Linkage disequilibrium(LD) can be applied for mapping the actual genes responsible for variation of economically important traits through association mapping.The feasibility and efficacy of association studies are str...Linkage disequilibrium(LD) can be applied for mapping the actual genes responsible for variation of economically important traits through association mapping.The feasibility and efficacy of association studies are strongly dependent on the extent of LD which determines the number and density of markers in the studied population,as well as the experimental design for an association analysis.In this study,we first characterized the extent of LD in a wild population and a cultured mass-selected line of Pacific oyster(Crassostrea gigas).A total of 88 wild and 96 cultured individuals were selected to assess the level of genome-wide LD with 53 microsatellites,respectively.For syntenic marker pairs,no significant association was observed in the wild population;however,three significant associations occurred in the cultured population,and the significant LD extended up to 12.7 c M,indicating that strong artificial selection is a key force for substantial increase of genome-wide LD in cultured population.The difference of LD between wild and cultured populations showed that association studies in Pacific oyster can be achieved with reasonable marker densities at a relatively low cost by choosing an association mapping population.Furthermore,the frequent occurrence of LD between non-syntenic loci and rare alleles encourages the joint application of linkage analysis and LD mapping when mapping genes in oyster.The information on the linkage disequilibrium in the cultured population is useful for future association mapping in oyster.展开更多
With completion of the Populus genome sequencing project and the availability of many expressed sequence tags (ESTs) databases in forest trees, attention is now rapidly shifting towards the study of individual genet...With completion of the Populus genome sequencing project and the availability of many expressed sequence tags (ESTs) databases in forest trees, attention is now rapidly shifting towards the study of individual genetic variation in natural populations. The most abundant form of genetic variation in many eukaryotic species is represented by single nucleotide polymorphisms (SNPs), which can account for heritable inter-individual differences in complex phenotypes. Unlike humans, the linkage disequilibrium (LD) rapidly decays within candidate genes in forest trees. Thus, SNPs-based candidate gene association studies are considered to be a most effective approach to dissect the complex quantitative traits in forest trees. The present study demonstrates that LD mapping can be used to identify alleles associated with quantitative traits and suggests that this new approach could be particularly useful for performing breeding programs in forest trees. In this review, we will describe the fundamentals, patterns of SNPs distribution and frequency, summarize recent advances in SNPs discovery and LD and comment on the application of LD in the dissection of complex quantitative traits in forest tress. We also put forward the outlook for future SNPs-based association analysis of quantitative traits in forest trees.展开更多
In multiloci-based genetic association studies of complex diseases, a powerful and high efficient tool for analyses oflinkage disequilibrium (LD) between markers, haplotype distributions and many chi-square/p values w...In multiloci-based genetic association studies of complex diseases, a powerful and high efficient tool for analyses oflinkage disequilibrium (LD) between markers, haplotype distributions and many chi-square/p values with a large numberof samples has been sought for long. In order to achieve the goal of obtaining meaningful results directly from raw data,we developed a robust and user-friendly software platform with a series of tools for analysis in association study withhigh efficiency. The platform has been well evaluated by several sets of real data.展开更多
