Hopes have been raised of efficient breeding for grapevines resistant to downy mildew, alongside the better design of quarantine regulations, following the work of French scientists who have unpicked the arrival of the North American disease in Europe and its subsequent spread around the world.
France’s National Research Institute for Agriculture, Food and Environment (INRAE) notes that Plasmopara viticola , the pathogen responsible for grapevine downy mildew, causes destructive epidemics which can result in major losses for winegrowers and is responsible for much fungicide use in vineyards.
It explains that though we know much about the disease’s biology and reproduction, we know very little about its invasion history. INRAE researchers working in collaboration with the Université Paris-Saclay and CNRS have sought to fill this gap. In a paper published in Current Biology , they provide some of the keys for understanding the process by which downy mildew arrived in Europe before affecting wine-growing areas around the globe.
INRAE explains that there are several vine species, alongside several species of the pathogen that causes grapevine downy mildew. Each of the latter adapts to its host, making it complicated to understand its history and how it arrived in Europe. Downy mildew was first detected in France in 1878, but were one or several species behind its invasion of Europe?
INRAE explains: “The scientists adopted a multidisciplinary approach to answer these questions, and discovered that the first contamination of European vines occurred 150 years ago and involved a single species of mildew, that which infected the wild vine Vitis aestivalis .
“The team then tracked it back in order to understand how it managed to infect French vineyards. Their study suggests that the pathogen was introduced via wild American vines that were imported in order to control powdery mildew and phylloxera.
“Because France was the first country to be affected by phylloxera, it intensified varietal innovation by incorporating disease resistance from American wild vines in cultivated vines (V. vinifera ). These cultivated European vines then served as the source for the introduction of the disease into vineyards throughout the world.”
INRAE notes that from the 19th century onward, France was considered the model for the modern vineyards that have developed worldwide and so exported its hybrids and phylloxera-resistant rootstocks, including famous varieties such as Cabernet, Merlot, Chardonnay, Syrah etc. This means that international trade acted as a vector for the spread of downy mildew.
“This scientific study offers new insights on grapevine downy mildew and notably its spread throughout the world,” concludes INRAE. “It highlights the importance of regulating international trade in plant materials in order to prevent other mildew species from being introduced into our vineyards.”
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