Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

From varietal improvement to impoverishment: what is the reality?

19.01.2007
Fewer crop species, fewer cultivated varieties per species, less diversity within each variety are three "symptoms" of the erosion of biodiversity in cultivated plots.
It is commonly assumed that the massive use of improved varieties instead of local varieties and anthropic pressure are the prime culprits behind this impoverishment. Is this a cliché or reality? The only way to find out is to monitor the changes in crop genetic resources. This has now been done for local rice varieties in Guinea, a reserve country for the genetic diversity within the two cultivated rice species: Oryza glaberrima from Africa and O. sativa from Asia.

Are local rice varieties disappearing? What strategies are required to conserve them? CIRAD and its African partners have been working in Guinea since 2000 to find answers to those questions. Their research has been conducted on several levels.

Stable or even slightly greater diversity

On a national level, the researchers inventoried the common names of the varieties used by farmers between 1996 and 2001. This meant surveying almost 1700 farms in 79 villages. Furthermore, in 2003, samples were collected from six villages in Maritime Guinea and compared, using molecular markers, with samples taken by a survey mission to the same village in 1980 and kept in cold storage in Montpellier ever since. The results obtained ran counter to the alarmist vision of genetic erosion. The number of rice varieties and genetic diversity were stable, or had even increased slightly. Since 1996, when improved varieties were introduced, the number of varieties, which varied from 4 to 40 depending on the village and the region, had increased by 10%. There had thus not been any loss of local varieties in Guinea.

The substantial varietal diversity observed is typical of subsistence agriculture: more than 80% of the varieties grown were local. Each village could thus allow for the range of prevailing agroecological conditions and different uses of rice. However, almost 90% of the varieties inventoried were only grown by a small number of farmers, and despite the observed diversity, these "minor" varieties are now under strong threat of extinction. Moreover, there was not only diversity in terms of the number of varieties, but also within each of those varieties. Each variety was the sum of a large number of pure lines, and the proportion of those lines varied from one farm to another. This "multi-line" structure can be put down to how the farmers manage their rice varieties, ie frequent exchanges and replacement of varieties and seeds, and cropping and seed production practices that favour genetic mixes and recombination.

50% of the genetic wealth of varieties in a village held on a single farm

As regards preserving the diversity within each local variety, in situ conservation on farms, which is compatible with agricultural development, looks like the only feasible option. In fact, it would be impossible to sample all the lines that make up a variety and keep them ex situ, for instance in a cryobank. The researchers working on the study thus characterized the varieties grown in Maritime Guinea, in two villages with contrasting production systems. To this end, they used descriptors combining common names and molecular markers (short DNA sequences). The results showed that a single village may hold the equivalent of 70% of regional diversity. On a more detailed analysis level, a large farm may hold 50% of the genetic wealth of a village. As a result, a small number of villages and farms is therefore sufficient to cover the genetic diversity of a whole region such as Maritime Guinea. This type of structure could eventually be extended to cover the whole of the country.

Helen Burford | alfa
Further information:
http://www.cirad.fr/en/actualite/communique.php?id=594

More articles from Agricultural and Forestry Science:

nachricht Six-legged livestock -- sustainable food production
11.05.2017 | Faculty of Science - University of Copenhagen

nachricht Elephant Herpes: Super-Shedders Endanger Young Animals
04.05.2017 | Universität Zürich

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: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>