Genetic and environmental effects on crop development determining adaptation and yield

Abstract

Crop development is a sequence of phenological events controlled by the genetic background and influenced by external factors, which determines changes in the morphology and/or function of organs. Although development is a continuous process, the ontogeny of a crop is frequently divided into discrete periods, for instance ?vegetative?, ?reproductive? and ?grain filling? phases. Patterns of phenological development largely determine the adaptation of a crop to a certain range of environments. For example, genetic improvement in grain yield of wheat has been associated with shorter time from sowing to anthesis in Mediterranean environments of Western Australia, whereas no consistent trends in phenology were found where drought is present but not necessarily terminal, including environments of Argentina, Canada and the United States. Even in agricultural lands of the Mediterranean Basin where wheat has been grown for at least many centuries, breeding during the last century did not clearly changed phenological patterns.This chapter focuses on two major morphologically and physiologically contrasting grain crops: wheat and soybean. For both species, we have an advanced understanding of development and physiology in general. Wheat is a determinate, long-day grass of temperate origin, which is responsive to vernalization. Soybean is a typically indeterminate (but with determinate intermediate variants), short-day grain legume of tropical origin, which is insensitive to vernalization. Comparisons with other species are used to highlight the similarities and differences. The aims of this chapter are to outline the developmental characteristics of grain crops and the links between phenology and yield, to revise the mechanisms of environmental and genetic control of development and to explore the possibilities of improving crop adaptation and yield potential through the fine-tuning of developmental patterns.