Mosquitoes can detect a very fine chemical structure difference in octenol, a compound emitted by mammals, according to new research by ARS scientists. Click the image for more information about it.

ARS Study Provides a Better Understanding

 of How Mosquitoes Find a Host

The potentially deadly yellow-fever-transmitting Aedes aegypti mosquito detects the specific chemical structure of a compound called octenol as one way to find a mammalian host for a blood meal, Agricultural Research Service (ARS) scientists report.

Scientists have long known that mosquitoes can detect octenol, but this most recent finding by ARS entomologists Joseph Dickens and Jonathan Bohbot explains in greater detail how Ae. aegypti—and possibly other mosquito species—accomplish this.

Dickens and Bohbot, at the ARS Invasive Insect Biocontrol and Behavior Laboratory in Beltsville, Md., have shown that Ae. aegypti taps into the "right-handed" and "left-handed" structural nature of octenol, which is emitted by people, cattle and other mammals. This ability to detect the "handedness" of molecules has been shown in mammals, but the discovery is the first case of scientists finding out how it works in an insect, according to the researchers.

When they hunt for a blood meal, mosquitoes hone in on a variety of chemicals, including carbon dioxide, lactic acid, ammonia and octenol. Octenol is one of many carbon-based compounds that have a molecular structure that can take on either a "right-handed" or "left-handed" form. Each form is a mirror image of the other, and a form's "handedness" is determined by how its molecular bonds are assembled.

The scientists used frog eggs to help them make their discovery. They injected RNA from Ae. aegypti into the frog eggs, allowing the egg membranes to mimic the mosquito's ability to detect octenol. Then they attached microelectrodes to the frog egg cell membranes, passed octenol over them and recorded the electrical signals stimulated by the odors.

They ran the tests using both the right- and left-handed forms of octenol. The scientists found heightened electrical activity when the membrane was exposed to the right-handed form, and weakened activity when it was exposed to the left-handed form.

There are many natural compounds that can take on either a right-handed or left-handed form. While the effects of those differences on many plants and animals remains a mystery, the report, published in PLoS ONE, shows the effects of octenol's dual structure on the yellow fever mosquito and adds to scientists' understanding of how mosquitoes sense the world around them. It also may open the door to speedier development of better mosquito repellents and traps, according to Dickens.

The team's research is being funded by the Department of Defense Deployed War Fighter Protection Research Program.

ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture.

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Geraniums Could Help Control Devastating Japanese Beetle

ARS scientists have discovered that geraniums could be useful in helping control the Japanese beetle, a costly pest that feeds on nearly 300 plant species.

Within 30 minutes of consuming geranium petals, the beetle rolls over on its back, its legs and antennae slowly twitch, and it remains paralyzed for several hours. The beetles typically recover within 24 hours, but they often succumb to death after predators spot and devour the beetles while they are helpless.

Geraniums may hold the key to controlling the devastating Japanese beetle, which feeds on nearly 300 plant species and costs the ornamental plant industry $450 million in damage each year, according to scientists with the Agricultural Research Service (ARS).

The beetle, Popillia japonica Newman, can feast on a wide variety of plants, including ornamentals, soybean, maize, fruits and vegetables. But within 30 minutes of consuming geranium petals, the beetle rolls over on its back, its legs and antennae slowly twitch, and it remains paralyzed for several hours. The beetles typically recover within 24 hours when paralyzed under laboratory conditions, but they often succumb to death under field conditions after predators spot and devour the beetles while they are helpless.

ARS entomologist Chris Ranger at the agency’s Application Technology Research Unit in Wooster, Ohio, is working on developing a way to use geraniums to control the beetles.

Ohio and neighboring Michigan are some of the largest producers of horticultural plants, most of them grown in greenhouses. Other research to benefit the horticultural industry includes that of Susan Stieve, curator of Ohio State University’s Ornamental Plant Germplasm Center in Columbus, Ohio.

Stieve is working with OSU collaborators and horticulturist Jonathan Frantz of the ARS Greenhouse Production Research Group in Toledo, Ohio, to see whether a specialized breed of begonias can tolerate colder temperatures.

The scientists are screening the begonias at two production temperatures: 5 degrees Fahrenheit colder than normal, and 10 degrees F colder than normal. Begonias are found naturally in a wide variety of climates and altitudes—ecological clues that can be used to identify promising germplasm. Being able to grow begonias at cooler temperatures could reduce greenhouse heating bills for ornamental growers in northern climates.

ARS is U.S. Department of Agriculture’s principal intramural scientific research agency.

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ARS is studying how the antibiotic oxytetracycline, which is used on livestock, breaks down in cattle manure. Click the image for more information about it.

Assessing Antibiotic Breakdown in Manure

Agricultural Research Service (ARS) scientist Scott Yates is studying how oxytetracycline (OTC), an antibiotic that is administered to animals, breaks down in cattle manure.

