This document discusses applying genomic selection to a rice breeding program using a synthetic population and recurrent selection. Key points:
- Genomic selection was tested on 343 rice families from a synthetic population with 10 cycles of recombination to estimate its feasibility. Various regression models were evaluated.
- Accuracy of genomic selection was found to depend on trait architecture, heritability, and marker selection. Flowering date saw improved accuracy when markers were selected based on linkage disequilibrium.
- The results indicate genomic selection is feasible for this rice breeding program, though further data across sites and years is still needed to develop stronger prediction models. Genomic selection could help increase selection intensity and reduce time in the recurrent selection scheme.
Association genetics‟ or ‟association studies,” or ‟linkage disequilibrium mapping”.
Tool to resolve complex trait variation down to the sequence level by exploiting historical and evolutionary recombination events at the population level.
Natural population surveyed to determine MTA using LD.
Introduction:
Proposed by Meuwissen et al. (2001)
GS is a specialized form of MAS, in which information from genotype data on marker alleles covering the entire genome forms the basis of selection.
The effects associated with all the marker loci, irrespective of whether the effects are significant or not, covering the entire genome are estimated.
The marker effect estimates are used to calculate the genomic estimated breeding values (GEBVs) of different individuals/lines, which form the basis of selection.
Why to go for genomic selection:
Marker-assisted selection (MAS) is well-suited for handling oligogenes and quantitative trait loci (QTLs) with large effects but not for minor QTLs.
MARS attempts to take into account small effect QTLs by combining trait phenotype data with marker genotype data into a combined selection index.
Based on markers showing significant association with the trait(s) and for this reason has been criticized as inefficient
The genomic selection (GS) scheme was to rectify the deficiency of MAS and MARS schemes. The GS scheme utilizes information from genome-wide marker data whether or not their associations with the concerned trait(s) are significant.
GEBV: GenomicEstimated Breeding Values-
The sum total of effects associated with all the marker alleles present in the individual and included in the GS model applied to the population under selection
Calculated on a single individual basis
Gene-assisted genomic selection:
A GS model that uses information about prior known QTLs, the targeted QTLs were accumulated in much higher frequencies than when the standard ridge regression was used
The sum total of effects associated with all the marker alleles present in the individual and included in the GS model applied to the population under selection
Calculated on a single individual basis
Population used:
Training population: used for training of the GS model and for obtaining estimates of the marker-associated effects needed for estimation of GEBVs of individuals/lines in the breeding population.
Breeding population: the population subjected to GS for achieving the desired improvement and isolation of superior lines for use as new varieties/parents of new improved hybrids.
Training population-
large enough: must be representative of the breeding population: max. trait variance with marker : by cluster analysis
should have either equal or comparable LD, LD decay rates with breeding populations
Updated by including individuals/lines from the breeding population
Training more than one generation
Low colinearity between markers is needed since high colinearity tends to reduce prediction accuracy of certain GS models. (colinearity disturbed by recombination)
Association genetics‟ or ‟association studies,” or ‟linkage disequilibrium mapping”.
Tool to resolve complex trait variation down to the sequence level by exploiting historical and evolutionary recombination events at the population level.
Natural population surveyed to determine MTA using LD.
Introduction:
Proposed by Meuwissen et al. (2001)
GS is a specialized form of MAS, in which information from genotype data on marker alleles covering the entire genome forms the basis of selection.
The effects associated with all the marker loci, irrespective of whether the effects are significant or not, covering the entire genome are estimated.
The marker effect estimates are used to calculate the genomic estimated breeding values (GEBVs) of different individuals/lines, which form the basis of selection.
Why to go for genomic selection:
Marker-assisted selection (MAS) is well-suited for handling oligogenes and quantitative trait loci (QTLs) with large effects but not for minor QTLs.
MARS attempts to take into account small effect QTLs by combining trait phenotype data with marker genotype data into a combined selection index.
Based on markers showing significant association with the trait(s) and for this reason has been criticized as inefficient
The genomic selection (GS) scheme was to rectify the deficiency of MAS and MARS schemes. The GS scheme utilizes information from genome-wide marker data whether or not their associations with the concerned trait(s) are significant.
