The Generation Challenge Programme traces the historical migration of maize to improve breeding materials for modern cultivars.

With support from the Generation Challenge Programme (GCP) of the Consultative Group on International Agricultural Research, scientists have rolled back time, going back half a millennium to retrace the history of maize. The goal is not simply to tell a good story.

"We aim to better understand the diversity of maize," says Dr. Jean-Marcel Ribaut, GCP director. "Obviously, better crop characteristics and a broader genetic pool benefit breeding."

This landmark study, entitled "Characterization of genetic diversity of maize populations: Documenting global maize migration from the center of origin," is a multi-partner effort bringing together nine research institutions on four continents. The first objective is to gather maize landraces (or traditional varieties in farmers' fields) and - where possible - incorporate them into genebanks to safeguard diversity. Next, the researchers structurally characterize maize populations using genetic molecular markers. The idea is to shed light on how maize migrated across the world, assess current local diversity in target areas and thus join the dots in sketching the global picture of maize biodiversity for the benefit of modern breeding programs.

"Although maize is widely grown across the world, there are insufficient records to show where the maize came from in each case," explains Dr. Marilyn Warburton, a molecular geneticist at the International Maize and Wheat Improvement Center and the project's principal investigator. "This information is important for breeding for two reasons. When we want to improve maize in one country, we can find the most similar populations if we know how they are related. Then we can find a new, useful trait in a genetic background similar to what is already being grown. If, on the other hand, we need to expand overall diversity and bring in new favorable alleles for better crop performance, we look for populations that are totally different."

Drought tolerant crops for poor farmers is the key focus of GCP research and directly addressed by this project. After characterization, the next step is to select the most diverse and idiosyncratic populations, in the continuous quest for new alleles (or versions) of genes associated with drought tolerance and other positive traits. This will ensure that maize breeders have at their disposal as much genetic diversity as possible from which to craft new varieties.

The GCP-funded study completes the global maize picture started with funding from PROMAIS, a European maize consortium that focused on a few hundred populations from Europe and the Americas. More than 880 maize and teosinte populations from the entire world have now been studied.

Maize was originally domesticated from teosinte about 7,000 years ago by the early farmers of the Aztecs in today's southern Mexico. The crop experienced continual migration into new areas, selection by farmers to make it better adapted to the needs of the new region and re-introduction into existing growing areas. This has created new diversity and new combinations of alleles, giving farmers - and later breeders - an almost unlimited supply of useful new traits. The big challenge now is unraveling which genes and gene combinations are useful for which traits, and under which conditions.

For the full story, and for more on GCP research and partners, please see our Partner and Product Highlights 2006. And for the study of maize in Europe and North America, refer to Dubreuil P, Warburton M, Chastanet M, Hoisington D, Charcosset A. 2006. More on the introduction of temperate maize into Europe: Large-scale bulk SSR genotyping and new historical elements. Maydica 51: 281-291.