Resumen
Barley is currently the most cultivated crop in Spain with about three million ha. Its importance stems from its adaptation to areas with poor soil conditions and water stress. The aim of this work is to describe the historical evolution of barley types and varieties of barley grown by farmers in Spain. A historical review has been performed consulting articles and books on history, archeology, and agronomy related with the issue. Different web sites and articles have been also consulted about the current varietal state of barley in Spain. Another important information source came from the CRF (Center of Plant Genetic Resources) of Spain where a great collection of landraces is preserved. First barleys came to Spain about 7600 years BP by three sites: north, east and south. The south entrance is special, because those genotypes could came from a secondary domestication center of barley located in Morocco. Crop spread throughout the country and its cultivation were reported by Romans, Arabs, and Christians after the ?Reconquista? (re-conquest). At the beginning of the nineteenth century the first attempt of classification was carried out. Until the 1940s, most barley acreage was sown with ancient landraces, but from that period onward a steady varietal renovation took place up to the present. The history of barley types and varieties in Spain is rich, and a great set of landraces is preserved in seed banks. These landraces may contain genes for resistance and tolerance to biotic and abiotic stresses.