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Pan Z, Zhang J, Bai S, Li Z, Tong C. InDelGT: An integrated pipeline for extracting indel genotypes for genetic mapping in a hybrid population using next-generation sequencing data. APPLICATIONS IN PLANT SCIENCES 2022; 10:e11499. [PMID: 36518944 PMCID: PMC9742820 DOI: 10.1002/aps3.11499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 03/04/2022] [Accepted: 05/25/2022] [Indexed: 06/17/2023]
Abstract
PREMISE Although several software packages are available for genotyping insertion/deletion (indel) polymorphisms in genomes using next-generation sequencing data, simultaneously calling indel genotypes across many individuals for use in genetic mapping remains challenging. METHODS AND RESULTS We present an integrated pipeline, InDelGT, for the extraction of indel genotypes from a segregating population such as backcross or F2 lines, or from an F1 cross between outbred species. The InDelGT algorithm is implemented in three steps: generating an indel catalog, calling indel genotypes, and analyzing indel segregation. We demonstrated the use of the pipeline with an example data set from an F1 hybrid population of Populus and successfully constructed the two parental genetic linkage maps. CONCLUSIONS InDelGT is a practical tool that can quickly genotype a large number of indel markers within a population following Mendelian segregation. The InDelGT pipeline is freely available on GitHub (https://github.com/tongchf/InDelGT).
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Affiliation(s)
- Zhiliang Pan
- Co‐Innovation Center for Sustainable Forestry in Southern China, College of ForestryNanjing Forestry UniversityNanjing210037China
| | - Jinpeng Zhang
- Co‐Innovation Center for Sustainable Forestry in Southern China, College of ForestryNanjing Forestry UniversityNanjing210037China
| | - Shengjun Bai
- Co‐Innovation Center for Sustainable Forestry in Southern China, College of ForestryNanjing Forestry UniversityNanjing210037China
| | - Zhiting Li
- Co‐Innovation Center for Sustainable Forestry in Southern China, College of ForestryNanjing Forestry UniversityNanjing210037China
| | - Chunfa Tong
- Co‐Innovation Center for Sustainable Forestry in Southern China, College of ForestryNanjing Forestry UniversityNanjing210037China
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A Novel Strategy for Constructing an Integrated Linkage Map in an F1 Hybrid Population of Populus deltoides and Populus simonii. Genes (Basel) 2022; 13:genes13101731. [PMID: 36292616 PMCID: PMC9601732 DOI: 10.3390/genes13101731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 09/20/2022] [Accepted: 09/21/2022] [Indexed: 11/17/2022] Open
Abstract
The genetic linkage maps of the traditional F2 population in inbred lines were estimated from the frequency of recombination events in both parents, providing full genetic information for genetic and genomic studies. However, in outbred forest trees, it is almost impossible to generate the F2 population because of their high heterozygosity and long generation times. We proposed a novel strategy to construct an integrated genetic linkage map that contained both parental recombination information, with restriction-site-associated DNA sequencing (RADSeq) data in an F1 hybrid population of Populus deltoides and Populus simonii. We selected a large number of specific RAD tags to construct the linkage map, each of which contained two SNPs, one heterozygous only in the female parent and the other heterozygous only in the male. Consequently, the integrated map contained a total of 1154 RAD tags and 19 linkage groups, with a total length of 5255.49 cM and an average genetic distance of 4.63 cM. Meanwhile, the two parent-specific linkage maps were also constructed with SNPs that were heterozygous in one parent and homozygous in the other. We found that the integrated linkage map was more consensus with the genomic sequences of P. simonii and P. deltoides. Additionally, the likelihood of the marker order in each linkage group of the integrated map was greater than that in both parental maps. The integrated linkage map was more accurate than the parent-specific linkage maps constructed in the same F1 hybrid population, providing a powerful genetic resource for identifying the quantitative trait loci (QTLs) with dominant effects, assembling genomic sequences, and performing comparative genomics in related Populus species. More importantly, this novel strategy can be used in other outbred species to build an integrated linkage map.
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3
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Li Z, Zhao W, Zhang J, Pan Z, Bai S, Tong C. A Novel Strategy to Reveal the Landscape of Crossovers in an F1 Hybrid Population of Populus deltoides and Populus simonii. PLANTS 2022; 11:plants11081046. [PMID: 35448774 PMCID: PMC9025136 DOI: 10.3390/plants11081046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/03/2022] [Accepted: 04/07/2022] [Indexed: 11/16/2022]
Abstract
Although the crossover (CO) patterns of different species have been extensively investigated, little is known about the landscape of CO patterns in Populus because of its high heterozygosity and long-time generation. A novel strategy was proposed to reveal the difference of CO rate and interference between Populus deltoides and Populus simonii using their F1 hybrid population. We chose restriction site-associated DNA (RAD) tags that contained two SNPs, one only receiving the CO information from the female P. deltoides and the other from the male P. simonii. These RAD tags allowed us to investigate the CO patterns between the two outbred species, instead of using the traditional backcross populations in inbred lines. We found that the CO rate in P. deltoides was generally greater than that in P. simonii, and that the CO interference was a common phenomenon across the two genomes. The COs landscape of the different Populus species facilitates not only to understand the evolutionary mechanism for adaptability but also to rebuild the statistical model for precisely constructing genetic linkage maps that are critical in genome assembly in Populus. Additionally, the novel strategy could be applied in other outbred species for investigating the CO patterns.
