by Carolyn Bernhardt
May 21, 2025
Rust fungi are usually bad news for plants, but Jyoti Saini Sharma, PhD, a researcher in the Olivera Firpo Lab, sees them as a potential key to controlling one of Minnesota’s most stubborn invaders: common buckthorn. With a background in genomic analysis of host-pathogen interactions, particularly in wheat, Sharma has spent years developing tools to improve rust resistance in wheat lines and cultivars. Now, as part of a new MITPPC-funded project, she and her team are investigating whether crown rust fungi could help suppress the growth of buckthorn seedlings. Her team is identifying which rust species infect common buckthorn, documenting their host range and symptoms, and evaluating their impact on plant growth and mortality.
Rust fungi have complex life cycles, infecting woody plants during some growth stages and herbaceous plants during others. The research team is using crown rust species commonly found in Minnesota for their study — an approach Sharma considers one of the project’s strengths. “These species could be used in suppressing buckthorn and invasive grasses, and be another alternative to manage these invasive species,” she says.
To find the right candidates, Sharma and her team collected rust-infected buckthorn from around the state in 2023 and 2024, then used Nanopore sequencing of a key region of their DNA to identify them. According to her, this process offers a “fingerprint” of each fungal species. The team selected three rust species that infect non-native grasses and tested their effects on both buckthorn and grasses in greenhouse trials. However, infecting buckthorn seedlings with rust spores presented some challenges. The process requires many high-quality spores, so her team focused their collection efforts in the fall and spring.
The preliminary findings from those trials have been promising. “We identified six species of the crown rust complex infecting buckthorn in Minnesota, two of them observed for the first time in the state,” says Sharma. “The crown rust species that cycles between buckthorn and smooth brome is the predominant and most widely distributed.” And in the greenhouse, she says, the crown rust species that infect smooth brome and Kentucky bluegrass significantly reduced plant biomass in the two invasive plants. Kentucky bluegrass and smooth brome are problematic in many Minnesota prairies, but Kentucky bluegrass is also commonly planted in Minnesota lawns.
A future challenge for Sharma’s team will be to ensure the safety and efficacy of using these rust fungi as biocontrols. In the meantime, Sharma hopes the work will help land managers add a new control method to their arsenal. She adds that the project has also opened up new scientific terrain for her, expanding her knowledge from cereal research to invasive plants, brushing up her molecular skills, and offering her new expertise in field surveys.
Sharma also says one highlight of the work so far has been “curiosity among people about buckthorn research and its direct impact.” Meanwhile, she says, “We are very excited about the significant impact of rust infections in reducing plant biomass in Kentucky bluegrass and smooth brome.”
More information
- Effects of Puccinia species complex on common buckthorn, research project
- Buckthorn, MN Department of Natural Resources
- Smooth brome grass, MN Department of Natural Resources
- Kentucky bluegrass, US Department of Agriculture
Research from the Minnesota Invasive Terrestrial Plants and Pests Center is supported by the Environment and Natural Resources Trust Fund, as recommended by the Legislative-Citizen Commission on Minnesota Resources.
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