Identify Single Nucleotide Polymorphism Markers Research Articles

Genome-wide association study for the level of prolificacy in Cameroon’s native goat

ABSTRACT Income from goats highly depends on prolificacy, which is difficult to improve by traditional breeding methods. The study aimed to identify SNP markers for prolificacy, using a case–control genome-wide association study (GWAS) on 111 genotyped Cameroon native goat (CNG) does, based on the 50 K single nucleotide polymorphism (SNP) chip panel. None of the top SNPs reached the significant p-value of 5 × 10−8. The highest p-value was 0.0009. Despite the number of cases being about a quarter of the number of controls, the highest allele frequency of some of the top 20 variants in the cases was indicative of their potential role in the trait. These top variants included the following 15: rs268285661, rs268235169, rs268236449, rs268235135, rs268240394 in Sphingosine-1-phosphate phosphatase 2 (SGPP2) gene, rs268283635 in Solute carrier family 24 member 2 (SLC24A2) gene, rs268251678 in Androgen-induced gene 1 (AIG1) gene, rs268267018, rs268239617, rs268281364, rs268273029, rs268286941, rs268236144, rs268233233 in CEP126 gene and rs268278159, respectively. Our findings indicate that GWAS enable the identification of some loci within genes, with known biological functions and pathways in human being and mice animal model but far-ranging to what was previously hypothesized and tested in goat.

Kabuli chickpea seed quality diversity and preliminary genome‐wide association study identifies markers and potential candidate genes

AbstractMalnutrition due to macro‐ and micro‐nutrient deficiencies is one of the major global health concerns, especially in developing countries. Using genomics‐assisted breeding to enhance the nutritional value of important crops such as chickpea (Cicer arietinum L.) can help to address the problem. In this study, we conducted genome‐wide association studies to identify genes associated with protein, starch, oil, and fiber in chickpea to create resources to speed the breeding process. The USDA kabuli chickpea mini‐core of 88 accessions was genotyped using genotyped‐by‐sequencing, and 36,645 single nucleotide polymorphisms (SNPs) were identified across the eight chromosomes of the chickpea genome. A genome‐wide marker‐trait analysis using the FarmCPU model was conducted to identify SNP markers that can enable marker‐assisted breeding for seed protein, fiber, oil, and starch concentrations. The most significantly associated markers for seed protein concentration (p = 8.82E‐12), starch (p = 2.79E‐12), fiber (p = 7.65E‐12), and oil (p = 1.37E‐08) were found on chromosomes 1, 2, 6, and 7, controlling 11%, 12%, 20%, and 16% of the phenotypic variation, respectively. Validation of the SNP markers in a broader set of plant genetic resources and environments will be needed to determine their usefulness in breeding for end‐use characteristics.

Whole Genome Resequencing Identifies Single-Nucleotide Polymorphism Markers of Growth and Reproduction Traits in Zhedong and Zi Crossbred Geese.

The broodiness traits of domestic geese are a bottleneck that prevents the rapid development of the goose industry. To reduce the broodiness of the Zhedong goose and thus improve it, this study hybridized it with the Zi goose, which has almost no broody behavior. Genome resequencing was performed for the purebred Zhedong goose, as well as the F2 and F3 hybrids. The results showed that the F1 hybrids displayed significant heterosis in growth traits, and their body weight was significantly greater than those of the other groups. The F2 hybrids showed significant heterosis in egg-laying traits, and the number of eggs laid was significantly greater than those of the other groups. A total of 7,979,421 single-nucleotide polymorphisms (SNPs) were obtained, and three SNPs were screened. Molecular docking results showed that SNP11 located in the gene NUDT9 altered the structure and affinity of the binding pocket. The results suggested that SNP11 is an SNP related to goose broodiness. In the future, we will use the cage breeding method to sample the same half-sib families to accurately identify SNP markers of growth and reproductive traits.