Wheat powdery mildew(Blumeria graminis f.sp.tritici, Bgt) is a disease of increasing importance globally due to the adoption of high yielding varieties and modern sustainable farming technologies.Growing resistant cul...Wheat powdery mildew(Blumeria graminis f.sp.tritici, Bgt) is a disease of increasing importance globally due to the adoption of high yielding varieties and modern sustainable farming technologies.Growing resistant cultivars is a preferred approach to managing this disease, and novel powdery mildew resistance genes are urgently needed for new cultivar development.A genome-wide association study was performed on a panel of 1292 wheat landraces and historical cultivars using 5011 single nucleotide polymorphism(SNP)markers.The association panel was evaluated for reactions to three Bgt inoculants, OKS(14)-B-3-1, OKS(14)-C-2-1, and Bgt15.Linkage disequilibrum(LD) analysis indicated that genome-wide LD decayed to 0.1 at 23 Mb, and population structure analysis revealed seven subgroups in the panel.Association analysis using a mixed linear model(MLM) identified three loci for powdery mildew resistance on chromosome 2 B, designated QPm.stars-2BL1,QPm.stars-2BL2, and QPm.stars-2BL3.To evaluate the efficacy of GWAS in gene discovery,QPm.stars-2BL2 was validated using F2 and F2:3 populations derived from PI420646 × OK1059060-126135-3.Linkage analysis delimited the powdery mildew resistance gene in PI 420646 to an interval where QPm.stars-2BL2 was located, lending credence to the GWAS results.QPm.stars-2BL1 and QPm.stars-2BL3, which were associated with four SNPs located at 457.7–461.7 Mb and two SNPs located at 696.6–715.9 Mb in the Chinese Spring reference IWGSC RefSeq v1.0, respectively, are likely novel loci for powdery mildew resistance and can be used in wheat breeding to improve powdery mildew resistance.展开更多
In this study, we propose to use the principal component analysis (PCA) and regression model to incorporate linkage disequilibrium (LD) in genomic association data analysis. To accommodate LD in genomic data and r...In this study, we propose to use the principal component analysis (PCA) and regression model to incorporate linkage disequilibrium (LD) in genomic association data analysis. To accommodate LD in genomic data and reduce multiple testing, we suggest performing PCA and extracting the PCA score to capture the variation of genomic data, after which regression analysis is used to assess the association of the disease with the principal component score. An empirical analysis result shows that both genotype-based correlation matrix and haplotype-based LD matrix can produce similar results for PCA. Principal component score seems to be more powerful in detecting genetic association because the principal component score is quantitatively measured and may be able to capture the effect of multiple loci.展开更多
To investigate the distribution characteristics and linkage disequilibrium of T cell immunoglobulin domain and mucin domain protein 4 (TIM4) promoter polymorphisms in asthma patients of Chinese Han population, the p...To investigate the distribution characteristics and linkage disequilibrium of T cell immunoglobulin domain and mucin domain protein 4 (TIM4) promoter polymorphisms in asthma patients of Chinese Han population, the promoter region of TIM4 was re-sequenced by PCR-sequencing, and linkage disequilibrium was analyzed by SHEsis software. Four single nucleotide polymor- phisms (SNPs) in the promoter region of TIM4 were detected, including two new SNPs (at positions -1609, -153) and two reported SNPs (rs6874202, rs6882076). The frequency distribution of rs6882076 was different among different races (P〈0.05). In addition, linkage disequilibrium among the SNPs of the promoter region of TIM4 was found and GGTG was the predominant haplotype. There were four SNPs in the promoter region of TIM4 in asthma patients of Chinese Han population, which were in linkage disequilibrium.展开更多
To find the quantitative trait loci associated with wood density in teak(Tectona grandis L.f.), 21 co-dominant markers including 13 site specific recombinase and 8 EST-based co-dominant markers designed from lignin bi...To find the quantitative trait loci associated with wood density in teak(Tectona grandis L.f.), 21 co-dominant markers including 13 site specific recombinase and 8 EST-based co-dominant markers designed from lignin biosynthesis genes were applied to 174 teak plus tree clones at the National Germplasm Bank, Chandrapur,India. The germplasm bank exhibited 10.6% coefficient of variation for wood densities with 84.5 ± 31.3 genetic polymorphism(%). The highly panmictic set of genotypes(FST= 0.035 ± 0.004) harbored 96.47 ± 0.40 genetic variability(%). The average allelic frequency of the 21 codominant markers was 0.65 ± 0.11 with 12.9% pairs of loci in significant LD(p\0.05, R^2 values [ 0.1), confirming their suitability for a strong marker-trait association study. The marker CCoAMT-1 was significantly(p\0.01) associated with wood density showing stability by both GLM and MLM models and explained 4.3% of the phenotypic effect. The marker from the EST representing CCoAMT can be further developed for gene-assisted selection of elite genotypes of teak with greater wood density. Therefore, we believe that the report will help accelerate the genetic improvement and advance the breeding program of the species.展开更多
