Back at the research station, Borlaug found his seeds sprouted and the plants ready for cross-pollination. Wheat flowers, known as florets, grow in little bunches on the spikelets. Like most flowers, each floret is bisexual, with both male and female reproductive organs. Rising up on thin stalks from the center of the floret are the stamens, the male parts of the plant, which contain the pollen in little pods at the tips. Below these are the small, delicate filaments of the female part of the flower, the stigma, with the ovary below. When the stigma has developed enough to be capable of reproduction, a biochemical signal causes the stamen tips to burst, releasing spore-like grains of pollen in tiny golden puffs. In flowering plants like wheat, each pollen grain contains a generative cell and a vegetative cell. The former produces two sperm cells; the latter swings into action when the pollen settles on the fronds of the stigma. There it produces a germ or pollen tube, a cylindrical extension of the pollen grain that carries the actual sperm cells. Within as little as an hour of landing on the stigma, the pollen grain’s germ tube has penetrated the ovary beneath the stigma. Inside the ovary is the ovule, which contains the egg cell. Male and female mechanisms join and begin creating a seed, the grain that the farmer will harvest.
Because both sperm and egg come from the same plant, the new seed will be genetically identical to its parent. To create new varieties, plant breeders must stop wheat from fertilizing itself. In practice, this boiled down to Borlaug sitting on a little homemade stool in the sun, opening up every floret on every spikelet, carefully plucking out the pollen-containing stamens with tweezers, and discarding them. Every stamen in every plant had to be removed to ensure control. Now the entire field of wheat was entirely female—the plants had been, so to speak, emasculated. Only pollen from other plants could fertilize them.
The next step was to place a flattened paper cylinder over the heads of the now-female plants. Once it was in place, Borlaug folded over the top of the cylinder, sealing it with a paper clip. Now no pollen could enter. Each bagged plant had to be labeled and logged. And all of this had to be done in the few days between when the egg cell became fertile and when the pollen was released by the stamen.
A few days later, when the plants had recovered from surgery, Borlaug snipped off the florets from another wheat variety he hadn’t cut up. Opening the paper cylinders on the emasculated grain heads, he inserted the florets from the second variety, twirled them to release their pollen, then resealed the paper. Each spikelet on the plant had to be pollinated by the same pollen; no other pollen could enter. After a few days he removed the paper and let the fertilized florets produce grain. When the grain matured, he harvested it, separately packaging and labeling the seeds from every plant, and transported the lot to the Bajío, where he did it all over again.
The possibilities were almost endless, but they were slow to appear. The first generation of crosses usually would end up looking halfway between the two parents. But if breeders combined the offspring, the second generation would have many individuals with two identical copies of significant genes—and these would begin to look different from the original plants. Important positive or negative traits could show up. These would be amplified by the third or fourth generation of crosses. If one of these plants had especially desirable qualities, it would need to be studied and bred on a large scale before field trials could begin, which also took time. Borlaug’s shuttle breeding was intended to turn the wheel faster.
Hearteningly, the initial breeding at Sonora was successful. Seed from the four rust-resistant varieties produced plants that survived the annual onslaught of Puccinia graminis. By the fall Borlaug had five acres of tall wheat plants bending under the load of their grain-filled spikelets. Next Borlaug would have to harvest the grain and transport it to the Bajío for the next round of crosses. The tiny planes that flew between Ciudad Obregón and Mexico City could not carry hundreds of pounds of grain. In April 1946 Borlaug flew to Mexico City, where Harrar reluctantly allowed him to borrow the Rockefeller program’s sole vehicle, a Ford pickup truck.
In those days no paved roads crossed the mountains between Mexico City and Sonora. From the capital, drivers had to take a two-lane highway northwest three hundred miles to Guadalajara, then go six hundred miles north on a path through the brush, crossing deserts and fording rivers, carrying their own gasoline for most of the route. The prospect was so daunting that Borlaug decided to go the long way around: drive from Mexico City to El Paso, Texas; cross most of Arizona; re-enter Mexico at Nogales; then forge two hundred miles south through scrublands to Ciudad Obregón. To take shifts at the wheel, he recruited Joe Rupert, his apartment mate, and one of Harrar’s new hires, a Chapingo graduate named Teodoro Enciso.
