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.
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