Corn That Clones Itself

An hour outside of Mexico City, the taxi turns off the main road, and the noise and bustle of the highway fade away. Past a steel gate and a white guardhouse, we enter the well-tended grounds of the International Center for the Improvement of Maize and Wheat, known by its Spanish acronym, CIMMYT (pronounced SIM-it). It’s a farm masquerading as a small United Nations. An array of flags pays tribute to the countries that fund the organization’s work: creating better crops for the developing world’s poor farmers.

But wait. Isn’t this supposed to be the International Center for the Improvement of Maize and Wheat? Maize, as most of the world calls corn, is the second-most widely grown crop after rice; it’s a remarkably efficient factory for converting sunlight, soil, and water into food for people and animals. Within the next few years, corn is projected to pass rice and take over the top spot. So where’s the corn? Why is it missing from the Walk of Fame?

As anybody who has driven across the Midwest can attest, superior varieties of corn certainly do exist. But the robust, high-yield plants that cover the Iowa countryside are beyond the reach of the majority of the world’s poor and subsistence farmers-the very people CIMMYT was founded to help. The problem is, if farmers want to plant those top-of-the-line varieties-generally high-octane hybrids that seed companies create by crossbreeding two distinctly different inbred lines-they have to buy new seed every year. Poor farmers simply can’t afford to do that.

The annual requirement for fresh seed is in part a consequence of corn’s biological compulsion to mate freely and indiscriminately. Wheat, like rice, practices the safe sex of self-sex. Each flower pollinates itself, producing daughter plants that are nearly exact copies of their parents-at least that’s the case with purebred wheat varieties such as those released by CIMMYT. As a result, farmers can use part of each year’s harvest for seed, and varieties can easily be shared-passed from field to field, from one farmer to the next.

Corn, on the other hand, is the most promiscuous of plants. Its tassels-the male genitalia-dispense millions of pollen grains into the wind, randomly fertilizing nearby corn ears, the female genitalia. A plant’s offspring, therefore, can vary enormously, depending on which pollen wandered into the neighborhood. So no matter how carefully CIMMYT’s breeders construct improved varieties of corn, the genetic identity of those lines breaks down quickly when they are released into the genetic melting pot of farmers’ fields. The new traits-higher yield, ability to withstand drought, resistance to disease-tend to dissipate and even disappear.

Richard Jefferson, founder of the Center for the Application of Molecular Biology to International Agriculture in Canberra, Australia, says that the implications of apomixis go well beyond corn. The potential of self-cloning plants, he says, is so profound and subversive that plant breeders, generally a cautious and understated lot, “would never admit to dreaming about it unless you got them drunk first.”

In addition to bringing hybrid and other superior varieties of corn within reach of even the poorest farmer, apomixis would allow the widespread use of high-yield hybrid rice, plants whose seeds currently are expensive and difficult to produce in large quantities. And apomixis could help eliminate diseases from cassava, an African staple crop that is grown by replanting pieces of tubers from parent plants, some of which carry disease.

After more than a decade of work, researchers at CIMMYT and a handful of other laboratories around the world are finally homing in on apomixis. With the help of new genomic information and tools, they’re tweaking the genes that control plant reproduction, hoping to duplicate the self-cloning process in corn and other important crops. If they succeed-and they seem confident that eventually, perhaps in another decade, they will-apomixis will open the door to a “revolution in world food production,” says Wayne Hanna, a geneticist with the U.S. Department of Agriculture in Tifton, GA.

That may seem like a technology goal few could argue with. Yet there’s uncertainty about whether apomixis ever will be allowed into farmers’ fields. Two opposing forces could find themselves unlikely allies in an effort to block it: political opposition to genetic engineering and the financial considerations of agricultural companies that are among the primary sponsors of apomixis research.

