Perspectives Online

The Science Base<br />Four recent research projects illustrate how the N.C. Agricultural Research Service is continuing to fulfill its historic mission.

Photo by Daniel Kim

The pages of Perspectives regularly include news about the research activities in the College of Agriculture and Life Sciences. The North Carolina Agricultural Research Service is the research division through which the College seeks new knowledge, as it educates students through its Academic Programs and extends educational programs throughout the state through the North Carolina Cooperative Extension Service, in fulfillment of its land-grant mission. The teaching, research and extension functions are integrated within the College's 22 departments.

In the early years of the Agricultural Research Service, established first as the N.C. Agricultural Experiment Station in 1877, it was little more than a laboratory where fertilizer and soil were analyzed. In 1887, the federal Hatch Act provided funding for agricultural research at the new college (now N.C. State University) in Raleigh, and the Experiment Station became part of the campus. Today the reach of the Agricultural Research Service extends across North Carolina and beyond, with scientists, students and support staff working on the N.C. State campus, at 18 agricultural research stations, 10 College research centers and eight field laboratories statewide, in state-of-the-art laboratories and greenhouses.

The goal in 2006 remains the same as it was in 1887 - the betterment of North Carolina and North Carolinians. But today the scope is much wider and deeper, as methods range from the conventional agricultural techniques to the latest biotechnological approaches.

Areas of basic and applied research cover a range that includes innovation in crop production; applied genomics in plant and microbial systems; ecology and animal welfare, including behavioral biology; ornamentals, turfgrasses, small fruits and vegetables; aquaculture, fisheries and livestock biology and genomics; and sustainable and organic farming systems - to name a few.

The mission of the NCARS is to develop the knowledge and technology to improve productivity, profitability and sustainability of industries in agriculture and life sciences; conserve and improve the state's natural resources and environment; improve the health, well-being and quality of life of the state's citizens; and provide the science base for research, extension and academic programs.

In this feature we again turn the spotlight on some of our current research activities in fulfillment of that mission, with news about four projects in the areas of plant pathology, crop science, horticultural science and entomology. The goals of these projects reflect the evolution of the state's commodities and the College's research methods in the 21st century: combating disease that could devastate wine grape production, improving production of biobased fuels, adding value in the development of commercially viable trees, and making molecular-level discoveries about insect communication with possible implications for improved pest control.

All add chapters to an ongoing history of the Agricultural Research Service.

Living with Pierce's disease

By Dave Caldwell

Dr. Turner Sutton plans a three-year effort aimed at learning how to manage Pierce's disease in wine grapes.
Photo by Daniel Kim
The first symptoms usually appear in mid-July to August, the hottest part of a North Carolina summer. The leaves of grapevines turn brown at the edges, as though scorched by the summer heat. Then clusters of grapes shrivel up. Eventually, the entire vine dies.

This is Pierce's disease, and it is the bane of North Carolina's growing viticulture industry. It is also the object of Dr. Turner Sutton's scrutiny. Sutton, a professor of plant pathology and Extension specialist in the College of Agriculture and Life Sciences, is looking for ways to allow North Carolina wine grape growers to live with Pierce's disease.

"Growers are concerned about it, and they should be concerned about it," says Sutton.

Pierce's disease, he says, "has the potential to limit the success of North Carolina vineyards."

Growing European-type vinifera wine grapes and making wine is a growing industry in North Carolina. The number of wineries in the state has doubled since 2002, according to the North Carolina Wine and Grape Council. North Carolina is home to more than 50 wineries, with five more expected to open this year. How successful Sutton is in determining how to deal with Pierce's disease will likely affect the success of this expanding industry.

Pierce's disease is caused by a bacterium, Xylella fastidiosa, which is spread from a variety of plants to grapevines by insects such as leafhoppers and spittlebugs, Sutton says. Among the reservoir plants on which the bacterium is found are oak trees, blackberries, wild grapes and Virginia creeper. When the bacterium infects a grapevine, it plugs the xylem, the water-conducting tissue of the plant, cutting off the vine's water supply.

