A recent investigation by researchers at North Carolina State University sheds light on the widespread distribution of a fungus linked to powdery mildew, a harmful pathogen that significantly impacts blueberry plants by reducing their yield and necessitating the use of more fungicides.
The findings of this study offer blueberry farmers valuable tools for predicting, monitoring, and managing powdery mildew infections.
Geographic Spread of Erysiphe vaccinii
The research reveals that the fungus known as Erysiphe vaccinii has broadened its geographic reach beyond its native Eastern United States, spreading across several continents over the past 12 years.
Michael Bradshaw, the lead author and an assistant professor of plant pathology at NC State, emphasizes that this situation serves as a real-time example of global fungal dispersal.
Powdery mildew manifests as a white, powdery film on infected plants, obstructing nutrient absorption and photosynthesis while leaving the host plant alive.
This fungus doesn’t just target blueberries; it also affects a variety of crops, including wheat, hops, grapes, and strawberries.
Study Methodology and Findings
To conduct their study, the researchers analyzed a variety of historical and contemporary leaf samples infected with powdery mildew.
They amassed a diverse collection of 173 samples from North America, Europe, Africa, and Asia, ranging from a specimen over 150 years old to others collected in the last five years.
The fungus was first detected outside North America on a farm in Portugal in 2012, as reported by one of Bradshaw’s collaborators, who worked for a major berry company.
Through genetic analysis, the team traced the origins and spread of the powdery mildew.
Interestingly, the older samples did not possess the genetic markers found in the current strains rapidly dispersing worldwide.
The results indicate that E. vaccinii likely originated in the eastern United States and spread globally through two main pathways: one reaching areas such as China, Mexico, and California, while the other extended to Morocco, Peru, and Portugal.
The researchers propose that human activities, particularly the transportation of nursery plants, play a significant role in this dispersal.
Financial Impact and Agricultural Practices
Working alongside key industry stakeholders and farmers, the research estimates that powdery mildew inflicts a financial burden of approximately $47 million to $530 million each year in fungicide application costs alone for blueberry production.
The study acts as an early warning for regions with significant blueberry production, particularly the U.S. Pacific Northwest, where conditions favor the disease’s establishment and spread—even though it has not yet appeared there.
Moreover, Bradshaw pointed out that agricultural practices may influence how the disease manifests.
For instance, blueberries grown in enclosed or tunnel-like environments tend to show greater disease severity compared to those cultivated outdoors, such as in North Carolina.
To aid farmers and researchers in identifying E. vaccinii strains, the team tapped into a public database created at NC State by co-author Ignazio Carbone.
This resource enables farmers to input their data, helping them determine the specific strain affecting their fields.
Understanding these strains is crucial for assessing resistance to fungicides and the virulence of various E. vaccinii types.
The findings of this important research have been published in the journal New Phytologist.
Source: ScienceDaily