| Torbert Rocheford
Associate Professor of Plant Genetics
Department of Crop Sciences
For over a hundred years, there has been interest in modifying maize kernel composition to make the grain more suitable and valuable for specific end usages. Despite breeding research that showed levels of protein and oil in maize grain could be modified; mapping of chromosomal regions that control levels of starch, protein, and oil; and development of transgenics (genetically modified organisms [GMOs]) that alter kernel composition, there has not been substantial planting of value-added maize hybrids in the Midwest.
There has been success with some very specialized value-added hybrids, such as waxy and high amylose corn grain, but these represent a very small percentage of corn acreage. For dry milling, contracts can be arranged with a small premium paid for grain of preferred hybrids that is harvested and handled according to specifications. However, dry milling represents only 5 to 10 percent of the utilization of corn. High oil corn (HOC) hybrids for swine and poultry feeding efficiencies showed promise in the mid 1990s. However, a drop in the price of deep fryer waste fat used as a feed supplement for calories undermined the economics of the use of HOC by swine and poultry feeders. Currently, fewer than 300,000 acres are grown to HOC in the Midwest.
Figure 1. Variation in grain composition
and structure in response to 48 cycles
of breeding selection for levels of protein and levels of oil.
Since 70 percent or more of corn produced in Midwest is fed to animals, there is a need for value-added hybrids that cater to the animal feed market. Only when value-added hybrids are developed and economically beneficial to the animal feeding industry will there be a large impact on corn production in Illinois.
Examples of possible value-added corn grain other than HOC include higher levels of protein for feeding beef and dairy cattle; modification of fatty acid profiles for improvement of meat quality; higher levels of antioxidant vitamins, such as A and E, to provide nutritional and health advantages; and lower levels of phytate to reduce phosphorous in manure. One strategy is that a number of grain composition attributes may be modified slightly to collectively provide an overall improved feed value grain. Perhaps one grain composition could be developed for ruminants and another for monogastric animals. This type of goal may be more realistic, as pushing a single attribute to extreme levels, as is the case for HOC, may make it difficult to maintain yield and requires that one attribute bears the entire cost of identity preservation.
The success of value-added hybrids faces a number of challenges and issues. For example, there are costs to identity preserving grain. Frequently, a yield reduction is associated with grain composition modifications. Some yield reduction is due to linkage drag, bringing along in selection less-than-ideal-genes for agronomic performance. Recent developments in molecular marker mapping and transformation should help to reduce the grain yield reduction problem. Molecular marker assisted selection (MAS) could reduce linkage drag and does not involve the issue of GMOs. However, more genes may need to be introgressed with MAS, and they may not have as large an effect as a transgene. The transgenes involve GMOs, but it may be that only one transgene could be introduced to bring about a change in grain composition that provides value. Some combination of MAS and selective use of transgenes may be a viable strategy.
High-starch grain for efficiency in ethanol production is also a possible value-added hybrid. An advantage of high-starch grain is the absence of a negative association with grain yield. However, it may be difficult to receive a premium for higher starch; rather, the value may need to be captured through grower cooperatives that make ethanol. The downside of ethanol production is that various unforeseen market and political factors can bear on the economics.
College of Agriculture, Consumer and Environmental Sciences
University of Illinois Extension
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