Genotype by Environment Interactions in South African Pine Progeny Trials: Implications for Tree Breeding
Abstract
SYNOPSIS Genotype by environment interactions (GEI) can occur within a trial and between different sites. In the first case, more research is needed before deciding whether it is necessary to adopt single tree plot designs or to isolate the blocks and/or the genotypes which are responsible for the interactions. In case of GEI between sites, costly and complex ecophysiological studies are necessary to determine which factors of the environment are responsible for the interaction and how the genotypes react, if we must classify sites into subregions of minimal GEI and then adopt a multiple breeding and production population approach. The cheaper and quicker method, if it is feasible, is to eliminate the genotypes which mainly cause the interactions, thus breeding for stable genotypes. There are sites where tree breeding is uneconomical and other options should be considered, including silvicultural ones.