Sutton has studied how the disease is spread and how it survives and plans to test methods of managing it.

If winter temperatures drop low enough, the bacterium that causes Pierce's disease can't survive, Sutton says. Sutton has looked at the effect of winter temperature on Pierce's disease in North Carolina. What he found is not particularly good news for grape growers.

Winters are warm enough throughout eastern North Carolina and the southern and eastern piedmont that the Pierce's disease bacterium can overwinter. As a result, Sutton describes the risk of the disease in these areas as "quite high." He describes disease risk as "somewhat less" in the north and central piedmont, where winters are a little cooler but still not cool enough to kill Xylella fastidiosa. Sutton points out that as a result of warmer winters in recent years, the risk of the disease has increased throughout the piedmont.

One of Sutton's students recently looked at the vectors of the bacterium, the insects that transmit the disease to grapevines. In 2004 and 2005, insect traps were placed in vineyards in the piedmont and coastal plain. Four species of leafhopper were identified as being most abundant in the vineyards, and three of the species tested positive for the bacterium. At least two of these leafhopper species are thought to be the primary vectors for Pierce's disease on grapes in North Carolina.

Sutton and Dr. George Kennedy, William Neal Reynolds Professor of Entomology, are now working with a $72,000 grant from the N.C. Tobacco Trust Fund Commission to look at methods of managing Pierce's disease. They are attacking the disease on three fronts.

The grant is being used to develop an insecticide spray program designed to control the leafhoppers thought to be primarily responsible for spreading the disease. At the same time, Sutton plans to work on more specifically identifying the reservoir plants that harbor the Pierce's disease bacterium. If growers know where the bacterium resides when it's not on grapevines, it may be possible to eliminate these plants from the vicinity of a vineyard and reduce the likelihood of the disease.

Sutton is going to experiment with pruning to remove infected parts of the vine. It may be possible to halt the disease before it spreads too far on the vine. Sutton explains that the bacterium moves from grapevine leaves to the vine's cordon, the part of the vine that is trained to grow horizontally along a trellis. The bacterium then moves to the vine trunk, which kills the vine. If a grower sees infected leaves in July, he may be able to save the vine by pruning the infected shoots.

"We don't have a lot of answers at this time," says Sutton, who hopes to "come up with a plan that allows us to live with the disease."

Switchgrass to ethanol

By Suzanne Stanard

Dr. Ron Qu is part of a research team that won a grant from Golden LEAF to develop a technique for efficiently converting genetically engineered switchgrass into bioethanol.
It seems like a no-brainer. As the average gas price in North Carolina soars toward the $3-a-gallon mark, why not explore production of alternative fuels that can be derived from agricultural crops?

National news stories lately depict biofuels as a "hot" opportunity for the United States to establish greater energy independence and protect the environment. North Carolina in particular seems poised to be a major player in biofuel production, according to these reports, because the state has abundant biomass resources that could be processed for energy and fuels.

Switchgrass, for example, grows very well in North Carolina. The native grass is heat-tolerant, handles drought stress, requires very moderate levels of fertilizer, is highly disease-tolerant and commands essentially no herbicides after establishment. It's a hearty, tall-growing perennial, so once its root system develops, switchgrass will continue to emerge year after year.

Best of all, switchgrass yields a high amount of biomass that can be converted into ethanol, a clean-burning, environmentally friendly, economical alternative to gasoline.

Right now, much of the gasoline sold at pumps contains 10 percent ethanol, according to a recent article in the Raleigh News & Observer. Some automobile engines can use up to 85 percent ethanol, or "E85," but this blend is barely available in North Carolina. The News & Observer also reports that North Carolina soon will open its first ethanol plant in Aurora, a Beaufort County town southeast of Greenville.

"I am sure that sooner or later our automobiles won't run on gasoline," says Dr. Jay Cheng, associate professor of biological and agricultural engineering. "Right now, the most promising biofuel is ethanol. The only products from burning ethanol are water and carbon dioxide. It's the number one renewable fuel."