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Affiliation(s)
| | | | | | | | | | - Chunfa Tong
- Correspondence: ; Tel.: +86-025-85428817 (ext. 815)
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4
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Yang W, Yao D, Wu H, Zhao W, Chen Y, Tong C. Multivariate genome-wide association study of leaf shape in a Populus deltoides and P. simonii F1 pedigree. PLoS One 2021; 16:e0259278. [PMID: 34710178 PMCID: PMC8553126 DOI: 10.1371/journal.pone.0259278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 10/16/2021] [Indexed: 11/19/2022] Open
Abstract
Leaf morphology exhibits tremendous diversity between and within species, and is likely related to adaptation to environmental factors. Most poplar species are of great economic and ecological values and their leaf morphology can be a good predictor for wood productivity and environment adaptation. It is important to understand the genetic mechanism behind variation in leaf shape. Although some initial efforts have been made to identify quantitative trait loci (QTLs) for poplar leaf traits, more effort needs to be expended to unravel the polygenic architecture of the complex traits of leaf shape. Here, we performed a genome-wide association analysis (GWAS) of poplar leaf shape traits in a randomized complete block design with clones from F1 hybrids of Populus deltoides and Populus simonii. A total of 35 SNPs were identified as significantly associated with the multiple traits of a moderate number of regular polar radii between the leaf centroid and its edge points, which could represent the leaf shape, based on a multivariate linear mixed model. In contrast, the univariate linear mixed model was applied as single leaf traits for GWAS, leading to genomic inflation; thus, no significant SNPs were detected for leaf length, measures of leaf width, leaf area, or the ratio of leaf length to leaf width under genomic control. Investigation of the candidate genes showed that most flanking regions of the significant leaf shape-associated SNPs harbored genes that were related to leaf growth and development and to the regulation of leaf morphology. The combined use of the traditional experimental design and the multivariate linear mixed model could greatly improve the power in GWAS because the multiple trait data from a large number of individuals with replicates of clones were incorporated into the statistical model. The results of this study will enhance the understanding of the genetic mechanism of leaf shape variation in Populus. In addition, a moderate number of regular leaf polar radii can largely represent the leaf shape and can be used for GWAS of such a complicated trait in Populus, instead of the higher-dimensional regular radius data that were previously considered to well represent leaf shape.
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Affiliation(s)
- Wenguo Yang
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, Nanjing, Jiangsu Province, China
- School of Artificial Intelligence and Information Technology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, China
| | - Dan Yao
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, Nanjing, Jiangsu Province, China
| | - Hainan Wu
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, Nanjing, Jiangsu Province, China
| | - Wei Zhao
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, Nanjing, Jiangsu Province, China
| | - Yuhua Chen
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, Nanjing, Jiangsu Province, China
| | - Chunfa Tong
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, Nanjing, Jiangsu Province, China
- * E-mail:
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Bai S, Wu H, Zhang J, Pan Z, Zhao W, Li Z, Tong C. Genome Assembly of Salicaceae Populus deltoides (Eastern Cottonwood) I-69 Based on Nanopore Sequencing and Hi-C Technologies. J Hered 2021; 112:303-310. [PMID: 33730157 PMCID: PMC8141683 DOI: 10.1093/jhered/esab010] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 03/16/2021] [Indexed: 12/30/2022] Open
Abstract
Populus deltoides has important ecological and economic values, widely used in poplar breeding programs due to its superior characteristics such as rapid growth and resistance to disease. Although the genome sequence of P. deltoides WV94 is available, the assembly is fragmented. Here, we reported an improved chromosome-level assembly of the P. deltoides cultivar I-69 by combining Nanopore sequencing and chromosome conformation capture (Hi-C) technologies. The assembly was 429.3 Mb in size and contained 657 contigs with a contig N50 length of 2.62 Mb. Hi-C scaffolding of the contigs generated 19 chromosome-level sequences, which covered 97.4% (418 Mb) of the total assembly size. Moreover, repetitive sequences annotation showed that 39.28% of the P. deltoides genome was composed of interspersed elements, including retroelements (23.66%), DNA transposons (6.83%), and unclassified elements (8.79%). We also identified a total of 44 362 protein-coding genes in the current P. deltoides assembly. Compared with the previous genome assembly of P. deltoides WV94, the current assembly had some significantly improved qualities: the contig N50 increased 3.5-fold and the proportion of gaps decreased from 3.2% to 0.08%. This high-quality, well-annotated genome assembly provides a reliable genomic resource for identifying genome variants among individuals, mining candidate genes that control growth and wood quality traits, and facilitating further application of genomics-assisted breeding in populations related to P. deltoides.
