Integration of Conservation Strategies of Plant Genetic ... - Genres

Integrated approaches to ex-situ and in-situ conservation
J.J. HARDON, T.J.L. VAN HINTUM 1
Introduction
Biodiversity is the main strategy of survival of natural ecosystems and species within ecosystems.
Through processes of inter-specific competition and at the species level migration, mutation,
recombination, and selection dynamic equilibria are established with existing natural resources,
while maintaining genetic options for plasticity and change in response to diverse and sometimes
changing environments.
Traditional farming systems were and are based on similar concepts. Through mixtures of crops
and genetic variation within crops, yield security is a major objective. This is essentially achieved
through natural balances between crops and both biotic and abiotic stress factors at least partly
by maintaining appropriate levels of genetic diversity within and between crops. This process has
led over time to a multitude of landraces, resulting from both human and natural selection. These
landraces provide adaptation to a wide range of different environmental conditions. In these
cropping systems genetic diversity is naturally maintained in an evolutionary manner. Areas where
traditional agriculture is practised are therefor important reservoirs of still existing and evolving
genetic diversity.
The importance of landraces as a source of genetic diversity to plantbreeding is obvious. However
it should be realized that the objective of such cropping systems is not conservation per se. These
systems employ genetic diversity as a strategy for yield security and thereby maintain genetic
diversity. However there generally is a constant turn-over of different landraces, often obtained
by exchange within and between farming communities, combined with introgression and selection.
As agricultural systems change, so does genetic diversity within such systems. And agricultural
systems are changing due to cultural changes as a result of economical and social development,
but also due to environmental changes, inflow of modern and exotic varieties, and due to
calamities like droughts, floods or wars. Traditional agriculture is also increasingly being affected
by modern agricultural practices based on the use of external inputs to cope with rising population
pressure in many areas. Hence from the point of view of conservation, even traditional farming
systems are not secure, more so since changes in such systems are difficult to monitor. The
obvious conclusion is, that ex-situ conservation is essential as a back-up system to in-situ
conservation.
The basic changes affected by modern agriculture are, that rather than adapting crops and crop
complexes to different environments, the production environments are adapted to the
requirements of specific crops. Abiotic stress factors are dealt with by soil management, fertilizers,
1
Authors' address:
CPRO-DLO Centre for Genetic Resources (CGN)
P.O.Box 16
6700 AA Wageningen
The Netherlands.