UC Davis Releases Pest-Resistant Rootstocks

Nurseries now propagating rootstocks for commercial sales in 2010

by Jane Firstenfeld
UC Davis Releases Pest-Resistant Rootstocks
Dr. Andrew Walker
Davis, Calif. -- Five new rootstocks that promise to resist nematodes, aphids and other insects have been licensed to certified commercial grapevine nurseries for propagation and eventual sale to vineyards in California and elsewhere.

Developed over a period of 15 years by a research team led by UC Davis professor and geneticist Dr. Andrew Walker, the rootstocks involve combinations of pest-resistant native grapes including vitis riparia, vitis rufotomentosa and an unusual strain of vitis champinii, that Walker unearthed in Texas. The research was funded in large part by the California Grape Rootstock Research Foundation, which is supported by the grapevine nursery industry.

Walker said he hopes that these new rootstocks will enable winegrape growers to successfully graft to vinifera vines that are susceptible to these pests. In the past, fumigation has been the only means--not particularly successful--of eradication or control.

Walker told Wines & Vines that an agricultural weakness specific to viticulture is the lack of crop rotation and of fallow periods in the vineyard, a situation that encourages pests to adapt and become more aggressive and dangerous.

UC Davis Releases Pest-Resistant Rootstocks
Range of responses to dagger nematode damage on grape seedlings ranging from resistant (left) to very susceptible (right).
PHOTO: Yimin Jin
Nematodes, he explained, are tiny, almost microscopic soil-dwelling worms that feed on roots. He specified several species that feed on--and damage or kill--grapevines, including root-knot, ring and dagger nematodes, which, he said, can form complexes and become even more harmful.

With this particular project complete, Walker and his team are continuing their research to develop grapevine rootstocks with more salt tolerance and resistance to other vineyard threats, including Pierce's disease and grapevine fanleaf virus.

The new rootstocks, still in the patenting process, are referred to by the original code numbers used during Walker's research: 8909-05, for example. Now available in pro-rated shares to qualified registered vine nurseries, the rootstocks, which arrive at nurseries in gallon-sized containers, will require a minimum of two years to become available in commercial quantities.

"The procedure is, we'll propagate cuttings from these pots this year, plant them this year in 'increase blocks,' and get the first commercial cuttings for sale, in limited quantities, in 2010," according to Steve Maniaci, production manager for Sunridge Nurseries Inc., in Bakersfield, Calif.

UC Davis Releases Pest-Resistant Rootstocks
Egg masses of root-knot nematode on grape rootstock.
PHOTO: Peter Cousins.
Ernie Bowman, co-chair of the California Grape Rootstock Improvement Commission, parent organization of the CGRRF, called the release "exciting" for the vineyard industry.

"We need more rootstock," said Bowman, of Kendall-Jackson Nursery, Santa Rosa, Calif., adding, "One real issue is that there is no real viticultural evidence of how these will perform. We need data from the field. The rootstocks were tested in the greenhouse, and a couple of trial blocks have been put in the ground." The new rootstock, he said, is "at least three or four years away from commercially available stock."

Maniaci lauded Walker's selection process, which tested the prototypes for attributes like vigor and graftability, then chose the best for release. He explained that all five rootstocks would be suitable for grafting to different grape varieties, but choices would vary due to site suitability. Some sites might be more susceptible to certain types of nematodes; some rootstocks might be more useful in areas with shallow soils.

Sunridge has received its pro-rated allotment of all five rootstocks, and, Maniaci said, "Already a couple of customers have asked for them," illustrating industry demand for the improved product.
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