Progress in the genetic understanding of plant iron and zinc nutrition

In this review, we describe the need and progress to improve the iron and zinc contents in crop plants by genetic means. To achieve this goal either by transgenic approaches or classical breeding, knowledge about the physiological and molecular mechanisms of mineral uptake and mineral homeostasis will be very helpful. The progress in our understanding of the molecular processes and genes is described, and the use of the identified genes by transgenic approaches is illustrated. Genetic mapping of the existing variation will allow marker-assisted breeding to exploit the available natural variation in crop plants. For this application, ultimately the knowledge of the genes underlying this quantitative variation, called quantitative trait loci (QTL), will be required. It is expected that research in this field in the model species Arabidopsis thaliana, where the molecular tools are available, might help in the identification of the allelic variation at QTL