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WASHINGTON, May 2 (Xinhua) -- Rice originated in China, a team of U.S. genome researchers has concluded in a study tracing back thousands of years of evolutionary history through large-scale gene re-sequencing.Their findings, which appear Monday in the latest issue of the Proceedings of the National Academy of Sciences (PNAS), indicate that domesticated rice may have first appeared as far back as approximately 9,000 years ago in the Yangtze Valley of China. Previous research suggested domesticated rice may have two points of origin -- India as well as China.Asian rice, Oryza sativa, is one of world's oldest crop species. It is also a very diverse crop, with tens of thousands of varieties known throughout the world. Two major subspecies of rice -- japonica and indica -- represent most of the world's varieties. Sushi rice, for example, is a type of japonica, while most of the long-grain rice in risottos are indica.Because rice is so diverse, its origins have been the subject of scientific debate. One theory -- a single-origin model -- suggests that indica and japonica were domesticated once from the wild rice O. rufipogon.Another -- a multiple-origin model -- proposes that these two major rice types were domesticated separately and in different parts of Asia. The multiple-origin model has gained currency in recent years as biologists have observed significant genetic differences between indica and japonica, and several studies examining the evolutionary relationships among rice varieties supported more than domestication in both India and China.In the PNAS study, the researchers re-assessed the evolutionary history, or phylogeny, of domesticated rice using previously published datasets, some of which have been used to argue that indica and japonica rice have separate origins. Using more modern computer algorithms, however, the researchers concluded these two species have the same origin because they have a closer genetic relationship to each other than to any wild rice species found in either India or China.In addition, the study's authors examined the phylogeny of domesticated rice by re-sequencing 630 gene fragments on selected chromosomes from a diverse set of wild and domesticated rice varieties. Using new modeling techniques, which had previously been used to look at genomic data in human evolution, their results showed that the gene sequence data was more consistent with a single origin of rice.In the study, the investigators also used a "molecular clock" of rice genes to see when rice evolved. Depending on how the researchers calibrated their clock, they pinpointed the origin of rice at possibly 8,200 years ago, while japonica and indica split apart from each other about 3,900 years ago. The study's authors pointed out that these molecular dates were consistent with archaeological studies.Archaeologists have uncovered evidence in the last decade for rice domestication in the Yangtze Valley beginning approximately 8, 000 to 9,000 years ago while domestication of rice in the India's Ganges region was around about 4,000 years ago."As rice was brought in from China to India by traders and migrant farmers, it likely hybridized extensively with local wild rice," explained New York University biologist Michael Purugganan, one of the study's co-authors. "So domesticated rice that we may have once thought originated in India actually has its beginnings in China."

LOS ANGELES, April 29 (Xinhua) -- Clinical and teaching microbiology laboratories are linked with a nationwide salmonella outbreak in the United States that has killed one person and sickened dozens of others, health officials confirmed on Friday.Since August, about 73 people in 35 states have been sickened by salmonella bacteria, and some of those cases involve a strain of Salmonella typhimurium sold commercially to laboratories, officials from the Centers for Disease Control and Prevention (CDC) said in remarks published by msnbc.com.Illnesses have been tied to laboratories from Alaska to New York, with most reporting one or two cases. Five cases have been reported in Washington state and four in Minnesota.The first illness occurred late August and the most recent cases were reported March 8, according to the CDC.The patients include employees and students of the laboratories, as well as children in the homes of people who work or study at the labs.Patients ranged in age from less than one to 91, with a median age of 24, the CDC said.Cases that developed after March 19 may not yet be included in the total because of the lag time in assessing and reporting illness, said the report.CDC officials warned that bacteria used in the labs can be transmitted through contaminated lab coats, pens, notebooks, car keys and other items brought into the labs.The CDC is working with local and state health departments, the American Society for Microbiology and the Association of Public Health Laboratories to track the outbreak, the report said.Salmonella infections typically result in diarrhea, fever and abdominal cramps. They can be dangerous in very young children or people with compromised immune systems.

