Genetic Study Uncovers Growing Threat of Powdery Mildew to Blueberry Crops

By Dr. Chinta SidharthanReviewed by Lily Ramsey, LLMJan 16 2025

Powdery mildew is a fungal disease that affects many plants, including economically important crops such as blueberries. Historically, Erysiphe vaccinii, the fungus responsible for powdery mildew in blueberries, was confined to North America. However, recent discoveries indicate its presence in other major blueberry-producing regions, raising concerns about its global spread.

In a recent study published in the journal New Phytologist, a team of researchers examined the dissemination patterns and genetic diversity of E. vaccinii through historical and contemporary samples. The study aimed to uncover the mechanisms behind its spread and adaptation to new environments to develop better management strategies for this emerging threat.

Study: An emerging fungal disease is spreading across the globe and affecting the blueberry industry. Image Credit: Mr.Rahim Mia/Shutterstock.com

Background

Blueberries are a globally valued fruit crop known for their nutritional and economic importance. Powdery mildew, caused by various fungal pathogens, poses a significant challenge to most fruit and vegetable crops by reducing yields and quality. Among these pathogens, E. vaccinii is particularly concerning for blueberries.

Historically confined to North America, this fungus was rarely reported from elsewhere. However, recent evidence reveals its presence in regions such as China, Morocco, and Mexico, suggesting its rapid and concerning expansion. This spread coincides with the global increase in blueberry cultivation, which may inadvertently facilitate the pathogen's dissemination.

Despite its potential to severely impact blueberry production, information on the genetic diversity, adaptation, and global distribution of E. vaccinii remains limited. Understanding these aspects is essential to identify pathways of spread, assess risks, and develop effective control measures.

About the Study

The present study utilized a combination of historical and modern samples to investigate the spread and genetic diversity of E. vaccinii. The researchers analyzed herbarium specimens, some of them over 150 years old, to reconstruct the historical distribution of the pathogen.

These samples were complemented with contemporary collections from major blueberry-producing regions worldwide, including North America, China, Morocco, and Mexico.

The genetic analyses focused on sequencing the ribosomal deoxyribonucleic acid (DNA) internal transcribed spacer (ITS) region, which is commonly used for fungal identification and phylogenetic studies.

To visualize the genetic relationships among different strains, the study used a Tree-Based Alignment Selector (T-BAS) platform. This living phylogeny approach integrated historical and modern genetic data, allowing the researchers to map the evolution and spread of the pathogen. The analysis also identified distinct haplotypes, which provided insights into the diversity and evolutionary history of the fungus.

Additionally, the researchers investigated potential introduction pathways by analyzing genetic similarities and differences among geographically dispersed samples.

They inferred possible routes of spread and adaptation through a combination of genetic and geographic data. The findings were also cross-referenced with historical records of blueberry cultivation and trade to understand the role of human activities in the dissemination of the fungus.

Major Findings

The study found that E. vaccinii has significantly expanded its geographic range, evolving from a North American pathogen to a global threat to blueberry crops. The genetic analyses identified 50 distinct haplotypes, indicating high genetic diversity within the species. The data also revealed two major introduction events that likely facilitated its spread to other regions, including China, Morocco, and Mexico.

The results suggested that international trade and the expansion of blueberry cultivation are critical drivers of the global dissemination of the fungus. Notably, the study found evidence of a shift in the behavior of the fungus, with some strains adapting to become specialists that infect only blueberries.

This adaptation is believed to have increased the impact of the fungus by making it more effective at infecting its host in new environments.

Additionally, phylogenetic analyses showed clear genetic clustering of strains from different regions, suggesting multiple independent introductions rather than a single global spread.

Additionally, the historical data revealed that E. vaccinii's spread coincided with the worldwide expansion of commercial blueberry production over the past century. This correlation highlighted the role of human activities in facilitating the introduction and establishment of the fungus in new regions.

Overall, the study indicated that the rapid adaptation and diversification of E. vaccinii was a major and rapidly growing challenge for blueberry production. The findings also emphasized the importance of international cooperation and proactive measures to prevent further spread and mitigate the impact of this fungal disease.

Conclusions

To summarize, the findings revealed that the global spread and significant genetic diversity of E. vaccinii were linked to its evolution into a specialized pathogen threatening blueberry crops worldwide.

The study also highlighted the role of human activities in facilitating its dissemination and underscored the need for vigilant monitoring, international cooperation, and effective management strategies.

The researchers stated that addressing this emerging threat is crucial to sustaining global blueberry production and minimizing economic losses associated with powdery mildew.