Genotype by environment interactions in an Australia-wide radiata pine diallel mating experiment: Implications for regionalized breeding

Abstract

Genotype by site interactions were studied in an Australia-wide diallel experiment covering 10 testing sites for stem dbh, stem straightness, branch angle and size, and number of branch clusters on the stem at age 10.5 to 11.5 years. The size and practical importance of genotype by site interactions were examined by four approaches: (1) the ratio of interaction variance to general combining ability (GCA) variance; (2) additive genetic correlations among sites; (3) testing whether the interaction was a result of a few families reacting more than others; and (4) by the size of genetic gains through a proposed regionalization. The genotype by site interaction for dbh observed in this experiment was larger than reported earlier for radiata pine because two high-elevation sites were included. There were more interactions between the two high-elevation sites and other lower elevation sites than interactions between lower elevation sites. The large genotype by region interaction was attributed to the extensive snow loading at the two higher elevation sites. Gain predictions from five regionalization schemes in this experiment favor regionalization of radiata pine breeding into two main regions: higher elevation and lower elevation sites. Copyright © 2005 by the Society of American Foresters.