Quality Protein Maize: Overcoming the Hurdles

SUMMARY

Quality Protein Maize (QPM), a nutritionally enhanced maize, was developed by researchers from CIMMYT using too genetic systems–opaque-2 and genetic modifiers. The use of these two genetic systems overcame the highly complex problems that were inherent in the original soft endosperm opaques. This review describes the ever-evolving breeding options and strategies for the development of QPM with examples from the CIMMYT maize program, where much of the research and practical breeding work has been done. The soft endosperm opaque-2 materials developed earlier had poor agronomic performances and lacked producer and consumer acceptance. To overcome these constraints, subsequent research explored various options, with and without high lysine mutants. Like other institutions, CIMMYT researchers tried and critically examined the merits and demerits of different strategies. Of all the strategies available, the selection for modified kernels in which CIMMYT scientists had gained information, experience, and confidence seemed viable. To implement this strategy, modified opaque-2 donor stocks were built and were subsequently used for expanding the QPM developmental efforts. A large volume of QPM germplasm was developed using different breeding options, which were later merged and reorganized into a fixed number of pools and populations to permit working in homozygous opaque-2 genetic backgrounds. The development of QPM hybrids was the next turning point in the mid-80s. During the QPM developmental process, serious problems inherent in the opaques were circumvented and since then, rapid progress has been made. There is a renewed interest in QPM and several countries have recently released QPM varieties and hybrids. To further accelerate the QPM developmental process, to enhance its popularity amongst nations and its farmers, and to meet future challenges, innovative ideas and the tools of biotechnology will be needed.

KEYWORDS:

• Quality protein maize
• opaque-2 gene
• modified kernels
• breeding options
• strategies
• soft opaques
• tryptophan
• lysine