Gene drive put to work for first time

Facts about Drosophila suzukii:

A disruptive technology that potentially could eliminate or reduce the need for insecticides may soon be coming to market.

In a paper published April 17 in the Proceedings of the National Academy of Sciences, University of California, San Diego biologists announced they have developed a gene drive to control an agricultural pest. The pest is the spotted wing drosophila, a fruit fly that damages berry and fruit crops.

“This is the first gene drive system in a major worldwide crop pest,” said Omar Akbari, of UC San Diego. “This system could in the future be used to control populations of (drosophila).”

A gene drive is a tool to spread a genetic alteration into a wild population of a certain species.

In nature, there is on average a 50 percent chance of a parent passing a particular trait to an offspring.

With a gene drive, a specified gene is inherited by all offspring, even if it is present in only one parent.

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The technology could become important for a couple of key reasons:

  • It could reduce the population of crop pests by making females sterile, or cause all offspring to be male.
  • It could alter the genetics of insect pests so they can’t transmit diseases to crops.

UC San Diego estimated that drosophila causes US$700 million in revenue losses, annually, for U.S. fruit growers.

“If we don’t deal with Drosophila suzukii, crop losses will continue and might lead to higher prices,” said Anna Buchman, Akbari’s colleague at UC San Diego.

“So this gene drive system is a biologically friendly, environmentally friendly way to protect an important part of our food supply.”

Spotted-wing dropsphila is also a major pest in Ontario. It lays eggs in ripening fruit like blueberries, raspberries, strawberries, cherries and other soft-skinned fruit.

Producers control the fruit fly with insecticides and by picking fruit more frequently.

Buchman said it might be possible to drive a gene through a population of spotted wing drosophila that makes it more susceptible to pesticides.

Another option is a gene drive that introduces a temperature trigger, where the pest dies when the air temperature reaches a certain level.

The gene drive technology for a fruit fly may be a world’s first, but scientists are working on gene drives for other insects.

“Researchers are pursuing applications of gene drives to control a number of economically significant agricultural pests. These include Lepidopteran insects,” wrote Zachary Brown, an economist at North Carolina State, in Choices, a magazine of the U.S. Agricultural Economics Association.

The technology is more powerful than traditional biotechnology. Consequently, a number of scientists are worried about the unforeseen consequences of gene drive.

“It has great potential, which is why people are quite interested in it,” said Sally Otto, a University of British Columbia zoologist.

“What’s different about this technology is it’s not just capable of modifying a single organism, but spreading throughout a species…. (It’s) a much broader implication than genetic engineering of a single individual.”

The UC San Diego scientists say their gene drive system is specific to spotted-wing drosophila, so it won’t affect other species of fruit flies.

“It’s a new method for manipulating populations of these invasive pests, which don’t belong here in the first place,” Akbari said.

The spotted-wing drosophila is native to Japan and was first found on the U.S. West Coast in 2008. The fruit fly has now been reported in more than 40 states and in all Canadian provinces.

Facts about Drosophila suzukii:

  • This temperate fruit fly is native to southeast Asia and prefers temperatures of 20-30C.
  • This species can be found across the world in temperate fruit-producing areas, including North and South America, Europe and Asia. So far it has not been found in New Zealand or Australia.
  • It infests thin-skinned fruit such as berries, pitted fruits such as cherries, peaches and plums and occasionally in kiwi fruit. It has also been found in non-edible berry bearing tree species.
  • The female fly lays her eggs inside ropening fruit using a saw-like ovipositor, causing the fruit to become soft and full of larvae. One female fruit fly can lay up to 384 eggs.
  • Adult fruit flies have brownish bodies and red eyes with clear wings. Males have a grey or black spot on the end of each wing, as well as two black bands on their front legs. Females do not have these markings but can be distinguished by their saw-shaped ovipositor.
  • Management practices include using registered insecticides, culling soft fruit, destroying culled fruit and keeping processing areas and equipment free of old fruit.

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