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Affiliation(s)
- Shengjun Bai
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Hainan Wu
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Jinpeng Zhang
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Zhiliang Pan
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Wei Zhao
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Zhiting Li
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Chunfa Tong
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
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6
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Chen Y, Wu H, Yang W, Zhao W, Tong C. Multivariate linear mixed model enhanced the power of identifying genome-wide association to poplar tree heights in a randomized complete block design. G3-GENES GENOMES GENETICS 2021; 11:6064171. [PMID: 33604666 PMCID: PMC8022933 DOI: 10.1093/g3journal/jkaa053] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 11/01/2020] [Indexed: 01/09/2023]
Abstract
With the advances in high-throughput sequencing technologies, it is not difficult to extract tens of thousands of single-nucleotide polymorphisms (SNPs) across many individuals in a fast and cheap way, making it possible to perform genome-wide association studies (GWAS) of quantitative traits in outbred forest trees. It is very valuable to apply traditional breeding experiments in GWAS for identifying genome variants associated with ecologically and economically important traits in Populus. Here, we reported a GWAS of tree height measured at multiple time points from a randomized complete block design (RCBD), which was established with clones from an F1 hybrid population of Populus deltoides and Populus simonii. A total of 22,670 SNPs across 172 clones in the RCBD were obtained with restriction site-associated DNA sequencing (RADseq) technology. The multivariate mixed linear model was applied by incorporating the pedigree relationship matrix of individuals to test the association of each SNP to the tree heights over 8 time points. Consequently, 41 SNPs were identified significantly associated with the tree height under the P-value threshold determined by Bonferroni correction at the significant level of 0.01. These SNPs were distributed on all but two chromosomes (Chr02 and Chr18) and explained the phenotypic variance ranged from 0.26% to 2.64%, amounting to 63.68% in total. Comparison with previous mapping studies for poplar height as well as the candidate genes of these detected SNPs were also investigated. We therefore showed that the application of multivariate linear mixed model to the longitudinal phenotypic data from the traditional breeding experimental design facilitated to identify far more genome-wide variants for tree height in poplar. The significant SNPs identified in this study would enhance understanding of molecular mechanism for growth traits and would accelerate marker-assisted breeding programs in Populus.
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Affiliation(s)
- Yuhua Chen
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China.,School of Animal Science and Technology, Jingling Institute of Technology, Nanjing 210038, China
| | - Hainan Wu
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Wenguo Yang
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Wei Zhao
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Chunfa Tong
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
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7
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Tong C, Yao D, Wu H, Chen Y, Yang W, Zhao W. High-Quality SNP Linkage Maps Improved QTL Mapping and Genome Assembly in Populus. J Hered 2020; 111:515-530. [PMID: 32930789 PMCID: PMC7751148 DOI: 10.1093/jhered/esaa039] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 09/11/2020] [Indexed: 12/15/2022] Open
Abstract
With the advances in high-throughput sequencing technologies and the development of new software for extracting single nucleotide polymorphisms (SNPs) across a mapping population, it is possible to construct high-quality genetic maps with thousands of SNPs in outbred forest trees. Two parent-specific linkage maps were constructed with restriction site-associated DNA sequencing data from an F1 hybrid population derived from Populus deltoides and Populus simonii, and applied in QTL mapping and genome assembly. The female P. deltoides map contained 4018 SNPs, which were divided into 19 linkage groups under a wide range of LOD thresholds from 7 to 55. The male P. simonii map showed similar characteristics, consisting of 2097 SNPs, which also belonged to 19 linkage groups under LOD thresholds of 7 to 29. The SNP order of each linkage group was optimal among different ordering results from several available software. Moreover, the linkage maps allowed the detection of 39 QTLs underlying tree height and 47 for diameter at breast height. In addition, the linkage maps improved the anchoring of 689 contigs of P. simonii to chromosomes. The 2 parental genetic maps of Populus are of high quality, especially in terms of SNP data quality, the SNP order within linkage groups, and the perfect match between the number of linkage groups and the karyotype of Populus, as well as the excellent performances in QTL mapping and genome assembly. Both approaches for extracting and ordering SNPs could be applied to other species for constructing high-quality genetic maps.
