Tuesday, December 29, 2009

ICY MOONS OF SATURN AND JUPITER MAY HAVE CONDITIONS NEEDED FOR LIFE

0 comentarios

Scientists once thought that life could originate only within a solar system's "habitable zone," where a planet would be neither too hot nor too cold for liquid water to exist on its surface. But according to planetary scientist Francis Nimmo, evidence from recent NASA missions suggests that conditions necessary for life may exist on the icy satellites of Saturn and Jupiter.

"If these moons are habitable, it changes the whole idea of the habitable zone," said Nimmo, a professor of Earth and planetary sciences at UC Santa Cruz. "It changes our thinking about how and where we might find life outside of the solar system."

Nimmo discussed the impact of ice dynamics on the habitability of the moons of Saturn and Jupiter on Tuesday, December 15, at the annual meeting of the American Geophysical Union in San Francisco.

Jupiter's moon Europa and Saturn's moon Enceladus, in particular, have attracted attention because of evidence that oceans of liquid water may lie beneath their icy surfaces. This evidence, plus discoveries of deep-sea hydrothermal vent communities on Earth, suggests to some that these frozen moons just might harbor life.

"Liquid water is the one requirement for life that everyone can agree on," Nimmo said.

The icy surfaces may insulate deep oceans, shift and fracture like tectonic plates, and mediate the flow of material and energy between the moons and space.

Several lines of evidence support the presence of subsurface oceans on Europa and Enceladus, Nimmo said. In 2000, for example, NASA's Galileo spacecraft measured an unusual magnetic field around Europa that was attributed to the presence of an ocean beneath the moon's surface. On Enceladus, the Cassini spacecraft discovered geysers shooting ice crystals a hundred miles above the surface, which also suggests at least pockets of subsurface water, Nimmo said (see earlier story).

Liquid water isn't easy to find in the cold expanses beyond Earth's orbit. But according to Nimmo, tidal forces could keep subsurface oceans from freezing up. Europa and Enceladus both have eccentric orbits that bring them alternately close to and then far away from their respective planets. These elongated orbits create ebbs and flows of gravitational energy between the planets and their satellites.

"A moon like Enceladus is getting squeezed and stretched and squeezed and stretched," Nimmo said.

The extent to which this squeezing and stretching transforms into heat remains unclear, he said. Tidal forces likely shift plates in the lunar cores, creating friction and geothermal energy. This energy may also rub surface ice against itself at the sites of deep ice fissures, creating heat and melting, according to Nimmo. Enceladus's geysers appear to originate from these shifting faults, and the thin lines running along Europa's surface suggest geologically active plates, he said.

A frozen outer layer may be crucial to maintaining oceans that could harbor life on these moons. The icy surfaces may shield the oceans from the frigidity of space and from radiation harmful to living organisms.

"If you want to have life, you want the ocean to last a long time," Nimmo said. "The ice above acts like an insulating blanket."

Enceladus is so small and its ice so thin that scientists expect its oceans to freeze periodically, making habitability less likely, Nimmo said. Europa, however, is the perfect size to heat its oceans efficiently. It is larger than Enceladus but smaller than moons such as Ganymede, which has thick ice surrounding its core and blocking communication with the exterior. If liquid water exists on Ganymede, it may be trapped between layers of ice that separate it from both the core and the surface.

The core and the surface of these moons are both potential sources of the chemical building blocks needed for life. Solar radiation and comet impacts leave a chemical film on the surfaces. To sustain living organisms, these chemicals would have to migrate to the subsurface oceans, and this can occur periodically around ice fissures on moons with relatively thin ice shells like Europa and Enceladus. Organic molecules and minerals may also stream out of their cores, Nimmo said. These nutrients could support communities like those seen around hydrothermal vents on Earth.

Nimmo cautioned that being habitable is no guarantee that a planetary body is actually inhabited. It is unlikely that we will find life elsewhere in our solar system, despite all the time and resources devoted to the search, he said. But such a discovery would certainly be worth the effort.

