Research on a global virus and its carrier could lead to better resistance in crops, says a Washington State University plant virology professor.
Hanu Pappu, WSU professor of virus genomics and biotechnology, studied tomato spotted wilt virus with a team of researchers.
First found in tomatoes, the disease is part of a group of closely-related viruses, called tospoviruses. They affect vegetables and flower crops, including onions and peanuts, Pappu said.
According to WSU, tomato spotted wilt virus is estimated to cause more than $1 billion in global crop losses each year.
Pappu is working to understand how the virus spreads. It’s carried by the insect thrips, which feeds on many crops.
“So it’s a double whammy,” Pappu said. “Farmers spend a lot of money trying to control thrips. Unfortunately, there are not very many effective chemistries and chemicals against thrips, and not very many are actually approved.”
The viruses have developed a close relationship with thrips for their own survival, Pappu said.
“Not only do they infect and multiply in the plant, they can multiply in the thrips as well,” he said. “That’s very unique, because not many plant viruses can multiply in the insect.”
The viruses have so many hosts, they will survive year after year, but the goal is to keep them to a manageable level, Pappu said.
Plants have an immune system to fight the virus with disease-fighting molecules. Pappu wants to understand which parts of the virus the plant targets.
“It’s a tug of war between the virus and the plant,” he said. “Sometimes the plants win, so that means they become resistant, and sometimes the virus wins, so that means plants get diseased and eventually die.”
Pappu’s research team was able to identify regions of the virus genome targeted by plant defense systems. That information will enable strategies to trigger plant resistance responses.
“It’s like a flu shot,” Pappu said. “We are now trying to come up with an RNA vaccine that when we apply to the plant, the plant thinks it’s under attack.”
Breeders will use the information learned to eventually develop genetic material for resistant crops.
Information from the tomato spotted wilt virus applies directly to an important disease in Pacific Northwest onions, iris yellow spot virus.
A regional and national team of researchers are working on the onion virus, Pappu said. Progress has been made because of a large collaborator network and support from commodity groups, particularly onion grower groups, he said.
Next, the researchers hope to better understand the role of thrips, one of the most important contributing factors in disease outbreaks.
“If you remove thrips from the equation, the problem is almost solved,” Pappu said. “Thrips are the ones maintaining this virus out in the wild.”
Efforts to manage thrips populations have been somewhat effective, Pappu said. Researchers are looking for environmentally-friendly options, also developing an RNA vaccine to interfere in the thrips development cycle and slow reproduction.