ABSTRACT
Maize exhibits great genetic diversity in plant, ear, and seed characteristics, in resistance to diseases and insect pests, and in tolerance to various environmental stresses. The wild ancestors of maize evolved through natural selection caused by environmental stresses and by natural mutations and recombinations until its domestication by man 6,000 to 8,000 years ago. The network of germplasm banks that holds seed samples of most of the primitive cultivars and old landraces and varieties that have been collected in the past 50 years is an important source of maize genetic diversity. Publicly funded and privately funded maize research operations around the world are collectively improving a vast array of maize germplasm complexes. Individual scientists and maize research organizations can obtain samples of maize genetic resources from other national programs and from international programs and germplasm banks. Several publicly funded international and regional maize breeding programs operate in the Third World.