Cheng is part of a five-person team of College of Agriculture and Life Sciences and College of Natural Resources researchers who recently won a $142,800 grant from Golden LEAF to develop a technology that efficiently converts genetically engineered switchgrass into bioethanol.

Specifically, they plan to engineer a new type of switchgrass that has more cellulose, the useful component that can be converted into ethanol, and less lignin, which hinders the decomposition of cellulose.

Each researcher will tackle a specific step in the project, which they anticipate will take about three years.

Dr. Joseph Burns, professor of crop science, and plant physiologist with the USDA Agricultural Research Service, is an expert in growing switchgrass and has been studying its cultivation and forage use for more than 35 years. In cooperation with Dr. David Timothy, crop science professor emeritus who initiated a grass breeding program in the College, Burns has explored switchgrass and other different types of grasses for a number of uses, from feed for ruminants like dairy and beef cattle to biomass production.

"We've collected quite a bit of data on switchgrass over the years," Burns says. "Now that we're in a fuel shortage, interest in switchgrass as an energy crop has really grown. This region is one of the best in the country to produce switchgrass."

Dr. Rongda "Ron" Qu, associate professor of crop science, specializes in genetic engineering and turfgrass biotechnology. His role as a member of this research team is to develop a transformation protocol for switchgrass. Qu's lab has extensive experience in tissue culture and genetic transformation of various grass species.

In developing a transformation protocol for switchgrass, Dr. Qu experiments with tissue culture and genetic transformation of grass species.
A few years ago, Qu started thinking about ways to improve production of switchgrass as a biofuel crop. At the same time, faculty in the College of Natural Resources' Forest Biotechnology Group had completed a genetic transformation of the aspen tree, reducing lignin from the trees to improve paper production. Dr. Vincent Chiang, professor of forestry and environmental resources, and his former graduate student, Dr. Wen-Jing Hu, discovered that the genetically engineered trees grew faster and bigger and also contained higher quantities of cellulose.

Chiang and research associate professor Dr. Laigeng Li continued the research and were also successful in genetically altering the lignin structure so that lignin can be more easily extracted from wood for paper making as well as for ethanol production.

Qu recognized the potential to apply their research to switchgrass and approached Chiang and Li to participate in this study. Specifically, they'll work with Qu to identify - and eventually "knock out" - the gene responsible for lignin biosynthesis in switchgrass, which, in turn, increases cellulose biosynthesis, resulting in a genetically modified plant with increased levels of cellulose.

"It made good sense to apply their findings to switchgrass," Qu says. "If we have more cellulose, then we'll have more content that can be converted into ethanol."

Next, Cheng will work to streamline the process of converting cellulose from the genetically engineered switchgrass into ethanol. This boils down to three steps: pretreatment of the switchgrass, breakdown of the cellulose into sugars and fermentation of the sugars into ethanol.

With Golden LEAF backing the project for its first year, the team is pursuing additional funding from a variety of sources for the remaining two years.

While producing ethanol from switchgrass has tremendous potential, the group readily admits that one commodity alone cannot be the sole source for ethanol production in the United States, citing the success of ethanol production from sweetpotatoes in China and sugar cane in Brazil.

"We think switchgrass will play a major role in biofuel production in the future, especially since the costs and energy input for production are very low when compared to other crops," Cheng says.

Burns adds, "As long as oil prices stay high, everyone will be looking for an alternative."

New "Carolina" dogwoods

By Dee Shore

Intern Irene Palmer, who works with with Dr. Tom Ranney to propagate disease-resistant dogwoods at the Mountain Horticultural Crops Research and Extension Center, here pollinates a dogwood flower.
Photo courtesy Tom Ranney
With its four-petalled flower heralding spring from North Carolina's coast to its forested mountains, the dogwood has come to be known - and treasured - as a symbol of rebirth and revitalization. And N.C. State University researchers are working to make sure it stays that way.

