Researchers Sequence Genome of Desert Locust

by johnsmith

Scientists from USDA’s Agricultural Research Service have successfully produced the first high-quality genomic sequence for the desert locust (Schistocerca gregaria), a species of short-horned grasshopper that periodically changes its body shape, behavior, and reproduction rate in response to environmental conditions such as an abundance of rainfall and moisture.

A swarm of locusts by Emil Schmidt.

Locusts are a group of short-horned grasshopper species in the family Acrididae.

These insects are usually solitary, but under certain circumstances they become more abundant and change their behavior and habits, becoming gregarious.

The desert locust is potentially the most dangerous of the locust pests because of the ability of swarms to fly rapidly across great distances. It has two to five generations per year.

Plagues of desert locusts are cyclic and have been recorded since the times of the Pharaohs in ancient Egypt, as far back as 3200 BCE.

In recent decades, there have been desert locust swarms in 1967-1969, 1986-1989 and most lately 2020-2022.

They cause devastation in East Africa, the Middle East, and Southwest Asia, threatening food security in many countries.

Their damage can be massive. A small swarm can eat as much food in a day as would feed 35,000 people.

Current desert locust control mostly depends on locating swarms and spraying them with broad-spectrum pesticides.

“Having a high-quality genome is a big step toward finding targeted controls,” said Dr. Scott Geib, an entomologist with the Tropical Crop and Commodity Protection Research Unit at USDA’s Agricultural Research Service.

“It will also give us valuable information about relatives of the desert locust that are major pests in the Americas such the Mormon cricket (Anabrus simplex), another swarming species that can impact U.S. food security.”

Dr. Geib and his colleagues found that the desert locust genome is enormous; it has just under 9 billion base pairs — nearly three times the size of the human genome.

“The desert locust is one of the largest insect genomes ever completed and it was all done from a single locust,” Dr. Geib said.

“We were concerned that, faced with this huge and very likely complex desert locust genome, it was going to be an extremely long and difficult job.”

“However, we were able to go from sample collection to a final assembled genome in under 5 months.”

The size of the desert locust’s individual chromosomes is also remarkable;mMany of them are larger than the entire genome of the fruit fly.

“With the desert locust, we were dealing with a much larger genome in many fewer pieces — about 8.8 Gb in just 12 chromosomes,” Dr. Geib said.

“Next to the fruit fly, it’s like an 18-wheeler next to a compact car.”

“It was like sequencing a typical insect genome many, many times over. But with today’s advances in DNA sequencing technologies, we are now able to generate extremely accurate genomes of insects that previously would have been unapproachable.”

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