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Affiliation(s)
- Chunfa Tong
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Dan Yao
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Hainan Wu
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Yuhua Chen
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Wenguo Yang
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Wei Zhao
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China
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Huang K, Rieseberg LH. Frequency, Origins, and Evolutionary Role of Chromosomal Inversions in Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:296. [PMID: 32256515 DOI: 10.3389/fpls.2020.00296/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 02/27/2020] [Indexed: 05/24/2023]
Abstract
Chromosomal inversions have the potential to play an important role in evolution by reducing recombination between favorable combinations of alleles. Until recently, however, most evidence for their likely importance derived from dipteran flies, whose giant larval salivary chromosomes aided early cytogenetic studies. The widespread application of new genomic technologies has revealed that inversions are ubiquitous across much of the plant and animal kingdoms. Here we review the rapidly accumulating literature on inversions in the plant kingdom and discuss what we have learned about their establishment and likely evolutionary role. We show that inversions are prevalent across a wide range of plant groups. We find that inversions are often associated with locally favored traits, as well as with traits that contribute to assortative mating, suggesting that they may be key to adaptation and speciation in the face of gene flow. We also discuss the role of inversions in sex chromosome formation, and explore possible parallels with inversion establishment on autosomes. The identification of inversion origins, as well as the causal variants within them, will advance our understanding of chromosomal evolution in plants.
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Affiliation(s)
- Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
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Huang K, Rieseberg LH. Frequency, Origins, and Evolutionary Role of Chromosomal Inversions in Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:296. [PMID: 32256515 PMCID: PMC7093584 DOI: 10.3389/fpls.2020.00296] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 02/27/2020] [Indexed: 05/11/2023]
Abstract
Chromosomal inversions have the potential to play an important role in evolution by reducing recombination between favorable combinations of alleles. Until recently, however, most evidence for their likely importance derived from dipteran flies, whose giant larval salivary chromosomes aided early cytogenetic studies. The widespread application of new genomic technologies has revealed that inversions are ubiquitous across much of the plant and animal kingdoms. Here we review the rapidly accumulating literature on inversions in the plant kingdom and discuss what we have learned about their establishment and likely evolutionary role. We show that inversions are prevalent across a wide range of plant groups. We find that inversions are often associated with locally favored traits, as well as with traits that contribute to assortative mating, suggesting that they may be key to adaptation and speciation in the face of gene flow. We also discuss the role of inversions in sex chromosome formation, and explore possible parallels with inversion establishment on autosomes. The identification of inversion origins, as well as the causal variants within them, will advance our understanding of chromosomal evolution in plants.
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Affiliation(s)
- Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Loren H. Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
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10
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Update of Genetic Linkage Map and QTL Analysis for Growth Traits in Eucommia ulmoides Oliver. FORESTS 2020. [DOI: 10.3390/f11030311] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Eucommia ulmoides (Tu-chung) is an economically and ecologically important tree species which has attracted worldwide attention due to its application in pharmacology, landscaping, wind sheltering and sand fixation. Molecular marker technologies can elucidate the genetic mechanism and substantially improve the breeding efficiency of E. ulmoides. The current research updated the original linkage map, and quantitative trait loci (QTL) analysis was performed on tree growth traits measured over 10 consecutive years in an E. ulmoides F1 population (“Xiaoye” × “Qinzhong No.1”). In total, 452 polymorphic markers were scored from 365 simple sequence repeat (SSR) primers, with an average of 1.24 polymorphic markers per primer combination. The integrated map was 1913.29 cM (centimorgan) long, covering 94.10% of the estimated genome and with an average marker density of 2.20 cM. A total of 869 markers were mapped into 19 major independent linkage groups. Growth-related traits measured over 10 consecutive years showed a significant correlation, and 89 hypothetical QTLs were forecasted and divided into 27 distinct loci. Three traits for tree height, ground diameter and crown diameter detected 25 QTLs (13 loci), 32 QTLs (17 loci) and 15 QTLs (10 loci), respectively. Based on BLASTX search results in the NCBI database, six candidate genes were obtained. It is important to explore the growth-related genetic mechanism and lay the foundation for the genetic improvement of E. ulmoides at the molecular level.
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11
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Wu H, Yao D, Chen Y, Yang W, Zhao W, Gao H, Tong C. De Novo Genome Assembly of Populus simonii Further Supports That Populus simonii and Populus trichocarpa Belong to Different Sections. G3 (BETHESDA, MD.) 2020; 10:455-466. [PMID: 31806765 PMCID: PMC7003099 DOI: 10.1534/g3.119.400913] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 12/03/2019] [Indexed: 11/18/2022]
Abstract
Populus simonii is an important tree in the genus Populus, widely distributed in the Northern Hemisphere and having a long cultivation history. Although this species has ecologically and economically important values, its genome sequence is currently not available, hindering the development of new varieties with wider adaptive and commercial traits. Here, we report a chromosome-level genome assembly of P. simonii using PacBio long-read sequencing data aided by Illumina paired-end reads and related genetic linkage maps. The assembly is 441.38 Mb in length and contain 686 contigs with a contig N50 of 1.94 Mb. With the linkage maps, 336 contigs were successfully anchored into 19 pseudochromosomes, accounting for 90.2% of the assembled genome size. Genomic integrity assessment showed that 1,347 (97.9%) of the 1,375 genes conserved among all embryophytes can be found in the P. simonii assembly. Genomic repeat analysis revealed that 41.47% of the P. simonii genome is composed of repetitive elements, of which 40.17% contained interspersed repeats. A total of 45,459 genes were predicted from the P. simonii genome sequence and 39,833 (87.6%) of the genes were annotated with one or more related functions. Phylogenetic analysis indicated that P. simonii and Populus trichocarpa should be placed in different sections, contrary to the previous classification according to morphology. The genome assembly not only provides an important genetic resource for the comparative and functional genomics of different Populus species, but also furnishes one of the closest reference sequences for identifying genomic variants in an F1 hybrid population derived by crossing P. simonii with other Populus species.
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Affiliation(s)
- Hainan Wu
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Dan Yao
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Yuhua Chen
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Wenguo Yang
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Wei Zhao
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Hua Gao
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
| | - Chunfa Tong
- Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
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12
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Inferring the Genomic Landscape of Recombination Rate Variation in European Aspen ( Populus tremula). G3-GENES GENOMES GENETICS 2020; 10:299-309. [PMID: 31744900 PMCID: PMC6945010 DOI: 10.1534/g3.119.400504] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The rate of meiotic recombination is one of the central factors determining genome-wide levels of linkage disequilibrium which has important consequences for the efficiency of natural selection and for the dissection of quantitative traits. Here we present a new, high-resolution linkage map for Populus tremula that we use to anchor approximately two thirds of the P. tremula draft genome assembly on to the expected 19 chromosomes, providing us with the first chromosome-scale assembly for P. tremula (Table 2). We then use this resource to estimate variation in recombination rates across the P. tremula genome and compare these results to recombination rates based on linkage disequilibrium in a large number of unrelated individuals. We also assess how variation in recombination rates is associated with a number of genomic features, such as gene density, repeat density and methylation levels. We find that recombination rates obtained from the two methods largely agree, although the LD-based method identifies a number of genomic regions with very high recombination rates that the map-based method fails to detect. Linkage map and LD-based estimates of recombination rates are positively correlated and show similar correlations with other genomic features, showing that both methods can accurately infer recombination rate variation across the genome. Recombination rates are positively correlated with gene density and negatively correlated with repeat density and methylation levels, suggesting that recombination is largely directed toward gene regions in P. tremula.
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13
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Yao D, Wu H, Chen Y, Yang W, Gao H, Tong C. gmRAD: an integrated SNP calling pipeline for genetic mapping with RADseq across a hybrid population. Brief Bioinform 2018; 21:329-337. [PMID: 30445432 DOI: 10.1093/bib/bby114] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/21/2018] [Accepted: 10/23/2018] [Indexed: 11/14/2022] Open
Abstract
Restriction site-associated DNA sequencing (RADseq) is a powerful technology that has been extensively applied in population genetics, phylogenetics and genetic mapping. Although many software packages are available for ecological and evolutionary studies, a few effective tools are available for extracting genotype data with RADseq for genetic mapping, a prerequisite for quantitative trait locus mapping, comparative genomics and genome scaffold assembly. Here, we present an integrated pipeline called gmRAD for generating single nucleotide polymorphism (SNP) genotypes from RADseq data, de novo, across a genetic mapping population derived by crossing two parents. As an analytical strategy, the software takes five steps to implement the whole algorithms, including clustering the first (forward) reads of each parent, building two parental references, generating parental SNP catalogs, calling SNP genotypes across all individuals and filtering the genotype data for genetic linkage mapping. All the steps can be completed with a simple command line, but they can be also performed optionally if prerequisite files are available. To validate its application, we also performed a real data analysis with RADseq data from an F1 hybrid population derived by crossing Populus deltoides and Populus simonii. The software gmRAD is freely available at https://github.com/tongchf/gmRAD.
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Affiliation(s)
- Dan Yao
- Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Hainan Wu
- Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Yuhua Chen
- Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Wenguo Yang
- Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Hua Gao
- Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, China
| | - Chunfa Tong
- Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, China
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Tao S, Wu J, Yao D, Chen Y, Yang W, Tong C. Identification of recombination events in outbred species with next-generation sequencing data. BMC Genomics 2018; 19:398. [PMID: 29801431 PMCID: PMC5970487 DOI: 10.1186/s12864-018-4791-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 05/14/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Meiotic recombination events include crossovers and non-crossovers or gene conversions. Although the rate of crossovers is often used for genetic mapping, the gene conversion events are not well studied especially in outbred species, which could produce distorted markers and thus affect the precision of genetic maps. RESULTS We proposed a strategy for identifying gene conversion events in Populus with the next-generation sequencing (NGS) data from the two parents and their progeny in an F1 hybrid population. The strategy first involved phasing the heterozygous SNPs of the parents to obtain the parental haplotype blocks by NGS analytical tools, permitting to identify the parental gene conversion events with progeny genotypes. By incorporating available genetic linkage maps, longer haplotype blocks each corresponding to a chromosome can be created, not only allowing to detect crossover events but also possibly to locate a crossover in a small region. Our analysis revealed that gene conversions are more abundant than crossovers in Populus, with a higher probability to generate distorted markers in the regions involved than in the other regions on genome. The analytical procedures were implemented with Perl scripts as a freely available package, findGCO at https://github.com/tongchf/findGCO . CONCLUSIONS The novel strategy and the new developed Perl package permit to identify gene conversion events with the next-generation sequencing technology in a hybrid population of outbred species. The new method revealed that in a genetic mapping population some distorted genetic markers are possibly due to the gene conversion events.
