Phenotyping for abiotic stress tolerance in maize: drought stress. A field manual

Abstract

In agriculture, the term drought refers to a meteorological condition in which the amount of water available through rainfall and/or irrigation is insufficient to meet the crop needs for optimal growth and development; this eventually affects overall productivity. Rainfed maize crops grown during the rainy summer season in the tropics occasionally face extreme weather conditions. These extreme weather conditions translate into various abiotic stresses, such as drought, which constitutes one of the key abiotic constraints for maize production in many parts of the world, particularly the tropics. The erratic rain distribution pattern in the tropics due to climate variability occasionally causes prolonged dry spells at different crop growth stages; this has been identified as one of the major factors responsible for year-toyear fluctuations of rainfed maize. Crop breeding programs using conventional and/or molecular breeding approaches rely heavily on high-quality phenotypic data generated by evaluating genotypes in different environmental conditions, such as drought. In this manual, the traits of interest for phenotyping are those that mitigate yield losses rather than those involved in the survival or escape of plants exposed to drought stress. This manual is targeted at maize breeders and field technicians in tropical environments who are working on improving maize tolerance to drought stress.