Choices of Diverse Maize Breeding Materials: Accessions, Synthetics, Hybrids or Inbreds.

The first question is usually not which source is "best," but rather how does one legally acquire and use any of them intelligently, without excessive or uncertain restrictions. Our germplasm systems were built on the basis of free exchange of accessions; inbreds (restricted or otherwise) have become a concern only recently ‑ mostly as a result of the death of real public maize breeding programs in the US and the recent availability of ex‑PVP inbreds. Hybrids have been an enigma to germplasm banks since the first germplasm banks were founded. The result: many historically important inbreds and most hybrids are unavailable from any source for any reason. While synthetics have sometimes suffered similar fates, most did find germplasm‑bank homes. Few of these problems originated with intellectual property rights restrictions, but such "rights" have had highly detrimental effects on germplasm exchange and deployment. When today's maize breeders use exotic germplasm - and few do - they are likely to use modern inbreds and hybrids as source materials, while geneticists are often more interested in accessions or synthetics, with various goals related to "allele mining," for applied or purely research purposes. Ecology generally restricts germplasm utility, except in cases of fishing for single genes. Except for programs such as GEM and the NC breeding program, few attempts at  base‑broadening in maize exist in the US. Private company approaches to base‑broadening largely consist of recycling materials based on US germplasm that has been used in overseas production.