Structure ◽  
Linkage Disequilibrium ◽  
Plant Pathogens ◽  
Principal Component ◽  
Genotyping By Sequencing ◽  
Allelic Association ◽  
Nucleotide Polymorphisms ◽  
Entire Genome ◽  
Genome Wide ◽  
A Genome

ABSTRACTGenotyping by sequencing (GBS) is considered a powerful tool to discover single nucleotide polymorphisms (SNPs), which are useful to characterize closely related genomes of plant species and plant pathogens. We applied GBS to determine genome-wide variations in a panel of 187 isolates of three closely related Alternaria spp. that cause diseases on tomato and potato in North Carolina (NC) and Wisconsin (WI). To compare genetic variations, reads were mapped to both A. alternata and A. solani draft reference genomes and detected dramatic differences in SNPs among them. Comparison of A. linariae and A. solani populations by principal component analysis revealed the first (83.8% of variation) and second (8.0% of variation) components contained A. linariae from tomato in NC and A. solani from potato in WI, respectively, providing evidence of population structure. Genetic differentiation (Hedrick’s G’ST) in A. linariae populations from Haywood, Macon, and Madison counties in NC were little or no differentiated (G’ST 0.0 - 0.2). However, A. linariae population from Swain county appeared to be highly differentiated (G’ST > 0.8). To measure the strength of the linkage disequilibrium (LD), we also calculated the allelic association between pairs of loci. Lewontin’s D (measures the fraction of allelic variations) and physical distances provided evidence of linkage throughout the entire genome, consistent with the hypothesis of non-random association of alleles among loci. Our findings provide new insights into the understanding of clonal populations on a genome-wide scale and microevolutionary factors that might play an important role in population structure. Although we found limited genetic diversity, the three Alternaria spp. studied here are genetically distinct and each species is preferentially associated with one host.

scholarly journals Multi-locus genotyping reveals established endemicity of a geographically distinct Plasmodium vivax population in Mauritania, West Africa

2020 ◽  
Author(s):  
Hampate Ba ◽  
Sarah Auburn ◽  
Christopher G. Jacob ◽  
Sonia Goncalves ◽  
Craig W. Duffy ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Population Structure ◽  
Linkage Disequilibrium ◽  
West Africa ◽  
Plasmodium Vivax ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Genome Wide ◽  
A Genome ◽  
Endemic Transmission

AbstractBackgroundPlasmodium vivax has been recently discovered as a significant cause of malaria in Mauritania, although very rare elsewhere in West Africa. It has not been known if this is a recently introduced or locally remnant parasite population, nor whether the genetic structure reflects epidemic or endemic transmission.Methodology / Principal FindingsTo investigate the P. vivax population genetic structure in Mauritania and compare with populations previously analysed elsewhere, multi-locus genotyping was undertaken on 100 clinical isolates, using a genome-wide panel of 38 single nucleotide polymorphisms (SNPs), plus seven SNPs in drug resistance genes. The Mauritanian P. vivax population is shown to be genetically diverse and divergent from populations elsewhere, indicated consistently by genetic distance matrix analysis, principal components analyses, and fixation indices. Only one isolate had a genotype clearly indicating recent importation, from a southeast Asian source. There was no linkage disequilibrium in the local parasite population, and only a small number of infections appeared to be closely genetically related, indicating that there is ongoing genetic recombination consistent with endemic transmission. The P. vivax diversity in a remote mining town was similar to that in the capital Nouakchott, with no indication of local substructure or of epidemic population structure. Drug resistance alleles were virtually absent in Mauritania, in contrast with P. vivax in other areas of the world.Conclusions / SignificanceThe molecular epidemiology indicates that there is long-standing endemic transmission that will be very challenging to eliminate. The virtual absence of drug resistance alleles suggests that most infections have been untreated, and that this endemic infection has been more neglected in comparison to P. falciparum locally or to P. vivax elsewhere.Author SummaryPlasmodium vivax is a widespread cause of malaria in Mauritania, in contrast to its rarity elsewhere throughout West Africa. To investigate whether the parasite may be recently introduced or epidemic, multi-locus genotyping was performed on 100 Mauritanian P. vivax malaria cases. Analysis of a genome-wide panel of single nucleotide polymorphisms showed the P. vivax population to be genetically diverse and divergent from populations elsewhere, indicating that there has been long-standing endemic transmission. Almost all infections appear to be locally acquired, with the exception of one that was presumably imported with a genotype similar to infections seen in Southeast Asia. The Mauritanian P. vivax population shows no linkage disequilibrium, and very few infections have closely related genotypes, indicating ongoing recombination. The parasite showed no indication of local substructure or epidemic population structure. Drug resistance alleles were virtually absent, suggesting that most infections have been untreated historically. The molecular epidemiology indicates that there has been long-standing endemic transmission of this neglected parasite that requires special attention for control.

