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June, 2007
Source:
Consultative Group on
International Agricultural Research (CGIAR)
CGIAR
Newsletter June 2007
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. |
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