A novel method for haplotype phasing in families after joint estimation of recombination fraction and linkage disequilibrium is developed. Results from Monte Carlo computer simulations show that the newly developed E....A novel method for haplotype phasing in families after joint estimation of recombination fraction and linkage disequilibrium is developed. Results from Monte Carlo computer simulations show that the newly developed E.M. algorithm is accurate if true recombination fraction is 0 even for single families of relatively small sizes. Estimates of recombination fraction and linkage disequilibrium were 0.00 (SD 0.00) and 0.19 (SD 0.03) for simulated recombination fraction and linkage disequilibrium of 0.00 and 0.20, respectively. A genome fragmentation phasing strategy was developed and used for phasing haplotypes in a sire and 36 progeny using the 50 k Illumina BeadChip by: a) estimation of the recombination fraction and LD in consecutive SNPs using family information, b) linkage analyses between fragments, c) phasing of haplotypes in parents and progeny and in following generations. Homozygous SNPs in progeny allowed determination of paternal fragment inheritance, and deduction of SNP sequence information of haplotypes from dams. The strategy also allowed detection of genotyping errors. A total of 613 recombination events were detected after linkage analysis was carried out between fragments. Hot and cold spots were identified at the individual (sire level). SNPs for which the sire and calf were heterozygotes became informative (over 90%) after the phasing of haplotypes. Average of regions of identity between half-sibs when comparing its maternal inherited haplotypes (with at least 20 SNP) in common was 0.11 with a maximum of 0.29 and a minimum of 0.05. A Monte-Carlo simulation of BTA1 with the same linkage disequilibrium structure and genetic linkage as the cattle family yielded a 99.98 and 99.94% of correct phases for informative SNPs in sire and calves, respectively.展开更多
In this article, using the likelihood score theory extended to nuisance parameters we derive a new homogeneity score test for comparing linkage disequilibrium across several strata. Power and sample size formulae are...In this article, using the likelihood score theory extended to nuisance parameters we derive a new homogeneity score test for comparing linkage disequilibrium across several strata. Power and sample size formulae are also obtained.展开更多
Conducting genomic selection in admixed populations is challenging and its accuracy in this case largely depends on the persistence of linkage disequilibrium between single nucleotide polymorphisms (SNP) and quantitat...Conducting genomic selection in admixed populations is challenging and its accuracy in this case largely depends on the persistence of linkage disequilibrium between single nucleotide polymorphisms (SNP) and quantitative trait loci (QTL). Inferring linkage disequilibrium (LD) between SNP markers and QTLs could be important in understanding the change of SNP marker effects across different breeds. Predicting the change in linkage disequilibrium between markers and QTLs across two divergent breeds was explored using information from the genotype data. Two different models (M1, M2) that differ in the definition of the explanatory variables were used to infer the level of LD between SNP markers and QTLs using all markers in the panel or windows of fixed number of markers. Three simulation scenarios were conducted using different number of SNPs and QTLs. In the first scenario, the resulting coefficient of determination (R2) was 0.65 and 0.52 using M1 and M2, respectively. In the second scenario, average R2 equaled 0.12 using all markers in the panel and 0.25 using 100 marker windows. Across the three simulation scenarios, it was clear that a significant portion of the variation in the change in LD between SNP markers and QTLs could be explained by information already available in the observed SNP marker data.展开更多
