ABSTRACT
The use of agricultural biodiversity, and particularly crop biodiversity, is a necessary condition for crop improvement. In the absence of such diversity, it would be nearly impossible to develop the cultivars on which human societies rely to obtain food, feed, fibre, and fuel. The continuous development of new cultivars requires new genes or gene combinations conferring adaptation to changing environments, resistance to pathogens and pests, and tolerance to sometimes-contradictory stresses. Concurrently, these same cultivars have to satisfy consumer demand. A central question is to better understand the genetic diversity available to plant breeders for improvement, which is neither randomly nor equally distributed. Geographically, the genetic diversity of crops is generally concentrated in centres of diversity as observed by Vavilov and largely confirmed by subsequent studies. Identifying these centres of diversity is of paramount importance for the conservation and utilization of genetic diversity. Biologically, genetic diversity is distributed over several crossability gene pools, which are not equally accessible for transfer into the domesticated gene pool of crops. Similarly, the wild progenitors of our crops are generally considered to be more diverse than the crops themselves. To better understand these and other observations on the distribution and potential transfer of genetic diversity into improved cultivars, an evolutionary perspective is necessary because the distribution of diversity is the result of the evolutionary factors that have affected crops. In this chapter, I will focus on a series of issues that characterize crop biodiversity and have been affected by the process of domestication. Each section ends with a paragraph describing the consequences for conservation of crop diversity and utilization of this diversity in genetic improvement.
