AVF Proj. ID: 643
Year Funded: 2016
Category: Cultural Practices - Clones
Investigators: Lindsey Jordan

Evaluation of the Viticultural Performance of Newly Released Nematode Resistant Rootstocks in San Joaquin Valley Wine Grape Vineyards

Summary:

 


As microscopic plant parasites, nematodes can cause extensive damage to grape vineyards. As the nematodes feed on and damage root cells, vine health, vigor, and productivity will decline. Nematodes affect many regions of California, but vineyards within the San Joaquin Valley (SJV) are particularly vulnerable to nematode damage due to typically sandy soil profiles and the wide range of parasitic nematode species found within the region, coupled with many soils being in agricultural production for decades. Traditionally, fumigation has been a viable method to provide relief from nematode pressur, but the California Department of Pesticide Regulation continues to regulate the volatile organic compound (VOC) emissions from field fumigants and fumigation is increasingly unavailable to growers with properties near schools or housing. Grape growers must begin to consider ways to reduce or eliminate the need to fumigate in order to keep up with regulations, but still ensure that nematode damage does not diminish the economic viability of their grape production. Rootstocks can provide a non-chemical alternative to resist soil pests like nematodes and maintain vine productivity. In recent years, several rootstocks have been released for commercial production including two USDA-ARS selections developed by David Ramming and Michael McKenry, RS-3 and RS-9, and the “GRN” series by Andrew Walker. Extensive work has examined nematode parasitism and sources of grape rootstock resistance, but how these rootstocks will perform with regards to viticultural characteristics in commercial plantings is still largely unknown. To promote the use of these new nematode resistant releases and see grape growers benefit from the years of research that went into developing these rootstocks, as well as be protected from increasing VOC emission regulation and economically damaging nematode pressure over time, field-based data on how these recent nematode resistant rootstock releases effect vine growth, yields, and fruit characteristics in commercial scale production is needed. In this study, on established trial site in a commercial high-wire, mechanically pruned Petit Verdot vineyard has consistently shown that Freedom generated the highest yields, but GRN4 also produces high yields. Freedom and the GRN selections generated significantly more growth than the comparatively weak performance of RS3, RS9, and 1103P at this site. 1103P was also under-ripe at the time of harvest, compared to the other selections. Seeing that several of the GRN selections were able to produce similar yields and fruit chemistry to Freedom, this indicates they may be a valuable tool for SJV grape growers to use when nematodes are a concern when planting. A second large-scale trial testing the GRN and RS selections was planted with Malbec in 2016, and will be evaluated as it matures. By using these two sites with a history of nematode pressure and managed under commercial growing conditions in non-fumigated fields, grape growers from around the SJV and all of California can benefit from the better understanding of how these rootstocks may effect vine vigor and berry maturation, and accordingly make the best choices to remain economically viable while using the best rootstocks available to resist nematodes.

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