Bamboos are one of the most beautiful and useful plants on Earth.The genetic background and population structure of bamboos are well known,which helps accelerate the process of artificial domestication of bamboo.Parti...Bamboos are one of the most beautiful and useful plants on Earth.The genetic background and population structure of bamboos are well known,which helps accelerate the process of artificial domestication of bamboo.Partial sequences of six genes involved in nitrogen use efficiency in 32 different bamboo species were analyzed for occurrence of single nucleotide polymorphisms(SNPs).The nucleotide diversityθw and total nucleotide polymorphismsπT of the sequenced DNA regions was 0.05137 and 0.03332,respectively.Bothπnonsyn/πsyn and Ka/Ks values were<1.The nucleotide sequences of these six genes were inferred to be relatively conserved,and the haplotype diversity was relatively high.The results of evolutionary neutrality tests showed that the six genes were in line with neutral evolution,and that the NRT2.1 and AMT2.1 gene sequences may have experienced negative selection.An inter-SNP recombination event at the NRT2.1 gene in the all pooled sample,of all 32 bamboo species was the lowest at 0.0645,whereas the AMT gene recombination events were all>0.1.Estimation and analysis of linkage disequilibrium of five genes revealed that with the increase in nucleotide sequence length,the degree of SNP linkage disequilibrium decreased rapidly.We inferred the population genetic structure of 32 bamboo species based on the SNP loci of six genes with frequencies>18%.32 bamboo species were divided into five categories,which indicated that the combined population of all bamboo species had obvious multivariate characteristics and was heterogeneous;red(Group 1)and green(Group 2)were the main groups.展开更多
Quantitative trait loci (QTL) and their additive, dominance and epistatic effects play a critical role in complex trait variation. It is often infeasible to detect multiple interacting QTL due to main effects often be...Quantitative trait loci (QTL) and their additive, dominance and epistatic effects play a critical role in complex trait variation. It is often infeasible to detect multiple interacting QTL due to main effects often being confounded by interaction effects. Positioning interacting QTL within a small region is even more difficult. We present a variance component approach nested in an empirical Bayesian method, which simultaneously takes into account additive, dominance and epistatic effects due to multiple interacting QTL. The covariance structure used in the variance component approach is based on combined linkage disequilibrium and linkage (LDL) information. In a simulation study where there are complex epistatic interactions between QTL, it is possible to simultaneously fine map interacting QTL using the proposed approach. The present method combined with LDL information can efficiently detect QTL and their dominance and epistatic effects, making it possible to simultaneously fine map main and epistatic QTL.展开更多
Commercially grown sugarcane cultivars are advanced generation hybrids between two polyploid ancestor species, S. off icinarum L. (x=10, 2n=8x=80) and S. spontaneum (x= 8, 2n=5-16x=40-128). Modern cultivars
基金supported by the Shandong Seed Project and the National Natural Science Foundation of China (31372524)
文摘Linkage disequilibrium(LD) can be applied for mapping the actual genes responsible for variation of economically important traits through association mapping.The feasibility and efficacy of association studies are strongly dependent on the extent of LD which determines the number and density of markers in the studied population,as well as the experimental design for an association analysis.In this study,we first characterized the extent of LD in a wild population and a cultured mass-selected line of Pacific oyster(Crassostrea gigas).A total of 88 wild and 96 cultured individuals were selected to assess the level of genome-wide LD with 53 microsatellites,respectively.For syntenic marker pairs,no significant association was observed in the wild population;however,three significant associations occurred in the cultured population,and the significant LD extended up to 12.7 c M,indicating that strong artificial selection is a key force for substantial increase of genome-wide LD in cultured population.The difference of LD between wild and cultured populations showed that association studies in Pacific oyster can be achieved with reasonable marker densities at a relatively low cost by choosing an association mapping population.Furthermore,the frequent occurrence of LD between non-syntenic loci and rare alleles encourages the joint application of linkage analysis and LD mapping when mapping genes in oyster.The information on the linkage disequilibrium in the cultured population is useful for future association mapping in oyster.
