Characterising the crop environment – nature, significance and applications

While genotype × environment interactions (G × E) impede progress in plant breeding, efforts have focused more on their statistical analysis than on characterizing crop environments per se. Environmental conditions are commonly the major sources of yield variation across breeding trials, and their characterization may improve breeding efficiency. This chapter reviews different facets of environment characterization, including how to describe the target population of environments (TPE; i.e. conditions to which future-release cultivars might be subjected), and how to identify relevant environment classes where genotypes are expected to perform similarly. Due to seasonal variability and resource constraints, multienvironment breeding trials typically offer a biased representation of the TPE. Weighted analysis based on how representative trials can help breeders correct for this bias, and select for germplasm better adapted to the TPE. Managed-environment trials are another way to evaluate performance in representative environments or for particular stresses, allowing detailed assessment of germplasm, traits or genes of interest. While limited resources restrict the collection of experimental data, modeling tools offer a cost-effective avenue to explore the complex genotype × environment × management (G × E × M) interactions and, in particular, to assess the potential value of traits and alleles depending on 'genetic backgrounds' (G × G and trait × trait interactions), environments (e.g. current and future climates) and management practices. Challenges, significance and limitations of environment characterization are discussed in the context of crop improvement