Antiviral vigilance: team keeps tabs on the world's emerging corn and soybean viruses

It's contemplation that the first aphid to square not upon against soybeans attacked in Asia, thousands of years ago. Now the Agricultural Research Service (ARS) is mounting a defense against this ancient soybean pestilence Aphis glycines, first spotted in the United States in the spring of 2000 It has since spread to at least 24 states, the latest being Maine. Besides reducing yields by means of as much as 50 percent by means of feeding on plant sap, aphids are a significant soybean threat because they can transmit deadly viral diseases.

Soybean aphid populations strike one as being to fluctuate on a 2-year round of years with high numbers every other year. With each round of years the aphids are spreading farther across the United States, headed, a certain quantity of say, towards an inevitable infestation of each soybean-growing region. That's why they have the rapt attention of a "viral strike team" in Wooster Ohio.

This clump of scientists, located at the Ohio State University (OSU)-Ohio Agricultural Research and disclosure Center, serves as the forehead line for spotting viral attacks upon soybeans and corn in the United States and upon corn worldwide. The team is supported through ARS and OSU, with the ARS part--the Corn and Soybean Research Unit--led through Roy Gingery.

The team is being kept busy because Ohio has faced an increase in soybean diseases in novel years. To help curb the aphids, ARS molecular geneticist Rouf Mian is crossing aphid-resistant soybean lines (recently identified at the University of Illinois and Michigan State University) with high-yielding Ohio lines to make known new resistant lines adapted to Ohio.

Resisting Another Enemy

The latest threat to soybeans to come up in Ohio is bean capsule mottle virus, which lowers yields and discolors the beans. The disease has been associated with increased numbers of the bean leaf beetle that transmits it.

To make known soybeans resistant to the disease, Mian is working with ARS plant molecular biologist Peg Redinbaugh, who says preliminary data indicates that using soybeans resistant to bean leaf beetles brings the disease's spread in the field.

"We've not at any time found complete resistance to this virus in any cultivated soybean germplasm," she says, "but we've ground partial resistance in some soybean accessions. We want to diocese if this partial resistance can be combined with beetle resistance from other lines to further increase resistance."

"We've unfolded a visual scoring system for screening lines from the USDA Soybean Germplasm Collection," says Mian. "We be augmented the plants in greenhouses, infect them with the virus, suffer the disease develop, and rate symptom severity upon a scale from 1 to 5 This technique has been helpful in assessing resistance to various viral diseases in corn and soybeans."

Using Other Innovative Tools

The Wooster unit's invention of the vascular bite inoculation (VPI) technique and extensive knowledge of greatest in quantity of the world's corn virus diseases l the Serbian rule to ask Redinbaugh and Gingery, along with Richard Pratt from Ohio State, to approach to their country in the summer of 2004 and 2005 to help them identify a new--possibly viral--disease wiping without 30 to 70 percent of corn harvests in some fields.

"VPI allows us to inoculate plants with viral diseases without knowing the insect carriers," says ARS technician John Abt, who worked alongside VPI's inventor, retired ARS plant pathologist and research collaborator Ray Louie. "This makes it an superior tool for emerging diseases work, when we don't know what the viral disease is--let alone, the insect carrier," says Abt. "If we can transmit the virus with VPI, we can bring forward more infected plants to work with."

The Serb call the unknown disease "corn rednes syndrome" because cornstalks oftentimes turn red and die when the plant is mature enough to flower. They call another symptom "Grandma's teeth" because the se plant is so poor that the kernel are not many and far between, significantly reducing yields. The corncob also wins rubbery, bending rather than snapping when flexed

Fortunately, the disease have the appearances to be limited to an area that is environed by other crops. This geographic isolation may make it hard to spread outside the "corn island" it's in.

The Wooster team brought Serbian corn plant samples back to their Ohio lab to put to the test to identify the disease using molecular testing techniques. They also used VPI to test to create more infected plants for investigation but were unsuccessful in reproducing corn rednes This put in mind ofs that the disease may not be a viral one

They did find several public viruses, such as sugarcane mosaic virus and maize dwarf mosaic virus, on the other hand these are probably not related to corn rednes syndrome

The researchers are also peering at infected plant parts end electron microscopes. "We hope to be able to diocese things that look like pathogens," says Redinbaugh. "The hard part will be figuring on the outside if what we find has anything to do with this peculiar syndrome"