MODELS FOR ACTIVATION OF PLANT GENETIC-RESOURCES FOR CROP BREEDING PROGRAMS

Although plant breeders recognize that their working germplasm is constricted, most make little use of the extensive genetic variability in gene banks and other collections. This is because breeders continue to make reasonable progress in most crop species and broadening the activated genetic base generally will dilute agronomic performance. Yet new germplasm can (1) raise the genetic ceiling on improvement, (2) decrease vulnerability to biotic and abiotic stresses, and (3) add new developmental pathways and ecological adaptations. Two breeding systems - HOPE for corn and RIPE for barley - are described which can significantly broaden the genetic base deployed in breeding programs while still producing lines and cultivars with commercial potential. The Hierarchical Open-ended Population Enrichment (HOPE) breeding system consists of two complementary sets, each of four gene pools arranged in a hierarchy based on agronomic performance. Introductions are added continually and desirable genes and gene complexes can routinely move upward in the hierarchy. Increasingly stringent selection procedures at each higher level of the hierarchy shape the extensive variability at the lower levels into the quality germplasm at the Elite level, which serves as the source of inbred lines. The Recurrent Introgressive Population Enrichment (RIPE) breeding system for barley employs male sterile facilitated recurrent selection to progressively introgress new genes and gene complexes into an Elite population which serves as the source of potential new cultivars.