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Affiliation(s)
- Shentong Tao
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, No.159, Longpan Road, Xuanwu Qu, Nanjing, 210037, China
| | - Jiyan Wu
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, No.159, Longpan Road, Xuanwu Qu, Nanjing, 210037, China
| | - Dan Yao
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, No.159, Longpan Road, Xuanwu Qu, Nanjing, 210037, China
| | - Yuhua Chen
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, No.159, Longpan Road, Xuanwu Qu, Nanjing, 210037, China
| | - Wenguo Yang
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, No.159, Longpan Road, Xuanwu Qu, Nanjing, 210037, China
| | - Chunfa Tong
- Co-Innovation Center for Sustainable Forestry in South China, College of Forestry, Nanjing Forestry University, No.159, Longpan Road, Xuanwu Qu, Nanjing, 210037, China.
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15
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Haenel Q, Laurentino TG, Roesti M, Berner D. Meta-analysis of chromosome-scale crossover rate variation in eukaryotes and its significance to evolutionary genomics. Mol Ecol 2018; 27:2477-2497. [PMID: 29676042 DOI: 10.1111/mec.14699] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 03/23/2018] [Accepted: 03/26/2018] [Indexed: 01/02/2023]
Abstract
Understanding the distribution of crossovers along chromosomes is crucial to evolutionary genomics because the crossover rate determines how strongly a genome region is influenced by natural selection on linked sites. Nevertheless, generalities in the chromosome-scale distribution of crossovers have not been investigated formally. We fill this gap by synthesizing joint information on genetic and physical maps across 62 animal, plant and fungal species. Our quantitative analysis reveals a strong and taxonomically widespread reduction of the crossover rate in the centre of chromosomes relative to their peripheries. We demonstrate that this pattern is poorly explained by the position of the centromere, but find that the magnitude of the relative reduction in the crossover rate in chromosome centres increases with chromosome length. That is, long chromosomes often display a dramatically low crossover rate in their centre, whereas short chromosomes exhibit a relatively homogeneous crossover rate. This observation is compatible with a model in which crossover is initiated from the chromosome tips, an idea with preliminary support from mechanistic investigations of meiotic recombination. Consequently, we show that organisms achieve a higher genome-wide crossover rate by evolving smaller chromosomes. Summarizing theory and providing empirical examples, we finally highlight that taxonomically widespread and systematic heterogeneity in crossover rate along chromosomes generates predictable broad-scale trends in genetic diversity and population differentiation by modifying the impact of natural selection among regions within a genome. We conclude by emphasizing that chromosome-scale heterogeneity in crossover rate should urgently be incorporated into analytical tools in evolutionary genomics, and in the interpretation of resulting patterns.
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Affiliation(s)
- Quiterie Haenel
- Zoological Institute, University of Basel, Basel, Switzerland
| | | | - Marius Roesti
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Daniel Berner
- Zoological Institute, University of Basel, Basel, Switzerland
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Liu F, Tong C, Tao S, Wu J, Chen Y, Yao D, Li H, Shi J. MVQTLCIM: composite interval mapping of multivariate traits in a hybrid F 1 population of outbred species. BMC Bioinformatics 2017; 18:515. [PMID: 29169342 PMCID: PMC5701343 DOI: 10.1186/s12859-017-1908-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 11/01/2017] [Indexed: 01/02/2023] Open
Abstract
Background With the plummeting cost of the next-generation sequencing technologies, high-density genetic linkage maps could be constructed in a forest hybrid F1 population. However, based on such genetic maps, quantitative trait loci (QTL) mapping cannot be directly conducted with traditional statistical methods or tools because the linkage phase and segregation pattern of molecular markers are not always fixed as in inbred lines. Results We implemented the traditional composite interval mapping (CIM) method to multivariate trait data in forest trees and developed the corresponding software, mvqtlcim. Our method not only incorporated the various segregations and linkage phases of molecular markers, but also applied Takeuchi’s information criterion (TIC) to discriminate the QTL segregation type among several possible alternatives. QTL mapping was performed in a hybrid F1 population of Populus deltoides and P. simonii, and 12 QTLs were detected for tree height over 6 time points. The software package allowed many options for parameters as well as parallel computing for permutation tests. The features of the software were demonstrated with the real data analysis and a large number of Monte Carlo simulations. Conclusions We provided a powerful tool for QTL mapping of multiple or longitudinal traits in an outbred F1 population, in which the traditional software for QTL mapping cannot be used. This tool will facilitate studying of QTL mapping and thus will accelerate molecular breeding programs especially in forest trees. The tool package is freely available from https://github.com/tongchf /mvqtlcim. Electronic supplementary material The online version of this article (10.1186/s12859-017-1908-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Fenxiang Liu
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China.,College of Department of Computer Science and Engineering, Sanjiang University, Nanjing, 210012, China
| | - Chunfa Tong
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China.
