CHAPTER 9 PHYSIOLOGICAL PROCESSES TO UNDERSTAND GENOTYPE × ENVIRONMENT INTERACTIONS IN

Abstract. Variation in maize yield across environments often reflects genotype-specific responses in crop-flowering dynamics. The most widely observed effect is the temporal separation of male (anthesis) and female (silking) floral maturity, referred to as the anthesis–silking interval (ASI). Many studies have shown that maize yield also is a function of crop growth rate around flowering. At present, however, the relationship between growth rate and flowering dynamics is not fully understood. In this chapter, we present a conceptual basis and experimental approach for quantifying and analysing maize female flowering responses to variation in plant growth. We show how this approach can be applied to resolve contrasting genotypic behaviour under a range of environmental conditions. Because maize canopies are composed of plants exhibiting a range of growth rates, understanding plant-to-plant variability is critical for evaluating genotypic and environmental effects on female flowering dynamics. We propose a simple model, based on well-established population dynamics, to capture intrinsic plant-to-plant variability within maize canopies. Specific genotype parameters were identified that integrate biomass production and partitioning into a framework to describe the flowering response of a particular genotype in a particular environment. These results have important implications for understanding yield formation in maize. They provide an approach to evaluate genotype × environment interactions, and a framework to evaluate genes regulating flowering dynamics