June 19, 2009
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Varieties of four domesticated chiles. Credit: The Chile
Pepper Institute, New Mexico State University, Las
Cruces, New Mexico. |
Source:American
Journal of Botany
Without the process of
domestication, humans would still be hunters and gatherers, and
modern civilization would look very different. Fortunately, for
all of us who do not relish the thought of spending our days
searching for nuts and berries, early civilizations successfully
cultivated many species of animals and plants found in their
surroundings. Current studies of the domestication of various
species provide a fascinating glimpse into the past.
A recent article by Dr. Seung-Chul Kim and colleagues in the
June 2009 issue of the American
Journal of Botany explores the domestication of chiles.
These hot peppers, found in everything from hot chocolate to
salsa, have long played an important role in the diets of
Mesoamerican people, possibly since as early as ~8000 B.C.
Capsicum annuum is one of five domesticated species of chiles
and is notable as one of the primary components, along with
maize, of the diet of Mesoamerican peoples. However, little has
been known regarding the original location of domestication of
C. annuum, the number of times it was domesticated, and the
genetic diversity present in wild relatives.
To answer these questions, Dr. Kim and his team examined DNA
sequence variation and patterns at three nuclear loci in a broad
selection of semiwild and domesticated individuals. Dr. Kim et
al. found a large amount of diversity in individuals from the
Yucatan Peninsula, making this a center of diversity for chiles
and possibly a location of C. annuum domestication. Previously,
the eastern part of central Mexico had been considered to be the
primary center of domestication of C. annuum. On the basis of
patterns in the sequence data, Dr. Kim et al. hypothesize that
chiles were independently domesticated several times from
geographically distant wild progenitors by different prehistoric
cultures in Mexico, in contrast to maize and beans which appear
to have been domesticated only once.
Geographical separation among cultivated populations was
reflected in DNA sequence variation. This separation suggests
that seed exchange among farmers from distant locations is not
significantly influencing genetic diversity, in contrast to
maize and beans seeds, which are traded by farmers across long
distances. Less genetic diversification was seen in wild
populations of C. annuum from distant locales, perhaps as a
result of long-distance seed dispersal by birds and mammals.
Across the three loci studied, Dr. Kim and colleagues found an
average reduction in diversity of 10% in domesticated
individuals compared with the semiwild individuals. Domesticated
chiles in traditional agricultural habits, however, harbor
unique gene pools and serve as important reservoirs of genetic
diversity important for conserving biodiversity.
This work was conducted primarily by Araceli Aguilar-Meléndez
as her dissertation project under the guidance of Drs. Kim and
Mikeal Roose in the Department of Botany and Plant Sciences at
the University of California at Riverside. The research was
supported by the University of California Institute for Mexico
and the United States (UC MEXUS), El Coneso Nacional de Ciencia
y Technología (CONACYT), and a gift from the McIlhenny Company.
Aguilar-Meléndez, Kim, and their colleagues plan to continue
research on this remarkably variable and economically important
spice in Mesoamerica.
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study and inquiry into the form, function, development,
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Journal of Botany (www.amjbot.org) for nearly 100 years. For
further information, or for full access to this article, please
contact the AJB staff at
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