Livestock producers in the United States often use antibiotics to control disease in their animals, and confined U.S. livestock and poultry generate about 63.8 million tons of manure every year. The drugs are often only partially absorbed by the digestive tract, and the rest are excreted with their pharmaceutical activity intact.

Yates, who works at the ARS Contaminant Fate and Transport Research Unit in Riverside, Calif., found that in controlled laboratory conditions, OTC in cattle manure was degraded more quickly as temperatures increased and as the moisture content in the manure increased. But the OTC breakdown slowed as water saturation levels neared 100 percent. Yates concluded that this slowdown resulted when oxygen levels were not high enough to fuel the OTC biodegradation.

Yates also noted that OTC breaks down more quickly in manure than in soil. Compared to soil, manure has higher levels of organic material and moisture, which support the microorganisms that break down this pharmaceutical.

This laboratory research may be useful in designing studies that evaluate the potential effects of lagoons, holding ponds and manure pits on bacteria and antimicrobial resistance.

Livestock producers also might use the results from this study to maximize the breakdown of organic materials and potential antibiotics in manure by designing storage environments with optimum temperatures and moisture levels.

Results from this study were published in the Journal of Agricultural and Food Chemistry.

ARS is the chief intramural scientific research agency of the U.S. Department of Agriculture.

    

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Cattle grazing on rangeland with a taller canopy of plants with more and larger leaves take larger bites and meet their dietary needs with lower calorie expenditure, according to new research from ARS. Click the image for more information about it.

Cows Like Leaves

Their Tongues Can Wrap Around Easily

Lots of leaves growing in easy reach of a cow's tongue means less time and less land needed to raise beef cattle, according to Agricultural Research Service (ARS) and DairyNZ (New Zealand) scientists.

Ranchers may be able to tell how long to leave cattle in a pasture, and how large to make the pasture, by the height and leafiness of plants growing there, according to Stacey Gunter, research leader at the ARS Southern Plains Range Research Station in Woodward, Okla. He worked with former Ph.D. student Pablo Gregorini and colleagues at Woodward to demonstrate this approach with beef steers grazing in fenced-off corridors in wheat pastures.

The pastures were chosen to represent a range of natural variations in plant heights and upper plant leafiness. The steers were allowed to graze the corridors freely and were removed when they reached the end of the corridor, regardless of how much time the steers took. While grazing the corridors, each steer was videotaped and had two trained observers who counted bites and walking steps.

The reason for this real-life pasture study is that most studies of grazing behavior are done on "artificial seedings," specially planted pastures, or small plots that are fairly uniform. To provide the best possible recommendations to ranchers, Gunter and Gregorini integrated studies of the standard type with "in field" pasture conditions which are much less uniform.

Besides the taste and nutrition of large leaves, cattle like their food to be accessible, with leaves high on the plant and a minimum of stem interference with the cattle's tongues, which they use to wrap around and pull off leaves. Cattle faced with a nice canopy of luscious leaves took larger bites and were able to get their daily rations with lower calorie expenditure.

This resulted in greater eating efficiency. Gunter and Gregorini measured eating efficiency by dividing the total amount of pasture plants eaten per steer by the total eating time. This is known as herbage intake rate, a key determinant of weight gain for cattle grazing pasture.

The research was published in the Journal of Animal Science.

ARS is the principal intramural scientific research agency in the U.S. Department of Agriculture. The research supports the USDA priority of promoting international food security.

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Five new potato breeding lines now being tested by ARS scientists and collaborators could provide the basis for varieties that can handle powdery scab and black dot diseases. Photo courtesy of Microsoft Clipart

Tough New Spuds Take on Double Trouble

Americans love potatoes, consuming about 130 pounds per person annually. But it's a wonder the spuds even make it to the dinner table, given the many fungal diseases that attack the tuber crop—powdery scab and black dot among them.

Now, five new potato breeding lines being tested by Agricultural Research Service (ARS) scientists and collaborators could open the door to new varieties of the crop that resist powdery scab and black dot diseases, caused by the fungi Spongospora subterranea and Colletotrichum coccodes, respectively.

These fungi often occur together in the same soil, attacking the potato plant's roots, tubers or stems. Outbreaks can cause yield losses of up to 25 percent and prevent tubers from reaching the sizes needed by the french fry and fast-food industry. Of the two fungi, only black dot can be chemically controlled with fungicides; however, multiple applications are needed, ratcheting up production costs to prohibitive levels. A more sustainable alternative is genetic resistance, according to geneticist Chuck Brown, with the ARS Vegetable and Forage Crops Production Research Laboratory in Prosser, Wash.

In studies conducted there since 2004 with Washington State University professor Dennis Johnson, assistant Tom F. Cummings and postdoctoral associate Nadav Nitzan, Brown screened an existing collection of wild and cultivated potatoes for sources of natural resistance to powdery scab and black dot in a local grower's infested field.

