The centres of genetic diversity of all major food crops lie within countries of the tropics. The IARC's pass large quantities of crop varieies from the south to the north's breeders. Loss of agricultural biodiversity Thousands of years of evolution resulted in a massive diversity of landraces adapted to differing localised growing conditions. This diversity is rapidly being lost, a process which began in the nineteenth century, and has accelerated rapidly in the last 30 years. Static Seeds Modern commercial varieties are static, that is, bred and sold to farmers each year, rather than being replanted from farm saved seed.
Replanted seed is dynamic, co-evolving with an adaption to the local ecosystem.
There is a lack of commercial incentive for breeders to develop new open pollinated varieties. Such varieties could be replanted from saved seed allowing localised adaptations. . In landraces hundreds of genes may be involved in conferring resistance against a pathogen. Plant and pathogen co-evolve in the local environment, resistance is thereby dynamic and not stabilised. Modern plant varieties often rely on the same single gene to confer resistance.