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TMV: A good thing?

A plant-destroying virus farmers call one of their worst enemies may someday be an ally in the fight against crop pests and mosquitoes, say University of Florida researchers.

World Leaf News

Scientists have genetically modified tobacco mosaic virus (TMV) so that it produces a natural, environmentally friendly insecticide, turning the pathogen into a microscopic chemical factory, said Dov Borovsky, an entomologist with UF’s Institute of Food and Agricultural Sciences. The modified virus is almost completely harmless to plants and simply produces the insecticide.

Plants inoculated with the virus quickly accumulate enough of the insecticide to kill insect pests that consume their leaves. Once harvested, the plants can be processed to make mosquito control products.

A study using the modified virus in tobacco plants was published in the Proceedings of the National Academy of Sciences’ December journal. An extract from the plants was used to kill mosquito larvae.

“This is the first time we know of that anybody put … tobacco mosaic virus [on] something that actually can act as an insecticide and protect the plant,” said Borovsky, lead author of the paper. Tobacco mosaic virus is commonly used in genetic research because genes can be added to it easily.

The chemical, known as trypsin-modulating oostatic factor, or TMOF, stops insects from producing a crucial digestive enzyme called trypsin, he said. Like tobacco mosaic virus, TMOF has no effect on people. But it can cause insects to starve to death, unable to draw nutrients from food.

Though notorious for attacking tobacco and other plants in the solanaceae family—including tomatoes, eggplants, bell peppers and potatoes—the virus threatens eight other plant families, said Charles Powell, a plant pathologist with UF’s Indian River Research and Education Center in Fort Pierce and a co-author of the study. The bright side is that the modified virus can protect any of those plants.

“The virus has a very broad host range so it can be used for very many plants,” Powell said. “You can’t use it for monocotyledonous plants like corns and grasses. But many of the other broad-leafed plants, including many fruits and vegetables, could potentially be used with it.”

Because the virus multiplies, only a small dose is needed in each plant to get the job started. The virus reproduces well in plants, but it cannot replicate itself from one generation of plant to another, Powell said. Farmers would need to inoculate their crops each year.

When insects eat the plants, they also consume TMOF; death can occur within 72 hours if the insect is vulnerable. The exact range of pests susceptible to TMOF appears to be broad. There are two types of enzyme systems insects use to digest food: one includes trypsin, and all species with this system may be harmed by TMOF.

Crop pests proven vulnerable to TMOF include the tobacco budworm and citrus root weevil, Powell said. Mosquitoes and several other blood-feeding insects are also susceptible.

Tobacco mosaic virus might be suitable for delivering other insecticides, Powell said. Similar viruses that naturally occur in other plant species might also be modified for beneficial use.