8. Molecular biology and genetic conservation programmes

Abstract

The techniques of molecular biology will become a standard part of germplasm conservation and exploitation. They are being used to gather information very rapidly about chromosome structure and genetic variation within the major crop species. Genetic maps with hundreds of DNA sequence markers covering the whole genome have already been created for some crops, such as maize, soybean, wheat and potato. Genetic variation is being revealed by the combined use of restriction endonucleases, fractionation of DNA fragments by electrophoresis and investigation of the size of specific allelic fragments. This kind of approach offers new opportunities to assess the extent of genetic variation among accessions in germplasm collections, thereby helping to decide which accessions are essentially duplicates and which should be maintained in a core collection. I recommend that germplasm banks will in the future also contain diagnostic DNA markers for characterizing and screening germplasm. When material from germplasm banks is used in crop plant breeding programmes to transfer specific traits into the crop, the availability of a complete set of molecular markers covering the entire genome makes it straightforward to discover which segments have been transferred and which are essential to maintain, so as to preserve the introduced trait. Germplasm banks are obviously a source of new genetic variation for the molecular geneticist as well as the plant breeder. The isolation of specific alleles determining self-incompatibility from Brassica oleracea accessions for subsequent introduction into oil seed rape is described as an example.