Physiological Traits in Temperate Cereals to Breed New Cultivars in Water–Scarce Environments.

For most water-limited crops water-use efficiency (WUE) is a more desirable term than drought resistance. Unlike drought resistance, it has measurable units and therefore a benchmark can be set as a goal for researchers to exceed and farmers to achieve. For dryland temperate cereals in Australia, the WUE for biomass production is around 60 kg ha^-1mm^-1 whereas for grain the value is around 22 kg ha^-1mm^-1.

From an understanding of the physiology of temperate cereals and the environments in which they are grown, numerous physiological traits have been identified that, if altered genetically, should result in improved yield gains in water-limited environments and therefore an improved WUE for grain production. Examples will be given for three physiological traits in wheat which have resulted in new cultivars or novel germplasm for use in breeding wheat in water-limited environments. These are as follows: (i) improved crop establishment and vigour to increase crop water use and biomass, (ii) improved transpiration efficiency to increase CO₂ fixed per unit water transpired, (iii) altered xylem vessel anatomy in the seminal roots to regulate water use during grain filling so as to increase grain production.