Genotype x environment interactions and some considerations of their implications for wheat breeding in Australia

Genotypexenvironment (GxE) interactions complicate selection for broad adaptation, while their nature and causes need to be understood to utilise and exploit them in selection for specific adaptation. This invited review combines an assessment of the literature with the experience we have gained from involvement in wheat breeding and associated research programs to assess (1) the implications of GxE interactions for wheat breeding in Australia, (2) the impact that research into GxE interactions has had on breeding strategy, and (3) the evidence for impact from this research effort on genetic improvement of crop adaptation. The role of analytical methodology in this process is considered and some important issues are discussed. There are sufficient examples drawn from wheat breeding in Australia to suggest that progress in dealing with GxE interactions can be made and several of these are presented. They show that impact in plant breeding follows from achieving an appropriate level of understanding of the environmental and genetic factors causing the interactions as well as an assessment of their importance in the target genotype-environment system. An accurate definition of the environmental factor(s) contributing to the GxE interactions has been particularly important in determining the relevance of observed differences in plant adaptation to the target population of environments. From the combination of biological and statistical studies, a more comprehensive understanding of GxE interactions has emerged and contributed to new concepts and procedures for dealing with them. Distinguishing between what are repeatable and non-repeatable interactions is a key step. Genuine cases of positive specific adaptation observed in multi-environment trials (METs) can be exploited by appropriately targeted selection strategies, while non-repeatable interactions are accommodated by selection for broad adaptation. The investigation of GxE interactions for grain yield of wheat in Australia has matured to the point where an understanding of some of their causes has enabled wheat breeders to exploit positive components of specific adaptation. The experience that has been gained in achieving these advances indicates the importance of establishing a MET system that is relevant to the target population of environments of the breeding program. The investment of adequate resources into effective design, conduct, analysis, and interpretation of METs remains critical to continued progress from selection in complex genotype-environment systems that present large GxE interactions. Wheat breeders who understand their genetic material and the target population of environments can then use the generated information base to achieve impact from their breeding programs.