All these plants engage in an odd form of reproduction. Their ovaries produce new embryos on their own, as clones of the mother plant. Yet a few of these plants also engage in sex. So the elder statesmen of apomixis studied the patterns by which this particular genetic trait is inherited when apomictic plants mate with their nonapomictic relatives. “We ended up finding that the trait behaved like a single dominant gene,” says Savidan, who now directs the international partnerships of Agropolis, a publicly funded research consortium in Montpellier. It was an astounding conclusion, and Grimanelli says, it led to an audacious idea: “If it’s that simple, why not put it in crops? Why not crossbreed maize with an apomictic relative? Easy!”

“Easy,” echoes Grimanelli’s colleague Olivier Leblanc dourly.

Grimanelli and Leblanc represent a link between the early generation of such apomixis researchers as Savidan, who used traditional plant breeding, and a new wave of researchers who employ molecular markers, genomic data, and genetic engineering. Savidan moved his apomixis research to
CIMMYT in the late 1980s, and Leblanc and Grimanelli joined him a few years later. It seemed the perfect place. For one thing, CIMMYT’s climate-controlled vault full of seed samples held a treasure-trove of seeds from gamma grass, a bushlike plant that is corn’s closest apomictic relative. More important, CIMMYT’s mission of improving crops for farmers in the developing world squared perfectly with the potential benefits of apomixis.

But a decade of traditional plant breeding yielded only frustration. The researchers tried to crossbreed gamma grass and corn. They produced 300,000 hybrid plants, creations with strange combinations of features of both plants. They tried to backcross those hybrid plants with regular corn, hoping that each generation would bring them closer to an apomictic version of corn. Inevitably, somewhere on the long road toward corn, apomixis disappeared.

Crazy corn: CIMMYT crossed corn with gamma grass, generating a host of odd-looking plants. Gamma grass is in the center (also see top image).

But just as the old approach was dying, a new one was born. In 1999 CIMMYT signed an agreement with a French seed company, Limagrain; a division of Swiss pharmaceutical giant Novartis that has since become Syngenta; and the world’s largest seed company, Pioneer Hi-Bred. The agreement gave the center funding and access to private corn-genome databases. “The new tools have become so powerful,” says Grimanelli. “You can clone genes, modify genes, express genes.” He and Leblanc embarked on a search for apomixis genes, sifting through the sections of DNA that were present in the apomictic form of gamma grass but not in the sexual version. They tracked those genes to a large block of DNA, about one-third of a chromosome, that is always present in the apomictic form of gamma grass. To find the specific genes in this huge field of DNA, the researchers are throwing transposons-small bits of DNA that insert themselves randomly into chromosomes-at that block of DNA. They’re hoping that the transposons will insert themselves into genes that are important for apomixis, disrupting the process. When that occurs, the researchers should be able to locate the transposon and with it, the crucial gene-which they could then insert into corn. But the CIMMYT researchers are not alone in their search for the genetic keys to apomixis. A horde of other researchers, some of them sponsored by small biotech startups, have joined the hunt. Competing projects have sprouted in Germany, Switzerland, Australia, the United Kingdom, France, Mexico, California, Texas, and Utah. Most of the newcomers are not hoping to transfer apomixis genes from one species to another-from gamma grass to corn, for instance. Instead, they’re tinkering with the timing of plants’ own genes to trick them into reproducing without fertilization. The researchers are working out the details of this “synthetic” apomixis through experiments with their favorite “lab rat,” a small mustard plant called Arabidopsis thaliana. The CIMMYT researchers, whose effort also is going to rely heavily on genomics data from better-known plants such as Arabidopsis, say the leap from Arabidopsis to corn is likely to be more difficult than many researchers expect. But still, they say, it will happen. The “incredible dynamism of so many people working on this,” says Grimanelli, will not be denied.

So when scientists reported finding traces of genetically engineered corn in remote corn fields of southern Mexico a year and a half ago, it was particularly troubling to those worried about the genetic diversity of this unique resource. Indeed, although the study’s findings have been hotly contested by other researchers, some environmentalists believe it uncovered a disaster of epochal proportions. “The Mesoamerican centre of agricultural biodiversity is contaminated with GM [genetically modified] maize,” announced the ETC Group, an activist organization based in Winnipeg, Canada. Greenpeace declared that “this irresponsible contaminationis putting at risk the whole genetic structure of the corn populations.”

