New research has discovered a cause of the plant disease powdery mildew, which contributes to significant crop loss for the world's most popular grapevine vitis vinifera. 

The study was carried out by researchers at the University of Missouri (UM), who used frog eggs to determine how the fungus is able to spread through the plant.

Powdery mildew is one of the most widespread plant diseases, and thrives in cool, humid and semiarid conditions. It appears as white fuzzy blotches on the leaves, and is almost impossible to stop in the late flowering stage.

The researchers, led by professor Walter Gassmann from the Division of Plant Sciences at the UM , found a specific gene in the varietal Cabernet Sauvingon contributes to the plant's susceptibility.

Gassmann studied the biological role of specific grapevine genes in contributing to the plant's susceptibility to the disease by incubating them in frog eggs. He discovered that the fungus was able to trick the grapevine into providing nutrients, allowing the mildew to grow and devastate the plant.

"Powdery mildew disease causes the leaves of the grapevines to lose their chlorophyll and stop producing sugar. The grape berries also get infected, so the quality and yield are reduced in multiple ways," Gassmann said in a release.

The findings demonstrate one way Vitis vinifera is unable to fight the virus that causes the fungus is because of the plant's genetic makeup.

"Not much is known about the way a grapevine supports the growth of the powdery mildew disease, but the frogs help us provide a reasonable hypothesis for what is going on and why Cabernet Sauvingon could be susceptible," Gassmann said.

Gassmann hopes that this research will pave the way for discussing new techniques to breed more resistant forms of the grapevine in the future.

"The grapevine could be bred to prevent susceptibility and to keep the character of the wine intact. Isolating the genes that determine susceptibility could lead to developing immunities for different varietals and other crop plants and may contribute to general scientific knowledge of the grapevine, which has not been studied to the extent of other plants."

A report by the U.S. Department of Agriculture stated that powdery mildew can cause major yield losses if infection occurs early in the crop cycle and conditions remain favorable for development.

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