文摘With completion of the Populus genome sequencing project and the availability of many expressed sequence tags (ESTs) databases in forest trees, attention is now rapidly shifting towards the study of individual genetic variation in natural populations. The most abundant form of genetic variation in many eukaryotic species is represented by single nucleotide polymorphisms (SNPs), which can account for heritable inter-individual differences in complex phenotypes. Unlike humans, the linkage disequilibrium (LD) rapidly decays within candidate genes in forest trees. Thus, SNPs-based candidate gene association studies are considered to be a most effective approach to dissect the complex quantitative traits in forest trees. The present study demonstrates that LD mapping can be used to identify alleles associated with quantitative traits and suggests that this new approach could be particularly useful for performing breeding programs in forest trees. In this review, we will describe the fundamentals, patterns of SNPs distribution and frequency, summarize recent advances in SNPs discovery and LD and comment on the application of LD in the dissection of complex quantitative traits in forest tress. We also put forward the outlook for future SNPs-based association analysis of quantitative traits in forest trees.
基金This work was supported by the Major State Basic Research Development program of Chinathe National High Technology Research and Development Program of China.
文摘In multiloci-based genetic association studies of complex diseases, a powerful and high efficient tool for analyses oflinkage disequilibrium (LD) between markers, haplotype distributions and many chi-square/p values with a large numberof samples has been sought for long. In order to achieve the goal of obtaining meaningful results directly from raw data,we developed a robust and user-friendly software platform with a series of tools for analysis in association study withhigh efficiency. The platform has been well evaluated by several sets of real data.
文摘Wheat powdery mildew(Blumeria graminis f.sp.tritici, Bgt) is a disease of increasing importance globally due to the adoption of high yielding varieties and modern sustainable farming technologies.Growing resistant cultivars is a preferred approach to managing this disease, and novel powdery mildew resistance genes are urgently needed for new cultivar development.A genome-wide association study was performed on a panel of 1292 wheat landraces and historical cultivars using 5011 single nucleotide polymorphism(SNP)markers.The association panel was evaluated for reactions to three Bgt inoculants, OKS(14)-B-3-1, OKS(14)-C-2-1, and Bgt15.Linkage disequilibrum(LD) analysis indicated that genome-wide LD decayed to 0.1 at 23 Mb, and population structure analysis revealed seven subgroups in the panel.Association analysis using a mixed linear model(MLM) identified three loci for powdery mildew resistance on chromosome 2 B, designated QPm.stars-2BL1,QPm.stars-2BL2, and QPm.stars-2BL3.To evaluate the efficacy of GWAS in gene discovery,QPm.stars-2BL2 was validated using F2 and F2:3 populations derived from PI420646 × OK1059060-126135-3.Linkage analysis delimited the powdery mildew resistance gene in PI 420646 to an interval where QPm.stars-2BL2 was located, lending credence to the GWAS results.QPm.stars-2BL1 and QPm.stars-2BL3, which were associated with four SNPs located at 457.7–461.7 Mb and two SNPs located at 696.6–715.9 Mb in the Chinese Spring reference IWGSC RefSeq v1.0, respectively, are likely novel loci for powdery mildew resistance and can be used in wheat breeding to improve powdery mildew resistance.
文摘In this study, we propose to use the principal component analysis (PCA) and regression model to incorporate linkage disequilibrium (LD) in genomic association data analysis. To accommodate LD in genomic data and reduce multiple testing, we suggest performing PCA and extracting the PCA score to capture the variation of genomic data, after which regression analysis is used to assess the association of the disease with the principal component score. An empirical analysis result shows that both genotype-based correlation matrix and haplotype-based LD matrix can produce similar results for PCA. Principal component score seems to be more powerful in detecting genetic association because the principal component score is quantitatively measured and may be able to capture the effect of multiple loci.
