Quality protein maize

Maize (Zea mays L.) plays a very important role in human and animal nutrition in a number of developed and developing countries, worldwide. Breeding for improved protein quality in maize began in the mid-1960s with the discovery of mutants, such as opaque-2, that produce enhanced levels of lysine and tryptophan, the two amino acids deficient in maize endosperm proteins. However, adverse pleiotropic effects imposed severe constraints on successful exploitation of these mutants. Interdisciplinary and concerted research efforts led to amelioration of the negative features of the opaque phenotype, and the rebirth of Quality Protein Maize' (QPM). QPM holds superior nutritional and biological value and is essentially interchangeable with normal maize in cultivation and kernel phenotype. This paper deals with the salient sequence of events associated with the development of QPM, the present understanding of genetic, biochemical and molecular bases of QPM, and the recent technological developments that could potentially enhance the efficiency of QPM breeding and the reach of QPM cultivars.