Two-trait selection response with marker-based assortative mating |
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Authors: | R Bernardo |
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Institution: | (1) Department of Agronomy, Purdue University, 1150 Lilly Hall of Life Sciences, West Lafayette, IN 47907-1150, USA Fax: +1 765 496 2926 E-mail: bernardo@purdue.edu, US |
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Abstract: | Marker-based assortative mating (MAM) – the mating of individuals that have similar genotypes at random marker loci – can
increase selection response for a single trait by 3–8% over random mating (RM). Genetic gain is usually desired for multiple
traits rather than for a single trait. My objectives in this study were to (1) compare MAM, phenotypic assortative mating
(PAM), and RM of selected individuals for improving two traits and (2) determine when MAM will be most useful for improving
two traits. I simulated 20 generations of selecting 32 out of 200 individuals in an F2 population. The individuals were selected based on an index (SI) of two traits and were intermated by MAM, PAM, or RM. I
studied eight genetic models that differed in three contrasts: (1) weight, number of quantitative trait loci (QTL), and heritability
(h
2) for each trait; (2) linkage of QTL for each trait; and (3) trait means of the inbred parents of the F2. For SI and the two component traits, MAM increased short-term selection response by 5–8% in six out of the eight genetic
models. The MAM procedure was least effective in two genetic models, wherein the QTL for one trait were unlinked to the QTL
for the other trait and the parents of the F2 had divergent means for each trait. The loss of QTL heterozygosity was much greater with MAM than with PAM or RM. Consequently,
the advantage of MAM over RM dissipated after 5–7 generations. Differences were small between selection responses with PAM
and RM. The MAM procedure can enhance short-term selection response for two traits when selection is not stringent, h
2 is low, and the means of the parents of the F2 are equal for each trait.
Received: 10 June 1998 / Accepted: 5 August 1998 |
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Keywords: | Assortative mating Index selection Molecular markers Quantitative trait loci |
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