GEBV: GenomicEstimated Breeding Values-
The sum total of effects associated with all the marker alleles present in the individual and included in the GS model applied to the population under selection
Calculated on a single individual basis
Gene-assisted genomic selection:
A GS model that uses information about prior known QTLs, the targeted QTLs were accumulated in much higher frequencies than when the standard ridge regression was used
The sum total of effects associated with all the marker alleles present in the individual and included in the GS model applied to the population under selection
Calculated on a single individual basis
Population used:
Training population: used for training of the GS model and for obtaining estimates of the marker-associated effects needed for estimation of GEBVs of individuals/lines in the breeding population.
Breeding population: the population subjected to GS for achieving the desired improvement and isolation of superior lines for use as new varieties/parents of new improved hybrids.
Training population-
large enough: must be representative of the breeding population: max. trait variance with marker : by cluster analysis
should have either equal or comparable LD, LD decay rates with breeding populations
Updated by including individuals/lines from the breeding population
Training more than one generation
Low colinearity between markers is needed since high colinearity tends to reduce prediction accuracy of certain GS models. (colinearity disturbed by recombination)
Presentation delivered by Dr. Jesse Poland (Kansas State University, USA) at Borlaug Summit on Wheat for Food Security. March 25 - 28, 2014, Ciudad Obregon, Mexico.
http://www.borlaug100.org
Association mapping, also known as "linkage disequilibrium mapping", is a method of mapping quantitative trait loci (QTLs) that takes advantage of linkage disequilibrium to link phenotypes to genotypes.Varioius strategey involved in association mapping is discussed in this presentation
Advanced biometrical and quantitative genetics akshayAkshay Deshmukh
Additive and Multiplicative Model
Shifted Multiplicative Model
Analysis and Selection of Genotype
Methods and steps to select the best model
Bioplot and mapping genotype
Heterotic group “is a group of related or unrelated genotypes from the same or different populations, which display similar combining ability and heterotic response when crossed with genotypes from other genetically distinct germplasm groups.”
QTL is a gene or the chromosomal region that affects a quantitative trait, which should be polymorphic (have allelic variation) to have an effect in a population, must be linked to a polymorphic marker allele to be detected. The QTL mapping consists of 4 steps, like the development of mapping population, generation of polymorphic marker data set among the parents, construction of linkage map, and finally the QTL analysis
All the above steps are described in these slides very briefly along with two case studies.
Association mapping approaches for tagging quality traits in maizeSenthil Natesan
Association mapping has been widely used to study the genetic basis of complex traits in human and animal systems and is a very efficient and effective method for confirming candidate genes or for identifying new genes (Altshuler et al., 2008). Association mapping is now being increasingly used in a wide range of plants (Rafalski, 2010), where it appears to be more powerful than in humans or animals (Zhu et al., 2008). Unlike linkage mapping, association mapping can explore all the recombination events and mutations in a given population and with a higher resolution (Yu and Buckler, 2006). However, association mapping has a lower power to detect rare alleles in a population, even those with large effects, than linkage mapping (Hill et al., 2008). Yan et al., (2010) demonstrated that the gene encoding β-carotene hydroxylase 1 (crtRB1) underlies a principal quantitative trait locus associated with β-carotene concentration and conversion in maize kernels has been identified through candidate gene strategy of association mapping.
Power Point is deals with the different aspects of Quantitative genetics in plant breeding it converse Basic Principles of Biometrical Genetics, estimation of Variability, Correlation, Principal Component Analysis, Path analysis, Different Matting design and Stability so on
Research Program Genetic Gains (RPGG) Review Meeting 2021: From Discovery to ...ICRISAT
A number of advances in genetics and genomics research of pigeonpea. These advances have enhanced our understanding of structural and functional aspects of genome and also provided us opportunities to deal with constraints impeding production of pigeonpea in precise and faster manner. Availability of the draft genome sequence and large-scale molecular markers has made it possible to map traits of interest in speedy manner. Although germplasm re-sequencing has already been started in pigeonpea, large-scale germplasm including elite breeding line, landraces and wild species is expected to be fully sequenced very soon.
Presentation delivered by Dr. Jesse Poland (Kansas State University, USA) at Borlaug Summit on Wheat for Food Security. March 25 - 28, 2014, Ciudad Obregon, Mexico.
http://www.borlaug100.org
Association mapping, also known as "linkage disequilibrium mapping", is a method of mapping quantitative trait loci (QTLs) that takes advantage of linkage disequilibrium to link phenotypes to genotypes.Varioius strategey involved in association mapping is discussed in this presentation
Advanced biometrical and quantitative genetics akshayAkshay Deshmukh
Additive and Multiplicative Model
Shifted Multiplicative Model
Analysis and Selection of Genotype
Methods and steps to select the best model
Bioplot and mapping genotype
Heterotic group “is a group of related or unrelated genotypes from the same or different populations, which display similar combining ability and heterotic response when crossed with genotypes from other genetically distinct germplasm groups.”
