Introgression of trypanotolerance genes
2000
Koudandé, O.D.
Trypanosomosis is the most widespread parasitic disease of great importance in Africa affecting human and animals. There are breeds of cattle that are trypanotolerant. Trypanotolerance is an ability of these breeds to withstand the effects of trypanosome infections. The disease impedes production in Sub-Saharan Africa. In this thesis, the main focus is on marker-assisted breeding to improve trypanotolerance and mouse is used as model organism for cattle. We have concentrated on the opportunities to exploit individual genes (QTL) that affect trypanotolerance. We have shown how the size of a breeding experiment increases with the number and the size of the QTL region to introgress. Biological factors to be considered when estimating the required size of an introgression experiment are also highlighted. Strategies to optimize designs for introgression show that selecting two lines each carrying two of the donor's QTL allele during the backcross (when introgressing three QTL) is more advantageous than monitoring simultaneously the three QTL in terms of number of animals to maintain, number of genotyping and costs involved. An experiment in mice shows that QTL introgression is feasible and successful, and that the background genotype is an important factor to be considered when analyzing the results of such an experiment. This experiment is unique. The general discussion focuses on the introgression of trypanotolerance genes in cattle with an emphasis on SubSaharan zones of Africa. The introduction of trypanotolerant cattle in the humid and subhumid zones of Africa, however, should be done with care to avoid damage to the environment and bio-diversity.
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