Research Progress Report 405
April, 1972

The Status of Development of Maize with Improved Protein Quality
L. F. Bauman and E. T. Mertz, Purdue University*

The protein in ordinary maize has relatively low nutritional value, and early attempts to improve its quality were both unsuccessful and generally regarded as impractical. However, in 1964, Mertz, Bates and Nelson reported that the opaque-2 gene improved protein quality markedly by increasing the content of the nutritionally-limiting amino acids lysine and tryptophan. Subsequently, they reported that the floury-2 gene was intermediate between normal and opaque-2 and had an increased methionine content.
Nutritional studies that followed confirmed the potential value of opaque-2 maize in helping to solve the world's human and animal nutritional needs. Soon, many maize breeding researchers throughout the world had initiated programs to develop opaque-2 hybrids or varieties.
Today, it is apparent that opaque-2 types must, to some degree, overcome their generally-observed deficiencies when compared with normal maize. These deficiencies include (1) lower yield, (2) greater susceptibility to ear rot, (3) harvest and storage
problems, (4) higher moisture content at harvest, and (5) soft starch, which is unacceptable for some areas or uses. To help solve such problems and achieve greater nutritional improvement, there is need for simple and accurate analytical methods for amino acid determination with relatively unsophisticated equipment.
Because of increased breeding work over the past several years and the time-lag associated with publication in scientific journals, it seems appropriate to present here a brief summary of where we are in the development of high quality protein maize.
This report discusses the analytical and nutritional aspects first, then breeding and genetics. Some of the information is preliminary, and some ideas or conclusions will no doubt be modified or changed as more information becomes available.

ANALYSIS
Total protein. Total protein is usually determined by the micro-Kjeldahl method.
In 1971, ten normal field corn samples submitted to Purdue for analysis varied from 7.3

* Departments of Agronomy and Biochemistry. Supported by the Agency for International Development under a contract entitled, "Inheritance and Improvement of Protein Quality and content in Maize. "

PURDUE UNIVERSITY • Agricultural Experiment Station • Lafayette, Indiana