It came in silently and unseen, riding on the wind, just as a science-fiction writer might have imagined it, and threw a panic into the populace.

Almost instantly, the broad green carpet turned brown. The midwestern corn crop of 1970 was stricken, cutting the yield as much as 50 percent in some places, because man's penchant for manipulating nature had gone out of bounds.

The southern corn leaf blight was the culprit. It found a perfect target in the Corn Belt states, which were planted heavily with a seed that was economical and profitable to seed companies because of its inbred traits. As it turned out, the hybrid also was highly susceptible to the leaf blight.

Markets went crazy. Farmers lost money. Some sued the hybrid seed companies. Plant scientists at places like the University of Illinois and Iowa State University, world-renowned for their genetics work, clucked knowingly at the companies' plight.

The southern leaf blight carried a costly message, and the seed companies became more cautious. Different seed combinations were used in 1971, the next crop year, and rich yields again were the result.

Just as tinkering with hybrid lines produced a corn stain so vulnerable to the leaf blight, tinkering in the form of sophisticated research and science has made American corn-growing the most productive in the world. Before hybrids, farmers saved the best of their crop and planted it the next year. The system worked, but only marginally. Plant science showed it could be done better.

Those modern breeding techniques were employed to correct the genetic weakness that attracted the leaf blight to the 1970 crop. In combination with research being done at the universities with federal and state funds, the seed companies are steadily pushing corn yields to levels unimagined 30 years ago.

The seed researchers work in relative obscurity, modern-day Merlins, if you will, toiling with virtually no fanfare. But the implications of what they are doing are enormous in a world of hunger, diminishing land resources and rising energy costs.

Some of their hybrid developments rank right up there with the astonishing. In the process of doubling farmers' yields, for example, seed scientists have:

Found a way to make the leaves on a stalk stand taller, allowing more sunlight to find its way into the plant's energy system.

Produced a seed that will grow into an ear much more heavily laden with valuable, edible oil -- a step that has high potential for human feeding.

Developed a hybrid that contains less moisture, which means the farmer can dry his crop with less fuel.

The fruits of the seed scientists' labors can mean more food, at less cost in energy consumption. Or they could mean more diversification of crops -- more corn from less land would allow planting of other species, or the use of better soil conservation techniques. Corn with less starch and more protein, already developed, could feed people better. More disease-resistant corn would be a boon.

Some agricultural scientists are skeptical that U.S. farmland can be expected to produce an ever-increasing bounty, the general view of a major study done in 1975 by the National Academy of Sciences. But researchers here in Champaign don't buy the skepticism. They see a day in the near future when present corn yields can be doubled to well beyond 200 bushels per acre.

History suggests they have reason for this optimism. Since 1935, when hybrid seeds went into widespread use, U.S. average corn yields have gone straight up -- from 24.2 bushels then to 33.1 in 1945, to 42 in 1955, to 74 in 1965 and 109.4 in 1979, the record production year. The NAS study recognized those gains as "astounding."

Most experts attribute these increases to several factors. First is hybrid seed development -- seeds are carefully tailored for best results in different growing areas. Wider use of fertilizers and herbicides and improved farming techniques also have played an important role.

Farmers in many areas routinely produce more than 200 bushels per acre. Several, in Delaware, Nebraska, Michigan and Iowa, have gone over 300-bushel yields -- and are making a profit -- by carefully husbanding their crop.

Here at the University of Illinois' Maize Genetics Laboratory, academicians see those figures and the overall past gains in yield as really no more than the prologue to a dramatic in corn production. The laboratory, and extension of the school of agronomy, gets some federal financial aid, but like its counterparts at other mid-western universities, it is supported in the main by state money.

"After 50 years, we see as much genetic potential as when we began all this. We have fascinating potential," said Dr. D. E. Alexander, an articulate, cigar-smoking man who typifies the optimists of his breed.

"In yield, in quality, in disease resistance, we can continue to grow. There is now a real opportunity to marry molecular biology applications to corn. We know what we can deliver."

One of Alexander's research colleagues, Dr. J. W. Dudley, a statistical geneticist, agrees. "There's no indication yet that we're leveling off. . . . I say we can get 600 bushels an acre, which is pie in the sky, really, but we've had enough examples of farmers producing 300 bushels per acre with existing seeds. I'm saying it is theoretically possible to get to 600 bushels. We don't know enough about management technique, however."

What is known is that farmers generally tend to be conservative, not given to sudden breaks with farming custom and not prone to wild experimentation. Many seem satisfied with slow but steady gains in productivity, not compelled to produce more because there isn't much incentive to do so. Costs and risks outrun the profit.

"Remember, we've just come from a time when the nation's grain bins were full," Dudley said, "but all you have to do is look at world population figures and see the growing needs. . . . People have said we're crazy to be looking at higher yields, but you keep thinking it will be important to grow more grain down the road."

On the university's experimental plots here, Dr. R. J. Lambert is putting some new management approaches -- tillage, plant-spacing, fertilization -- to work with seeds readily available on the commerical market. He is regularly achieving yields that go over 200 bushels per acre.

"It is kind of startling to me that we could find hybrids on the market that would give us this," Lambert said. "So the potential for getting more yield is even greater -- there is no problem in getting it."

Better yield, however, is just one of the things the corn breeders are looking for. "Breeders have a whole series of problems they must deal with," Alexander said, "but to put all the answers together in one hybrid is agony."

