Abstract
The paper describes the sequence of breeding stages that led to the development of acceptable quality protein maize (QPM) germplasm at the Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT). Initial emphasis was on the development of soft opaque-2 (o2) maize varieties, but these had undesirable consumer characteristics, among other problems. Research then shifted to the development of hard-textured QPM germplasm. Several breeding approaches were explored and tested in early 1970. The combined use of two genetic systems involving the o2 gene and the genetic modifiers of the o2 locus appeared to be the most promising approach. This strategy first involved the development of donor stocks from which a large volume of QPM germplasm was generated through a modified backcross programme and various recurrent selection procedures. Later merging and reorganization of QPM germplasm was undertaken, which resulted in a definite number of QPM populations and pools to meet germplasm needs for various agroclimatic conditions. This was a turning point in the breeding strategy that permitted work with homozygous o2 genetic backgrounds. In the mid-1980s, a hybrid development initiative was started. Basic information on combining ability and heterotic pattern(s) of QPM germplasm was generated. Later emphasis was shifted to development efforts for inbred and hybrid QPM. Several superior QPM germplasm products are now spreading commercially in several developing countries of Asia, Central and South America, and Africa