Published on 03/10/97

Biotech Breakthrough to Fight Killer Virus

In past years, Georgia farmers had a tough row to hoe in many crops in fighting the deadly tomato spotted wilt virus. Now, new technology can give them an edge in managing the virus.

For the first time, Georgia scientists can learn in just one day if insects in the field are actually transmitting the virus.

"Tomato spotted wilt virus is the No. 1 problem in the state's crops," said Hanu R. Pappu, a plant pathologist at the Coastal Plain Experiment Station. "Last year alone, it caused an average 10 percent loss in many affected crops."

The three main crops the virus affects are peanuts, tobacco and tomatoes. But many others are affected. In these three crops alone, Georgia farmers lost $63.8 million in 1996. The virus affects the crops differently, but the results are the same: decreased yields and crop loss.

Pappu points out, too, that the 10 percent average is just that. "Some farmers lost only 1 percent or 2 percent," he said. "Others may have lost close to 50 percent."

The first problem farmers have with the virus is knowing when it's in their fields. Since it's a virus, Pappu said, there's no cure.

"So prevention is extremely important," he said. "There is no control, so we're trying to get it to a point where we can manage the disease through other means."

Viruses rely on carrier insects, he said. The TSWV relies on tiny insects called thrips to move from plant to plant and field to field.

But while about a dozen species of thrips live in Georgia, only two can transmit TSWV. "And those two species can transmit the virus only when the insect was infected as a juvenile," Pappu said.

Past efforts to control tomato spotted wilt by controlling the insects didn't work. "We just didn't know at the time that only certain populations were transmitting," he said.

Pappu is working with another plant pathologist and an entomologist at the experiment station to learn the secrets of the virus that causes tomato spotted wilt. Once they learn its secrets, they can use them to fight against the tiny but destructive organism.

Pappu worked to find the secret of when the thrips can transmit TSWV. He's using new biotech methods to detect specific proteins that appear only when the insect can transmit the virus. And they're doing it quickly.

The method he uses is called TAS ELISA; Triple Antibody Sandwich, Enzyme-Linked ImmunoSorbent Assay. It uses virus-specific antibodies that reveal if viral proteins are in the insect.

"The presence of the viral protein is a good indication that the insect was capable of transmitting the virus," Pappu said.

Before, scientists needed six to eight weeks to find out if a thrips population was transmitting the virus. "Now this technology can tell us in one to two days," he said.

Pappu's goal is to forecast when a transmitting population is moving into a field. Armed with that knowledge, farmers can apply pesticides to kill the insects before they can transmit the virus into the plants.

"This information will allow them (farmers) to be more precise in applying chemicals," Pappu said. "To be effective with our applications, we needed an efficient, quick way to know if the population was transmitting." Now they have it.