Research & Development

Initiative to overcome challenges for quality protein maize output

Maize occupies an important position in the world economy and trade as a food, feed, and industrial grain crop. Several million people in the developing world consume maize as an important staple food and derive their protein and energy requirements from it. In Bangladesh, acreage of Maize production has grown over the years and is used by the processing industry as well as feed for the poultry industry. This was revealed in an article by Prof. Lutfur Rahman, Advisor, ACI Agribusiness & Head of Advanced, Seed Research & Biotech Centre, at “BioLife” newsletter released by ACI Agribusinesses on Thursday.

The poor nutritional value of maize grain is well known, and the need to improvement has been recognised for a long time. Most of the protein in a mature maize kernel is contained in the endosperm and the germ. However, because the endosperm constitutes the bulk of the grain, contributing as much as 80 percent of the total kernel protein, any major improvements for quality protein must target the endosperm. Serious efforts to improve the nutritional quality of maize endosperm protein began in the mid-1960s, where the biochemical effects of two mutant alleles, opaque-2 (O2) and floury-2 (fl2), shone light on the path towards improving the quality of maize endosperm protein.

These mutants altered the amino acid profile and composition of maize endosperm protein, which resulted in a twofold increase in the levels of lysine and tryptophan, the article revealed. Unfortunately, the mutations adversely affected agronomic performance, including yield, and consumer aspects, particularly kernel characteristics. The lower yield resulted from reduced accumulation of dry matter. The appearance of the kernel altered to a soft, chalky phenotype that is unattractive to maize growers in the developing countries. Physiological drying was also affected. The germplasm became vulnerable to ear rot, resulting in high pest and infestation rates in stored grain. Researchers in CIMMYT approached the problem in another way, by emphasising the development of market-competitive Quality Protein Maize (QPM) genotypes with quality protein as a bonus. To achieve this goal, a conservative approach was used initially with respect to biochemical characteristics. Since the opaque gene boosts lysine levels by twofold, efforts were devoted to maintenance rather than further enhancing the levels of lysine at protein levels of 9 percent to 10 percent in the whole grain. This greatly facilitated breeding agronomically superior QPM genotypes while focusing on critical and key consumer characteristic problems.

The next step in the breeding process was the development of QPM donour stocks with modified kernel phenotype and good protein quality. This also turned out to be a time-consuming and tedious process, but the incidence of ear rot in QPM materials has been gradually reduced. Practically, all QPM research programmes in several countries are now using this approach, based on the combined use of the O2 gene and genetic modifiers. Hybrid development efforts in QPM have become increasingly important, as is evident from recent experience. It is expected that many countries now involved in the QPM network will be able to select one or two of the most promising hybrids for release in their respective countries.