In the fungal kingdom, no one is safe from parasites – not even other parasites.
A new study from North Carolina State University finds that Ampelomyces, an intracellular fungus that infects the plant disease powdery mildew, is far more common than previously known. By screening museum samples of powdery mildews up to around 150 years old, researchers discovered that not only is Ampelomyces quite common, but many specimens labeled as Ampelomyces are misidentified.
Because powdery mildews cannot be cultured, researchers screened over 600 dried samples from the NC State herbarium (a collection of plant and/or fungal samples) to collect data on the prevalence of Ampelomyces. These samples were collected across 28 countries over the past 150 years, and were analyzed alongside samples available on GenBank, a public database of DNA sequences used by scientists to share and study genetic data. In total, scientists screened over 600 samples between GenBank and the herbarium. Researchers found that around 7% of all powdery mildew specimens analyzed were infected by this parasite.
Michael Bradshaw, corresponding author of the study and an assistant professor of entomology and plant pathology at NC State, said that understanding hyperparasites (parasites of parasites) could open doors to better control methods for the fungi they infect.
“By understanding hyperparasite diversity and how many different strains are out there, it might give us insights on if some are better at controlling the fungus than others,” Bradshaw said. “There is a degree of host specificity to these hyperparasites, and if we are able to delve deeper they may be very useful in containing this plant disease.”
Another significant finding was that among the GenBank specimens screened, around 15% of those labeled as Ampelomyces were misidentified. Bradshaw said that this level of inaccuracy is part of the risk when relying on large data sets where anyone can input information.
“These parasites are hard to identify, so what happens is someone misidentifies them and enters incorrect data,” Bradshaw said. “Then someone else sees that wrong data and uses it to classify their own samples, which leads to more wrong data, and it amplifies that way.”
These findings demonstrate how herbaria can act as powerful tools for observing a range of biological phenomena such as studying hyperparasites and their interactions with plants and fungi. Further research could focus on expanding sampling across broader geographic regions and diverse host types.
The paper, “Parasites of Parasites: Herbaria as Archives of Hidden Ecological Interactions,” is published in Proceedings B. Funding for the project comes from the National Science Foundation, Award Number 2402193. This work was also supported by the Research Capacity Fund (HATCH), project award no. 7006142, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.
Co-authors include Jacklyn Thomas, Andrew Paul, Uma Crouch and Ignazio Carbone, NC State; Uwe Braun, Martin Luther University; Susumu Takamatsu, Mie University, retired; Márk Z. Németh, HUN-REN Centre for Agricultural Research and ELTE Eötvös Loránd University; Levente Kiss, HUN-REN Centre for Agricultural Research and University of Southern Queensland; James Mitchell, Harvard University; and Henry Van T. Cotter, University of North Carolina at Chapel Hill.
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