Breeders can, for instance, produce a corn that has far higher oil content than was once believed possible. Although this corn brings a premium price on specialty markets, the breeders have not yet found a way to combine the higher oil content with a high-yield trait.

Why not try to get more ears of corn to the stalk? The corn plant can be manipulated to do just that. But then there is a problem with the stalk -- it won't hold up that much weight. Or the ears will be smaller. Breed a tougher stalk and new disease susceptibility might result.

How about a corn plant that would have less mositure in its kernels? That could save the farmer energy in drying his harvested crop. It is being done, and the hybrid is in demand, but it had yield problems.

If it has more fuel -- that is, more sunlight -- the miniature factory that is the corn plant becomes more efficient. Breeders produced a seed in the 1970s that grew into a plant with more erect leaves, allowing more sunshine in and allowing more plants to grow in a given area of ground.

Much of that work was pioneered by Dr. Arnel R. Hallauer, a leading geneticist at Iowa State. That seed is used widely today in the Corn Belt, and breeders are pushing ahead with other leaf configurations that may permit even greater exposure to sunlight.

Challenges of this sort are dealt with by a small cadre of scientists working at the universities and in the country's nearly 400 seed corn companies.

They are motivated in large part by a vision of the perfect seed -- high yield, disease resistance, superior nutrition -- that will help the farmer and provide more abundant food for the world. Their hybrids, however, have created a kind of genetic sameness that alarms some scientists. The fear is that without more diversity, corn crops will become increasingly vulnerable to blight and disease.

They are working with a genetically simple grass that traces back thousands of years to origins in southern Mexico. Until the modern era of the hybrid, corn evolved largely on its own, although farmers would select the best of each year's crop and save if for planting.

That was hit-and-miss barnyard science, always subject to the vagaries of weather, pest and blight. The hybrid developers found that by painstakingly separating the best of a crop, replanting it under controlled conditions, separating and again separating each succeeding generation, they could work marvels.

The process continues today in much that fashion. The seeds are planted in isolated test fields, away from the commercial corn crops. As many as 99 percent of the newly developed plants are discarded because of inferior traits. pThe best are kept, replanted and grown on a large scale for eventual commercialization.

"Corn researchers are restless souls who see an opportunity in corn that is not evident in other species," said Alexander, whose own work has led to higher-oil corn. "They are, well, intellectually different. The nature of the plant and the kind of people it has attracted foreordained the success of corn in the United States."

It is worth noting here that one of those restless souls was Henry A. Wallace, a vice president and secretary of agriculture under Franklin D. Roosevelt. Wallace is remembered more as an architect of modern U.S. farm policy, but it was he and a group of cronies who set up the first company devoted solely to hybrid seed corn research and production. Their Pioneer Hi-Bred Corn Co. is still the dominant hybrid corn firm in the world.

The rich soil, the flat topography and the perfect corn-growing climate of the Midwest obviously had a lot to do with the success of Pioneer and the evangels of corn. The harsh winters help stem disease. The summer heat and moisture are just right for the corn.

But the restless souls Alexander talks about play a vital role. One of them is Harry Brokish, 33, a scientist who wears jeans and a flannel shirt, gets tractor grease on his hands and works in the most improbable of laboratories -- a cornfield.

As the plant breeder for Golden Harvest Seeds, one of the major hybrid firms at Clinton in nearby Dewitt County, Brokish's job is to convert the research of academia to practicality. Along the way, using his own field research and selection techniques, he must make his company's seeds sought-after by farmers for their productive attributes and reliability.

Last year's drought, although disastrous for corn farmers, was the sort of quirk of nature that sent Brokish's heart skipping. It provided a research bonanza.

"When nature gives you a disaster like that, it can be of enormous benefit to the breeder," he said. "I could select out the most resistant seeds -- find the ones that survived the drought, or the corn borer or leaf disease -- and work on those to produce new lines.

"We are trying to give the farmer corn of real diverse genetic backgrounds so he doesn't lose his whole crop. Disease resistance, drought tolerance. These are precautionary steps to protect the farmer."

None of this is the romantic stuff of television, where a scientist exclaims "Eureka!" as he unlocks a genetic code. It is back-breaking work that makes breeders like Brokish part farmer, part scientist, part mechanic, part dreamer.

In recent weeks, just before planting time, Brokish got his new seed lines ready and devoted himself to tuning up the big red International Harvester tractor he would use to pull his planter. He would put his heavy equipment on a long trailor and pull it around to Golden Harvest test plots in the Corn Belt states, then plant his seeds.

During the summer growing months he will be back checking the crop, making tests, and then in the fall return again with his combine and harvest the corn. tFrom those test plots he will pick out the ears of corn with the traits he is seeking and return to his lab in Dewitt County.

The more promising seeds will be selected, and between now and next year he will go to the Golden Harvest experimental tracts in Hawaii, where a second crop can be attained in the same year, to do more research. His findings will be incorporated into future Golden Harvest seed offerings.

Brokish grew up on a farm in Wisconsin, thinking he probably would become a farmer. At the University of Wisconsin, the world of botany entranced him and the move to corn genetics was easy and natural.

"We're working with genetics -- the basics of inheritance," he said one recent spring day, pausing as he adjusted the engine on his red tractor. "There's nothing more exciting or challenging. And we're just getting started on some of this stuff."

One of the challenges was laid out by Illinois' Alexander. " . . . If we could decode the corn genes," he said, "and if we could engineer a new protein in the endosperm, we could meet 100 percent of the nutritional needs of humans. We should be able to do that kind of thing and we should be thinking about it."