Genetic aspects of Booroola introgression in breeding programs

This paper describes the genetic aspects of introgressing a major gene from a donor breed into a commercial recipient breed. The efficiency of the introgression process can be derived from the merit of the introgression population versus that of the commercial population at a certain time following the commencement of the program. The relative merit depends not only on the effect of the major gene and the genetic difference between the donor breed and the commercial breed, but also on the rate of genetic gain in the commercial breed and the genetic lag of the introgressed breed. Generally, several generations of backcrossing are required to recover the recipient genome. The efficiency of marker-assisted introgression is compared to introgression without markers. This difference can be small for traits that are easy to measure but is larger for reproduction traits, as in the case of Booroola. Various introgression strategies are compared for efficiency, including strategies for efficient dissemination of improved nucleus animals into the wider population.