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
Cascading use is also beneficial for wood
11.12.2017 | Technische Universität München
The future of crop engineering
08.12.2017 | Max-Planck-Institut für Biochemie
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,...
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...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications
Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...
Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.
The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...
08.12.2017 | Event News
07.12.2017 | Event News
05.12.2017 | Event News
11.12.2017 | Physics and Astronomy
11.12.2017 | Materials Sciences
11.12.2017 | Earth Sciences