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Selection Response with Marker‐Based Assortative Mating
Author(s) -
Bernardo Rex
Publication year - 1999
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1999.0011183x003900010011x
Subject(s) - assortative mating , biology , centimorgan , heritability , selection (genetic algorithm) , mating , genetics , quantitative trait locus , evolutionary biology , gene mapping , gene , machine learning , chromosome , computer science
Assortative mating can increase additive variance (V A ) and, consequently, selection response. Marker‐based assortative mating (MAM— the mating of individuals that have similar marker genotypes—has not been studied. My objectives in this simulation study were to (i) compare the selection response associated with MAM, phenotypic assortative mating (PAM), and random mating (RM) of selected individuals and (ii) determine when MAM will be most useful breeding programs. I simulated 25 generations of selection among 200 individuals, followed by MAM, PAM, or RM, in a cross between two inbreds. A total of 100 codominant marker loci and 100 quantitative trait loci (QTL) were randomly distributed across 10 chromosomes, each 100 centimorgans (cM) long. The effects of QTL were additive and followed an exponential distribution. Cumulative selection response was determined for different initial levels of heritability ( h 2 = 0.20, 0.50, and 0.80) and different numbers of individuals selected ( N = 4, 8,16, and 32) in each generation. Compared with RM, MAM resulted in slight increases of 3 to 8% in selection response during the first several generations, particularly when h 2 = 0.20 and N = 32. The PAM procedure led to slight increases of 2 to 4% when h 2 = 0.80 and N = 32. Any advantage of assortative mating over RM dissipated by Generation 8 for MAM and Generation 15 for PAM. The loss of QTL heterozygosity was much greater with MAM than with PAM or RM. For long‐term improvement, selected individuals should be intermated by RM. The MAM procedure will be most useful for short‐term improvement in a biparental cross, particularly when h 2 and selection pressure are low.