"I think pretty much everyone can agree that finding life anywhere else in the solar system would be the scientific discovery of the millennium," Nimmo said.

(Photo: NASA/JPL/Space Science Institute)

University of California

SUPERNOVA EXPLOSIONS STAY IN SHAPE

0 comentarios

At a very early age, children learn how to classify objects according to their shape. Now, new research suggests studying the shape of the aftermath of supernovas may allow astronomers to do the same.

A new study of images from NASA's Chandra X-ray Observatory on supernova remnants - the debris from exploded stars - shows that the symmetry of the remnants, or lack thereof, reveals how the star exploded. This is an important discovery because it shows that the remnants retain information about how the star exploded even though hundreds or thousands of years have passed.

"It's almost like the supernova remnants have a 'memory' of the original explosion," said Laura Lopez of the University of California at Santa Cruz, who led the study. "This is the first time anyone has systematically compared the shape of these remnants in X-rays in this way."

Astronomers sort supernovas into several categories, or "types", based on properties observed days after the explosion and which reflect very different physical mechanisms that cause stars to explode. But, since observed remnants of supernovas are leftover from explosions that occurred long ago, other methods are needed to accurately classify the original supernovas.

Lopez and colleagues focused on the relatively young supernova remnants that exhibited strong X-ray emission from silicon ejected by the explosion so as to rule out the effects of interstellar matter surrounding the explosion. Their analysis showed that the X-ray images of the ejecta can be used to identify the way the star exploded. The team studied 17 supernova remnants both in the Milky Way galaxy and a neighboring galaxy, the Large Magellanic Cloud.

For each of these remnants there is independent information about the type of supernova involved, based not on the shape of the remnant but, for example, on the elements observed in it. The researchers found that one type of supernova explosion - the so-called Type Ia - left behind relatively symmetric, circular remnants. This type of supernova is thought to be caused by a thermonuclear explosion of a white dwarf, and is often used by astronomers as "standard candles" for measuring cosmic distances.

On the other hand, the remnants tied to the "core-collapse" supernova explosions were distinctly more asymmetric. This type of supernova occurs when a very massive, young star collapses onto itself and then explodes.

"If we can link supernova remnants with the type of explosion", said co-author Enrico Ramirez-Ruiz, also of University of California, Santa Cruz, "then we can use that information in theoretical models to really help us nail down the details of how the supernovas went off."

Models of core-collapse supernovas must include a way to reproduce the asymmetries measured in this work and models of Type Ia supernovas must produce the symmetric, circular remnants that have been observed.

Out of the 17 supernova remnants sampled, ten were classified as the core-collapse variety, while the remaining seven of them were classified as Type Ia. One of these, a remnant known as SNR 0548-70.4, was a bit of an "oddball". This one was considered a Type Ia based on its chemical abundances, but Lopez finds it has the asymmetry of a core-collapse remnant.

"We do have one mysterious object, but we think that is probably a Type Ia with an unusual orientation to our line of sight," said Lopez. "But we'll definitely be looking at that one again."

While the supernova remnants in the Lopez sample were taken from the Milky Way and its close neighbor, it is possible this technique could be extended to remnants at even greater distances. For example, large, bright supernova remnants in the galaxy M33 could be included in future studies to determine the types of supernova that generated them.

(Photo: NASA/CXC/UCSC/L. Lopez et al.)

Harvard-Smithsonian Center for Astrophysics

UMBILICAL CORD COULD BE NEW SOURCE OF PLENTIFUL STEM CELLS

0 comentarios
Stem cells that could one day provide therapeutic options for muscle and bone disorders can be easily harvested from the tissue of the umbilical cord, just as the blood that goes through it provides precursor cells to treat some blood disorders, said University of Pittsburgh School of Medicine researchers in the online version of the Journal of Biomedicine and Biotechnology.