At the Mountain Horticultural Crops Research and Extension Center in Fletcher, Dr. Tom Ranney and his colleagues have spent the past five years working to breed hardier cultivars that withstand two diseases that have ravaged native flowering dogwoods. Recent grants from the N.C. Association of Nurserymen and Golden LEAF, a nonprofit organization focused on economic development, have allowed them to expand and accelerate these efforts.

Dogwood anthracnose has been particularly problematic over the past 15 years at mountain elevations of more than 3,000 feet, where the disease can wipe out entire stands of trees. And powdery mildew has taken a toll across the state, where it has resulted in deformed, dying and slow-growing dogwoods.

"The holy grail," says Ranney, "is to get resistance to these two diseases."

To that end, Ranney recently secured a $40,000 grant to help enhance his work with flowering dogwoods.

He and his colleagues in the College of Agriculture and Life Sciences have since been scouring the state to find dogwood trees that seem naturally resistant to the diseases. That involves combing mountainsides with global-positioning system equipment in tow to find and keep track of trees that have survived where they shouldn't have.

The researchers then take samples of those trees and propagate them at the research station. With the help of Dr. Kelly Ivors from the Department of Plant Pathology, they then deliberately expose them to both dogwood anthracnose and powdery mildew to see if they are indeed resistant.

Those that prove to be robust can then be released to commercial nurseries for sale to those who want hardier trees for use in home and commercial landscapes, Ranney says. They also can form the basis for a breeding program to develop new types of dogwoods.

Ranney, a professor of horticultural science and a breeder of trees and other woody plants, is particularly interested in pursuing new hybrids that combine the best of North Carolina's flowering dogwoods and the kousa and evergreen dogwoods found in China. Over the past decade, a collection of more than 60 types of Asian dogwood cultivars has been acquired at the Fletcher research station.

With such breeding stock at his disposal, Ranney sees the potential for developing a series of "Carolina" dogwood varieties that not only are resistant to major diseases but also have unusual characteristics that gardeners and landscapers would find attractive - ones with weeping forms, evergreen foliage or different color flowers, for example.

But Ranney's goals go far deeper than his desire to develop interesting plants for the landscape. He is driven by a commitment to ensuring the continued growth of North Carolina's leading crop - not tobacco any more, but greenhouse and nursery plants.

In North Carolina, more than 1,800 nursery operations generate annual sales of more than $845 million annually and employ some 63,000 people. The state ranks fourth in the nation in nursery crops production, behind only California, Florida and Texas.

Just one exceptional new nursery cultivar can generate wholesale sales of between $1 million and $2 million per year, Ranney says, and retail sales and installation can potentially be twice that amount.

His earlier breeding projects include the development of the Venus sweetshrub, a flowering plant that is now widely grown by North Carolina nurseries, and Ranney has also helped patent and introduce the Summer Cascade and Shiloh Splash river birches.

With the "Carolina" dogwood series, Ranney expects that new introductions could begin as early as 2008. Through partnerships with the North Carolina Association of Nurserymen, North Carolina Cooperative Extension, the JC Raulston Arboretum at N.C. State and others, he intends to back the release of such trees with the grower education, promotion and marketing that are essential to commercial success.

"Each year, Americans buy 1.5 million dogwood trees," he says. "With each tree selling for about $75, that translates into a $112 million industry every year - before you even consider the value of landscaping and design services, fertilizers and so on.

"The potential for economic growth is huge."

And evolutionary twist

By Suzanne Stanard

Dr. Astrid Groot (left), Dr. Fred Gould and colleagues are learning how selection causes evolutionary changes in moth pheromone communication. This information could have future implications in controlling moth populations.
Photo by BEcky Kirkland
Birds, frogs, flies - all species, in fact, including humans - use pheromone (sexual) communication signals. Whether audio, visual or chemical, the signals work like a lock-and-key mechanism, ensuring that males and females of the same species are able to identify mates. Of particular interest to agricultural researchers in recent decades is pheromone communication in moths, many of which are significant agricultural pests.