QTL is a gene or the chromosomal region that affects a quantitative trait, which should be polymorphic (have allelic variation) to have an effect in a population, must be linked to a polymorphic marker allele to be detected. The QTL mapping consists of 4 steps, like the development of mapping population, generation of polymorphic marker data set among the parents, construction of linkage map, and finally the QTL analysis
All the above steps are described in these slides very briefly along with two case studies.
Association mapping approaches for tagging quality traits in maizeSenthil Natesan
Association mapping has been widely used to study the genetic basis of complex traits in human and animal systems and is a very efficient and effective method for confirming candidate genes or for identifying new genes (Altshuler et al., 2008). Association mapping is now being increasingly used in a wide range of plants (Rafalski, 2010), where it appears to be more powerful than in humans or animals (Zhu et al., 2008). Unlike linkage mapping, association mapping can explore all the recombination events and mutations in a given population and with a higher resolution (Yu and Buckler, 2006). However, association mapping has a lower power to detect rare alleles in a population, even those with large effects, than linkage mapping (Hill et al., 2008). Yan et al., (2010) demonstrated that the gene encoding β-carotene hydroxylase 1 (crtRB1) underlies a principal quantitative trait locus associated with β-carotene concentration and conversion in maize kernels has been identified through candidate gene strategy of association mapping.
Power Point is deals with the different aspects of Quantitative genetics in plant breeding it converse Basic Principles of Biometrical Genetics, estimation of Variability, Correlation, Principal Component Analysis, Path analysis, Different Matting design and Stability so on
Research Program Genetic Gains (RPGG) Review Meeting 2021: From Discovery to ...ICRISAT
A number of advances in genetics and genomics research of pigeonpea. These advances have enhanced our understanding of structural and functional aspects of genome and also provided us opportunities to deal with constraints impeding production of pigeonpea in precise and faster manner. Availability of the draft genome sequence and large-scale molecular markers has made it possible to map traits of interest in speedy manner. Although germplasm re-sequencing has already been started in pigeonpea, large-scale germplasm including elite breeding line, landraces and wild species is expected to be fully sequenced very soon.
Rice breeding is both challenged and benefited by the fact that a successful varietal improvement program must embrace both the integration single genes that segregate in a simple Mendelian fashion as well as complex traits that are inherited in more quantitative ways. For decades the rice genetics community has produced a wealth of knowledge about these single genes and has developed markers that allow a breeder to track them in a population. However, marker assisted selection (MAS) alone is insufficient to drive the rates of genetic gain for more complex traits that are equally necessary. This presentation will describe the attempts made in the Favorable Environments Breeding program at IRRI to integrate the selection for single genes appropriate for MAS into a more complex population improvement strategy designed to improve quantitatively inherited traits.
Genetic Dissection of Compositional & Anatomical Characteristics Associated w...Jonathan Clarke
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- Final Remarks
Next generation genomics for chickpea (Cicer arietinum L.) improvementICRISAT
Large scale genomic resources including draft genome sequence, re-sequencing of 90 lines, comprehensive transcriptome assembly and high density genetic maps have been developed for chickpea. Linkage mapping and genome wide association studies (GWAS) are being used for trait
mapping.
26 Feb 2014
Development of a high-throughput high-density SNP genotyping array for bovineAffymetrix
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Durante la Semana de la Agricultura y la Alimentación, el Programa de Investigación del CGIAR en Cambio Climático, Agricultura y Seguridad Alimentaria – CCAFS, la Organización de las Naciones Unidas para la Alimentación y la Agricultura, FAO, y el Centro Internacional de Agricultura Tropical – CIAT, apoyaron la II Reunión Internacional de Ministros y altas autoridades de agricultura sobre agricultura sostenible y cambio climático con un documento base y su presentación sobre los retos que representa el cambio climático para la agricultura en Latino América y el Caribe.