Genome‐wide association study of variation in cooking time among common bean (Phaseolus vulgaris L.) accessions using Diversity Arrays Technology markers

AbstractStored grains of common bean (Phaseolus vulgaris L.) develop the hard‐to‐cook trait (HTC), which is manifested in a prolonged cooking time, thereby imposing time and energy constraints. The objective of this study was to determine variation in cooking time among common bean genotypes and to identify single nucleotide polymorphism (SNP) markers associated with cooking time.Seeds of 222 common bean accessions sourced from Kenyan institutions were multiplied in the Jomo Kenyatta University of Agriculture and Technology (JKUAT) field in 2019. The freshly harvested seeds and those stored at 35°C and 50% red haricot (RH) for 4 months for accelerated aging were soaked in distilled water for 16 h and evaluated for cooking time using the finger‐pressing method. The accessions were also genotyped to determine variation in SNP markers using Diversity Arrays Technology Sequencing (DArTseq). Genome‐wide association study (GWAS) analysis was conducted to identify SNPs significantly associated with cooking time.The study revealed significant differences (p ≤ 0.05) within and between fresh and aged bean accessions. Fresh seeds had a lower cooking time with a mean of 40.8 min and ranged from 28.1 to 72.2 min, whereas aged seeds had a higher average cooking time of 54.1 min and ranged from 32.1 to 96.3 min. GWAS identified a region in Chromosome 10 to be significantly (p ≤ 0.05) associated with the cooking time of aged seeds. Consequently, two potential candidate genes Phvul.010G038000 and Phvul.010G038100 were revealed. The characterized common bean accessions and the identified SNP markers can be utilized in breeding programs to improve the cooking quality of the common bean.

Genome-Wide Association Study and Genomic Prediction for Bacterial Wilt Resistance in Common Bean (Phaseolus vulgaris) Core Collection

Common bean (Phaseolus vulgaris) is one of the major legume crops cultivated worldwide. Bacterial wilt (BW) of common bean (Curtobacterium flaccumfaciens pv. flaccumfaciens), being a seed-borne disease, has been a challenge in common bean producing regions. A genome-wide association study (GWAS) was conducted to identify SNP markers associated with BW resistance in the USDA common bean core collection. A total of 168 accessions were evaluated for resistance against three different isolates of BW. Our study identified a total of 14 single nucleotide polymorphism (SNP) markers associated with the resistance to BW isolates 528, 557, and 597 using mixed linear models (MLMs) in BLINK, FarmCPU, GAPIT, and TASSEL 5. These SNPs were located on chromosomes Phaseolus vulgaris [Pv]02, Pv04, Pv08, and Pv09 for isolate 528; Pv07, Pv10, and Pv11 for isolate 557; and Pv04, Pv08, and Pv10 for isolate 597. The genomic prediction accuracy was assessed by utilizing seven GP models with 1) all the 4,568 SNPs and 2) the 14 SNP markers. The overall prediction accuracy (PA) ranged from 0.30 to 0.56 for resistance against the three BW isolates. A total of 14 candidate genes were discovered for BW resistance located on chromosomes Pv02, Pv04, Pv07, Pv08, and Pv09. This study revealed vital information for developing genetic resistance against the BW pathogen in common bean. Accordingly, the identified SNP markers and candidate genes can be utilized in common bean molecular breeding programs to develop novel resistant cultivars.

Population Structure and Genetic Diversity of Two-Rowed Barley Accessions from Kazakhstan Based on SNP Genotyping Data.

The genetic relationship and population structure of two-rowed barley accessions from Kazakhstan were assessed using single-nucleotide polymorphism (SNP) markers. Two different approaches were employed in the analysis: (1) the accessions from Kazakhstan were compared with barley samples from six different regions around the world using 1955 polymorphic SNPs, and (2) 94 accessions collected from six breeding programs from Kazakhstan were studied using 5636 polymorphic SNPs using a 9K Illumina Infinium assay. In the first approach, the neighbor-joining tree showed that the majority of the accessions from Kazakhstan were grouped in a separate subcluster with a common ancestral node; there was a sister subcluster that comprised mainly barley samples that originated in Europe. The Pearson’s correlation analysis suggested that Kazakh accessions were genetically close to samples from Africa and Europe. In the second approach, the application of the STRUCTURE package using 5636 polymorphic SNPs suggested that Kazakh barley samples consisted of five subclusters in three major clusters. The principal coordinate analysis plot showed that, among six breeding origins in Kazakhstan, the Krasnovodopad (KV) and Karaganda (KA) samples were the most distant groups. The assessment of the pedigrees in the KV and KA samples showed that the hybridization schemes in these breeding stations heavily used accessions from Ethiopia and Ukraine, respectively. The comparative analysis of the KV and KA samples allowed us to identify 214 SNPs with opposite allele frequencies that were tightly linked to 60 genes/gene blocks associated with plant adaptation traits, such as the heading date and plant height. The identified SNP markers can be efficiently used in studies of barley adaptation and deployed in breeding projects to develop new competitive cultivars.

