Selection against genetic defects in conservation schemes while controlling inbreeding

Abstract

-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

Effects on inbreeding of different strategies aimed at eliminating scrapie sensitivity alleles in rare sheep breeds in The Netherlands

“…PrP genotype frequencies have been assessed in a large number of breeds (e.g. Bossers et al, 1999;Drögemüller et al, 2001;O'Doherty et al, 2002;Palhière et al, 2002) and strategies for scrapie eradication in large commercial breeds have been modelled (Kao et al, 2001;Arnold et al, 2002;Sonesson et al, 2003). Our research shows that, in rare breeds, attention to inbreeding is of vital importance.…”

“…The optimized contribution algorithm (Meuwissen, 1997) follows this approach, and at the same time optimizes selection. Sonesson et al (2003) evaluated this approach for the elimination of single gene genetic defects. Provided that a reliable pedigree is present, optimal contribution will accelerate the increase of the ARR allele at the same or a lower rate of inbreeding than that obtained following the advice of this paper.…”

Consequences for diversity when animals are prioritized for conservation of the whole genome or of one specific allele

“…For example, selection for an allele that is mainly present in one family may result in a higher loss of diversity. Methods have been developed to eliminate or conserve alleles at a specific locus while controlling overall genetic diversity (Sonesson et al 2003;Fernandez et al 2006). An important unanswered question however is how strong the effect of allele frequency and population stratification is on the risk of losing diversity across the genome, using these methods.…”

Opinion of the Scientific Panel on biological hazards (BIOHAZ) on the Breeding programme for TSE resistance in sheep

“…The selection on PrP genotype belongs to this category of actions and the scientific efforts presently made on the subject will help its management. The literature already offers a number of contributions to the optimisation of the selection efficiency in the long term (Larzul, Manfredi et al 1997;Meuwissen 1997;Dekkers and Van Arendonk 1998;Grundy, Villanueva et al 1998;Meuwissen and Sonesson 1998;Caballero and Toro 2002;Villanueva, Pong-Wong et al 2002;Sonesson, Janss et al 2003).…”