13 Herons Quay, Sandside, Milnthorpe, Cumbria LA7 7HN, UK

The genetic diversity of economic plants, including crop plants, wild relatives of crops, forages and forest trees, is the most valuable part of biodiversity and of paramount importance for future world food and timber production [1, 2]. During the past 15 years, biodiversity has become a major world issue linked strongly to increasing concerns about environmental degradation [3]. The Convention on Biological Diversity, and the associated Agenda 21 process, have even more sharply focused global attention on the need to conserve economic plants for future use. The genetic vulnerability of economic plants to disease epidemics caused by dynamic pathogen populations is a major justification for continued support for the conservation of crops, their wild relatives, and forest trees.

This symposium on the Biodiversity and Conservation of Economic Plants for Disease Resistance has a broad coverage befitting its global perspective. Common and important issues, however, link all of the papers. The two keynote papers will emphasize the need to understand host-pathogen systems in developing appropriate conservation strategies for crop plants and their wild relatives for disease resistance. The importance of understanding disease processes in the development of strategies for forest conservation will be discussed in the third paper. That landraces of common beans in the southern highlands of Tanzania are a rich source of (often unique) disease-resistance genes worthy of conservation will be presented by the fourth paper as a model for similar studies in areas still rich in landrace biodiversity. As seed movement continues to be a vital process in the wider utilization of the biodiversity of economic plants, the final paper will look at the role of germplasm health in the conservation of economic plants.

Improved knowledge of the identity and global distribution of major diseases is essential for assessing their effects on the biodiversity of economic plants and to aid the development of appropriate conservation strategies [4]. The advantages and disadvantages of the many available conservation strategies for crop plants will be discussed in this paper. Pathogens can cause major losses to economic plants, but they also play an important role in creating and fostering diversity in agroecosystems and forest systems [5]. It is ironic that the biodiversity of an ecosystem may depend on the presence of a healthy, dynamic population of pathogens [6].

1. Wood D, Lenné JM, 1997. Biodiversity and Conservation 6, 109-129.
2. Lenné JM, Wood D, 1991. Annual Review of Phytopathology 29, 35-68.
3. Frankel OH, Brown AHD, Burdon JJ, 1995. The Conservation of Plant Biodiversity. Cambridge University Press, UK.
4. Boyle T, Lenné JM, 1996. An International Workshop on Biodiversity Information, Imperial College, London. CAB International, Wallingford, UK, pp. 31-54.
5. Gillet JB, 1962. Associated Publications 4, 37-46.
6. Wills C, 1996. New Scientist 2022, 31-36.