Featured Research

from universities, journals, and other organizations

Preventing Head Blight in Barley, Wheat: Biochemical Pathways Hold Key to Resistance

Date:
March 19, 2014
Source:
South Dakota State University
Summary:
Despite major research funding, scientists have had only limited success in controlling fusarium head blight, a fungal disease that not only dramatically shrinks yields in wheat and barely, but produces toxins that make the grain dangerous for human or animal consumption. Using advanced genetic and molecular technologies, biologists have begun tracing the biochemical pathways that make wheat susceptible or resistant to head blight. The researchers believes the key to head blight resistance lies in its ability to block production of two key hormones.

Graduate student Aravind Galla is checking a wheat head that was inoculated with a Fusarium graminearum mutant strain in which one gene is blocked out. This is part of an effort to determine how the gene functions in relationship to disease development.
Credit: Eric Landwehr

Pale, shriveled heads of grain spell trouble for wheat and barley farmers -- they're the telltale signs of fusarium head blight. The fungal disease, commonly known as scab, not only dramatically shrinks yields but produces toxins that make the grain dangerous for human or animal consumption.

Related Articles


From 1991 to 1996, head blight caused $2.6 billion in losses to the U.S. wheat crop. At its peak, the fungus destroyed the entire malting barley crop in the Red River and Ohio River Valleys, according to molecular biologist Yang Yen, an Agricultural Experiment Station researcher and professor at South Dakota State University.

Two decades later the U.S. Department of Agriculture still ranks head blight as "the worst plant disease to hit the U.S. since the rust epidemics in the 1950s." Wheat and barley farmers have lost more than $3 billion since 1990 from blight outbreaks.

Despite major research funding -- including the U.S. Wheat and Barley Scab Initiative, scientists admit that efforts to control this devastating disease have met with limited success.

"This is an extraordinary disease that requires extraordinary means to combat it," says Yen, who began working on head blight in 1997.

Using advanced genetic and molecular technologies, Yen has begun tracing the biochemical pathways that make wheat susceptible or resistant to head blight. Three graduate students and two postdoctoral scientists have worked on this research over the last 16 years.

Multiple hosts and pathogens

Head blight can be caused by multiple pathogens, and these pathogens can attack multiple hosts including grasses and corn, Yen explains. This makes the disease tougher to combat.

Researchers are working to develop resistant types of grain, alter tillage practices and apply fungicides to fight the disease.

"This disease is not new," Yen says. It was first reported in England in 1884 and in North America in 1890. Over the last century, serious outbreaks have occurred in Asia, Canada, Europe and South America.

If this disease could be controlled through breeding, Yen believes that scientists would have done so by now. Varieties of wheat with some resistance to blight were collected in China during the 1950s and breeding for better resistance has been done since. The most resistant variety of wheat, Sumai 3, was released in China in the 1960s, Yen explains, "but it still gets the disease."

Fusarium spores exist during winter in the plant debris. Even plowing the stubble under does not eliminate the problem because the fungus also survives in the ground. Wind and rain splash carry the spores onto the head when it flowers, but the weather conditions must be just right -- warm, humid and wet.

The wheat flower must be open for the fungus to enter, Yen explains. In susceptible varieties, the fungus kills the infected cells in the head thereby plugging the transport of water and nutrients to the upper part of the head.

While diseases such as stem rust want the host to survive, Yen says, "fusarium attacks the wheat or barley spikes and the kernels collapse because the fungus kills them and lives on the dead cells."

Sumai 3 successfully delays the development of the disease. Though the kernel on which the spore has landed will be empty, it won't affect the rest of the head, he explains. But this variety has other undesirable characteristics and cannot be used here.

Gene expression

Yen has undertaken a molecular study of the disease, investigating how the fungal infection impacts wheat gene expression. He compared the most resistant varieties of wheat with the most susceptible ones. By looking at how genes were expressed, the molecular biologist narrowed the possibilities from thousands of genes to 608, then to 47 and eventually to three.

