Scientists Sequence Genome of Colorado Potato Beetle

Researchers have for the first time mapped the entire genome of the Colorado potato beetle (Leptinotarsa decemlineata), one of the most challenging agricultural pests to manage. The results appear in the journal Scientific Reports.

The Colorado potato beetle (Leptinotarsa decemlineata). Image credit: Ben Pélissié / University of Wisconsin – Madison.

The Colorado potato beetle (Leptinotarsa decemlineata). Image credit: Ben Pélissié / University of Wisconsin – Madison.

The Colorado potato beetle, also known as the Colorado beetle, the ten-striped spearman, the ten-lined potato beetle or the potato bug, is widely considered one of the world’s most successful globally-invasive insect herbivores, with costs of ongoing management reaching tens of millions of dollars annually and projected costs if unmanaged reaching billions of dollars.

The beetle was first identified as a pest in 1859 in the Midwestern United States, after it expanded from its native host plant, the buffalobur nightshade (Solanum rostratum), onto potato (Solanum tuberosum).

To better understand this tenacious pest, University of Wisconsin-Madison entomologist Sean Schoville and colleagues sequenced its genome, probing its genes for clues to its surprising adaptability to new environments and insecticides.

“All that effort of trying to develop new insecticides is just blown out of the water by a pest like this that can just very quickly overcome it,” Dr. Schoville said.

“That poses a challenge for potato growers and for the agricultural entomologists trying to manage it. And it’s just fascinating from an evolutionary perspective.”

Within the Colorado beetle genome, the researchers found a diverse and large array of genes used for digesting plant proteins, helping the beetle thrive on its hosts.

The beetle also had an expanded number of genes for sensing bitter tastes, likely because of their preference for the bitter nightshade family of plants, of which potatoes are a member.

But when it came to the pest’s infamous ability to overcome insecticides, the authors were surprised to find that the Colorado beetle’s genome looked much like those of its less-hardy cousins.

They did not find new resistance-related genes to explain the insect’s tenaciousness.

“So this is what’s interesting — it wasn’t by diversifying their genome, adding new genes, that would explain rapid pesticide evolution,” Dr. Schoville said.

“So it leaves us with a whole bunch of new questions to pursue how that works.”

“What this genome will do is enable us to ask all sorts of new questions around insects, why they’re pests and how they’ve evolved. And that’s why we’re excited about it,” said co-author Dr. Yolanda Chen, from the University of Vermont.

The genome also provided a clue to the beetle’s known sensitivity to an alternative control system, known as RNA interference, or RNAi for short.

The nucleic acid RNA translates the genetic instructions from DNA into proteins, and RNAi uses gene-specific strands of RNA to interfere with and degrade those messages.

In the beetle, RNAi can be used to gum up its cellular machinery and act as a kind of insecticide.

The Colorado beetle has an expanded RNAi processing pathway, meaning it could be particularly amenable to experimental RNAi control methods.

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Sean D. Schoville et al. 2018. A model species for agricultural pest genomics: the genome of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae). Scientific Reports 8, article number: 1931; doi: 10.1038/s41598-018-20154-1

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