Umbilical cord tissue cells can be expanded to greater number, are remarkably stable and might not trigger strong immune responses, said senior investigator Bridget M. Deasy, Ph.D., assistant professor in the Department of Orthopaedic Surgery, Pitt School of Medicine. The cells are obtained from the gelatinous material in the cord known as Wharton's jelly and from blood vessel walls.

"Our experiments indicate also that at least 21 million stem cells, and possibly as many as 500 million, could be banked from a single umbilical cord after the birth of a baby," she noted. "So, the cord could become an accessible source of a multitude of stem cells that overcomes many of the restrictions, such as limited quantity as well as donor age and donor sex issues, that come with other adult stem cell populations."

Dr. Deasy and her team analyzed sections of two-foot-long human umbilical cords that were donated for research, looking for cells in Wharton's jelly and blood vessel walls that displayed the characteristic protein markers found in stem cells derived from other sources. The researchers then sought to find the best way to isolate the stem cells from the cords, and tested them in the lab to confirm their ability to produce specialized cells, such as bone and cartilage, while retaining their invaluable ability to renew themselves.

To build on these findings, the team will test the umbilical cord stem cells in animal models of cartilage and bone repair, as well as muscle regeneration.

University of Pittsburgh

DNA OF JESUS-ERA SHROUDED MAN IN JERUSALEM REVEALS EARLIEST CASE OF LEPROSY

0 comentarios

The DNA of a 1st century shrouded man found in a tomb on the edge of the Old City of Jerusalem has revealed the earliest proven case of leprosy. Details of the research were published December 16 in the PloS ONE Journal.

The molecular investigation was undertaken by Prof. Mark Spigelman and Prof. Charles Greenblatt and of the Sanford F. Kuvin Center for the Study of Infectious and Tropical Diseases at the Hebrew University of Jerusalem, Prof. Carney Matheson and Ms. Kim Vernon of Lakehead University, Canada, Prof. Azriel Gorski of New Haven University and Dr. Helen Donoghue of University College London. The archaeological excavation was led by Prof. Shimon Gibson, Dr. Boaz Zissu and Prof. James Tabor on behalf of the Israel Antiquities Authority and the University of North Carolina at Charlotte.

The burial cave, which is known as the Tomb of the Shroud, is located in the lower Hinnom Valley and is part of a 1st century C.E. cemetery known as Akeldama or 'Field of Blood' (Matthew 27:3-8; Acts 1:19) - next to the area where Judas is said to have committed suicide. The tomb of the shrouded man is located next to the tomb of Annas, the high priest (6-15 C.E.), who was the father in law of Caiaphas, the high priest who betrayed Jesus to the Romans. It is thus thought that this shrouded man was either a priest or a member of the aristocracy. According to Prof. Gibson, the view from the tomb would have looked directly toward the Jewish Temple.

What is particularly rare about this tomb is that it was clear this man, which is dated by radiocarbon methods to 1-50 C.E., did not receive a secondary burial. Secondary burials were common practice at the time, where the bones were removed after a year and placed in an ossuary (a stone bone box). In this case, however, the entrance to this part of the tomb was completely sealed with plaster. Prof. Spigelman believes this is due to the fact that this man had suffered from leprosy and died of tuberculosis, as the DNA of both diseases was found in his bones.

Historically, disfiguring diseases - particularly leprosy - caused the afflicted individuals to be ostracized from their communities. However, a number of indications – the location and size of the tomb, the type of textiles used as shroud wrappings, and the clean state of the hair – suggest that the shrouded individual was a fairly affluent member of society in Jerusalem and that tuberculosis and leprosy may have crossed social boundaries in the first century C.E.

This is also the first time fragments of a burial shroud have been found from the time of Jesus in Jerusalem. The shroud is very different to that of the Turin Shroud, hitherto assumed to be the one that was used to wrap the body of Jesus. Unlike the complex weave of the Turin Shroud, this is made up of a simple two-way weave, as the textiles historian Dr. Orit Shamir was able to show.

Based on the assumption that this is representative of a typical burial shroud widely used at the time of Jesus, the researchers conclude that the Turin Shroud did not originate from Jesus-era Jerusalem.