基金the National Natural Sciences Foundation of China (No. 30672008)
文摘To investigate the distribution characteristics and linkage disequilibrium of T cell immunoglobulin domain and mucin domain protein 4 (TIM4) promoter polymorphisms in asthma patients of Chinese Han population, the promoter region of TIM4 was re-sequenced by PCR-sequencing, and linkage disequilibrium was analyzed by SHEsis software. Four single nucleotide polymor- phisms (SNPs) in the promoter region of TIM4 were detected, including two new SNPs (at positions -1609, -153) and two reported SNPs (rs6874202, rs6882076). The frequency distribution of rs6882076 was different among different races (P〈0.05). In addition, linkage disequilibrium among the SNPs of the promoter region of TIM4 was found and GGTG was the predominant haplotype. There were four SNPs in the promoter region of TIM4 in asthma patients of Chinese Han population, which were in linkage disequilibrium.
基金partially funded in the form of Senior Research Fellowship(vide No.09/1164(0001)/2016-EMR-I)awarded to the first author(Vivek Vaishnav)by Government of India Council of Scientific and Industrial Research,New Delhi,which is gratefully acknowledged
文摘To find the quantitative trait loci associated with wood density in teak(Tectona grandis L.f.), 21 co-dominant markers including 13 site specific recombinase and 8 EST-based co-dominant markers designed from lignin biosynthesis genes were applied to 174 teak plus tree clones at the National Germplasm Bank, Chandrapur,India. The germplasm bank exhibited 10.6% coefficient of variation for wood densities with 84.5 ± 31.3 genetic polymorphism(%). The highly panmictic set of genotypes(FST= 0.035 ± 0.004) harbored 96.47 ± 0.40 genetic variability(%). The average allelic frequency of the 21 codominant markers was 0.65 ± 0.11 with 12.9% pairs of loci in significant LD(p\0.05, R^2 values [ 0.1), confirming their suitability for a strong marker-trait association study. The marker CCoAMT-1 was significantly(p\0.01) associated with wood density showing stability by both GLM and MLM models and explained 4.3% of the phenotypic effect. The marker from the EST representing CCoAMT can be further developed for gene-assisted selection of elite genotypes of teak with greater wood density. Therefore, we believe that the report will help accelerate the genetic improvement and advance the breeding program of the species.
基金support from a Marie Curie International Reintegration Grant from the European Union,project no.PIRG08-GA-2010-277031 "SelectionForWelfare"LGR and WMR acknowledge support from project AGL2012-39137
文摘A novel method for haplotype phasing in families after joint estimation of recombination fraction and linkage disequilibrium is developed. Results from Monte Carlo computer simulations show that the newly developed E.M. algorithm is accurate if true recombination fraction is 0 even for single families of relatively small sizes. Estimates of recombination fraction and linkage disequilibrium were 0.00 (SD 0.00) and 0.19 (SD 0.03) for simulated recombination fraction and linkage disequilibrium of 0.00 and 0.20, respectively. A genome fragmentation phasing strategy was developed and used for phasing haplotypes in a sire and 36 progeny using the 50 k Illumina BeadChip by: a) estimation of the recombination fraction and LD in consecutive SNPs using family information, b) linkage analyses between fragments, c) phasing of haplotypes in parents and progeny and in following generations. Homozygous SNPs in progeny allowed determination of paternal fragment inheritance, and deduction of SNP sequence information of haplotypes from dams. The strategy also allowed detection of genotyping errors. A total of 613 recombination events were detected after linkage analysis was carried out between fragments. Hot and cold spots were identified at the individual (sire level). SNPs for which the sire and calf were heterozygotes became informative (over 90%) after the phasing of haplotypes. Average of regions of identity between half-sibs when comparing its maternal inherited haplotypes (with at least 20 SNP) in common was 0.11 with a maximum of 0.29 and a minimum of 0.05. A Monte-Carlo simulation of BTA1 with the same linkage disequilibrium structure and genetic linkage as the cattle family yielded a 99.98 and 99.94% of correct phases for informative SNPs in sire and calves, respectively.
基金The NNSF (10371015, 10329102) of China, and the Science Foundation (20060101) for Young Teachers of Northeast Normal University.