A team of researchers in the College of Agriculture and Life Sciences recently discovered that interference in moth pheromone communication between closely related species could be a strong enough selection force to alter these signals. These findings open doors to new thought on the evolution of moth pheromone communication, and they also could play a role in future applied research on controlling moth populations in agricultural crops.

The study, published in the Proceedings of the National Academy of Sciences, was conducted by Dr. Astrid Groot when she was a postdoctoral research associate in the laboratories of Dr. Fred Gould, William Neal Reynolds professor of entomology and the senior leader of the project; and Dr. Coby Schal, Blanton J. Whitmire professor of entomology. Research technicians Joy Horovitz, Jennifer Hamilton and Richard Santangelo were crucial contributors for the success of the project, which was funded by grants from the National Science Foundation, the W.M. Keck Center for Behavioral Biology and the Blanton J. Whitmire Endowment at N.C. State.

The researchers obtained the first experimental evidence that communication interference significantly affects how moth communication pheromones evolve, Groot said. Her team studied two closely related moth species, one of which, Heliothis virescens (above), is also known as the tobacco budworm.
Photo by Becky Kirkland
"This is the first experimental evidence that communication interference can play an important role in how moth communication pheromones evolve," said Groot, now a research assistant professor in the Department of Entomology. "People have theorized about it for years, but it had not yet been shown, at least not in chemical communication, until now."

The team worked with two closely related moth species: Heliothis subflexa (Hs) and Heliothis virescens (Hv). The latter is also known as the agricultural pest tobacco budworm. The questions they set out to answer: How can pheromone blends change, or evolve, from one species to the next? In other words, which selection forces play a role? And specifically, could communication interference from males of closely related species exert strong enough directional selection to cause evolution of these signals?

"If you have a couple of different species in the same area and they are similar in their pheromone blend, there's a chance they could attract the wrong mates," Groot said. "So, closely related species can exert selection on each other. With moths, you have two forces at work: mate recognition and communication interference."

To figure out which selection forces are strongest and how those forces can cause evolutionary changes in moth pheromone communication, the team took a unique approach. First, they crossed and backcrossed the two species of moths, using Hs females and Hv males, to create offspring females that had a different pheromone "blend" than a normal Hs female.

The pheromone blends of these genetically modified female offspring lacked three particular compounds typical to normal Hs female pheromone composition. These three compounds, or acetates, had been identified in previous research as critical to repelling males of the closely related Hv species.

Next, they tested the females in the field, which had never been done, according to Groot, using traps baited with normal Hs females as well as traps with the genetically altered females, whose pheromone blends were missing the three acetates. The results were stunning: Ten times more Hv males were captured in traps baited with the genetically altered Hs females than in traps with the normal females.

"This shows that the three acetates actually are important in the attraction of their own males," Groot says. "But what was surprising to us was the cross attraction, because we didn't expect that at all. We had thought that the subflexa [Hs] blend would stay species-specific even when you take out the acetates."

Using data collected over the last 40 years, the team was able to estimate quantitatively that the directional selection force exerted by Hv males on Hs females to produce relatively high amounts of acetates can be as high as 23 percent.

"It really is important for the females not to attract mates from the opposite species, because doing so can reduce their reproductive output by 23 percent," Groot said. "In the evolutionary sense, that's huge . it's incredible. One percent is already a lot."

In prior studies, synthetic chemicals have been used to mimic pheromone blends. When tested in the same traps in the field, Hs males were attracted, but Hv males have never been found to be attracted. According to Groot, this shows that testing the attraction of live females is much more accurate than experiments using synthetic interpretations of the pheromone blend. In fact, she said, without testing live females, the team would not have made their discovery.

For Groot, these findings will lead to further study, from North Carolina to the west coast of Mexico, on how geographic variation affects the pheromone blends of the two species of moths.

"Our approach could be used with other moth species to determine the generality of this evolutionary pathway," she said. "I'm very excited about the possibilities."