It is a distressing truism that the human race during the last millennium has caused the exponential loss of plant genetic diversity throughout the world. This has had direct and negative economic, political and social consequences for the human race, which at the same time has failed to exploit fully the positive benefits that might result from conserving and exploiting the world's plant genetic resources. However, a strong movement to halt this loss of plant diversity and enhance its utilisation for the benefit of all humanity has been underway since the 1960's (Frankel and Bennett, 1970; Frankel and Hawkes, 1975). This initiative was taken up by the Convention on Biological Diversity (CBD, 1992) that not only expounds the need to conserve biological diversity but links conservation to exploitation and development for the benefit of all. Article 8 of the Convention clearly states the need to develop more effective and efficient guidelines to conserve biological diversity, while Article 9, along with the FAO International Undertaking on Plant Genetic Resources, promotes the adoption of a complementary approach to conservation that incorporates both ex situ and in situ techniques.

We live in critical times for the world's diversity of plants and animals. It is universally agreed that a catastrophic loss of biological diversity is occurring at the moment, with species, and equally importantly, genes being lost forever. However, the signing of the Biodiversity Convention at the Earth Summit in 1992 drew attention to the need to conserve and equitably utilize biological diversity for the benefit of all humankind. The convention placed emphasis on the need for a complementary approach to conservation that employed both ex situ and in situ techniques. Though much conservation and genetic research has focused on ex situ techniques, where the biological diversity is moved from its original location for safe storage, relatively little progress has been made in developing strategies appropriate for the genetic conservation of biological diversity in situ, in its native environment. The time is right for a definitive assessment of the principles required to conserve the genetic diversity of crops, their wild relatives and wild species within natural habitats. This book therefore provides a practical and theoretical introduction to the techniques of in situ conservation of plant genetic resources. It includes methodologies, case studies and in-depth discussion of on-farm and genetic reserve conservation, written by acknowledged international experts on the subject.

It is a distressing truism that the human race during the last millennium has caused the exponential loss of plant genetic diversity throughout the world. This has had direct and negative economic, political and social consequences for the human race, which at the same time has failed to exploit fully the positive benefits that might result from conserving and exploiting the world's plant genetic resources. However, a strong movement to halt this loss of plant diversity and enhance its utilisation for the benefit of all humanity has been underway since the 1960's (Frankel and Bennett, 1970; Frankel and Hawkes, 1975). This initiative was taken up by the Convention on Biological Diversity (CBD, 1992) that not only expounds the need to conserve biological diversity but links conservation to exploitation and development for the benefit of all. Article 8 of the Convention clearly states the need to develop more effective and efficient guidelines to conserve biological diversity, while Article 9, along with the FAO International Undertaking on Plant Genetic Resources, promotes the adoption of a complementary approach to conservation that incorporates both ex situ and in situ techniques.

The recent development of ideas on biodiversity conservation was already being considered almost three-quarters of a century ago for crop plants and the wild species related to them, by the Russian geneticist N. . Vavilov. He was undoubtedly the first scientist to understand the impor tance for humankind of conserving for utilization the genetic diversity of our ancient crop plants and their wild relatives from their centres of diversity. His collections showed various traits of adaptation to environ mental extremes and biotypes of crop diseases and pests which were unknown to most plant breeders in the first quarter of the twentieth cen tury. Later, in the 1940s-1960s scientists began to realize that the pool of genetic diversity known to Vavilov and his colleagues was beginning to disappear. Through the replacement of the old, primitive and highly diverse land races by uniform modem varieties created by plant breed ers, the crop gene pool was being eroded. The genetic diversity of wild species was equally being threatened by human activities: over-exploita tion, habitat destruction or fragmentation, competition resulting from the introduction of alien species or varieties, changes and intensification of land use, environmental pollution and possible climate change."