SNP Alleles Associated With Low Bolting Tendency in Sugar Beet.

The identification of efficient molecular markers related to low bolting tendency is a priority in sugar beet (Beta vulgaris L.) breeding. This study aimed to identify SNP markers associated with low bolting tendency by establishing a genome-wide association study. An elaborate 3-year field trial comprising 13 sugar beet lines identified L14 as the one exhibiting the lowest bolting tendency along with an increased survival rate after autumnal sowing. For SNP discovery following phenotyping, contrasting phenotypes of 24 non-bolting and 15 bolting plants of the L14 line were sequenced by restriction site-associated DNA sequencing (RAD-seq). An association model was established with a set of 10,924 RAD-based single nucleotide polymorphism (SNP) markers. The allelic status of the most significantly associated SNPs ranked based on their differential allelic status between contrasting phenotypes (p < 0.01) was confirmed on three different validation datasets comprising diverse sugar beet lines and varieties adopting a range of SNP detection technologies. This study has led to the identification of SNP_36780842 and SNP_48607347 linked to low bolting tendency and can be used for marker-assisted breeding and selection in sugar beet.

Genome wide association study for the identification of genes associated with tail fat deposition in Chinese sheep breeds.

ABSTRACTChinese indigenous sheep can be classified into three types based on tail morphology: fat-tailed, fat-rumped, and thin-tailed sheep, of which the typical breeds are large-tailed Han sheep, Altay sheep, and Tibetan sheep, respectively. To unravel the molecular genetic basis underlying the phenotypic differences among Chinese indigenous sheep with these three different tail types, we used ovine high-density 600K single nucleotide polymorphism (SNP) arrays to detect genome-wide associations, and performed general linear model analysis to identify candidate genes, using genotyping technology to validate the candidate genes. Tail type is an important economic trait in sheep. However, the candidate genes associated with tail type are not known. The objective of this study was to identify SNP markers, genes, and chromosomal regions related to tail traits. We performed a genome-wide association study (GWAS) using data from 40 large-tailed Han sheep, 40 Altay sheep (cases) and 40 Tibetan sheep (controls). A total of 31 significant (P<0.05) SNPs associated with tail-type traits were detected. For significant SNPs' loci, we determined their physical location and performed a screening of candidate genes within each region. By combining information from previously reported and annotated biological functional genes, we identified SPAG17, Tbx15, VRTN, NPC2, BMP2 and PDGFD as the most promising candidate genes for tail-type traits. Based on the above identified candidate genes for tail-type traits, BMP2 and PDGFD genes were selected to investigate the relationship between SNPs within the tails in the Altay and Tibetan populations. rs119 T>C in exon1 of the BMP2 gene and one SNP in exon4 (rs69 C>A) of the PDGFD gene were detected. rs119 was of the TT genotype in Altay sheep, while it was of the CC genotype in Tibetan sheep. On rs69 of the PDGFD gene, Altay sheep presented with the CC genotype; however, Tibetan sheep presented with the AA genotype.

Genotyping by Sequencing-Based Discovery of SNP Markers and Construction of Linkage Map from F5 Population of Pepper with Contrasting Powdery Mildew Resistance Trait.