The excavation also found a clump of the shrouded man's hair, which had been ritually cut prior to his burial. These are both unique discoveries because organic remains are hardly ever preserved in the Jerusalem area owing to high humidity levels in the ground.

According to Prof. Spigelman and Prof. Greenblatt, the origins and development of leprosy are largely obscure. Leprosy in the Old Testament may well refer to skin rashes such as psoriasis. The leprosy known to us today was thought to have originated in India and brought over to the Near East and to Mediterranean countries in the Hellenistic period. The results from the first-century C.E. Tomb of the Shroud fill a vital gap in our knowledge of this disease.

Furthermore, the new research has shown that molecular pathology clearly adds a new dimension to the archaeological exploration of disease in ancient times and provides us with a better understanding of the evolution, geographic distribution and epidemiology of disease and social health in antiquity.

The co-infection of both leprosy and tuberculosis here and in 30 percent of DNA remains in Israel and Europe from the ancient and modern period provided evidence for the postulate that the medieval plague of leprosy was eliminated by an increased level of tuberculosis in Europe as the area urbanized.

(Photo: Prof. Shimon Gibson)

The Hebrew University of Jerusalem

AMONG APES, TEETH ARE MADE FOR THE TOUGHEST TIMES

0 comentarios
The teeth of some apes are formed primarily to handle the most stressful times when food is scarce, according to new research performed at the National Institute of Standards and Technology (NIST). The findings imply that if humanity is serious about protecting its close evolutionary cousins, the food apes eat during these tough periods—and where they find it—must be included in conservation efforts.

The interdisciplinary team, which brought together anthropologists from George Washington University (GWU) and fracture mechanics experts from NIST, has provided the first evidence that natural selection in three ape species has favored individuals whose teeth can most easily handle the "fallback foods" they choose when their preferred fare is less available. All of these apes—gorillas, orangutans and chimpanzees—favor a diet of fruit whenever possible. But when fruit disappears from their usual foraging grounds, each species responds in a different way—and has developed teeth formed to reflect the differences.

"It makes sense if you think about it," says GWU's Paul Constantino. "When resources are scarce, that's when natural selection is highly active in weeding out the less fit, so animals without the necessary equipment to get through those tough times won't pass on their genes to the next generation."

In this case, the necessary equipment is the right set of molars. The team examined ape tooth enamel and found that several aspects of molar shape and structure can be explained in terms of adapting to eat fallback foods. For instance, gorillas' second choice is leaves and tree bark, which are much tougher than fruit, while orangutans fall back to nuts and seeds, which are comparatively hard.

For these reasons, the researchers theorized that gorillas would have evolved broader back teeth than a fruit diet would require in order to chew leaves, but orangutans would have thicker enamel to handle the increased stress of crunching seeds.

NIST scientists developed models of how teeth fracture while chewing different foods. By fracturing teeth in the laboratory, they verified fundamental fracture mechanics models incorporating tooth shape and structure. These efforts revealed the effects of food stiffness and how various foods likely would damage ape teeth. "The research at NIST supports our theories and several related ones," Constantino says. "It's likely that fallback foods have influenced jaw and skull shape as well."

Constantino adds that the findings suggest mankind must protect not only forest areas where commonly eaten fruits grow, but also the places where apes' fallback resources appear. While identifying precisely what these resources are is a job for ecologists, he says, the new research shows just how important and influential these foods are in primate ecology.

"Among orangutans, for example, timber companies are harvesting the sources of their fallbacks," Constantino says. "These apes have evolved the right tools to survive on fallback foods, but they need to be able to find these foods in the first place."

National Institute of Standards and Technology

RESEARCHERS DISCOVER NEW 'GOLDEN RATIOS' FOR FEMALE FACIAL BEAUTY

0 comentarios
Beauty is not only in the eye of the beholder but also in the relationship of the eyes and mouth of the beholden. The distance between a woman's eyes and the distance between her eyes and her mouth are key factors in determining how attractive she is to others, according to new psychology research from the University of California, San Diego and the University of Toronto.

