Is native maize diversity
being lost in Mexico?

Evidence from CIMMYT suggests that maize landraces in a major farming zone in the southeastern Mexican state of Chiapas have been replaced by hybrids and other improved varieties, as a result of state programs to promote modern, more productive agriculture.

“Maize landraces have virtually disappeared in La Frailesca,” says research assistant Dagoberto Flores, referring to a large, commercial farming region in southern Chiapas state, southeastern Mexico. “In 2000, 90% of the area was sown to improved open-pollinated maize varieties and landraces; now the breakdown is probably 90% hybrids, 5% landraces, and 5% OPVs. The traditional practice of exchanging seed has almost disappeared.”

Flores, who has interviewed hundreds of Mexican farmers in his 23 or so years at CIMMYT, is now assisting PhD student Joost van Heerwaarden in a detailed study of gene flow among maize varieties in La Frailesca and several other areas of southeastern Mexico. The work combines geographic information system mapping, extensive interviews with farmers about the maize types they and their neighbors grow, genetic analysis of seed of those maize types using DNA markers, and intricate computer models of probable movements of pollen among neighboring fields.

The purpose? To understand what happens when hybrids or improved, open-pollinated varieties (OPVs) are introduced into areas where landraces are grown. “We’re trying to bring some precision to the discussions on diversity,” says van Heerwaarden. “You can have diversity—that is, two things that are different—but to what degree do they differ, and how significant or useful is the difference? If the diversity present is the result of thousands of years of farmer selection, then losing it will be more significant than losing something brought in more recently.”

CIMMYT has studied maize diversity and farmer seed management extensively in this region, but both appear to be changing along with demography, policy, and the economy. La Frailesca furnishes a sort of “laboratory” where many such changes are occurring especially fast. Near the mountainous countryside that bred the Zapatista uprising and a gateway for undocumented immigrants from Central America, La Frailesca is dominated by cattle and coffee, but maize provides food and extra income through sale of grain. Poverty still pervades local communities, and many working-age men migrate to the USA, often leaving women and the elderly to tend fields.

Until recently farmers grew mostly locally-bred landrace varieties, which gave a better grain type for tortillas and other preferred foods, but relatively low yields. A little more than a decade ago, many switched to improved, hybrid maize, through a state-sponsored program that offers seed plus other inputs (e.g. fertilizer and pesticides) and services (such as technical advice and crop loss insurance) on credit, to be repaid at harvest. The use of hybrids varies radically from season to season. Risk is a significant factor for farmers, says Flores: “In a good year, it’s worth it to grow the hybrid—the average profit is 80% more than with a landrace. The problem is when you have a bad year, like recent ones with hurricanes or droughts. The investment in seed and other inputs exposes farmers to potential losses many cannot afford.”

An important factor is that farmers can save and replant OPV seed—either improved or landrace—without losing yield or other qualities, whereas with hybrids they must purchase fresh seed each season to obtain high yields. Landraces are found more often at higher elevations and among people of indigenous background. Men and women also differ in the maize types they prefer, says Flores: “For men yield is important, but women value quality traits, such as better tortilla-making quality or requiring less fuel to cook.”

Flores and van Heerwaarden have found that farmers often grow several different maize types—hybrids, landraces, and improved OPVs—in their fields, and these may be surrounded by other varieties or hybrids in neighboring farmers’ fields. There is probably considerable gene flow among these different types, according to van Heerwaarden: “Many of the varieties that farmers call landraces or manage like landraces are actually recycled improved varieties.”

Van Heerwaarden expects to wrap up his study by January 2007. Changing circumstances in southeastern Mexico, the relative unprofitability of maize farming, and the migration of youth from the region could portend profound changes in maize genetic diversity in farmers’ fields. In lowland areas, according to Flores, some farmers have abandoned maize altogether and use subsidies to underwrite cattle raising. The results of van Heerwaarden’s research should provide a better idea of the status of maize diversity and the costs of maintaining it, as rural inhabitants seek to escape poverty via improved varieties, diversified agriculture, or alternative livelihoods.

For more information, contact Jonathan Hellin, Poverty Specialist, (j.hellin@cgiar.org)