The three men loaded equipment into the truck—two small, battered threshing machines, four spare tires, and a pile of gunny sacks to use as mattresses—and headed north. When they reached the border at El Paso, three days of rough road later, the U.S. Customs guard stopped them, claiming that Mexican government vehicles were not allowed to enter the United States. Borlaug told him that the two countries had agreed to permit official vehicles to cross the border freely. The guard responded that the truck could enter, but not its contents. To ensure that the researchers could not illegally sell equipment, they would have to unload the machines, tires, and sacks, and hire a bonded freight company to carry them to Nogales.
Before modern techniques, wheat breeders like Norman Borlaug had to plant thousands of different varieties, hoping that chance would produce favor-able variants. Each plant had to be checked by hand for desirable characteristics—early flowering, perhaps, or disease resistance. Then breeders tried to mate them to produce plants with both good traits. Credit 30
To mate two wheat plants, people tweezer out the anthers, creating a purely “female” plant. Then they cover the now emasculated plant with a small envelope to block off errant pollen.
Meanwhile the breeder snips off the floret of the second plant, opens the envelope atop the first wheat plant, and twirls the floret—releasing the pollen and fertilizing the first wheat plant. The fertilized floret then turns into a seed—a kernel of wheat.
Each plant is harvested by itself, with the grain placed in a separate envelope and labeled with the information about its parents. These are then sown in the next season. And so the cycle begins again.
Even when breeders create a wheat variety that combines all their desired characteristics, their work is not done. Varieties must be constantly adjusted for different conditions, new strains of pests and pathogens, and new farming techniques. The work can be tedious, but it is one of the foundations of the modern world.
Borlaug was irate. Every minute of delay meant that they could miss the harvest. Even if the grain were still in good shape, he still needed to reap, winnow, dry, and pack it, measuring the weight and characteristics of every spikelet, in time to haul it to the Bajío and plant it before winter set in. The three men pushed from Nogales to the Yaqui Valley in a hot-brained hurry. To Borlaug’s relief, the wheat was harvestable.
Not wanting another run-in with U.S. Customs, Borlaug, Rupert, and Enciso decided to come back through Mexico with the grain. The main peril was the rivers coursing down the flanks of the western Sierra Madre, many of which had to be driven through, a risky business in the spring rains. Bushed, battered, and bruised, the three banged across the mountains, then went to the Bajío and Chapingo to plant the second generation.
In July 1947 the wheat project was visited by Herbert K. Hayes, a revered Minnesota plant breeder who had helped develop both hybrid maize and wheat. Touring Chapingo, Hayes was shocked to learn that Borlaug, a Minnesota graduate, was trying to breed the same wheat in two different latitudes and climates, a violation of basic botanical dogma. Had Borlaug taken any courses in plant breeding, he would have found this dictum etched in the textbooks, including Breeding Crop Plants, a classic whose senior author was Herbert K. Hayes.
Borlaug stood his ground; Hayes was just a
visitor. But he had a harder time fending off criticism that October, when Rupert and he were summoned to Harrar’s office. Funds were running short, Harrar said. Although Borlaug was spending almost no money in Sonora, the Rockefeller Foundation was effectively paying other people to do Borlaug’s job while he was there, pursuing a private obsession that flouted well-known scientific principles. Shuttle breeding had to stop. His tone, Borlaug said later, was icy. Borlaug again laid out his argument: conditions in the Bajío were too poor to solve Mexico’s wheat problem. Possibly, Harrar said, but that is where our hosts have asked us to work. Borlaug replied, in his later recollection,
“With the water facilities and the land resources that are available, this is, in effect, tying one arm behind my back, and I can’t do it. And if this is a firm decision that’s been made, you better find someone else to execute this, because I will stay [only] till you find my replacement. If Joe Rupert here wants to take it over as I leave this door, why as far as I’m concerned it’s to be executed.” And before I got to the door, Joe stood up and said, “This goes for me, too.” And we both walked out.