Powdery mildew (PM) is a common fungal disease infecting pepper plants worldwide. Molecular breeding of pepper cultivars with powdery mildew resistance is desirable for the economic improvement of pepper cultivation. In the present study, 188 F5 population derived from AR1 (PM resistant) and TF68 (PM sensitive) parents were subjected to high-throughput genotyping by sequencing (GBS) for the identification of single nucleotide polymorphism (SNP) markers. Further, the identified SNP markers were utilized for the construction of genetic linkage map and QTL analysis. Overall read mapping percentage of 87.29% was achieved in this study with the total length of mapped region ranging from 2,956,730 to 25,537,525 bp. A total of 41,111 polymorphic SNPs were identified, and a final of 1,841 SNPs were filtered for the construction of a linkage map. A total of 12 linkage groups were constructed corresponding to each chromosome with 1,308 SNP markers with the map length of 2506.8 cM. Further, two QTLs such as Pm-2.1 and Pm-5.1 were identified in chromosomes 2 and 5, respectively, for the PM resistance. Overall, the outcomes of the present endeavor can be utilized for the marker-assisted selection of pepper with powdery mildew-resistant trait.

Unannotated single nucleotide polymorphisms in the TATA box of erythropoiesis genes show in vitro positive involvements in cognitive and mental disorders

BackgroundHemoglobin is a tetramer consisting of two α-chains and two β-chains of globin. Hereditary aberrations in the synthesis of one of the globin chains are at the root of thalassemia, one of the most prevalent monogenic diseases worldwide. In humans, in addition to α- and β-globins, embryonic zeta-globin and fetal γ-globin are expressed. Immediately after birth, the expression of fetal Aγ- and Gγ-globin ceases, and then adult β-globin is mostly expressed. It has been shown that in addition to erythroid cells, hemoglobin is widely expressed in nonerythroid cells including neurons of the cortex, hippocampus, and cerebellum in rodents; embryonic and adult brain neurons in mice; and mesencephalic dopaminergic brain cells in humans, mice, and rats. Lately, there is growing evidence that different forms of anemia (changes in the number and quality of blood cells) may be involved in (or may accompany) the pathogenesis of various cognitive and mental disorders, such as Alzheimer’s and Parkinson’s diseases, depression of various severity levels, bipolar disorders, and schizophrenia. Higher hemoglobin concentrations in the blood may lead to hyperviscosity, hypovolemia, and lung diseases, which may cause brain hypoxia and anomalies of brain function, which may also result in cognitive deficits.MethodsIn this study, a search for unannotated single-nucleotide polymorphisms (SNPs) of erythroid genes was initially performed using our previously created and published SNP-TATA_Z-tester, which is a Web service for computational analysis of a given SNP for in silico estimation of its influence on the affinity of TATA-binding protein (TBP) for TATA and TATA-like sequences. The obtained predictions were finally verified in vitro by an electrophoretic mobility shift assay (EMSA).ResultsOn the basis of these experimental in vitro results and literature data, we studied TATA box SNPs influencing both human erythropoiesis and cognitive abilities. For instance, TBP–TATA affinity in the HbZ promoter decreases 6.6-fold as a result of a substitution in the TATA box (rs113180943), thereby possibly disrupting stage-dependent events of “switching” of hemoglobin genes and thus causing erythroblastosis. Therefore, rs113180943 may be a candidate marker of severe hemoglobinopathies with comorbid cognitive and mental disorders associated with cerebral blood flow disturbances.ConclusionsThe literature data and experimental and computations results suggest that the uncovered candidate SNP markers of erythropoiesis anomalies may also be studied in cohorts of patients with cognitive and/or mental disorders with comorbid erythropoiesis diseases in comparison to conventionally healthy volunteers. Research into the regulatory mechanisms by which the identified SNP markers contribute to the development of hemoglobinopathies and of the associated cognitive deficits will allow physicians not only to take timely and adequate measures against hemoglobinopathies but also to implement strategies preventing cognitive and mental disorders.

