University of Massachusetts

Supermaize research
--Galinat, WC

The U.S. Cornbelt maize as well as European maize is undergoing an adaptation in plant and ear architecture that allows the plant to grow and produce a good ear despite the stress of extreme crowding. During the last 20 years, the concentration rate and drought tolerance have increased dramatically together with a decrease in row width to about 15 inches. Neither man nor horse can now enter a field of mature maize but there is no problem with the combine harvester. The goal of this practice is to saturate the field with tightly packed maize plants in order that virtually all of the solar radiation is intercepted by the maize and its energy is chemically fixed by photosynthesis and translocated into storage as carbohydrates and other foods in grain on ears. The plant and ear should be designed for maximum energy storage and minimum energy wastage to barren ears, excess vegetation, weeds, insects and diseases. To achieve this goal, the necessary genes must be assembled by recombination. Shading from tassels should be reduced in the farmers' crop field and yet the seedsman must have adequate pollen production by the male rows to fertilize production of hybrid seed in crossing fields with three or four times as many female rows as male rows. Ideally, the solar energy intercepting canopy should be close to and just above the storage facility, the ear with kernels. The leaves from adjacent plants should not significantly overlap and shade each other in a lethal competition for solar energy.

All of these problems may be resolved to various degrees with the assemblage of a family of yield enhancing genes. The ultimate construction will be a supermaize of the future (Table 1).

Table 1. A family of genes leading to supermaize.
Trait name Gene Problem solved
unbranched tassel ub Reduces shading of leaves by tassels
tassel ramosa ra-D Restores good pollen production to male rows in crossing field hybrid seed production
eye stabber es Upright short leaves for tolerance to crowding
umbrella umb Radial whorl of leaves, the solar panel, above ear
broad leaf Bl Wider leaves intercept more solar energy
long ear Le Larger energy storage facility

The changes in the architecture of the maize plant suggested by use of the genes listed above are going to work as an extension of the evolutionary trends already present in Cornbelt maize for adaptation to increasingly higher density plant populations. They build upon the present background foundations by enhancing the elite changes already established. They do the same thing - only better. Their use is based on common knowledge of how the plant works and how it is leading toward a supermaize for the future (Fig. 1).

Figure 1. Three forward looking farmer-breeders from three different ages.

1-1, The first Americans had gardens of selected teosinte.

-2, Most secondary branches were condensed into fascicles of ears.

-3, Apical dominance of the uppermost ear with recombination of four ranking and paired female spikelets concentrated the energy into an eight-rowed ear of maize.

-4, Year 1620. The Northern Flints received by the Pilgrims from the American Indians.

-5,-6, Years 1950 to 1990. The modern farmer with hybrid maize, tractor and harvesting machines increases the density of plant populations.

-7, Supermaize of the future.

The making of supermaize, like the wisdom of evolution along a pathway toward adaptation to a certain environment, depends on the recombination of genes which cooperatively serve the adaptive purpose. Under natural selection, the encounter of such cooperating genes is due to random chance and so progress is usually slow. Under domestication, it is the human mind which finds and brings together by recombination those genes which cooperate to serve mankind's purposes of abundant food and/or beauty and progress is usually rapid. It is hoped that humans will have the necessary wisdom to direct maize evolution along a domestic pathway that will serve human survival, civilization, peace and democracy.

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors

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