Fuming, Borlaug stomped into his office, Rupert in tow. There he found a stack of mail. He swept it to the floor in annoyance—then realized that one of the letters was from the farmer next door to the agricultural experimental station, the man who had loaned his tractor. To Borlaug’s surprise, it was a copy of a note to Harrar. It began by congratulating the Rockefeller Foundation:
Perhaps it is the first time in the history of Mexico that any scientist tried to help our farmers….But why is it, with such a great force like the Rockefeller Foundation, that you do not give your men the tools and machinery they must have to fight with? Why does he come like a beggar to borrow the tools to grow new wheat?
On Borlaug’s copy of the letter the farmer had written, “It’s time somebody was helping you fight inside your own organization!”
Borlaug and Rupert were stricken with guilt—they had, after all, just quit. They stalked into a cantina and drank themselves into a near stupor. When they stumbled home that night, Margaret angrily refused to let them in. The hallway filled with their argument, Margaret shouting in the apartment, Borlaug bellowing in the hallway, Rupert sheepish and silent. A comic-opera scene, Borlaug said later. Eventually Margaret unlocked the door. Early the next morning, hungover and abashed, Borlaug slipped out of the apartment.
I walked into the office, and here’s Stakman, sitting, smoking his pipe. Have you ever seen Stakman at seven o’clock in the morning? I never have before or since. And he said, “You people act like children!”
He told Borlaug he would see what he could do. Borlaug went to Chapingo for the day. It was no consolation to see how well his wheat was growing. When he returned, he went to Harrar’s office. Stakman was there. Without looking up, Harrar said, Go back to Sonora. Borlaug realized that he must have read the farmer’s letter. With the ongoing problems of the maize initiative, the project couldn’t ignore a project that farmers seemed to support, even if they were not the farmers Rockefeller was supposed to be working with, even if the project was not going to work.
Again Borlaug took the truck over the mountains. Landslides left him stranded in the heights for days. In Sonora he worked through the winter, mostly alone. Some of his new plants seemed to be strongly resistant to rust. That spring he organized a demonstration of his new seed for Sonora farmers. It was like a cold shower. Only a few people showed up, one of whom was the neighbor who had written a letter to Harrar. The others did not share his enthusiasm. Some loudly ridiculed Borlaug. Not one took advantage of his offer of free seed.
Green Revolution
Plant breeding in that time was a black art. A few laboratory researchers were beginning to wonder whether a molecule called DNA played a role in heredity and reproduction, but that suspicion had not filtered into the world of practical science. And even the white-coated boffins didn’t know that clusters of interacting genes resided on twined DNA strands wrapped into bodies called chromosomes within the cell nucleus. Today this information is taught in elementary-school science classes, but it was unknown when Borlaug was working in Mexico. Now-familiar terms like “DNA” and “gene” do not figure in his reports or work notes.
Because Borlaug knew little about the molecular basis of heredity, he worked exclusively with plants’ physical features—the thickness of their stalks, the number of leaves, the time of flowering, and so on. Thus he might give a high-yielding “female” plant pollen from a “male” disease-resistant plant (or vice versa). Or he might mate a fast-growing but rust-susceptible plant with a slower-growing but resistant plant in the knock-on-wood hope of producing offspring with the two desirable traits, not the two undesirable ones. In both cases, he couldn’t know the results of these matches until the plants grew in the field.
Worse, wheat has about four times as many genes as humans, many present in multiple interacting versions. For breeders, this enormous genetic diversity is a source of both hope and frustration. On the positive side, it means that wheat has many hidden genetic treasures—valuable genes are concealed in the thickets. But on the negative side it means that these valuable genes are, needle-in-haystack-style, hard to find.
