Potential benefit from using  an identified major gene in BLUP  evaluation with truncation  and optimal selection

Villanueva, Beatriz; Pong‐Wong, Ricardo; Grundy, B.; Woolliams, John

doi:10.1051/gse:19990202

Cited by 6 publications

(14 citation statements)

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“…The results for a favourable linkage would be expected to be similar to those for gene-assisted selection on a trait controlled by a quantitative trait locus and polygenes e.g. [26]. In this situation, there would be an increase in the rates of genetic gain (at least in the early generations of PrP selection) and inbreeding.…”

Section: Discussionmentioning

confidence: 85%

Predicting the consequences of selecting on PrP genotypes on PrP frequencies, performance and inbreeding in commercial meat sheep populations

et al. 2007

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-Selection programmes based on prion protein (PrP) genotypes are being implemented for increasing resistance to scrapie. Commercial meat sheep populations participating in sire-referencing schemes were simulated to investigate the effect of selection on PrP genotypes on ARR and VRQ allele frequencies, inbreeding and genetic gain in a performance trait under selection. PrP selection strategies modelled included selection against the VRQ allele and in favour of the ARR allele. Assuming realistic initial PrP frequencies, selection against the VRQ allele had a minimal impact on performance and inbreeding. However, when selection was also in favour of the ARR allele and the frequency of this allele was relatively low, there was a loss of up to three to four years of genetic gain over the 15 years of selection. Most loss in gain occurred during the first five years. In general, the rate of inbreeding was reduced when applying PrP selection. Since animals were first selected on their PrP genotype before being selected on the performance trait, the intensity of selection on performance was weaker under PrP selection (compared with no PrP selection). Eradication of the VRQ allele or fixation of the ARR allele within 15 years of selection was possible only with PrP selection targeting all breeding animals. sire referencing / scrapie / prion / PrP selection / inbreeding

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Section: Discussionmentioning

confidence: 85%

Predicting the consequences of selecting on PrP genotypes on PrP frequencies, performance and inbreeding in commercial meat sheep populations

et al. 2007

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“…In general, the results can also be applied to major genes in mixed inheritance models, where a major gene has a large effect on the trait, and many background genes have small effects [4]. Villanueva et al [23] simulated schemes with a mixed model inheritance for BLUP optimum contribution selection (similar to our BLUP scheme). They found that the frequency of the favourable allele had reached 0.95 after eight generations for a gene with recessive inheritance.…”

Section: Relaxation Of Assumptionsmentioning

confidence: 99%

“…This finding is similar to the results in Figure 1, although the schemes differed considerably (the genotypic values (2.0 and dominance deviation was −0.5), initial frequency (0.15) of the non-disease allele, and size of the scheme (120 animals per generation)). In the case where a major (disease) gene and other (economic) polygenic traits are included in the breeding goal, the question arises how much weight should be given to the major gene relative to that of the polygenic traits in the short and long term [4,9,16,21,23]. This question is beyond the scope of this paper and is currently under active investigation [24,25].…”

Section: Relaxation Of Assumptionsmentioning

confidence: 99%

Selection against genetic defects in conservation schemes while controlling inbreeding

Sonesson

Janss²,

Meuwissen³

2003

Genet. Sel. Evol.

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-We studied different genetic models and evaluation systems to select against a genetic disease with additive, recessive or polygenic inheritance in genetic conservation schemes. When using optimum contribution selection with a restriction on the rate of inbreeding (∆F) to select against a disease allele, selection directly on DNA-genotypes is, as expected, the most efficient strategy. Selection for BLUP or segregation analysis breeding value estimates both need 1-2 generations more to halve the frequency of the disease allele, while these methods do not require knowledge of the disease mutation at the DNA level. BLUP and segregation analysis methods were equally efficient when selecting against a disease with single gene or complex polygene inheritance, i.e. knowledge about the mode of inheritance of the disease was not needed for efficient selection against the disease. Smaller schemes or schemes with a more stringent restriction on ∆F needed more generations to halve the frequency of the disease alleles or the fraction of diseased animals. Optimum contribution selection maintained ∆F at its predefined level, even when selection of females was at random. It is argued that in the investigated small conservation schemes with selection against a genetic defect, control of ∆F is very important. genetic defects / selection / inbreeding / conservation

