GENETIC-RESOURCES IN BREEDING FOR ADAPTATION

A crop's ability to productively exploit its environment depends on ma ny adaptive features which are controlled by multiple genes, interacti ng among themselves and with the environment in complex ways. To promo te widespread adoption, breeders frequently seek to develop broad adap tation in their varieties, often through the use of genes having a lar ge effect on a single adaptive feature. Such genes may occur within th e crop, its wild relatives, or unrelated taxa. Genes for many adaptive features (e.g. temperature tolerance) may be found in extreme environ ments. Others (e.g. photoperiod insensitivity) may have evolved away f rom primary centres of origin. Well characterized and documented ex si tu germplasm collections aim to serve plant breeders' need for genes. Molecular marker and geographic information system (GIS) techniques ar e proving useful for locating and characterizing genetic diversity. Ne w techniques (e.g. core collections and electronic information systems ) are adding to the value of collections. Ex situ and in situ conserva tion of wild crop relatives are receiving increased attention. With al l organisms becoming a potential source of genes for breeding, in situ ecosystem conservation is assuming added significance. Farmers, parti cularly in diverse, marginal environments in developing countries, con tinue to breed landraces adapted to their specific circumstances. In a reas of high ecological diversity, a multitude of adaptive gene comple xes have been selected within small geographic areas. Conventional bre eding frequently neglects such farmers, and participatory methods base d on locally adapted diversity, coupled with appropriate technical and policy support, may prove more effective in meeting their needs. Such dynamic, on-farm conservation and management systems would also enabl e genetic diversity to continue to evolve as a resource for convention al breeding. For genetic resources to remain a foundation for future s ustainable agricultural development, complementary conservation and br eeding strategies are needed.