STOCKHOLM, Feb. 20 (Xinhua) -- The exhibition of the Chinese Terra-cotta Army here was an enormous success, project organizer Sanne Houby-Nielsen said Sunday.About 320 objects, including terra-cotta warriors from the ancient Chinese Qin Dynasty and other terra-cotta figures from Han Dynasty, were exhibited at the Far Eastern Antiquities Museum during the event, which ended Sunday.Houby-Nielsen, who is director of the museum and also director-general of the country's National Museums of World Culture, told Xinhua in an exclusive interview that the total number of visitors was around 350,000, more than double the expected turnout.This was the highest number of visitors the museum has ever experienced in its history since it was established in the 1940s, said Houby-Nielsen, adding that the exhibition was originally scheduled to end on Jan. 16, but "a great pressure from the audiences" prompted the museum to extend it till Sunday."It is an exhibition which won the most audience for many years in Sweden. We feel particularly happy because it was a very good display of the story of the first emperor and the early Han Dynasty," she said."We felt such a huge interest that we have to prolong it. So we were very grateful that it was possible to prolong the exhibition," she added.The exhibition was declared open by Swedish King Carl XVI Gustaf in August. Many of the ancient Chinese artifacts have never been exhibited outside China.Swedish Sinologist Cecelia Lindqvist commented that the event helped people understand the current China by looking at the history of China presented in the exhibition.

WASHINGTON, May 20 (Xinhua) -- Two U.S. astronauts conducted the first of four spacewalks for space shuttle Endeavour's STS-134 mission on Friday morning, the U.S. National Aeronautics and Space Administration (NASA) said.According to the U.S. space agency, Endeavour's mission specialists Andrew Feustel and Greg Chamitoff completed the six-hour, 19-minute spacewalk at 9:29 a.m. EDT (1329 GMT). They successfully installed antennas for the External Wireless Communication system, routing cables, setting up the antenna, installing handrails, and connecting power cables.Because of a carbon dioxide sensor failure in Chamitoff's spacesuit, flight controllers limited his spacewalk time to about six hours 20 minutes, 10 minutes less than the planned six hours and 30 minutes. There was no indication his suit's carbon dioxide levels would rise. However, they deferred tasks to remove a micrometeoroid debris shield to access and attach some of the connection points.This was the 245th spacewalk conducted by U.S. astronauts. It was Feustel's fourth spacewalk for a total time of 27 hours and 17 minutes, and Chamitoff's first.Endeavour lifted off on Monday morning from Kennedy Space Center in Florida, to deliver to the International Space Station a 2-billion-dollar, multinational particle detector known as the Alpha Magnetic Spectrometer (AMS).AMS, a particle physics detector, is designed to search for various types of unusual matter by measuring cosmic rays. Its experiments are designed to help researchers study the formation of the universe and search for evidence of dark matter, strange matter and antimatter.

BEIJING, March 24 (Xinhuanet) -- A new study has found that many overweight women and children often underestimate how heavy they are, according to media reports Wednesday.The study, conducted by researchers from Columbia University Medical Center in New York City, surveyed 111 women with the average age of 39 and 111 children aged between 7 and 13.Among the participants, about 66 percent of the women and 39 percent of the kids were overweight or obese.They were shown images of different body silhouettes representing a range of weights, including underweight, normal weight, overweight, obese and extremely obese.The research findings showed that 82 percent of obese women and 43 percent of overweight women underestimated their weight, while only 13 percent of normal weight women did so.As to the children group, about 86 percent overweight or obese kids low-balled their weight.Lead author Dr. Nicole Dumas said, "The implications of this is the overwhelming impact of obesity on children who are growing up in communities where obesity and overweight is the norm rather than the exception."  She added, "Strategies to overcome the obesity epidemic will need to address this barrier to weight loss."

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