Introduction

Based on the concept of gene centres, developed by N.I. Vavilov in the 1920s, Ethiopia represents one of the eight centres in the world where crop plant diversity is strikingly high and where some of the crops concerned became domesticated. The concepts of centres of origin and diversity have evolved considerably since Vavilov's days as shown for instance by Harlan (1975) and by Hawkes (1983). Nevertheless, some of the basic characteristics which apply to the majority of the world's gene centres generally hold also for Ethiopia though varying from one crop to another. The highly dissected highland of Ethiopia includes natural barriers formed by mountains (up to approximately 5000 m above sea level) or ravines (sometimes more than 1300 m deep) where crop plants would have evolved in isolation under primitive agricultural conditions. To this must be added the ancient and very diverse cultural history of its people, thus providing many thousands of years of artificial selection within the landrace populations since the early days of agriculture. However, several crops which possess an extremely high diversity in Ethiopia do not follow all the basic principles required for a centre of origin in a given crop. In the case of barley, for instance, no wild relatives are known within the country nor is there any archaeological evidence to indicate early cultivation or domestication.