| | - Shentong Tao
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Jiyan Wu
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Yuhua Chen
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Dan Yao
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Huogen Li
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Jisen Shi
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
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Zhigunov AV, Ulianich PS, Lebedeva MV, Chang PL, Nuzhdin SV, Potokina EK. Development of F1 hybrid population and the high-density linkage map for European aspen (Populus tremula L.) using RADseq technology. BMC PLANT BIOLOGY 2017; 17:180. [PMID: 29143610 PMCID: PMC5688504 DOI: 10.1186/s12870-017-1127-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
BACKGROUND Restriction-site associated DNA sequencing (RADseq) technology was recently employed to identify a large number of single nucleotide polymorphisms (SNP) for linkage mapping of a North American and Eastern Asian Populus species. However, there is also the need for high-density genetic linkage maps for the European aspen (P. tremula) as a tool for further mapping of quantitative trait loci (QTLs) and marker-assisted selection of the Populus species native to Europe. RESULTS We established a hybrid F1 population from the cross of two aspen parental genotypes diverged in their phenological and morphological traits. We performed RADseq of 122 F1 progenies and two parents yielding 15,732 high-quality SNPs that were successfully identified using the reference genome of P. trichocarpa. 2055 SNPs were employed for the construction of maternal and paternal linkage maps. The maternal linkage map was assembled with 1000 SNPs, containing 19 linkage groups and spanning 3054.9 cM of the genome, with an average distance of 3.05 cM between adjacent markers. The paternal map consisted of 1055 SNPs and the same number of linkage groups with a total length of 3090.56 cM and average interval distance of 2.93 cM. The linkage maps were employed for QTL mapping of one-year-old seedlings height variation. The most significant QTL (LOD = 5.73) was localized to LG5 (96.94 cM) of the male linkage map, explaining 18% of the phenotypic variation. CONCLUSIONS The set of 15,732 SNPs polymorphic in aspen and high-density genetic linkage maps constructed for the P. tremula intra-specific cross will provide a valuable source for QTL mapping and identification of candidate genes facilitating marker-assisted selection in European aspen.
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Affiliation(s)
- Anatoly V Zhigunov
- Saint Petersburg State Forest Technical University, Institutskiy per, 5, 194021, St. Petersburg, Russia
| | - Pavel S Ulianich
- Saint Petersburg State Forest Technical University, Institutskiy per, 5, 194021, St. Petersburg, Russia
- Vavilov Institute of Plant Genetic Resources (VIR), Bolshaya Morskaya, 42-44, 190000, St. Petersburg, Russia
| | - Marina V Lebedeva
- Saint Petersburg State Forest Technical University, Institutskiy per, 5, 194021, St. Petersburg, Russia
- Vavilov Institute of Plant Genetic Resources (VIR), Bolshaya Morskaya, 42-44, 190000, St. Petersburg, Russia
| | - Peter L Chang
- University of Southern California, Los Angeles, CA, 90089, USA
| | | | - Elena K Potokina
- Saint Petersburg State Forest Technical University, Institutskiy per, 5, 194021, St. Petersburg, Russia.
- Vavilov Institute of Plant Genetic Resources (VIR), Bolshaya Morskaya, 42-44, 190000, St. Petersburg, Russia.
- Saint Petersburg State University, Universitetskaya emb. 7/9, St. Petersburg, 199034, Russia.
