Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mexican farmers effectively cultivate phenotypic diversity in maize

30.04.2004


Erosion of genetic diversity of crop plants has for several decades been making it necessary to develop initiatives for protecting these plant resources. One strategy is in-situ conservation of crop plants. The model currently advanced involves maintaining the varieties to be conserved isolated in reserves, protected from entry of other varieties from elsewhere and cultivated according to ancestral farming practices. Researchers from the IRD and the CIMMYT of Mexico (1) used work previously conducted in Mexico on maize varieties, or landraces, to devise a different, dynamic, model judged more compatible with agricultural development and closer to the real conditions in which these plants diversified under the constant action of farmers (2). Insofar as local landraces are still grown as crops on sufficiently large areas of land, the introduction of others from outside, favouring a certain rate of gene flow, would in fact be a source of diversity rather than a factor of genetic erosion.



Mexico, the cradle of maize cultivation, is where this member of the Graminae family, a descendent of a local wild grass, teosinte, was domesticated and phenotypically diversified by human action, at least 6 000 years B.P. An in-situ conservation programme jointly run by CIMMYT, INIFAP (Mexican National Institute of Research in Forestry and Agriculture and Livestock Breeding) and the IRD, conducted in the central valleys of Oaxaca, enabled the research team to characterize the genetic structure of the different populations of local maize landraces and measured the impact of farming practices on this diversity. They focused on two types of diversity: phenotypic (concerning the morphological characters of the plants) and the genetic diversity (observed using genetic markers).

Study of the populations of maize landraces cultivated in six villages of this central region of Mexico has revealed that the morphological and agronomic characters in the field, such as ear size, kernel colour, or flowering period, vary depending on the farmer. At genome scale, genetic markers have shown strong homogeneity between the maize populations within the same village and, more surprisingly, between distant villages. This means that the local varieties possess a common genetic base. The diversity observed in characters of direct pertinence to farmers would consequently be the result of the latter’s personal decisions on seed selection, which they make before each crop cycle.


This region’s farmers currently grow the maize according to ancestral practices, established over hundreds of years. The fields are sown from one crop cycle to another with the seeds of the ears from the previous harvest. However, from time to time farmers decide to exchange seed batches with other neighbouring farmers, situated more or less geographically distant, in order to run experimental crops from these seeds. Each farmer thus judges the value of these seeds according to their characteristics. Selection criteria are still a highly individual choice and depend on a number of factors. For instance taste, colour, and cooking quality characteristics come into consideration as culinary criteria, leaf characteristics as forage quality criteria.

This investigation has brought the first genetic proof that these cultivation practices, conducted on a small scale (village and region), are a key element in the evolution of maize and its diversity. In-situ conservation of so-called "farm" varieties of crop plants, following the example of maize, could therefore be perceived in terms not of isolation, but of dynamic means of genetic material flow between the different populations of the same region in which the farmers play a predominant role. They thus appear to cultivate maize population diversity. These populations appear as open genetic systems, maintaining the centres of diversity of this major food cereal. The research conducted in this context on the inter-population gene flow should lead to better assessment of the risks from a spread of genetically modified –transgenic-corn varieties that might possibly be introduced into Mexico among traditional local landraces. Such work could therefore help provide some answers for the public debate which for many years has been running on this issue (3).


###
Marie Guillaume - DIC

(1) This investigation involved jointly research unit UR 141 "Diversité et génomes des plantes cultivées" and the CIMMYT (International Centre for Maize and Wheat Improvement) located in Mexico City.
(2) See FAS N°32, February 1997.
(3) A symposium on this topic is being held by the Commission for Environmental Cooperation of North America, in Oaxaca, Mexico, 11 March 2004. See www.cec.org

An article has also appeared: M. R. Bellon and J. Berthaud, 2004 – Transgenic maize and the evolution of landrace diversity in Mexico: The importance of farmers’ behavior, Plant Physiology, 1st March 2004, 134 (3).

FOR FURTHER INFORMATION

Contacter: Julien Berthaud – IRD UR 141 – " Diversité et génomes des plantes cultivées ", 911 avenue Agropolis, BP 64501, 34394 Montpellier cedex 5. Tel.:33-4-67-41-61-65. Email: Berthaud@ird.fr

Contacts IRD Communication: Marie Guillaume (editor), Tel.:33-1-48-03-76-07, Email: guillaum@paris.ird.fr ; Bénédicte Robert (press officer), Tel.: 33-1-48-03-75-19, Email:presse@paris.ird.fr

References :

G. Pressoir and J. Berthaud, 2004 – Patterns of population structure in maize landraces from the Central Valleys of Oaxaca in Mexico, Heredity, 92, 88 - 94 (01 February 2004)
G. Pressoir and J. Berthaud, 2004 – Population structure and strong divergent selection shape phenotypic diversification in Maize landraces, Heredity, 92, 95-101 (01 February 2004)
M. R. Bellon, J. Berthaud et al., 2003 - Participatory landrace selection for on farm conservation : an example from the Central Valleys of Oaxaca, Mexico, Genetic Resources and Crop Evolution, 50, 401-416

To obtain illustrations concerning this research
Contact Indigo Base, IRD picture library, Claire Lissalde or Danièle Cavanna, Tel.: 33-1-48-03-78-99, Email: indigo@paris.ird.fr

Bénédicte Robert | EurekAlert!
Further information:
http://www.ird.fr/fr/actualites/fiches/2004/fiche197.htm

More articles from Agricultural and Forestry Science:

nachricht Cascading use is also beneficial for wood
11.12.2017 | Technische Universität München

nachricht The future of crop engineering
08.12.2017 | Max-Planck-Institut für Biochemie

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>