The effort ultimately led to five advanced potato breeding lines that had been developed from a wild species from Mexico, Solanum hougasii, and a recent commercial release, Summit Russet. In three years of field trials in Washington State and Idaho, the potato breeding lines consistently showed fewer disease symptoms—root galling for powdery scab and sclerotia-infected stems for black dot—than other lines and varieties tested.

The potato breeding lines themselves aren't intended for production. Instead, they'll be made available as seed for use in breeding programs aimed at developing the first commercial varieties with dual resistance to the fungal diseases, according to Brown, who discussed the research at the 48th Annual Washington State Potato Conference in January.

The research findings have been published in the journal Plant Disease.

ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture (USDA). This research supports the USDA priority of promoting international food security.

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Children taking an intensive, instructor-led weight control course had significantly greater weight loss than did children in a self-taught program, according to preliminary results from ARS-funded studies. Click the image for more information about it.

Kids Lose Pounds, Gain Fitness, in Houston Study

Innovative, kid-friendly strategies for losing weight and gaining nutrition savvy—plus physical fitness skills—are emerging from scientific studies funded by the Agricultural Research Service (ARS).

For example, investigators Craig A. Johnston, John P. Foreyt and Chermaine Tyler and their colleagues are building upon one of their earlier studies in which many of their Texas middle-school participants achieved weight-management success. The volunteers were primarily Hispanic children who were either overweight or at risk of becoming so.

The researchers are with the ARS Children's Nutrition Research Center at Baylor College of Medicine in Houston, Texas, where Johnston and Tyler are instructors in nutrition and Foreyt is a professor of medicine.

Statistics that the scientists reported for the 6-month study were based on 57 overweight kids who were assigned to either a self- and parent-taught program, or, instead, an intensive, instructor-led regimen.

For instance, once a week for the first 3 months of the investigation, kids in the self-taught group spent time in study hall reading a self-help weight-management textbook for youngsters. Meanwhile, their peers in the instructor-led team spent four class periods a week outdoors, improving their physical fitness, with a fifth session each week—indoors—learning about nutrition, healthy eating, and behavior-change skills essential for living an active lifestyle and making healthful food choices.

When evaluated at the end of the 6-month study, kids in the intensive, instructor-led course had significantly greater weight loss as well as greater "physical quality of life"—as measured by their answers to a standard questionnaire—than did the kids in the self-taught program. What's more, one and two years later, youngsters in the instructor-led team had significantly greater decreases in their body mass index, or BMI, than did the self-taught youngsters.

These preliminary results suggest that a school-based weight-management program might be effective in reaching large numbers of kids, according to the scientists. They published their findings in the journal Obesity in 2009 and in Pediatrics in 2007.

Read more about this research in the March 2010 Agricultural Research magazine special issue on preventing childhood obesity.

ARS is the chief intramural scientific research agency of the U.S. Department of Agriculture. The Houston research helps improve children's nutrition and health, a USDA top priority.

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ARS and international cooperators have established the Winter Wheat Stem Rust Resistance Nursery in Ankara, Turkey, to propagate and distribute winter wheat varieties that have been identified as resistant to Ug99. Click the image for more information about it.

Nursery is New Tool in the Fight

 against Ug99 Wheat Stem Rust

The first Winter Wheat Stem Rust Resistance Nursery, a key tool in the fight against the rust strain Ug99, has been established by the Agricultural Research Service (ARS) and international cooperators.

The nursery, established by ARS and the International Maize and Wheat Improvement Center (CIMMYT), is located in Ankara, Turkey, where CIMMYT coordinates its global winter wheat breeding program. It is the first of its kind for winter wheats, and is a joint effort to distribute 100 lines that have been identified by international scientists as having resistance to the deadly Ug99 stem rust and its descendants.

Thirty of the 100 lines in the nursery were developed by ARS scientists and contain resistance to stem rust races in Kenya and the United States. The lines developed by ARS focus on the use of four or five resistance genes that have been incorporated into various combinations in winter wheat lines.

According to David Marshall, research leader of the ARS Plant Science Research Unit in Raleigh, N.C., and coordinator of the wheat screening conducted in Kenya, multiple genes for resistance will slow the pathogen’s ability to readily overcome the new wheat varieties that breeders develop. The amount of time these genes can remain effective is key to maintaining resistance to stem rust in the United States.

Winter wheat lines in the nursery are being distributed by CIMMYT to wheat breeders and geneticists in 34 countries, including those that have been hit hardest by the disease.

Ug99, Puccinia graminis f. sp. tritici, is the most virulent race of stem rust fungus yet to emerge. First discovered in Uganda in 1999, the fungus has spread across Africa, Asia and the Middle East. Ug99 has been able to overcome most of the stem-rust-resistant wheat varieties developed during the past several decades. While other rusts only partially affect crop yields, Ug99 can wipe out entire wheat fields, resulting in 100 percent crop loss.

ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture (USDA). This research supports the USDA priority of promoting international food security.

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