Pamela Pallett and Stephen Link of UC San Diego and Kang Lee of the University of Toronto tested the existence of an ideal facial feature arrangement. They successfully identified the optimal relation between the eyes, the mouth and the edge of the face for individual beauty.

In four separate experiments, the researchers asked university students to make paired comparisons of attractiveness between female faces with identical facial features but different eye-mouth distances and different distances between the eyes.

They discovered two "golden ratios," one for length and one for width. Female faces were judged more attractive when the vertical distance between their eyes and the mouth was approximately 36 percent of the face's length, and the horizontal distance between their eyes was approximately 46 percent of the face's width.

Interestingly, these proportions correspond with those of an average face.

"People have tried and failed to find these ratios since antiquity. The ancient Greeks found what they believed was a 'golden ratio' – also known as 'phi' or the 'divine proportion' – and used it in their architecture and art. Some even suggest that Leonardo Da Vinci used the golden ratio when painting his 'Mona Lisa.' But there was never any proof that the golden ratio was special. As it turns out, it isn't. Instead of phi, we showed that average distances between the eyes, mouth and face contour form the true golden ratios," said Pallett, a post-doctoral fellow in psychology at UC San Diego and also an alumna of the department.

"We already know that different facial features make a female face attractive – large eyes, for example, or full lips," said Lee, a professor at University of Toronto and the director of the Institute of Child Study at the Ontario Institute for Studies in Education. "Our study conclusively proves that the structure of faces – the relation between our face contour and the eyes, mouth and nose – also contributes to our perception of facial attractiveness. Our finding also explains why sometimes an attractive person looks unattractive or vice versa after a haircut, because hairdos change the ratios."

The researchers suggest that the perception of facial attractiveness is a result of a cognitive averaging process by which people take in all the faces they see and average them to get an ideal width ratio and an ideal length ratio. They also posit that "averageness" (like symmetry) is a proxy for health, and that we may be predisposed by biology and evolution to find average faces attractive.

University of Toronto

ETHANOL-POWERED VEHICLES GENERATE MORE OZONE THAN GAS-POWERED ONES

0 comentarios

Ethanol, often promoted as a clean-burning, renewable fuel that could help wean the nation from oil, would likely worsen health problems caused by ozone, compared with gasoline, especially in winter, according to a new study led by Stanford researchers.

Ozone production from both gasoline and E85, a blend of gasoline and ethanol that is 85 percent ethanol, is greater in warm sunny weather than during the cold weather and short days of winter, because heat and sunlight contribute to ozone formation. But E85 produces different byproducts of combustion than gasoline and generates substantially more aldehydes, which are precursors to ozone.

"What we found is that at the warmer temperatures, with E85, there is a slight increase in ozone compared to what gasoline would produce," said Diana Ginnebaugh, a doctoral candidate in civil and environmental engineering, who worked on the study. She presented the results of the study on Tuesday, Dec. 15, at the American Geophysical Union meeting in San Francisco. "But even a slight increase is a concern, especially in a place like Los Angeles, because you already have episodes of high ozone that you have to be concerned about, so you don't want any increase."

But it was at colder temperatures, below freezing, that it appeared the health impacts of E85 would be felt most strongly.

"We found a pretty substantial increase in ozone production from E85 at cold temperatures, relative to gasoline when emissions and atmospheric chemistry alone were considered," Ginnebaugh said. Although ozone is generally lower under cold-temperature winter conditions, "If you switched to E85, suddenly you could have a place like Denver exceeding ozone health-effects limits and then they would have a health concern that they don't have now."

The problem with cold weather emissions arises because the catalytic converters used on vehicles have to warm up before they reach full efficiency. So until they get warm, a larger proportion of pollutants escapes from the tailpipe into the air.

