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Why are ancient gray poplar trees suddenly targeted by deadly pathogens?
With the changes in the global ecological environment, many plant species are facing unprecedented challenges. In Europe in particular, a deadly fungus, Hymenoscyphus fraxineus, is pushing ancient gray poplar trees to the brink of extinction. Since it was first reported in Poland in 1992, the poplar wilt disease caused by this fungus has continued to spread and has had a devastating impact on forest ecosystems in many countries.
Studies have shown that mortality rates among poplar trees can be as high as 85 percent, and in forests as high as 69 percent.
The charm and danger of the gray poplar
Gray poplars (Fraxinus excelsior) are an important component of European forests. Its wood is used for a variety of purposes and provides habitat for many species of plants and animals. However, these trees are under serious threat due to the spread of Hymenoscyphus fraxineus. According to research, this pathogen not only affects the growth of poplar trees, but also causes a chain reaction in the entire ecosystem.
Pathogenic mechanism
The fungus, which has an asexual and sexual life cycle, produces spores that are dispersed by wind. Infected trees develop initial necrotic spots, which eventually lead to crown shrinkage and death. The pathogen is particularly devastating to young poplar trees, causing death in just one growing season.
A combined attack by Hymenoscyphus fraxineus and other pests could lead to the extinction of the European gray poplar, according to a 2016 report published in the Journal of Ecology.
History of Diffusion
The pathogen was first documented in 1992 and was subsequently reported in the mid-1990s in the Baltic States and Germany. By 2012, the disease had spread to several countries, including the United Kingdom and Ireland. Since 2006, scholars have studied its transmissibility and pathogenicity through genetic analysis.
Management Challenges
Currently, effective strategies for managing poplar wilt have not emerged. Many countries have tried to control the spread of the disease with little success. Even felling infected trees has not been effective in reducing the spread of the disease because the pathogen survives in leaf litter on the forest floor. Researchers are trying to extract branches from some disease-resistant trees for grafting, hoping to cultivate more resistant offspring.
In a trial in Lithuania, 50 trees with disease resistance were eventually selected and a breeding population was established.
Situation in the UK and Ireland
The disease was first discovered in the UK in 2012, prompting a swift ban on imports of poplar trees from other European countries. According to reports from the German and French governments, the pathogen has already had a major impact in several regions and may cause widespread tree deaths in the coming decades.
Ecological impact
Due to the impact of Hymenoscyphus fraxineus on the gray poplar ecosystem, many species that rely on it for habitat are also facing survival crisis. The study showed that on the beautiful island of Gotland, the pathogen poses a co-extinction risk of up to 0.38 for rare mosses.
Future Outlook
With further research into the pathogen's genome, scientists hope to find a comprehensive solution to combat the disease. Ongoing breeding programs and gene-editing techniques may offer hope for future tree conservation efforts.
How will Europe's future change in the face of this deadly pathogen, or will it depend on our current actions and research?
