Resolving the patched rusty bee genome may offer a new approach

LOGAN, Utah, June 20, 2023 — A detailed, high-resolution map of the rusty bee wasp genome has been released by the US Department of Agriculture (USDA) Agricultural Research Service (ARS) and US Fish and Wildlife Service (USFWS) scientists, offering possible new approaches to bringing native pollinators back from harm extinction.

Assembling the patched rusty bee genome is part of the Beenome 100 project, the first attempt of its kind to create a library of high-quality, highly detailed genome maps of the 100 or so diverse bee species found in the United States. Beenome 100 is a collaboration between ARS and the University of Illinois. It is hoped that the library will help researchers answer big questions about bees such as what genetic differences make bee species more vulnerable to climate change or whether bee species are likely to be more susceptible to pesticides.

Rusty rusty bee (A linked bomb) is an important pollinator of bergamot (Monarda fistulosa), milkweed, and other wildflowers, as well as plants such as cranberries, plums, apples, and alfalfa. But in the last 20 years or so, the population is estimated to have declined by 87 percent.

As of 2017, this species is listed as “endangered”. Rusty patched bees were once common in the Upper Midwest and Northeast in 28 states and 2 Canadian provinces, now their range is down to the point of being cut off in 13 states and one Canadian province. Among several places that are still frequently found is around Minneapolis-St. Paul’s Area in Minnesota and in Wisconsin.

“With the amount of detailed information that we and other researchers can now access into this newly sequenced genome, we have the opportunity to find an entirely different approach to amplifying rusty bee populations,” said research entomologist Jonathan B. Uhaud Koch with the Research Unit. Insect-Biology, Management, Systematics of ARS Pollination in Logan, Utah.

Koch explained that several factors contributing to the decline of bumblebee bumblebees are well known: loss of habitat, reduced variety of nectar sources, climate change, exposure to pesticides, and more pathogens and pests.

While scientists have known the existence of pathogenic fungi widely Varimorpha bombi (previously called Nosema bombi) had a detrimental impact on many rusty bee populations, Koch was a bit surprised by how much Varimorpha genetic material he found in bee samples that was used to develop genome maps.

“We used a small piece of stomach tissue from one male collected from a hive in Minnesota, which, given the rusty hornet’s endangered status, seemed like a really good idea,” Koch said. “Only with the most advanced equipment can you complete the entire genome of 15,252 genes and 18 chromosomes from one little bee.

It turned out that about 4.5 percent of the DNA the researchers sequenced came from Microsporidia, the group of fungi that it belongs to Varimorpha bombi. “That’s a huge amount of genetic information from a sample of bee tissue to relate to Varimorpha bombi. It shows how widespread the pathogen is,” said Koch.

“Having this high-quality genome will support the identification of genetic differences between rusty bee populations that appear to be doing well versus those in which they are in decline,” said Koch. “This may give us a handle on identifying genes that confer flexibility in populations that are better able to cope with their environment. We can also gain a better understanding of the genetic basis of bee behavior, physiology, and adaptation to changing environmental conditions.”

Once genes that are more successful for certain types of local conditions are identified, researchers will be able to give the population a push in the right direction when it comes to restoring rusty bees to an area through captive programs.

This research was funded by ARS and USFWS. This research is published in the journal G3: Gen | Genome | Genetics (https://doi.org/10.1093/g3journal/jkad119) and the genome is available on the National Center for Biotechnology Information website https://www.ncbi.nlm.nih.gov/assembly/GCF_024516045.1/.

The Agricultural Research Service is the principal internal research agency of the US Department of Agriculture. Daily, ARS focuses on solutions to agricultural problems affecting America. Every dollar invested in US agricultural research generates a $20 economic impact.

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