There are other pollutants that would increase in the atmosphere from burning E85 instead of gasoline, some of which are irritants to eyes, throats and lungs, and can also damage crops, but the aldehydes are the biggest contributors to ozone production, as well as being carcinogenic.

Ginnebaugh worked with Mark Z. Jacobson, professor of civil and environmental engineering, using vehicle emissions data from some earlier studies and applying it to the Los Angeles area to model the likely output of pollutants from vehicles.

Because E85 is only now beginning to be used in mass-produced vehicles, the researchers projected for the year 2020, when more "flex fuel" vehicles, which can run on E85, will likely be in use. They estimated that vehicle emissions would be about 60 percent less than today, because automotive technology will likely continue to become cleaner over time. They investigated two scenarios, one that had all the vehicles running on E85 and another in which the vehicles all ran on gasoline.

Running a widely used, complex model involving over 13,000 chemical reactions, they did repeated simulations at different ambient temperatures for the two scenarios, each time simulating a 48-hour period. They used the average ozone concentrations during each of those periods for comparison.

They found that at warm temperatures, from freezing up to 41 degrees Celsius (give F conversion), in bright sunlight, E85 raised the concentration of ozone in the air by up to 7 parts per billion more than produced by gasoline. At cold temperatures, from freezing down to minus 37 degrees Celsius, they found E85 raised ozone concentrations by up to 39 parts per billion more than gasoline.

"What we are saying with these results is that you see an increase," Ginnebaugh said. "We are not saying that this is the exact magnitude you are going to get in a given urban area, because it is really going to vary from city to city depending on a lot of other factors such as the amount of natural vegetation, traffic levels, and local weather patterns."

Ginnebaugh said the results of the study represent a preliminary analysis of the impact of E85. More data from studies of the emissions of flex fuel vehicles at various temperatures would help refine the estimates, she said.

(Photo: Beth McConnell)

Stanford University

KANSAS SCIENTISTS PROBE MYSTERIOUS POSSIBLE COMET STRIKES ON EARTH

0 comentarios
It's the stuff of a Hollywood disaster epic: A comet plunges from outer space into the Earth's atmosphere, splitting the sky with a devastating shock wave that flattens forests and shakes the countryside. But this isn't a disaster movie plotline.

"Comet impacts might be much more frequent than we expect," said Adrian Melott, professor of physics and astronomy at the University of Kansas. "There's a lot of interest in the rate of impact events upon the Earth. We really don't know the rate very well because most craters end up being destroyed by erosion or the comets go into the ocean and we don't know that they're there. We really don't have a good handle on the rate of impacts on the Earth."

An investigation by Melott and colleagues reveals a promising new method of detecting past comet strikes upon Earth and gauging their frequency. The results will be unveiled at the American Geophysical Union's Fall Meeting, to be held Dec. 14-18 in San Francisco.

The research shows a potential signature of nitrate and ammonia that can be found in ice cores corresponding to suspected impacts. Although high nitrate levels previously have been tied to space impacts, scientists have never before seen atmospheric ammonia spikes as indicators of space impacts with our planet.

"Now we have a possible new marker for extraterrestrial events in ice," Melott said. "You don't just look for nitrates, you also look for ammonia."

Melott studied two possible cometary airbursts with Brian Thomas, assistant professor of physics and astronomy at Washburn University, Gisela Dreschhoff, KU adjunct associate professor of physics and astronomy, and Carey Johnson, KU professor of chemistry.

In June 1908, a puzzling explosion rocked central Siberia in Russia; it came to be known as the "Tunguska event." A later expedition found that 20 miles of trees had been knocked down and set alight by the blast. Today, scientists have coalesced around the idea that Tunguska's devastation was caused by a 100-foot asteroid that had entered Earth's atmosphere, causing an airburst.

Some 13,000 years earlier, an occurrence thought by some researchers to be an extraterrestrial impact set off cooler weather and large-scale extinctions in North America. The "Younger Dryas event," as it is known, coincided with the end of the prehistoric Clovis culture.