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Jennifer Twyman, Líder de investigación de Género en el CIAT
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The 4 per 1000 Africa Symposium - Building synergies across Africa to advance on soils for food security and climate, Johannesburg, South Africa 24-26 October 2018
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El taller ‘Cacao libre de cadmio’, organizado por el CIAT, CIRAD, y la AFD, se lleva a cabo del 12 al 14 de marzo en la sede del CIAT en Palmira,y tiene como objetivo integrar un consorcio de actores y disciplinas claves de la región, así como elaborar un proyecto de investigación aplicada que dé respuesta a este problema que afecta a los cacaoteros de Colombia, Perú y Ecuador. http://ow.ly/J43p30iU0UZ
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El taller ‘Cacao libre de cadmio’, organizado por el CIAT, CIRAD, y la AFD, se lleva a cabo del 12 al 14 de marzo en la sede del CIAT en Palmira,y tiene como objetivo integrar un consorcio de actores y disciplinas claves de la región, así como elaborar un proyecto de investigación aplicada que dé respuesta a este problema que afecta a los cacaoteros de Colombia, Perú y Ecuador. http://ow.ly/J43p30iU0UZ
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1. Genomic selection on rice
Early generation selection in a recurrent
selection breeding program within a
synthetic population
Since 1967 / Science to cultivate change
Cécile Grenier
Tuong-Vi Cao
2. Genomic selection
Since 1967 / Science to cultivate change
• Decreased genotyping costs and
new statistical methods enable
simultaneous estimation of all
marker effects!
• GS – a new form of MAS that
estimates all marker effects across
the whole genome to calculate
genome estimated breeding values
(GEBVs )
• Markers are not tested for
significance – all markers are used
in selection
3. Genomic selection on Rice
Can genomic selection can be applied on rice synthetic population (SP)
managed through recurrent selection (RS)?
Can GS be adapted to Recurrent Genomic Selection (RGS)?
Since 1967 / Science to cultivate change
Theme 2 – Varietal Development
4. The breeding scheme
Since 1967 / Science to cultivate change
Recombination
Candidate
units
Evaluation
Phenotype in target
environments
Synthetic Population
3000 S0 plants
Varieties
Selected
units
Evaluations
5. The SP derived training and
breeding population
Fixation through
SSD for ~350 lines
Since 1967 / Science to cultivate change
Synthetic Population
3000 S0 plants 343 S2:4 and S3:5 families
Extraction of
400 S0 plants
Recombination
(35 plants)
Training Population
Breeding Population
6. Testing the Feasibility of Genomic Selection through Cross-Validations
Phenotypes (Y) Genotypes (X)
Since 1967 / Science to cultivate change
343 families
(from a SP with 10 cycles of recombination)
Whole Genome Regression Model
7. Since 1967 / Science to cultivate change
GBS technology
6,874 SNP with MAF ≥ 2.5% (1 marker every ~ 57 kb)
4,098 SNP with MAF ≥ 10.0% (1 marker every ~ 95 kb)
LD decay curve for chromosome 1 and MAF ≥ 10%
For ½ initial r², the average extent of LD is ~ 0.639 Mb, i.e. at least 610
markers are required to cover the whole genome
8. Heatmap (G matrix of 343 individuals with
Un-rooted Neighbor Joining
(dissimilarity matrix among 343 individuals with 6874 SNP)
6874 SNP)
Since 1967 / Science to cultivate change
The genetic material
9. Since 1967 / Science to cultivate change
The genetic material
Evaluation of the 343 families (301 S2:4 and 42 S3:5) under a Lattice Design with 2 repetitions
Panicle weight (h2=0.19) Grain yield (h2=0.30)
Flowering date (h2=0.86)
Plant height (h2=0.61)
10. Testing the Feasibility of Genomic Selection through Cross-Validations
Phenotypes (Y) Genotypes (X)
Since 1967 / Science to cultivate change
343 families
(from a SP with 10 cycles of recombination)
Whole Genome Regression Model
k-folds cross-validation:
100 samplings of Training Population (TP) and Validation Population (VP)
100 cor(y, X)
Mean of correlations: ‘Predictive ability of genomic selection’
11. GS in Rice synthetic populations
Regression models
G-BLUP
Ridged Regression
Bayesian LASSO
Bayesian RR
Since 1967 / Science to cultivate change
Limit for r² MAF (%) No. SNP
r² <= 0.75
2.5 1758
5 1158
10 678
r² <= 0.90
2.5 4314
5 3268
10 2152
r² <= 1.00
2.5 6874
5 5605
10 4098
k No. ind.