The image of engineered plants poisoning a biological well is powerful but misleading, says Mauricio Bellon, a CIMMYT human ecologist who has been studying Mexican farmers’ maintenance of their traditional varieties, or landraces: “People think that landraces are like fragile vases in a museum, but that’s not the case.” Landraces aren’t pure, and they aren’t static, says Bellon. Mexican farmers, he discovered, continually bring in new seed from neighbors and even from faraway villages to add to and, they hope, invigorate their fields. It’s a bit like shuffling in cards from a new deck to increase the odds of a winning hand. The good cards-the superior genetic traits-stand a chance of staying in the game. Farmers try to choose them for replanting the following year, and they discard the bad cards.

There’s no apparent reason why genetically engineered crops should displace or destroy Mexico’s genetic diversity, Bellon says. The new genes would become part of the mix, and they’d persist only if farmers liked the results. But, he hastens to add, genetically engineered corn in Mexico may pose other risks that need careful consideration.

Indeed, nearly everyone who has explored the surge of opposition to genetically engineered crops-in Mexico and elsewhere-has discovered a mlange of motivations. Concerns about the integrity of nature and the safety of food are mixed with hostility for the corporations that have been driving this technology into the marketplace. Mexico imposed a moratorium on the planting of all genetically engineered corn, for instance, not when CIMMYT conducted its first field trials, but when St. Louis-based Monsanto and other companies began lobbying for approval to sell their genetically engineered crops to Mexican farmers.

One encounters antipathy toward biotechnology, in fact, within CIMMYT as well. CIMMYT’s crusty plant breeders sometimes dismiss their organization’s biotech program as a boondoggle, an expensive fad that has squandered millions of dollars without delivering, so far, a single useful product to farmers. Many resent the deals-accompanied by confidentiality clauses and agreements to protect intellectual property-CIMMYT’s biotechnologists have struck with companies. The center should be accountable only to the world’s poorest farmers, these critics say, not multinational biotechnology empires. At this point-where the humanitarian mission of CIMMYT encounters the goals of private enterprise-the tale of apomixis takes its final ironic twist. For according to some observers, the corporate friends of apomixis are also its worst enemies.

In 1998 Jefferson of Australia’s Center for the Application of Molecular Biology to International Agriculture helped persuade more than 20 leading apomixis researchers from around the world to declare their opposition to corporate control of the research. The so-called Apomixis Declaration stated, “We are deeply concernedthat the current trend towards consolidation of plant biotechnology ownership in a few hands may severely restrict access to affordable apomixis technology.” Unfortunately, says Jefferson, “scientists are sluttish beyond words.” Many apomixis researchers have since signed up with private companies.

CIMMYT’s scientists insist there’s no problem. They maintain that their corporate sponsors have agreed to allow the center to distribute apomictic corn to poor farmers in developing nations. “It’s perfectly clear,” says Olivier Leblanc. “For CIMMYT clients, there is complete freedom.” But even Yves Savidan, the architect of CIMMYT’s apomixis collaboration with industry, has grown skeptical. “If you’re not in control of everything, you’re not in control of anything,” he says.

Even before the first apomictic self-cloning corn seeds are ready to be sown, the prospect looms that political debates and corporate interests will poison the ground. And that would be a blight not only on the future of poor farmers, but also on the reputation of agricultural biotechnology-a field already dogged by accusations that its science has not done enough for the human good.

Producing biotech crops that feed the poor and improve the lives of farmers in the developing world would convincingly refute such accusations. David Hoisington, director of CIMMYT’s biotechnology program, believes that such crops are on their way. CIMMYT’s first genetically engineered corn, a nonapomictic variety that repels the stem borer worm, is ready for field tests. In another decade or so, plots of apomictic corn could mark a new entry in the CIMMYT Walk of Fame. “The technology is such a powerful tool for solving problems,” says Hoisington, “that it has to be accepted.”