Single nucleotide polymorphisms in candidate genes are significantly associated with resistance to Haemonchus contortus infection in goats

BackgroundHaemonchosis is a major economic problem in goat production in humid, tropical and subtropical regions. The disease is caused by an abomasal nematode, Haemonchus contortus, which is highly pathogenic in small ruminants. The aim of this study was to identifying single-nucleotide polymorphisms (SNP) that were associated with fecal egg counts (FEC) and could be used as markers to identify resistance to H. contortus in goats.ResultsTen novel variants in the CIITA, ATP2A3, HSPA8, STAT5B, ESYT1, and SERPING1 genes were associated with FEC in goats with a nominal significance level of P < 0.05. Two missense mutation in the exon region of the caprine CIITA gene resulted in replacement of arginine with cysteine at position 9473550 (R9473550C) and aspartic acid with glutamic acid at position 9473870 (D9473870E). Chinese goat breeds had significantly higher FEC than Bangladeshi goat breeds within their respective genotypes. Polymorphism information content (PIC), effective allele number (Ne), and heterozygosity (He) were greatest for the STAT5B_197_A > G SNP locus in all goat breeds. Pairwise coefficients of linkage disequilibrium (D´, r2) revealed complete LD (r2 = 1) between significant SNP polymorphisms in CIITA and SERPING1 and strong LD (r2 = 0.93 and 0.98) between polymorphisms in HSPA8 and ATP2A3, respectively. Correlation coefficient (r) between FEC and body weight (BW) was significantly positive (r = 0.56***, P < 0.001) but that between FEC and packed cell volume (PCV) was negatively significant (r = − 0.47**, P < 0.01) in the total population of goats. On the other hand, correlation coefficient (r) between BW and PCV was not significant in total population of goats. Association analysis revealed that haplotypes within ATP2A3, HSPA8, and SERPING1 were significantly associated with FEC. Quantitative real-time PCR revealed that the relative expression of mRNA was higher (P < 0.001) for resistant, compared to susceptible, groups of goats for all candidate genes except CIITA.ConclusionsThis study identified SNP markers that can potentially be used in marker-assisted selection programs to develop goat breeds that are resistant to H. contortus.

Genome analysis to identify SNPs associated with oil content and fatty acid components in soybean

The nutritional value, flavor and stability of soybean oil are determined by its five dominant fatty acids: saturated palmitic and stearic, monounsaturated oleic, and polyunsaturated linoleic and linolenic acids. Identifying molecular markers or quantitative trait loci associated with these components has the potential to facilitate the development of improved varieties and thus improve soybean oil content and quality. In this study, we used the BARCSoySNP6K BeadChip array to conduct a genome analysis of diverse soybean accessions evaluated for 2 years under Brazilian field conditions. The results demonstrated high broad-sense heritability, suggesting that the soybean genotype panel could be useful for oil trait breeding programs. Moreover, the range of oil trait variation among the plant introductions (PIs) was superior to that among the Brazilian cultivars in this study, indicating that a PI population could be used to find genes controlling these traits. The genome analysis showed that the genetic structure of the soybean germplasm comprised two main genetic groups, and it revealed linkage disequilibrium decay of approximately 300 kb. A total of 19 single-nucleotide polymorphism (SNP) loci on ten different chromosomes significantly associated with palmitic acid, oleic acid and total oil contents were discovered. Analysis of the SNP annotations revealed enzymes associated with several oil-related physiological metabolisms. Loci and specific alleles in our soybean panel that contributed to lower palmitic acid contents and higher oleic acid and total oil contents were identified. Overall, this genome analysis confirmed previous findings and identified SNP markers that may be useful to rapidly improve oil traits in soybean.

Genome-wide association mapping of spot blotch resistance in wheat association mapping initiative (WAMI) panel of spring wheat (Triticum aestivum L.).

Spot blotch (SB) caused by Bipolaris sorokiniana, is one of the most important diseases of wheat in the eastern part of south Asia causing considerable yield loss to the wheat crop. There is an urgent need to identify genetic loci closely associated with resistance to this pathogen for developing resistant cultivars. Hence, genomic regions responsible for SB resistance were searched using a wheat association mapping initiative (WAMI) panel involving 287 spring wheat genotypes of different origin. Genome-wide association mapping (GWAM) was performed using single nucleotide polymorphism (SNP) markers from a custom 90 K wheat SNP array. A mixed linear model (MLM) was used for assessing the association of SNP markers with spot blotch resistance in three consecutive years. Three traits were measured: incubation period, lesion number and area under the disease progress curve (AUDPC). Significant SNP markers were found linked to five, six and four quantitative trait loci (QTLs) for incubation period, lesion number and AUDPC respectively. They were detected on 11 different chromosomes: 1A, 1B, 1D, 4A, 5A, 5B, 6A, 6B, 6D, 7A, 7B with marker R2 range of 0.083 to 0.11. The greatest number of significant SNP-markers was found for lesion number and AUDPC on chromosome 6B and 5B, respectively, representing a better coverage of B-genome by SNPs. On the other hand, the most significant and largest SNP markers for incubation period were detected on 6A and 4A chromosomes indicating that this trait is associated with the A-genome of wheat. Although, QTLs for spot blotch resistance have been reported in wheat on these same chromosomes, the association of incubation period and lesion number with SB resistance has not been reported in previous studies. The panel exhibits considerable variation for SB resistance and also provides a good scope of marker-assisted selection using the identified SNP markers linked to resistant QTLs.