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Konar A, Choudhury O, Bullis R, Fiedler L, Kruser JM, Stephens MT, Gailing O, Schlarbaum S, Coggeshall MV, Staton ME, Carlson JE, Emrich S, Romero-Severson J. High-quality genetic mapping with ddRADseq in the non-model tree Quercus rubra. BMC Genomics 2017; 18:417. [PMID: 28558688 PMCID: PMC5450186 DOI: 10.1186/s12864-017-3765-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 05/04/2017] [Indexed: 11/10/2022] Open
Abstract
Background Restriction site associated DNA sequencing (RADseq) has the potential to be a broadly applicable, low-cost approach for high-quality genetic linkage mapping in forest trees lacking a reference genome. The statistical inference of linear order must be as accurate as possible for the correct ordering of sequence scaffolds and contigs to chromosomal locations. Accurate maps also facilitate the discovery of chromosome segments containing allelic variants conferring resistance to the biotic and abiotic stresses that threaten forest trees worldwide. We used ddRADseq for genetic mapping in the tree Quercus rubra, with an approach optimized to produce a high-quality map. Our study design also enabled us to model the results we would have obtained with less depth of coverage. Results Our sequencing design produced a high sequencing depth in the parents (248×) and a moderate sequencing depth (15×) in the progeny. The digital normalization method of generating a de novo reference and the SAMtools SNP variant caller yielded the most SNP calls (78,725). The major drivers of map inflation were multiple SNPs located within the same sequence (77% of SNPs called). The highest quality map was generated with a low level of missing data (5%) and a genome-wide threshold of 0.025 for deviation from Mendelian expectation. The final map included 849 SNP markers (1.8% of the 78,725 SNPs called). Downsampling the individual FASTQ files to model lower depth of coverage revealed that sequencing the progeny using 96 samples per lane would have yielded too few SNP markers to generate a map, even if we had sequenced the parents at depth 248×. Conclusions The ddRADseq technology produced enough high-quality SNP markers to make a moderately dense, high-quality map. The success of this project was due to high depth of coverage of the parents, moderate depth of coverage of the progeny, a good framework map, an optimized bioinformatics pipeline, and rigorous premapping filters. The ddRADseq approach is useful for the construction of high-quality genetic maps in organisms lacking a reference genome if the parents and progeny are sequenced at sufficient depth. Technical improvements in reduced representation sequencing (RRS) approaches are needed to reduce the amount of missing data. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3765-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Arpita Konar
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Olivia Choudhury
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Rebecca Bullis
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Lauren Fiedler
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | | | - Melissa T Stephens
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Oliver Gailing
- School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI, 49931, USA
| | - Scott Schlarbaum
- Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, 37996, USA
| | - Mark V Coggeshall
- School of Natural Resources, University of Missouri-Columbia, Columbia, MO, 65211, USA.,Hardwood Tree Improvement and Regeneration Center, USDA Forest Service Northern Research Station, West Lafayette, IN, 47907, USA
| | - Margaret E Staton
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN, 37996, USA
| | - John E Carlson
- Department of Ecosystem Science and Management, Penn State, University Park, State College, PA, 16802, USA
| | - Scott Emrich
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Jeanne Romero-Severson
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.
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Mousavi M, Tong C, Liu F, Tao S, Wu J, Li H, Shi J. De novo SNP discovery and genetic linkage mapping in poplar using restriction site associated DNA and whole-genome sequencing technologies. BMC Genomics 2016; 17:656. [PMID: 27538483 PMCID: PMC4991039 DOI: 10.1186/s12864-016-3003-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 08/09/2016] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Restriction site associated DNA sequencing (RAD-seq), a next-generation sequencing technology, has greatly facilitated genetic linkage mapping studies in outbred species. RAD-seq is capable of discovering thousands of genetic markers for linkage mapping across many individuals, and can be applied in species with or without a reference genome. Although several analytical tools are available for RAD-seq data, alternative strategies are necessary for improving the marker quality and hence the genetic mapping accuracy. RESULTS We demonstrate a strategy for constructing dense genetic linkage maps in hybrid forest trees by combining RAD-seq and whole-genome sequencing technologies. We performed RAD-seq of 150 progeny and whole-genome sequencing of the two parents in an F1 hybrid population of Populus deltoides × P. simonii. Two rough references were assembled from the whole-genome sequencing reads of the two parents separately. Based on the parental reference sequences, 3442 high-quality single nucleotide polymorphisms (SNPs) were identified that segregate in the ratio of 1:1. The maternal linkage map of P. deltoides was constructed with 2012 SNPs, containing 19 linkage groups and spanning 4067.16 cM of the genome with an average distance of 2.04 cM between adjacent markers, while the male map of P. simonii consisted of 1430 SNPs and the same number of linkage groups with a total length of 4356.04 cM and an average interval distance of 3.09 cM. Collinearity between the parental linkage maps and the reference genome of P. trichocarpa was also investigated. Compared with the result on the basis of the existing reference genome, our strategy identified more high-quality SNPs and generated parental linkage groups that nicely match the karyotype of Populus. CONCLUSIONS The strategy of simultaneously using RAD and whole-genome sequencing technologies can be applied to constructing high-density genetic maps in forest trees regardless of whether a reference genome exists. The two parental linkage maps constructed here provide more accurate genetic resources for unraveling quantitative trait loci and accelerating molecular breeding programs, as well as for comparative genomics in Populus.
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Affiliation(s)
- Mohaddeseh Mousavi
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037 China
| | - Chunfa Tong
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037 China
| | - Fenxiang Liu
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037 China
| | - Shentong Tao
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037 China
| | - Jiyan Wu
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037 China
| | - Huogen Li
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037 China
| | - Jisen Shi
- The Southern Modern Forestry Collaborative Innovation Center, College of Forestry, Nanjing Forestry University, Nanjing, 210037 China
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