scholarly journals Genomic analysis reveals the genetic diversity, population structure, evolutionary history and relationships of Chinese pepper

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Shijing Feng ◽  
Zhenshan Liu ◽  
Yang Hu ◽  
Jieyun Tian ◽  
Tuxi Yang ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Demographic History ◽  
Genomic Analysis ◽  
Genotyping By Sequencing ◽  
Gansu Province ◽  
Climatic Oscillations ◽  
Genome Wide ◽  
A Genome ◽  
Wild Accessions

Abstract Chinese pepper, mainly including Zanthoxylum bungeanum and Zanthoxylum armatum, is an economically important crop popular in Asian countries due to its unique taste characteristics and potential medical uses. Numerous cultivars of Chinese pepper have been developed in China through long-term domestication. To better understand the population structure, demographic history, and speciation of Chinese pepper, we performed a comprehensive analysis at a genome-wide level by analyzing 38,395 genomic SNPs that were identified in 112 cultivated and wild accessions using a high-throughput genome-wide genotyping-by-sequencing (GBS) approach. Our analysis provides genetic evidence of multiple splitting events occurring between and within species, resulting in at least four clades in Z. bungeanum and two clades in Z. armatum. Despite no evidence of recent admixture between species, we detected substantial gene flow within species. Estimates of demographic dynamics and species distribution modeling suggest that climatic oscillations during the Pleistocene (including the Penultimate Glaciation and the Last Glacial Maximum) and recent domestication events together shaped the demography and evolution of Chinese pepper. Our analyses also suggest that southeastern Gansu province is the most likely origin of Z. bungeanum in China. These findings provide comprehensive insights into genetic diversity, population structure, demography, and adaptation in Zanthoxylum.

scholarly journals Evidence for Strong Kinship Influence on the Extent of Linkage Disequilibrium in Cultivated Common Beans

Genes ◽  
2018 ◽  
Vol 10 (1) ◽  
pp. 5 ◽  
Author(s):  
Augusto Lima Diniz ◽  
Willian Giordani ◽  
Zirlane Portugal Costa ◽  
Gabriel R. A. Margarido ◽  
Juliana Morini K. C. Perseguini ◽  
...  
Keyword(s):  
Population Structure ◽  
Linkage Disequilibrium ◽  
Association Mapping ◽  
Genotyping By Sequencing ◽  
Grain Legume ◽  
Human Consumption ◽  
Common Beans ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
True Association

Phaseolus vulgaris is an important grain legume for human consumption. Recently, association mapping studies have been performed for the species aiming to identify loci underlying quantitative variation of traits. It is now imperative to know whether the linkage disequilibrium (LD) reflects the true association between a marker and causative loci. The aim of this study was to estimate and analyze LD on a diversity panel of common beans using ordinary r2 and r2 extensions which correct bias due to population structure (rS2), kinship (rV2), and both (rVS2). A total of 10,362 single nucleotide polymorphisms (SNPs) were identified by genotyping by sequencing (GBS), and polymorphisms were found to be widely distributed along the 11 chromosomes. In terms of r2, high values of LD (over 0.8) were identified between SNPs located at opposite chromosomal ends. Estimates for rV2 were lower than those for rS2. Results for rV2 and rVS2 were similar, suggesting that kinship may also include information on population structure. Over genetic distance, LD decayed to 0.1 at a distance of 1 Mb for rVS2. Inter-chromosomal LD was also evidenced. This study showed that LD estimates decay dramatically according to the population structure, and especially the degree of kinship. Importantly, the LD estimates reported herein may influence our ability to perform association mapping studies on P. vulgaris.

