An increasing body of evidence indicates that the engineering of root system architecture has the potential to support a second green revolution targeting crop performance under suboptimal water and nutrient supply. This chapter summarizes the recent evolution of this field and underlines important challenges to be addressed in a near future. Due to its importance for many plant functions, root system architecture has become a topic on its own in many research communities. Impressive progress has been achieved in our understanding of the developmental processes underlying root system architecture, and, in parallel, a large number of QTL studies have been reported for root architectural traits. We discuss several limitations that impede the exploitation of the genetic variability and available functional information on root system architecture in conventional breeding.
