THE NATURE OF PLANT GENETIC RESOURCES

In this report the terms variety and cultivar are used interchangeably to mean cultivated forms within a species. The cultivated plant materials that are conserved are of five general kinds: landrace, folk, or primitive varieties; obsolete varieties; commercial varieties or cultivars; plant breeders' lines; and genetic stocks.

Landrace, folk, or primitive varieties are local varieties developed by indigenous farmers in traditional agricultural systems, over hundreds of years. By modern standards such varieties are often highly variable. Landrace cultivars have generally been replace by modern scientifically bred cultivars in most crops but may still be locally important in some farming systems.

Obsolete varieties are varieties developed since the advent of scientific agriculture in the late nineteenth century and that are no longer cultivated. Although no longer grown commercially, such varieties are usually maintained in collections for use in current and future breeding programs.

Commercial varieties or cultivars are elite high-yielding lines in current use, developed by scientific plant breeding for modern intensive agriculture. The average life of modern varieties is relatively short (5 to 10 years) when they are replaced by more recent products of breeding programs.

Plant breeders lines are as-yet unreleased lines, mutations, or parents of hybrids maintained by breeders as part of their working stocks. Breeders usually develop and carry many lines in their programs, of which only a very small number are ever released into commercial production.

Genetic stocks are genetically characterized lines of a species principally used in genetics and plant breeding research. They rarely have any commercial value but are nevertheless an important germplasm resource because of their usefulness in basic and applied research. Genetic stocks can be conveniently divided into the following three classes: