Euphytica 10 (1961): 152-156
BREEDING FOR OIL AND PROTEIN CONTENT IN MAIZE
R. W. JUGENHEIMER
University of Illinois, Urbana, Illinois, U.S.A.
With 2 figures
Received 4 Febr. 1961
Three newly-developed maize hybrids, Illinois 6021, Illinois 6052, and Illinois 6001 yield about 30% more oil, and 10% more protein than present commercial hybrids. In addition they are similar to standard hybrids in other agronomic traits.
In order to make the results of high-oil research available to the public, the University of Illinois has released nine inbred lines with high-oil or protein content.
Breeding for high yields has been very effective. Most of the outstanding maize hybrids grown in Illinois 10 years ago have been replaced by better ones. New hybrids give greater yields, stand much better, and are more resistant to heavy plant populations, diseases and insects.
We have such an abundance of maize in the United States that I believe breeders should be devoting more attention to types of maize for special purposes. Some effort has been spent along these lines; however, quality has been given far less consideration than has quantity of grain.
Waxy maize was developed to meet a critical need for a tapiocalike starch in World War II. Waxy maize contains 100 percent. amylopectin, the branched molecular form of starch.
Efforts are being made to develop a high amylose maize. Such a type would be very useful for plastics, cellophane and films. Several hybrids, containing at least 50 percent. amylose are being grown on an experimental basis.
Sweet, stalked strains may be more valuable for silage than present strains. Zein is being used to produce synthetic fibers for special fabrics.
New maize hybrids, developed in the Agronomy Department of the University of Illinois, yield about 30 percent. more oil and 10 percent. more protein than present commercial hybrids. In addition, they are similar to standard hybrids in grain yield, standability, and other agronomic traits. Nation-wide use of adapted high-oil hybrids would produce almost as much oil as is now obtained from butterfat, soybeans, cotton and flax.
Comparisons in central Illinois of the new hybrids Illinois 6021 and Illinois 6052 with U.S. 13, a standard hybrid, are shown in Table 1.
TABLE 1. PERFORMANCE OF OIL HYBRIDS
|Oil in grain, %||6.39||6.27||4.77|
|Percent. of U.S.13||134||131||100|
|Oil per acre, lb||393||390||311
|Protein in grain, %||11.06||11.42||10.24|
|Percent. of U.S.13||108||112||100|
|Protein per acre, lb||679||707||665
|Acre yield, bu||110||112||116|
|Moisture in grain, %||20||22||20|
|Erect plants, %||83||81||86|
MAIZE OIL HAS MANY USES
Maize oil is high in energy value for livestock feeding and is a valuable by-product of the starch industry. Most of the oil is in the germ of the kernel. The high-oil hybrids have a high proportion of germ to endosperm. Consequently, they should benefit both the starch industry and livestock feeders.
High-oil is a more efficient feed for livestock than normal field maize. Oil is a highcalorie livestock feed ingredient. One pound of oil supplies about 4,100 calories; it has about 2 1/4 times the energy of a pound of starch. In feeding trials at the University of Illinois, market lambs averaged faster gains on 6 to 7 percent. less feed when they were fed the special high-oil maize. Grain from the new hybrids also contains more high-quality germ protein than common hybrids furnish. Larger quantities of this nutritionally balanced protein are expected to mean that less expensive protein supplement will be needed to balance future livestock rations.
The nutritional properties of refined maize oil make it a valuable food. It is easy to digest and contains some of the rare oily compounds now classified, like the vitamins, among the protective foods. Research on saturated and unsaturated fats, and their influence upon cholesterol, have brought maize oil into a favorable dietary spotlight. Maize oil can be used in bakery products, cooking oil, oleomargerine, mayonnaise, salad dressing, pharmaceuticals, shortening, and soups. Non-food uses of refined maize oil include ammunition, chemicals, paint, varnish, rubber substitutes, rust preventive, soap, soluble oil, and textiles. Because oil is not assimilated so quickly as carbohydrates and proteins, it provides energy to the body over an extended period. Certain unsaturated fatty acids in oil are essential for growth, pregnancy, and lactation and for the maintenance of normal skin, liver and kidney functions.
USES OF PROTEIN
Protein is an expensive but necessary constituent of both food and feed. Its quality is fully as important as its quantity. The maize kernel contains two main types of protein. One type, found in the endosperm, is primarily zein. Zein is deficient in tryptophane and lysine, which are essential for animal nutrition. However, zein has been used to produce "Vicara", a fiber that is used in blends with wool. The other type of protein, which is found in both endosperm and germ, contains both tryptophane and lysine and is biologically balanced. Maize breeders would like to increase the percentage of these amino acids in the endosperm protein. The alternative is to add them to the diet from other sources, such as soybean meal.
DEVELOPMENT OF HIGH-OIL AND HIGH-PROTEIN MAIZE HYBRIDS
Selection for high-oil and protein content has been in progress at the University of Illinois for more than 60 years. Oil and protein contents have been increased to levels almost twice as high as those of the original grain. However, the yields of these open-pollinated strains are too low to be practical for commercial planting (Figure 1). The development of the new high-oil hybrids took more than 10 years. Standard inbred lines, contributing high yield and standability, were crossed to Illinois high-oil and Illinois high protein strains; then the hybrids were back-crossed to both parents. Since most of the oil is in the germ, ears bearing kernels with large germs were selected in each generation. Selection for high protein content was carried on by retaining ears with hard, flinty kernels, a property closely related to high protein content.
The next step was to evaluate the inbred lines in hybrid combinations. This evaluation required several years of careful tests and chemical analyses. The better-performing inbred lines were then combined in many double crosses which were tested for several years. Illinois 6021, Illinois 6052, and Illinois 6001 are the better-performing survivors of these double-cross hybrids. It is believed that still more promising material will soon be available.
The increase of the parental inbred lines took place in 1957. Foundation single-cross seed for the production of these hybrids has been available from the Illinois Seed Producer's Association, Champaign, Illinois, U.S.A., since 1958. Double-cross seed for farm use has been available since the 1959 growing season (Figure 2).
In order to make the results of high-oil research available to the public, the University of Illinois has released the following inbred lines with high-oil or protein content: R 75, R 76, R 78, R 84, R 158, R 182, R 193, R 196, and R 197. Hand-pollinated seed of these and other released Illinois inbred lines usually is available for a fee in packets containing 25-100 kernels. Inquiries may be addressed to the Agronomy Department, University of Illinois, Urbana, Illinois, U.S.A.