QTL Mapping Combined With Bulked Segregant Analysis Identify SNP Markers Linked to Leaf Shape Traits in Pisum sativum Using SLAF Sequencing.

Leaf shape is an important trait that influences the utilization rate of light, and affects quality and yield of pea (Pisum sativum). In the present study, a joint method of high-density genetic mapping using specific locus amplified fragment sequencing (SLAF-seq) and bulked segregant analysis (BSA) was applied to rapidly detect loci with leaf shape traits. A total of 7,146 polymorphic SLAFs containing 12,213 SNP markers were employed to construct a high-density genetic map for pea. We conducted quantitative trait locus (QTL) mapping on an F2 population to identify QTLs associated with leaf shape traits. Moreover, SLAF-BSA was conducted on the same F2 population to identify the single nucleotide polymorphism (SNP) markers linked to leaf shape in pea. Two QTLs (qLeaf_or-1, qLeaf_or-2) were mapped on linkage group 7 (LG7) for pea leaf shape. Through alignment of SLAF markers with Cicer arietinum, Medicago truncatula, and Glycine max, the pea LGs were assigned to their corresponding homologous chromosomal groups. The comparative genetic analysis showed that pea is more closely related to M. truncatula. Based on the sequencing results of two pools with different leaf shape, 179 associated markers were obtained after association analysis. The joint analysis of SLAF-seq and BSA showed that the QTLs obtained from mapping on a high-density genetic map are convincing due to the closely associated map region with the BSA results, which provided more potential markers related to leaf shape. Thus, the identified QTLs could be used in marker-assisted selection for pea breeding in the future. Our study revealed that joint analysis of QTL mapping on a high-density genetic map and BSA-seq is a cost-effective and accurate method to reveal genetic architecture of target traits in plant species without a reference genome.

Identification of molecular markers associated with genic male sterility in tetraploid cotton (Gossypium hirsutum L.) through bulk segregant analysis using a cotton SNP 63K array

Genic male sterility (GMS) is one of the most important economic traits for cotton (Gossypium hirsutum L.) hybrid seed production. The GMS trait conferred by two recessive alleles ms5 and ms6 in homozygous constitution is widely used for cotton hybrid seed production in India. Identification of molecular markers closely linked to the ms5 and ms6 alleles would be useful in effective transferring in a short time male-sterility genes into cultivars or elite lines using marker-assisted backcrossing. Here, we describe a quick method to identify markers for GMS genes using bulk segregant analysis (BSA) in the interspecific (G. hirsutum × G. hirsutum) biparental population. The parents and bulks were genotyped with a cotton single nucleotide polymorphism (SNP) 63K array that contains 63 058 SNP markers including 45 104 intraspecific and 17 954 interspecific SNP markers. Four SNP markers were found to be linked with the Ms5 and Ms6 genes. The markers i23493Gh and i46470Gh linked with the Ms5 gene, and other two markers i08605Gh and i08573Gh linked with the Ms6 gene are located on chromosome 12 and 26, respectively. A simple and cost effective tetra-primer amplification refractory mutation system PCR (tetra-primer ARMS-PCR) assay was optimized for screening a large number of breeding samples with the identified SNP markers in a short time. The molecular markers developed in this study will facilitate the marker-assisted selection (MAS) and accelerate the development of new GMS lines to use in cotton hybrid seed production.

Sociality genes are associated with human-directed social behaviour in golden and Labrador retriever dogs.

