It has been accepted for 80 years that American elms (Ulmus americana) are tetraploids, trees with four copies of each chromosome. But there have also been persistent but dismissed rumors of trees that had fewer copies—triploids, which have three copies of chromosomes, or diploids, which have two copies.
Now botanist Alan T. Whittemore and geneticist Richard T. Olsen with USDA's Agricultural Research Service (ARS) have proven beyond question that diploid American elms exist as a subset of elms in the wild. Their findings will be published in the April edition of the American Journal of Botany. Whittemore and Olsen work at the U.S. National Arboretum operated by ARS in Washington, D.C.
American elms once lined the country's streets and dominated eastern forests until they succumbed by the millions after Dutch elm disease arrived in the United States in 1931. Yet elms are still one of the most important tree crops for the $4.7 billion-a-year nursery industry, especially since the introduction of a very few new trees with some tolerance to the disease. American elms remain popular because of their stately beauty, their rapid leaf litter decay and their ability to stand up to city air pollution.
It was one of the disease-tolerant elm trees—Jefferson, released jointly by ARS and the National Park Service in 2005—that put Whittemore and Olsen on the trail of the diploid.
"Jefferson is a triploid. To get a triploid elm, we thought there had to be a diploid parent out there somewhere in the wild that had crossed with a tetraploid," said Whittemore.
To settle the question, the two scientists tested elm trees from across the species' eastern and central U.S. range. About 21 percent of the wild elms sampled were diploid; some grew in stands with tetraploids, while others were larger groupings of diploids.
The small amount of genetic data now available suggests that at least some tetraploid and diploid elm populations have diverged significantly from one another, which strengthens the possibility of the diploid trees having genes for disease resistance that the tetraploids don't have, Whittemore said.
"We can't say yet whether this is a distinct race of U. americana or if we are really talking about a separate species," he said. "That's a job we will tackle this summer."
Kim Kaplan | EurekAlert!
Climate change, population growth may lead to open ocean aquaculture
05.10.2017 | Oregon State University
New machine evaluates soybean at harvest for quality
04.10.2017 | University of Illinois College of Agricultural, Consumer and Environmental Sciences
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research