文摘In this article, using the likelihood score theory extended to nuisance parameters we derive a new homogeneity score test for comparing linkage disequilibrium across several strata. Power and sample size formulae are also obtained.
文摘Conducting genomic selection in admixed populations is challenging and its accuracy in this case largely depends on the persistence of linkage disequilibrium between single nucleotide polymorphisms (SNP) and quantitative trait loci (QTL). Inferring linkage disequilibrium (LD) between SNP markers and QTLs could be important in understanding the change of SNP marker effects across different breeds. Predicting the change in linkage disequilibrium between markers and QTLs across two divergent breeds was explored using information from the genotype data. Two different models (M1, M2) that differ in the definition of the explanatory variables were used to infer the level of LD between SNP markers and QTLs using all markers in the panel or windows of fixed number of markers. Three simulation scenarios were conducted using different number of SNPs and QTLs. In the first scenario, the resulting coefficient of determination (R2) was 0.65 and 0.52 using M1 and M2, respectively. In the second scenario, average R2 equaled 0.12 using all markers in the panel and 0.25 using 100 marker windows. Across the three simulation scenarios, it was clear that a significant portion of the variation in the change in LD between SNP markers and QTLs could be explained by information already available in the observed SNP marker data.
基金This study was financially supported by the National Natural Science Foundation of China(41301346)the Natural Science Foundation of Fujian Province(2020J01375)the Natural Science Foundation of Fujian Province(2015N0034).
文摘Bamboos are one of the most beautiful and useful plants on Earth.The genetic background and population structure of bamboos are well known,which helps accelerate the process of artificial domestication of bamboo.Partial sequences of six genes involved in nitrogen use efficiency in 32 different bamboo species were analyzed for occurrence of single nucleotide polymorphisms(SNPs).The nucleotide diversityθw and total nucleotide polymorphismsπT of the sequenced DNA regions was 0.05137 and 0.03332,respectively.Bothπnonsyn/πsyn and Ka/Ks values were<1.The nucleotide sequences of these six genes were inferred to be relatively conserved,and the haplotype diversity was relatively high.The results of evolutionary neutrality tests showed that the six genes were in line with neutral evolution,and that the NRT2.1 and AMT2.1 gene sequences may have experienced negative selection.An inter-SNP recombination event at the NRT2.1 gene in the all pooled sample,of all 32 bamboo species was the lowest at 0.0645,whereas the AMT gene recombination events were all>0.1.Estimation and analysis of linkage disequilibrium of five genes revealed that with the increase in nucleotide sequence length,the degree of SNP linkage disequilibrium decreased rapidly.We inferred the population genetic structure of 32 bamboo species based on the SNP loci of six genes with frequencies>18%.32 bamboo species were divided into five categories,which indicated that the combined population of all bamboo species had obvious multivariate characteristics and was heterogeneous;red(Group 1)and green(Group 2)were the main groups.
基金Project supported by the International Pig Improvement Company(PIC) and Sheep Genomics, Australia
文摘Quantitative trait loci (QTL) and their additive, dominance and epistatic effects play a critical role in complex trait variation. It is often infeasible to detect multiple interacting QTL due to main effects often being confounded by interaction effects. Positioning interacting QTL within a small region is even more difficult. We present a variance component approach nested in an empirical Bayesian method, which simultaneously takes into account additive, dominance and epistatic effects due to multiple interacting QTL. The covariance structure used in the variance component approach is based on combined linkage disequilibrium and linkage (LDL) information. In a simulation study where there are complex epistatic interactions between QTL, it is possible to simultaneously fine map interacting QTL using the proposed approach. The present method combined with LDL information can efficiently detect QTL and their dominance and epistatic effects, making it possible to simultaneously fine map main and epistatic QTL.
文摘Commercially grown sugarcane cultivars are advanced generation hybrids between two polyploid ancestor species, S. off icinarum L. (x=10, 2n=8x=80) and S. spontaneum (x= 8, 2n=5-16x=40-128). Modern cultivars