scholarly journals Identification and tagging of QTLs for arjunolic acid in Terminalia arjuna among Indian sub populations by association mapping and linkage disequilibrium

2020 ◽  
Vol 15 (2) ◽  
pp. 121-134
Author(s):  
Sonu Bharti
Keyword(s):  
Population Structure ◽  
Linkage Disequilibrium ◽  
Association Mapping ◽  
Dry Weight ◽  
Terminalia Arjuna ◽  
Fresh Weight ◽  
Genome Wide ◽  
A Genome ◽  
Arjunolic Acid ◽  
Agroclimatic Zones

The content of cardiotonic arjunolic acid in Terminalia arjuna vary among the population. We studied the population structure and the association between the molecular markers and its active ingredient among 140 plants collected from various agroclimatic zones in India. Large variation was detected for the arjunolic acid in this study showing suitableness of the genotypes. The maximum arjunolic acid content was approximately 238 per cent higher than the lowest value for the genotypes and was found to be considerably correlated to bark thickness, bark fresh weight and bark dry weight. The population structure studies described the existence of nine subpopulations. As the distance increased between the associated markers, Linkage disequilibrium (LD) reduction and a considerable reduction in LD decay was ascertained. Eleven QTL regions associated with arjunolic acid were identified from a genome-wide marker-trait association study. Fine-scale resolution detected significant LD among 3.4 per cent RAPD paired loci and 8.7 per cent ISSR paired loci and 6.7 per cent RAPD paired loci and 13.3 per cent ISSR paired loci. Importantly LD decay found to start at a distance of >20bp from the loci on the genome of T. arjuna accessions. Finally, association mapping (AM) in arjun tightly linked to OPT09 which can be a possible substitute to QTL mapping methodology.

scholarly journals Genome-Wide and Mla Locus-Specific Characterisation of Latvian Barley Varieties

2008 ◽  
Vol 62 (3) ◽  
pp. 103-109
Author(s):  
Agnese Kokina ◽  
Nils Rostoks
Keyword(s):  
Genetic Diversity ◽  
Linkage Disequilibrium ◽  
Crop Improvement ◽  
Nucleotide Polymorphisms ◽  
Phenotypic Data ◽  
Genome Wide ◽  
A Genome ◽  
Wide Scale ◽  
Barley Germplasm ◽  
Mla Locus

Genome-Wide and Mla Locus-Specific Characterisation of Latvian Barley Varieties Genetic diversity in locally adapted germplasm forms the basis for crop improvement through breeding. While single loci have been routinely used for studies of genetic diversity, the highthroughput genotyping platforms that have recently become available for large genome crop plants offer an unbiased view on genetic diversity on a genome-wide scale. We assessed genetic diversity in Latvian barley varieties and some progenitors using DArT markers and studied the extent of linkage disequilibrium in Latvian germplasm. Further, genetic diversity at three loci flanking the barley powdery mildew Mla locus conferring race-specific resistance was studied in Latvian barley germplasm. The Mla locus encompasses several closely related resistance gene homologues with a complex evolutionary history, which complicates the design of molecular markers for different Mla genes. We observed significant linkage disequilibrium between the single nucleotide polymorphisms (SNPs) at the three loci, 206i20_T7, ABC15612, and 538P8, flanking the Mla locus. SNP haplotypes were largely in agreement with known phenotypic data and, thus, may be potentially diagnostic for Mla resistance genes in hybrids.

scholarly journals The multi-allelic APRR2 gene is associated with fruit pigment accumulation in melon and watermelon

