March 2003

Corn That Clones Itself

If they're allowed out of the lab and into the field, crops genetically engineered to reproduce through cloning could feed the world's poor.

By Daniel Charles

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.

Further ahead is a line of white signs, each standing in front of a small square plot where hairy heads of wheat sway in the breeze. This is agriculture's Walk of Fame; on those signs are the names of wheat varieties that emerged from CIMMYT's breeding grounds four decades ago: Sonora, Yaqui, Kauz, Sujata, Sonalika, and others. These varieties, which resist disease and produce unprecedented yields, conquered Asia, displacing traditional wheat varieties and older methods of farming. The stars of the Green Revolution, the new varieties unleashed a phenomenal rise in grain production that allowed China and India to feed themselves. Indeed, the impact of the new grains was so great that they earned Norman Borlaug, the original director of CIMMYT's wheat program, the Nobel Peace Prize in 1970.

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.