BackgroundDogs have human-directed social skills that allow them to communicate and cooperate with humans. We have previously identified two loci on chromosome 26 associated with human contact-seeking behaviors during an unsolvable problem task in laboratory beagles (Persson et al., 2016). The aim of the present study was to verify the single nucleotide polymorphisms (SNPs) in additional dog breeds. We also studied how the allele frequencies have changed during domestication and recent selection.MethodsDogs of two breeds, 61 golden retrievers and 100 Labrador retrievers, were phenotyped and genotyped, and 19 wolves were genotyped. The Labrador retrievers were divided into common and field type by pedigree data to make it possible to study the effects of recent selection. All dogs were tested in an unsolvable problem task where human-directed social behaviors were scored. DNA from dogs (buccal swabs) and wolves (blood or brain tissue) was analyzed for genotype on two of the previously identified SNP markers, BICF2G630798942 (SNP1) and BICF2S23712114 (SNP2), by pyrosequencing.ResultsThere was genetic variation for SNP1 in both dog breeds whereas the wolves were fixed for this polymorphism, and for SNP2 there was variation in both dogs and wolves. For both SNPs, Labrador retriever types differed significantly in allele frequencies. We found associations between SNPs and human-directed social behavior in both dog breeds. In golden retrievers, SNP1 was associated with physical contact variables, for example, with the duration of physical contact with the owner (F2,56 = 4.389, p = 0.017). SNP2 was associated with several behavioral variables in both breeds, among others owner gazing frequency in both golden retrievers (F2,55 = 6.330, p = 0.003) and Labradors (F1,93 = 5.209, p = 0.025).DiscussionOur results verify the association between the previously identified SNPs and human-directed social behavior scored in an unsolvable problem task. Differences in allele frequencies suggest that these loci have been affected by selection. The results indicate that these genomic regions are involved in human-directed social behavior in not only beagles but in other dog breeds as well. We hypothesize that they may have been important during dog domestication.

Genetic diversity and association mapping of mineral element concentrations in spinach leaves

BackgroundSpinach is a useful source of dietary vitamins and mineral elements. Breeding new spinach cultivars with high nutritional value is one of the main goals in spinach breeding programs worldwide, and identification of single nucleotide polymorphism (SNP) markers for mineral element concentrations is necessary to support spinach molecular breeding. The purpose of this study was to conduct a genome-wide association study (GWAS) and to identify SNP markers associated with mineral elements in the USDA-GRIN spinach germplasm collection.ResultsA total of 14 mineral elements: boron (B), calcium (Ca), cobalt (Co), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), sodium (Na), nickel (Ni), phosphorus (P), sulfur (S), and zinc (Zn) were evaluated in 292 spinach accessions originally collected from 29 countries. Significant genetic variations were found among the tested genotypes as evidenced by the 2 to 42 times difference in mineral concentrations. A total of 2402 SNPs identified from genotyping by sequencing (GBS) approach were used for genetic diversity and GWAS. Six statistical methods were used for association analysis. Forty-five SNP markers were identified to be strongly associated with the concentrations of 13 mineral elements. Only two weakly associated SNP markers were associated with K concentration. Co-localized SNPs for different elemental concentrations were discovered in this research. Three SNP markers, AYZV02017731_40, AYZV02094133_57, and AYZV02281036_185 were identified to be associated with concentrations of four mineral components, Co, Mn, S, and Zn. There is a high validating correlation coefficient with r > 0.7 among concentrations of the four elements. Thirty-one spinach accessions, which rank in the top three highest concentrations in each of the 14 mineral elements, were identified as potential parents for spinach breeding programs in the future.ConclusionsThe 45 SNP markers strongly associated with the concentrations of the 13 mineral elements: B, Ca, Co, Cu, Fe, Mg, Mn, Mo, Na, Ni, P, S, and Zn could be used in breeding programs to improve the nutritional quality of spinach through marker-assisted selection (MAS). The 31 spinach accessions with high concentrations of one to several mineral elements can be used as potential parents for spinach breeding programs.

Fine Mapping of QTLs for Ascochyta Blight Resistance in Pea Using Heterogeneous Inbred Families.

