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 Alkaline soil, sensible sensor
03.08.2017 | American Society of Agronomy

nachricht New 3-D model predicts best planting practices for farmers
26.06.2017 | Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Nagoya physicists resolve long-standing mystery of structure-less transition

21.08.2017 | Materials Sciences

Chronic stress induces fatal organ dysfunctions via a new neural circuit

21.08.2017 | Health and Medicine

Scientists from the MSU studied new liquid-crystalline photochrom

21.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>