"These genes are functional in both resistant and susceptible varieties. How they respond to regulations triggered by the fungal infection makes the difference" he says. "That's why normal gene cloning didn't work."

Resistance to the disease is controlled by the chemical pathways of two growth hormones, jasmonate and ethylene, Yen explains. To prove this, he took a susceptible wheat variety, treated it with jasmonate and ethylene and then exposed it to head blight. The wheat resisted the fungi.

"Two of the three genes are directly involved in the chemical pathways," Yen explains. "How the third one is involved we still do not know, but it may play a key role because suppressing its function in the first eight to 60 hours after the infection causes the disease development."

Through funding from USDA and the South Dakota Wheat Commission, he has identified biomarkers that will allow breeders to screen for this resistance.

Disease development

Essentially, Yen hypothesizes that the fungus softens the host cell wall during infection and triggers a chain of host resistance responses.

"In the resistant wheat, the key resistance gene may delay this chain of reactions until the host tissue is too hard for the disease to develop," Yen explains. "In the susceptible wheat, the disease makes the plant drop this gene expression, so the fungus can get established."

Yen has received a three-year USDA grant for nearly $363,000 to test this hypothesis.

In addition, Yen must find out where the signal is coming from and how the fungus suppresses the gene expression. Only then can the researcher figure out how to prevent the disease from becoming an epidemic.

"Fusarium head blight results from close interaction between the fungus and the host. We need to understand how this interaction is occurring and identify which step is the easiest to manipulate to control the disease," he explains.

That will then allow researchers to determine how to neutralize its power to infect small grains.


Story Source:

The above story is based on materials provided by South Dakota State University. Note: Materials may be edited for content and length.


Cite This Page:

South Dakota State University. "Preventing Head Blight in Barley, Wheat: Biochemical Pathways Hold Key to Resistance." ScienceDaily. ScienceDaily, 19 March 2014. <www.sciencedaily.com/releases/2014/03/140319093832.htm>.
South Dakota State University. (2014, March 19). Preventing Head Blight in Barley, Wheat: Biochemical Pathways Hold Key to Resistance. ScienceDaily. Retrieved December 17, 2014 from www.sciencedaily.com/releases/2014/03/140319093832.htm
South Dakota State University. "Preventing Head Blight in Barley, Wheat: Biochemical Pathways Hold Key to Resistance." ScienceDaily. www.sciencedaily.com/releases/2014/03/140319093832.htm (accessed December 17, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Wednesday, December 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Ivory Trade Boom Swamps Law Efforts

Ivory Trade Boom Swamps Law Efforts

Reuters - Business Video Online (Dec. 17, 2014) Demand for ivory has claimed the lives of tens of thousands of African elephants and now a conservation report says the illegal trade is overwhelming efforts to enforce the law. Amy Pollock reports. Video provided by Reuters
Powered by NewsLook.com
Uphill Battle to Tackle Indonesian Shark Fishing

Uphill Battle to Tackle Indonesian Shark Fishing

AFP (Dec. 17, 2014) Sharks are hauled ashore every day at a busy market on the central Indonesian island of Lombok, the hub of a booming trade that provides a livelihood for local fishermen but is increasingly alarming environmentalists. Duration: 00:42 Video provided by AFP
Powered by NewsLook.com
Fla. Man Flies 3,000th Rescue Animal in Plane

Fla. Man Flies 3,000th Rescue Animal in Plane

AP (Dec. 17, 2014) A retired Florida businessman is using his skills as a small plane pilot to rescue animals from overcrowded shelters and place them where they have a second chance at life. He recently transported his 3,000th animal. (Dec. 17) Video provided by AP
Powered by NewsLook.com
Feeling Young Might Mean A Longer Life Span

Feeling Young Might Mean A Longer Life Span

Newsy (Dec. 16, 2014) A study published in JAMA shows that people who feel younger than their chronological age might actually live longer than those who feel old. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins