科学家改变果蝇基因以帮助农民

Paul Nelson runs a raspberry farm in the northern U.S. state of Minnesota.

Raspberries are a popular red fruit that people like to eat in the summer.

At the farm, Nelson and his team spend a lot of time worrying about fruit flies.

The insect pest that hurts their berries is known as the spotted wing drosophila. The flies are from Asia and first came to the U.S. about 15 years ago. The flies hurt blueberries in Maine, as well.

As winters get warmer and springtime comes earlier, farmers in states such as Maine and Minnesota are having more trouble with the flies. Warmer winters permit the fruit flies to survive and have more babies each year. They are also becoming resistant to some pesticides, which are chemicals used to kill pests.

The flies cause damage by laying eggs in the fruit.

Nelson said the flies can ruin fruit farms if farmers are not willing to put the time in to fight them.

Farmers use chemicals to kill the flies or place covers over the fruit plants to protect them. It is a lot of work, and even with the hard work, they lose 20 to 30 percent of their crop each year.

Researchers at North Carolina State University are working to solve the problem. In the laboratory, they are changing the DNA of female flies to make sure that any babies they have are not able to reproduce.

The scientists published their work recently in a publication called the Proceedings of the National Academy of Sciences. They found that if they mated one of their flies with a normal fly, 99 percent of the offspring would be sterile, or not be able to reproduce.

The scientists used computer models to make predictions and found that by releasing modified flies over time, they could reduce the population of fruit flies in an area like a farm in only five months.

It is not the first time scientists have considered modifying the DNA of an insect. Scientists are using genetically modified mosquitoes to reduce the population of the insects that cause diseases such as yellow fever, dengue and Zika. The use of gene modification technology has not been used as often in agriculture because it is easier to use pesticides.

Max Scott is a professor who studies insects at North Carolina State. He worked on the study. He said past methods for releasing genetically modified insects would be costly for farmers if they were used. However, his group's study shows a new method could reduce the population of fruit flies so fast that it would not cost so much.

"We're really excited about this," Scott said. "The system is working really efficiently."

Bill Hutchison is an insect professor at the University of Minnesota. He agreed that if the gene modification works, it will help farms in the northern U.S. that now have more flies because of climate change.

Until recently, farmers in Minnesota did not think they had to worry about seeing flies in their fruit that would be ready to pick in June. But Nelson said that is no longer true. While he has not seen the flies this year, he has seen them before.

Two professors who were not part of the study said the North Carolina State research looks promising. Luciano Matzkin is at the University of Arizona. He said Scott's team's plan to center on producing sterile insects is better than past plans that attempted to modify another part of the flies' DNA.

Lyric Bartholomay is a professor at the University of Wisconsin. She said "increasingly tailored genetic approaches" will be required as insects gain more resistance to chemical treatments.

However, the work by the scientists in North Carolina is many years away from being used outside of a laboratory.

Scott said he and his team still need to do more work. They have to confirm their computer models and get permission from government officials to test their plan in nature. The scientists need to learn more about how changing the DNA of the fruit flies will affect other insects and whether the DNA changes will work on slightly different fruit flies.

Matzkin was happy to learn about the North Carolina team's research, saying that a "bio-control approach is always preferable" to chemicals. That is why other insect experts are working on similar projects.

Nelson, the farmer, worries that all the research may take too long to help his farm. He is concerned about his farm today.

He said farmers wonder if research will help the next generation. He currently works with his son, who is 24. He hopes they have an answer by the time he is older.

Today, he just wants to be able to sell enough berries to keep the farm going.

"If we lose our sales on our crops of berries, that's a very large deal for our farm," he said.

I'm Dan Friedell.

Dan Friedell adapted this story for Learning English based on a story by The Associated Press.

____________________________________________________________________

pest –n. an animal such as an insect that causes problems on farms or in homes by damaging food or other things

pesticide –n. a chemical that is used to kill pests

efficiently –adj. done in a quick and effective way

tailor –v. to change something so that it fits the situation very well

approach –n. a way of solving a problem