Biologists from Washington University in St. Louis and their collaborators from Taiwan have examined the DNA sequence family trees of rice varieties and have determined that the crop was domesticated independently at least twice in various Asian locales.
Jason Londo, Washington University in Arts & Sciences biology doctoral candidate, and his adviser, Barbara A. Schaal, Ph.D., Washington University Spencer T. Olin Professor of Biology in Arts & Sciences, ran genetic tests of more than 300 types of rice, including both wild and domesticated, and found genetic markers that reveal the two major rice types grown today were first grown by humans in India and Myanmar and Thailand (Oryza sativa indica) and in areas in southern China (Oryza sativa japonica).
A paper describing the research was published June 9, 2006, in the on-line issue of the Proceedings of the U.S. National Academy of Science.
"We look where the genetic signature of clusters on a haplotype tree (family tree)," explained Londo. "We chose samples across the entire range of rice and looked for DNA sequences that were shared by both wild and domesticated types. These two major groups clustered out by geography."
DNA is comprised of vast, varied combinations of chemical subunits known as base pairs. Londo, Schaal and their collaborators concentrated on finding genetic markers shared by both cultivated and wild rice types that ranged from 800 to 1,300 base pairs.
Cultivated rice has a genetic signature that defines it as cultivated, Schaal explained.
"What you do is go out and sample all the wild rice across regions and you look for that signature in the wild," said Schaal, who has done similar work with cassava and jocote, a tropical fruit. "You find that the unique signature of cultivated rice is only found in certain geographic regions. And that's how you make the determination of where it came from."
Schaal said that she was surprised and "delighted" by their results.
"People have moved rice around so much and the crop crosses with its wild ancestors pretty readily, so I was fully prepared to see no domestication signal whatsoever," Schaal said. "I would have expected to see clustering of the cultivated rice, but I was delighted to see geographical clustering of the wild rice. I was thrilled that there was even any sort of genetic structure in the wild rice."
In contrast to rice, other staple crops such as wheat, barley and corn appear to have been domesticated just once in history.
Rice is the largest staple crop for human consumption, supplying 20 percent of caloric content for the world.
By finding the geographic origins of rice, researchers can consider ways to improve the crop's nutritional value and disease resistance, which in turn can help impoverished populations in Asia and elsewhere that rely heavily on the crop.
Londo expects to find even more evidence for differing geographic domestication. He said that by using the database that they've gathered, they could design a sampling to target specialty rices such as the aromatic rices basmati and jasmine.
For instance, one direction that the researchers are going is Thailand, where the Karen tribe has been using multiple landraces of rice for many hundreds of years.
Landraces are localized varieties of rice that have been cultivated by traditional methods and have been passed down many generations, Schaal said.
"We're going to try to find out how landrace varieties change after domestication," Schaal said. "These landraces are ancient varieties, which are high in genetic diversity, thus valuable to breeders looking for new traits."
Tony Fitzpatrick | EurekAlert!
Copper hydroxide nanoparticles provide protection against toxic oxygen radicals in cigarette smoke
29.05.2017 | Johannes Gutenberg-Universität Mainz
Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University
The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.
The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
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....
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...
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...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
29.05.2017 | Physics and Astronomy
29.05.2017 | Physics and Astronomy
29.05.2017 | Earth Sciences