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Monday, August 2, 2021

UC Davis researchers find grape rootstocks resistant to vineyard pests

After over a decade of research, UC Davis scientists have found five strains of grape rootstocks resistant to several strains of soil-born pests in California vineyards.

The rootstocks were released to commercial nurseries on Mar. 31.

Howard Ferris, professor of nematology at UC Davis and Andrew Walker, professor of viticulture at UC Davis, conducted the study along with assistance from staff research associate Liang Zheng.

The research primarily targets the plants’ resistance to nematodes, microscopic worms that feed on a range of soil organisms, including plant roots. The rootstocks were also found to be resistant to grape phylloxera, a root aphid that feeds on grape vines.

Walker said the research started because “the rootstocks we had available weren’t resistant enough to these pests.”

“There are a full range of nematodes that attack grape vines, some with minor consequences, but many with rather serious consequences,” Ferris said.

A rootstock contains the trunk and the roots of a grape plant where many different grape varieties can be grafted.

“There are already a few rootstocks that have resistance to one nematode type, but since many nematode species occur in the same vineyard, it seems more valuable to have rootstocks that have resistance to several species of nematodes,” Ferris said.

“Most nematodes feeding on plants, if at high enough population levels, will decrease plant growth and yield,” he said. “They will damage root systems and disrupt physiology of plant growth.”

“Consequently, plants are stunted, and yields of grapes are reduced,” Ferris said.

One species of nematode the researchers have been targeting is known as the dagger nematode. “[The dagger nematode] is important because it both causes direct damage to grape roots, and is also the vector of the grapevine fanleaf virus,” said Zheng in an e-mail interview. Zheng screened the resistance of rootstock selections to strains of nematodes and tested the durability of resistance when the rootstocks were subjected to various stressors.

“It was a 10-year process,” Ferris said. “[We] started off with 4,000 selections. We screened them individually against four different types of nematodes.”

If a rootstock was resistant to one type of nematode, it would then be tested against other types of nematodes.

“Out of the 4,000 [selections] that we started off with, we have five with resistance to this range of nematode species,” he said.

“Nurseries will graft desirable varieties of grapes on the new rootstocks so that growers should be able to plant them without using pesticides to kill the nematodes,” Zheng said.

“[These findings should] be useful for both wine grapes and table grapes across the state,” Walker said.

Wine from the rootstocks could be available by 2013, with table grapes available in 2012, according to a UC Davis press release.

Karen Ross, the president of the California Association of Winegrape Growers said the research is “great.”

“When you plant a vineyard, it’s a long-term investment. You figure the life of the vineyard is going to last at least 25 years,” she said.

Growers want to be confident that what they plant is going to last and be productive, and also be resistant to pests and disease, she said.

Sustainability is also an issue.

A healthy rootstock means using less pesticide, she said.

“There are [fewer] inputs and fewer costs in maintaining the life of the vineyard,” Ross said. “This creates a healthier vineyard environment.”

 

ANNA OPALKA can be reached at campus@californiaaggie.com. XXX

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