Even if Borlaug’s crosses turned out well—he bred plants that resisted stem rust, say, or bore extra-plentiful grain—there was no telling if those traits could be passed on to the next generation. Most observable physical traits are associated with multiple genes; human eye color, for instance, is associated with about fifteen. If all the interacting, beneficial versions of genes were not passed on together, or if breeders unknowingly introduced other genes that canceled out the favorable effect, or if environmental conditions changed and the proper genes were not switched on, the desired characteristic could vanish. Breeders could combat this uncertainty only by performing huge numbers of crosses—throwing darts by the thousand, so to speak, praying for bull’s-eyes.
Borlaug got lucky—“a case of serendipity,” he later called it. Like many other plants, wheat controls its growth by a kind of biochemical clock that measures day length. Winter wheat stays dormant until the clock “observes” the days growing longer, which signals the advent of warmer spring weather. The plant then “knows” that the danger of frost has probably passed and it is safe to flower. Sensitivity to day length is called “photoperiodicity.” Multiple genes direct wheat photoperiodicity, of which the most important is known as Ppd-D1. When Borlaug moved his wheat from Sonora to the Bajío, he was conducting an unknowing experiment to discover whether any of his varieties were not controlled by Ppd-D1.
By chance, a few of them weren’t under its thumb. In a long-ago genetic accident, a snippet of DNA in one Korean wheat plant had dropped out of the gene, crippling the intricate workings of Ppd-D1 in somewhat the way that removing a single small chip from a computer can disrupt its function. Equally fortuitously, the mutated gene had been passed on through the generations—ending up, geneticists believe, in the fields of an Italian breeder, from which it passed to Kenya, where it was collected by the Texas breeder and passed on, all unknowing, to Borlaug. Wheat with malfunctioning Ppd-D1 is called “photoperiod-insensitive”—a fancy way of saying that it has a clock that can no longer tell time. Rather than waiting for the day to grow long, the plant sprouts and grows as soon as it can.
Photoperiodicity was why, as Hayes said, crops had to be developed locally. Plants bred in one area had clocks adapted for that area, and moving them too far away would confuse them, so to speak. When Hayes and Harrar told Borlaug that his experiments with shuttle breeding would just end up with dead plants, they were correct—about normal wheat. But it turned out that not all of Borlaug’s wheat was normal. Stubborn ignorance allowed him to discover that the offspring of some of his crosses with the Kenyan wheat were photoperiod-insensitive, and would grow whenever he planted them. He had taken advantage of that lucky break to breed wheat twice as fast as anyone else—wheat that could withstand a much wi
der range of conditions than other varieties.
He would soon need more luck. By crossbreeding the four wheat types that had survived stem rust with hundreds of others, he succeeded in producing five new varieties that were photoperiod-insensitive, rust-resistant, and highly productive. Despite their doubts, a few Sonora farmers tried them out—and nearly doubled their wheat harvests. Others quickly jumped on the bandwagon. Farmers in Sonora had already been benefiting from increased irrigation, which allowed them to plant more land. Production soared further when they adopted Borlaug’s rust-resistant seeds.
Borlaug was achieving his goal, but he couldn’t enjoy it. He spent the entire time worrying that the triumph would be short-lived. As more and more farmers planted the new varieties, two problems had appeared.
The first was lodging. To achieve their maximum potential yield, his new varieties needed more nutrients than Mexico’s poor soils could provide. When Sonora farmers added chemical fertilizer, the new Kenya-based varieties responded avidly, bearing huge heads of grain. Too avidly, in fact: the heads in Borlaug’s wheat—unlike those in the traditional types it was replacing—were so large that in high winds the top-heavy plants fell over easily, one knocking down the next, domino-style. Lodging leads to disaster, because the crimped, bent-over stems can’t deliver the water and nutrients the juvenile grain needs to mature. The new varieties were wildly productive but vulnerable to wind and rain in a way that the traditional varieties never had been. Entire fields could be destroyed by a single hard gust.