Quality protein maize

Maize (Zea mays L.) plays a very important role in human and animal nutriti on in a number of developed and developing countries, worldwide. Breeding f or improved protein quality in maize began in the mid-1960s with the discov ery of mutants, such as opaque-2, that produce enhanced levels of lysine an d tryptophan, the two amino acids deficient in maize endosperm proteins. Ho wever, adverse pleiotropic effects imposed severe constraints on successful exploitation of these mutants. Interdisciplinary and concerted research ef forts led to amelioration of the negative features of the opaque phenotype, and the rebirth of 'Quality Protein Maize' (QPM). QPM holds superior nutri tional and biological value and is essentially interchangeable with normal maize in cultivation and kernel phenotype. This paper deals with the salien t sequence of events associated with the development of QPM, the present un derstanding of genetic, biochemical and molecular bases of QPM, and the rec ent technological developments that could potentially enhance the efficienc y of QPM breeding and the reach of QPM cultivars.