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“…However, the vast majority of the research directed to evaluate the potential benefits of using information on identified quantitative trait loci or QTL (GAS) or on markers linked to them (MAS) in artificial selection has been focused on singletrait scenarios (e.g., Ruane and Colleau, 1995;Villanueva et al, 1999Villanueva et al, , 2002Abdel-Azim and Freeman, 2002).…”

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confidence: 99%

“…Dynamic selection tools that optimise genetic contributions of selection candidates for obtaining maximum genetic gain while constraining the rate of inbreeding (∆F) to a pre-defined value have been used under single trait scenarios with GAS or MAS (Villanueva et al, 1999. These tools are implemented as quadratic indexes in which the desired ∆F is achieved by applying a quadratic constraint on the average coancestry of selection candidates weighted by their projected use .…”

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Response to selection from using identified genes and quadratic indices in two-traits breeding goals

Avendaño

Visscher

Villanueva³

2008

Span. j. agric. res.

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Benefits from the use of optimised selection for maximising genetic gain while constraining the rate of inbreeding were evaluated through stochastic simulation for scenarios where the breeding goal includes two negatively correlated traits. One of the traits was controlled only by polygenes and had a heritability of 0.3 while the other trait was controlled by an identified additive biallelic QTL (with an initial allele frequency of 0.15) and by polygenes and had a polygenic heritability of 0.1. Optimised selection was compared to standard truncation selection both when the information on the QTL was used and when it was ignored. Extra gains in the breeding goal were observed throughout the 10 simulated generations from the combined use of optimised contributions and QTL information although, as expected, this scheme was not the most effective for improving individual traits. By generation ten, the gain in the aggregate breeding value with optimised selection was about 12% higher than with truncation selection. Optimised selection allowed extra polygenic responses in both traits but these extra responses were negative for the trait under mixed inheritance. The use of the QTL allowed not only positive gains in the trait with the lowest heritability, but also avoided the loss of the favourable allele. The effect of selecting for the QTL on each trait depended on its relative weight in the selection index and not exclusively on the inheritance model. Additional key words: GAS, inbreeding, multiple traits, optimised selection, QTL. ResumenRespuesta a la selección utilizando genes identificados e índices cuadráticos para la mejora simultánea de dos caracteres En este trabajo se han evaluado, mediante simulación estocástica, los beneficios de utilizar selección optimizada para maximizar la respuesta genética, controlando al mismo tiempo la tasa de consanguinidad, en un contexto en el cual el objetivo de mejora incluye dos caracteres correlacionados negativamente. Uno de los caracteres (con heredabilidad de 0,3) fue poligénico mientras que el segundo (con heredabilidad de 0,1) estaba controlado por un QTL bialélico y por poligenes. La frecuencia alélica inicial para el QTL fue 0,15. La estrategia de selección optimizada se comparó con la de selección clásica por truncamiento, tanto en el caso de utilizar la información del QTL, como en el caso de ignorarla. El uso simultáneo de contribuciones optimizadas y del QTL produjo una mayor ganancia en el objetivo de mejora en las 10 generaciones de selección simuladas, si bien este esquema no fue el más eficiente para mejorar los caracteres individualmente. En la generación 10, la ganancia obtenida en el objetivo de mejora con selección optimizada fue aproximadamente un 12% más alta que aplicando la selección por truncamiento. La selección optimizada produjo una respuesta poligénica adicional en ambos caracteres, mientras que esta respuesta fue negativa para el carácter controlado por el QTL. El uso del QTL no solo proporcionó respuestas positivas en el carácter con her...

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Potential benefit from using an identified major gene in BLUP evaluation with truncation and optimal selection

Abstract: -This study investigates the benefit of including information on an identified major gene

Cited by 6 publications

References 8 publications

Predicting the consequences of selecting on PrP genotypes on PrP frequencies, performance and inbreeding in commercial meat sheep populations

Predicting the consequences of selecting on PrP genotypes on PrP frequencies, performance and inbreeding in commercial meat sheep populations

Selection against genetic defects in conservation schemes while controlling inbreeding

Response to selection from using identified genes and quadratic indices in two-traits breeding goals

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