2019 ◽  
Vol 70 (15) ◽  
pp. 3781-3794 ◽  
Author(s):  
Elad Oren ◽  
Galil Tzuri ◽  
Lea Vexler ◽  
Asaf Dafna ◽  
Ayala Meir ◽  
...  
Keyword(s):  
Genome Wide Association Study ◽  
Qualitative Difference ◽  
Genotyping By Sequencing ◽  
Color Variation ◽  
Nucleotide Polymorphisms ◽  
Genome Wide ◽  
Haplotypic Diversity ◽  
A Genome ◽  
Allelism Tests ◽  
Pigment Accumulation

Abstract Color and pigment contents are important aspects of fruit quality and consumer acceptance of cucurbit crops. Here, we describe the independent mapping and cloning of a common causative APRR2 gene regulating pigment accumulation in melon and watermelon. We initially show that the APRR2 transcription factor is causative for the qualitative difference between dark and light green rind in both crops. Further analyses establish the link between sequence or expression level variations in the CmAPRR2 gene and pigment content in the rind and flesh of mature melon fruits. A genome-wide association study (GWAS) of young fruit rind color in a panel composed of 177 diverse melon accessions did not result in any significant association, leading to an earlier assumption that multiple genes are involved in shaping the overall phenotypic variation in this trait. Through resequencing of 25 representative accessions and allelism tests between light rind accessions, we show that multiple independent single nucleotide polymorphisms in the CmAPRR2 gene are causative of the light rind phenotype. The multi-haplotypic nature of this gene explains the lack of detection power obtained through genotyping by sequencing-based GWAS and confirms the pivotal role of this gene in shaping fruit color variation in melon. This study demonstrates the power of combining bi- and multi-allelic designs with deep sequencing, to resolve lack of power due to high haplotypic diversity and low allele frequencies. Due to its central role and broad effect on pigment accumulation in fruits, the APRR2 gene is an attractive target for carotenoid bio-fortification of cucurbit crops.

scholarly journals Genetic Diversity and Population Structure Analysis of Bigleaf Hydrangea Using Genotyping-by-sequencing

2019 ◽  
Vol 144 (4) ◽  
pp. 257-263 ◽  
Author(s):  
Xingbo Wu ◽  
Lisa W. Alexander
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Structure Analysis ◽  
Principal Component ◽  
Genotyping By Sequencing ◽  
Breeding Cycle ◽  
Nucleotide Polymorphisms ◽  
Hydrangea Macrophylla ◽  
High Quality Snps ◽  
Population Structure Analysis

Hydrangea macrophylla (bigleaf hydrangea) is one of the most important floral and nursery crops worldwide. However, breeding of new bigleaf hydrangea cultivars has been hampered by a long breeding cycle and lack of genetic resources. This study investigated the genetic diversity and population structure of 82 bigleaf hydrangea cultivars using single-nucleotide polymorphisms (SNPs) originated from genotyping-by-sequencing. A total of 5803 high-quality SNPs were discovered in a bigleaf hydrangea cultivar panel. A phylogenetic analysis and analysis of molecular variance based on discovered SNPs concluded the taxonomic classification of H. macrophylla ssp. serrata as a subspecies of H. macrophylla. Principal component analysis confirmed ‘Preziosa’ as a hybrid between H. macrophylla ssp. macrophylla and H. macrophylla ssp. serrata. In addition, the cultivar Lady in Red was also found to be a hybrid between the two subspecies. The population structure analysis identified three groups among the 82 cultivars. All H. macrophylla ssp. serrata cultivars belonged to one group, and two groups were revealed within H. macrophylla ssp. macrophylla. The separation within H. macrophylla ssp. macrophylla indicated a second gene pool due to breeding efforts that have targeted similar breeding goals for bigleaf hydrangea. The discovered SNPs and the phylogenetic results will facilitate further exploitation and understanding of phylogenetic relationships of bigleaf hydrangea and will serve as a reference for hydrangea breeding improvements.

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