Effect of Hybrid Breeding on Genetic Diversity in Maize

The extent and quality of maize (Zea mays L.) germplasm diversity that is widely cultivated in the USA reflects usage by farmers and breeders in this and previous centuries. The hybrid breeding and production method is conceptually simple and highly effective and hybrids provide a natural form of intellectual property protection that early on helped to attract privately funded commercial investments. Plant breeders use and release genetic diversity in time. This chapter examines changes in diversity among a set of inbreds that formed parents of hybrids that were widely used in the U.S. Corn Belt during each decade from 1930 to the present. It also examines genetic diversity using pedigree and isozymic data for 71 inbreds that formed parents of 44 important widely used U.S. Corn Belt hybrids released by Pioneer Hi-Bred International, Inc. since 1930.