Conventional breeding approaches for drought-prone environments: an overview

In agricultural systems, plant productivity in strongly influenced by environmental conditions and yield potentialin crops is limited due to different abiotic stresses. Among them, drought is the single most important factorlimiting crop yield. Breeding for drought resistance is required for both mild and severe stress conditions. Thisimplies a need for a better characterization of the biodiversity available for drought and a deeper comprehensionof the physiological mechanisms, which are crucial to assure yield when drought occurs. Traits related to droughtresistance and to high yield potential should be favored in crop breeding programs. The diversity for yieldperformance has been evaluated under rainfed conditions and with supplementary irrigation in a set of barleycultivars in a Mediterranean environment subjected to mild drought. The results indicate that the ideotype forthese environments should have minimal GE interaction, so that genotypes with both high yield potential andstable yield would be selected. Recent developments in plant molecular biology have allowed to identify manygenes involved in plant adaptation to drought. New transcription factors involved in the drought response hasbeen identified indicating that they may play a regulatory role in drought stress response. To locate the geneticdeterminants for drought adaptation, a doubled-haploid barley map population has been developed with thepurpose of identifying the genomic regions responsible for drought adaptation. A QTL analysis in terms of yieldin drought, yield “stability” and yield reduction was performed. Several QTLs were identified on differentlocations of the barley genome. The most interesting locus, responsible for both yield in drought and yieldstability, has been mapped on chromosome 6H. The construction of a functional map to identify candidategenes for drought tolerance has been used