Melott and fellow researchers examined data from ice cores extracted in Greenland to compare atmospheric chemistry during the Tunguska and Younger Dryas events. In both instances, Melott's group found evidence that the Haber process — whereby a nitrogen fixation reaction produces ammonia — may have occurred on a large scale.

"A comet entering the atmosphere makes a big shock wave with high pressure — 6,000 times the pressure of air," said Melott. "It can be shown that under those conditions you can make ammonia. Plus the Tunguska comet, or some fragments of it, landed in a swamp. And any Younger Dryas comet presumably hit an ice sheet, or at least part of it did. So there should have been lots of water around for this Haber process to work. We think the simplest way to explain the signal in both objects is the Haber process. Comets hit the atmosphere in the presence of a lot of water and you get both nitrate and ammonia, which is what both ice cores show."

Melott cautions that the results are inconclusive because the ice cores are sampled at five-year intervals only, not sufficient resolution to pinpoint peaks of atmospheric nitrates and ammonia, which rapidly would have been dissipated by rains following a comet strike.

But the KU researcher contends that ammonia enhancement resulting from the Haber process could serve as a useful marker for detecting possible comet impacts. He encourages more sampling and analysis of ice cores to see where the nitrate-ammonia signal might line up with suspected cometary collisions with the Earth.

Such information could help humankind more accurately gauge the danger of a comet hitting the Earth in the future.

"There's a whole program to watch for near-Earth asteroids as they go around the sun repeatedly, and some of them have close brushes with the Earth," said Melott. "But comets are a whole different ball game. They don't do that circular thing. They come straight in from far, far out — and you don't see them coming until they push out a tail only a few years before they would enter the inner solar system. So we could be hit by a comet and only have a few years' warning — possibly not enough time to do anything about it."

Kansas University

UNDERSTANDING APPLES' ANCESTORS

0 comentarios

Wild Malus orientalis—species of wild apples that could be an ancestor of today's domesticated apples—are native to the Middle East and Central Asia. A new study comparing the diversity of recently acquired M. orientalis varieties from Georgia and Armenia with previously collected varieties originating in Russia and Turkey narrows the large population and establishes a core collection that will make M. orientalis more accessible to the breeding and research communities.

To identify and record the genetic diversity of these wild apples, Gayle Volk and Christopher Richards at the National Center for Genetic Resources Preservation, U.S. Department of Agriculture (USDA), performed genetic diversity analyses on trees grown from Malus orientalis seeds collected in Georgia, Armenia, Russia, and Turkey. The trees are located at the USDA-ARS Plant Genetic Resources Unit (PGRU) in Geneva, New York. Seedling trees were evaluated for resistance to critical diseases such as fire blight, apple scab, and cedar apple rust. The full report was published in a recent issue of the Journal of the American Society for Horticultural Science.

Seeds from wild Malus orientalis trees were collected from 1998-2004 during explorations to Armenia, Georgia, Turkey, and Russia. Seedling orchards with between eight and 171 "individuals" from each collection location were established, and disease resistance data were collected for 776 trees. The genetic diversity of the 280 individuals from Armenia and Georgia was compared with results obtained for individuals from Russia and Turkey. A total of 106 alleles were identified in the trees from Georgia and Armenia. The average gene diversity ranged from 0.47 to 0.85 per locus. The researchers concluded that "the genetic differentiation among sampling locations was greater than that found between the two countries."

Six individuals from Armenia exhibited resistance to fire blight, apple scab, and cedar apple rust. According to Volk; "The data suggest wild populations of M. orientalis from regions around the Black Sea are genetically distinguishable and show high levels of diversity."

A core set of 27 trees that captures 93% of the alleles in the PGRU M. orientalis collection will be maintained in the field at the PGRU in Geneva, New York.

(Photo: Phil Forsline)

American Society for Horticultural Science

Followers

Archive

 

Selected Science News. Copyright 2008 All Rights Reserved Revolution Two Church theme by Brian Gardner Converted into Blogger Template by Bloganol dot com