Drought Adaptation in Wheat

Globally, water deficit is a more common scenario for cultivated wheat than water sufficiency, and wheat is a relatively drought resistant species. Its ancestors were most likely weedy ephemerals selected by nature to produce seed with the water available in a given season. Modern cultivated wheat demonstrates a large degree of plasticity in response to water shortage in terms of yield as well as in its morphology and phenology. Evidence for this comes from experiments using a line-source gradient to create different intensities of drought stress where linear relationships between water application and grain yield have been observed in the 1 to 5 t-ha -1 range ( Sayre et al., 1995 ). The problem of drought is most serious in terms of human welfare in the developing world, where wheat is cultivated under moisture stress on approximately 60 million hectares with national average yields ranging from 0.8 to 1.5 t-ha -1 , only a fraction of their yield potential ( Morris et al., 1991 ). Soil water deficits are also a chronic limitation to productivity in the developed world, in most of the Australian wheat-growing areas, in the midwestern areas of North America, throughout the Mediterranean region, and in drier than average years in Northern Europe.