[tst]
3 114
6 57
9 38
Incidence matrix
choice of SNP markers based on LD and MAF
FD (Flowering date) {h2 = 0.86}
PH (Plant height) {h2 = 0.61}
PW (Panicle weight) {h2 = 0.19}
GY (Grain yield) {h2 = 0.30}
k-folds cross-validation
fraction k of the population (n=343)
used for validation
Traits
12. Statistical models for GS
Criteria rrBLUP B-RR B-LASSO
Variable selection No No Yes
Marker effects All markers with same
2 σ2, λ2
Since 1967 / Science to cultivate change
Penalized regressions
– Parametric linear regression models (frequentist and Bayesians)
• Ridge Regression (RR), Best Linear Unbiased Predictors (BLUP), Least Absolute Shrinkage and
Selection Operator (LASSO), G-BLUP, RR-BLUP, LASSO, Bayesian RR, Bayesian LASSO…
effect
– Non-parametric nonlinear models
• RKHS, NN, RBFNN
All marker have an effect Some markers have null
effect
Parameter shrinkage
of estimates effects
Same extend of
shrinkage
Same extend of
shrinkage
Marker-specific shrinkage
Hyper-parameters No σβ
Distribution of effects Gaussian Gaussian Double exponential
Best for… Trait controlled by many
loci w. small effects
Trait controlled by few loci
varying in effect size
13. Regression model and marker effects
Bayesian LASSO (MAF2.5 - r2≤0.75) with 9-fold CV -- Grain yield
cor(ŷ[tst], y[tst]) = 0.25
cor(ŷ, y) = 0.84
Since 1967 / Science to cultivate change
Marker Effects
14. Accuracy is function of trait genetic architecture,
heritability and, for FD, of choice of markers
Bayesian LASSO (9 X matrices) with 9-fold CV
Grain yield {h2 = 0.30} Panicle weight {h2 = 0.19}
Since 1967 / Science to cultivate change
0.600
0.500
0.400
0.300
0.200
0.100
0.600
0.500
0.400
0.300
0.200
0.100
0.000
0 2000 4000 6000 8000
0.600
0.500
0.400
0.300
0.200
0.100
0.000
0 2000 4000 6000 8000
0.600
0.500
0.400
0.300
0.200
0.100
0.000
0 2000 4000 6000 8000
0.000
0 2000 4000 6000 8000
Flowering date {h2 = 0.86}
Plant height {h2 = 0.61}
No. SNP
Accuracy (cor(ŷ, y))
No. SNP
Accuracy (cor(ŷ, y))
15. Selection of markers (predictors) based on LD
improved the accuracy for oligogenic traits
Flowering date (9 X matrices, 3-fold CV, Ridged Regression)
2.5%
5.0%
Since 1967 / Science to cultivate change
7.5%
10%
0.50
0.40
0.30
0.20
0.10
0.00
-0.10
0 1000 2000 3000 4000 5000 6000 7000
Accuracy = corr(Yobs, Yhat)
Number of SNP
No. SNP
r² <= 0.75 r² <= 0.80 r² <= 0.90 r² <= 1.00
Series5 Series6 Series7
Accuracy (cor(ŷ, y))
16. Slight superiority of the Bayesian Statistics
Since 1967 / Science to cultivate change
Grain Yield (9 X matrices with 9-fold CV)
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0.000
0 2000 4000 6000 8000
BL
BRR
GBLUP
RR
No. SNP
Accuracy (cor(ŷ, y))
17. The RS breeding scheme
Since 1967 / Science to cultivate change
Recombination
Candidate
units
Evaluation
Phenotype in target
environments
Synthetic Population
3000 S0 plants
Varieties
Selected
units
Evaluations
18. The RGS breeding scheme
Since 1967 / Science to cultivate change
Recombination
Candidate
units
Whole
Genome
Genotyping
Breeding Population
3000 S0 plants
Promising lines
Selected
units
GEBVs
Genomic
prediction
MET Evaluations
GS models
Evaluations
Training Population New varieties
19. Since 1967 / Science to cultivate change
Conclusions
• Yes, GS on rice synthetic population is feasible!
• Although not fantastic accuracies were achieved, it was 1 site, 1 year and a
first promising result
• Small accuracy may still be worth considering the cost of field evaluation,
the gain in time to select during the off-season and the possibility to apply
stronger selection intensity
• Soon to come:
More data, more sites, and more adequate statistics (experimental
design and multi-site evaluations accounted in the model) for
nonparametric non linear models
GS on the breeding population using the entire training population
to develop the genomic prediction model
Maximizing the benefit of GS on earlier generation of the RS
scheme (S0 generation)