Incorporation of Competitive Effects in Forest Tree or Animal Breeding Programs

Abstract

Competition among domesticated plants or animals can have a dramatic negative impact on yield of a stand or farm. The usual quantitative genetic model ignores these competitive interactions and could result in seriously incorrect breeding decisions and acerbate animal well-being. A general solution to this problem is given, for either forest tree breeding or penned animals, with mixed-model methodology (BLUP) utilized to separate effects on the phenotype due to the individuals' own genes (direct effects) and those from competing individuals (associative effects) and thereby to allow an optimum index selection on those effects. Biological verification was based on two lines of Japanese quail selected for 6-week weight; one line was selected only for direct effects (D-BLUP) while the other was selected on an optimal index for both direct and associative effects (C-BLUP). Results over 23 cycles of selection showed that C-BLUP produced a significant positive response to selection (b ϭ 0.52 Ϯ 0.25 g/hatch) whereas D-BLUP resulted in a nonsignificant negative response (b ϭ Ϫ0.10 Ϯ 0.25 g/hatch). The regression of percentage of mortality on hatch number was significantly different between methods, decreasing with C-BLUP (b ϭ Ϫ0.06 Ϯ 0.15 deaths/hatch) and increasing with D-BLUP (b ϭ 0.32 Ϯ 0.15 deaths/hatch). These results demonstrate that the traditional D-BLUP approach without associative effects not only is detrimental to response to selection but also compromises the well-being of animals. The differences in response show that competitive effects can be included in breeding programs, without measuring new traits, so that costs of the breeding program need not increase.

The quantitative genetics of indirect genetic effects: a selective review of modelling issues

“…Griffing (1967) referred to the IGE as an associative effect, indicating that it originates from individuals associated with the focal individual. This terminology has later been used also by Muir et al (1996Muir et al ( , 2005. The variance-component model does not specify the phenotypic trait values that cause the indirect effects.…”

“…The classical example of an IGE is the maternal genetic effect of a mother on the trait values of her offspring in a mammal (Dickerson, 1947;Willham, 1963;Falconer, 1965;Kirkpatrick and Lande, 1989). Other examples of IGEs are mortality due to cannibalistic interactions in domestic chicken (Muir, 1996(Muir, , 2005, the effect of competition among trees on growth rate in bark diameter (Brotherstone et al, 2011), the outcome of dyadic interactions in deer , social behaviours in microorganisms (Crespi, 2001), size, developmental and fitness-related traits in Arabidopsis (Mutic and Wolf, 2007;Wolf et al, 2011), and growth rate in Medaka (Ruzzante and Doyle, 1991).…”

“…At present, however, IGEs are receiving increasing attention and the number of publications referring to IGEs is increasing rapidly, both in agricultural sciences and in biology. The integration of IGEs in the ordinary linear mixed models used for the estimation of breeding values and variance components has greatly facilitated empirical research on IGEs, both in animal breeding and other disciplines (Muir and Schinkel, 2002;Muir, 2005). In animal breeding, the integration of IGEs within the ordinary quantitative genetic framework has increased their understanding and acceptance, and clarified their potential role in response to selection (Bijma et al, 2007a).…”

Future trends in Animal Breeding due to new genetic technologies

“…Experimental evidence supporting Griffing's theory was obtained using the above experimental design in Drosophila melanogaster (Pé rez-Tome and Toro, 1982;Martin et al, 1988;Ló pezSuá rez et al, 1993) and Tribolium castaneum Toro, 1992 and. More sophisticated designs and analyses involving the estimation of variance components using mixed-model methodologies have been developed by Muir (2005), Van Vleck and Cassady (2005), Van Vleck and Cassady (2006), Cantet and Cappa (2008) and also implemented in Drosophila (Wolf, 2003), trees (Cappa and Cantet, 2006), (mussels (Brichette et al, 2001), poultry (Craig and Muir, 1989), cattle (Van Vleck et al, 2007) and pigs (Arango et al, 2005)). …”

On the definition and utilization of heritable variation among hosts in reproduction ratio R0 for infectious diseases

“…We use results from the field of IGEs to define breeding value for R 0 . An IGE is heritable effect of an individual on the trait value of another individual (Griffing, 1967(Griffing, , 1976(Griffing, , 1981Moore et al, 1997;Wolf et al, 1998;Muir, 2005). Hence, infectivity is an IGE, as an individual's infectivity affects the disease status of its contacts.…”