The reduction of linkage drag around introgressions in marker-assisted backcross programs [MAS] | [Perspectives pour les méthodes d'amélioration. La réduction du segment de linkage autour d'introgressions dans les programmes de backcross assistés par marqueurs, SAM]
2001
Hospital, F. ((Institut National de la Recherche Agronomique, Gif sur Yvette (France). Centre de Versailles Grignon, Station de Génétique Végétale))
I investigate the efficiency of marker-assisted selection to reduce the length of the chromosome segment of donor type retained around a locus held heterozygous by backcrossing. First, the efficiency of marker-assisted selection is evaluated from the length of the donor segment in backcross individuals that are (double) recombinants for two markers flanking the introgressed gene on each side. Analytical expressions for the probability density function, the mean and the variance of this length are given for any number of backcross generations, as well as numerical applications. For a given marker distance, the number of backcross generations performed has little impact on the reduction of donor segment length, except for distant markers. In practical situations, the most important parameter is the distance between the introgressed gene and the flanking markers, which should then be chosen as closely linked as possible to the introgressed gene. Second, the minimal population sizes required to obtain double recombinants for such closely linked markers are computed and optimized in the context of a multi-generation backcross program. The results indicate that it is generally more profitable to allow for three or more successive backcross generations, rather than favour early generation recombinations
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