Ascochyta blight (AB) is an important disease of pea which can cause severe grain yield loss under wet conditions. In our previous study, we identified two quantitative trait loci (QTLs) abIII-1 and abI-IV-2 for AB resistance and these QTLs were consistent across locations and/or years in an inter-specific pea population (PR-19) developed from a cross between Alfetta (Pisum sativum) and P651 (P. fulvum). The objectives of this study were to fine map the abIII-1 and abI-IV-2 QTLs using a high density single nucleotide polymorphism (SNP)-based genetic linkage map and analyze identified markers in heterogeneous inbred family (HIF) populations. Selective genotyping of 51 PR-19 recombinant inbred lines was performed using genotyping-by-sequencing (GBS) and the resulting high density genetic linkage map was used to identify eight new SNP markers within the abI-IV-2 QTL, whereas no additional SNPs were identified within the abIII-1 QTL. Two HIF populations HIF-224 (143 lines) and HIF-173 (126 lines) were developed from F6 RILs PR-19-224 and PR-19-173, respectively. The HIF populations evaluated under field conditions in 2015 and 2016 showed a wide range of variation for reaction to AB resistance. Lodging score had significant positive (P < 0.001) correlation with AB scores. HIFs were genotyped using SNP markers within targeted QTLs. The genotypic and phenotypic data of the HIFs were used to identify two new QTLs, abI-IV-2.1 and abI-IV-2.2 for AB resistance within the abI-IV-2 QTL. These QTLs individually explained 5.5 to 14% of the total phenotypic variation. Resistance to lodging was also associated with these two QTLs. Identified SNP markers will be useful in marker assisted selection for development of pea cultivars with improved AB resistance.

Molecular markers for improving control of soil-borne pathogen Fusarium oxysporum in sugar beet

Fusarium spp. cause severe damage in many agricultural crops, including sugar beet, with Fusarium oxysporum historically being considered as the most damaging of all species. Sugar beet needs to be protected from this class of soil-borne pathogens in order to ensure an optimal sugar yield in the field. Genetic control of the disease is crucial in managing these pathogens. Identification of single nucleotide polymorphism (SNP) markers linked to resistance can be a powerful tool for the introgression of valuable genes needed to develop Fusarium-resistant varieties. A candidate gene approach was carried out to identify SNP markers linked to putative Fusarium resistance sources in sugar beet. Five resistant analogue genes (RGAs) were screened by means of high resolution melting (HRM) analysis in a set of sugar beet lines, considered as resistant and susceptible to Fusarium oxysporum. HRM polymorphisms were observed in 80% of amplicons. Two HRM polymorphisms were significantly associated with Fusarium resistance (P < 0.05). The amplicons that showed association were sequenced and two SNPs were identified. The association was further validated on 96 susceptible and 96 resistant plants using competitive allele-specific PCR (KASPar) technology. The selected SNPs could be used for marker-assisted breeding of Fusarium resistance in sugar beet.

Genome-Wide Association Mapping of Rice Resistance Genes Against Magnaporthe oryzae Isolates from Four African Countries.

Rice blast disease is emerging as a major constraint to rice production in Africa. Although a traditional gene-tagging strategy using biparental crosses can effectively identify resistance (R) genes or quantitative trait loci (QTL) against Magnaporthe oryzae, the mapping procedure required is time consuming and requires many populations to investigate the genetics of resistance. In this report, we conducted a genome-wide association study (GWAS) to rapidly map rice genes conferring resistance against eight M. oryzae isolates from four African countries. We inoculated 162 rice cultivars, which were part of the rice diversity panel 1 (RDP1) and were previously genotyped with the 44,000 single-nucleotide polymorphism (SNP) chip, with the eight isolates. The GWAS identified 31 genomic regions associated with blast resistance (RABR) in the rice genome. In addition, we used polymerase chain reaction analysis to confirm the association between the Pish gene and a major RABR on chromosome 1 that was associated with resistance to four M. oryzae isolates. Our study has demonstrated the power of GWAS for the rapid identification of rice blast R or QTL genes that are effective against African populations of M. oryzae. The identified SNP markers associated with RABR can be used in breeding for resistance against rice blast in Africa.