Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The role of the slave trade in the evolution of American wild rice species

28.10.2008
Rice is the world’s foremost cereal crop as a human food source. Today’s cultivated varieties derive from the species Oryza sativa and Oryza glaberrina, domesticated respectively in Asia and West Africa. Besides these two domestic taxa, there are around 20 species of wild rice of the genus Oryza, all located in the tropics.

Their common ancestor appears to have emerged from Eurasia about 50 million years B.P. For several decades, scientists have been using molecular biology techniques to explore the evolutionary path which has led to the current diversity of wild rice species. A study published by an IRD research team has shed light on the origin of the settlement of wild rice on the American continent.

Three colonization theories for evolution of rice in the Neotropical region have been confronting each other for many years. The first one takes continental drift as the basis for explaining the current distribution of American rice in the tropical zone, considering that their ancestors already existed before Africa separated from South America. The second postulates the major role of natural seed dispersion across extremely long distances, with migrating birds as agents. The third links the arrival of rice in America to the great exploratory voyages and to the slave trade run by Europeans between West Africa and America. Recent dating methods using the “molecular clock” were applied to the species present in the American tropical zone.

This method, founded on the principle that genetic mutations accumulate in a genome at a rate globally proportional to the time that has elapsed, arrived at an estimated date for the appearance of American wild rice of 300 000 years. However, a relative genetic proximity for certain fractions of the genome of these cereals suggests a much more recent origin by the interaction of crossings between different species. To overcome the constraints imposed by molecular study of a hybrid species grouping together several genomes in one, the IRD team took advantage of available historical documentation.

Investigation of the main European herbarium collections compiled by XVIIth and XIXth Century naturalist explorers who travelled around the American continent revealed that almost all the rice specimens listed during this period belong to the same hybrid species. Moreover, contrary to what the first flora describe concerning a number of neighbouring species, the distribution area of American rice is in fact clearly delimited by the activity of Europeans. Examination of the historical literature also shows that the triangular trade that became established from the XVIth Century between Europe, West Africa and America was the decisive factor in the appearance of the first species of the genus Oryza on the American continent. At that time, seeds were first transported inadvertently in the holds of slave-ships.

It was also established that sailors deliberately took with them seeds of a range of exotic plant species, including wild rice, on their many transoceanic voyages. The hybrid rice first emerged among crops cultivated on the Caribbean islands, were then transported to the mainland by sea, mixed with stocks of cultivated rice seed. The presence of the hybrid rice species inland was for a long time limited to a perimeter around the first Brazilian gold mines that had attracted the colonists with their slaves. The location of this mine on the watershed between the River Amazon and the River Paraguay then enabled new rice species, born of crosses between wild rice of the Old World and domestic rice, to be conveyed by the current of the two rivers and gradually to invade a large area of South America.

The particularly vigorous American rice therefore seems to be the fruit of human migrations across the oceans. They appear to have the special feature of combining in the same genome the genetic characters of many different wild species of the Old World and rice that was already being grown there. This arrangement provided them with a number of qualities, including abundant seed production, ability to be pollinated by cultivated rice varieties, or high resistance to disease. Confirmation of this theory at molecular level could make these Neotropical species potential candidates for development of a new type of domestic rice. In contrast to a hybrid rice currently being developed by China, the “super-hybrid” rice that could be derived from domestication of American species would offer the advantage that rice-growers could multiply it empirically, in the same way as for the traditional varieties they grow already.

Grégory Fléchet -DIC

Grégory Fléchet | alfa
Further information:
http://www.ird.fr/fr/actualites/fiches/2008/fas304.pdf

More articles from Agricultural and Forestry Science:

nachricht Energy crop production on conservation lands may not boost greenhouse gases
13.03.2017 | Penn State

nachricht How nature creates forest diversity
07.03.2017 | International Institute for Applied Systems Analysis (IIASA)

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>