Winter Newsletter 2024
This edition features updates from the UDSA, Update from the Northwest Berry Foundation, our latest industry fact sheets, and industry announcements.
Risk assessment of nematode-transmitted viruses of small fruit crops in the Pacific Northwest
The Pacific Northwest (PNW) maintains a $840 million small fruit industry susceptible to nepoviruses, which are viruses that are transmitted by dagger nematodes. The association of viruses with nematodes is complicated with many nepoviruses, taxonomic confusion among vector nematodes, and limited data on the ability of Xiphinema spp. populations to vector many of the nepoviruses. Research was conducted to provide an up-to- date assessment of the problem in the region and to develop new molecular tools to improve detection of this disease complex. Over two years, 96 small fruit fields and vineyards were sampled in the PNW. In total 43 vineyard, 24 blueberry, 15 raspberry, 8 blackberry, 5 strawberry and one ribes fields were assessed for dagger nematode and nepoviruses. The highest incidence of dagger nematode was found in grape vines (79 %) followed by raspberry and blueberries. The population densities were 56 and 37 nematodes per 250 cc of soil in grapes and blueberry, respectively. Tomato ringspot virus (ToRSV) was found in three blueberry fields, while, in grape, raspberry and ribes only one field each. Tobacco ringspot virus (TRSV) was found in six vineyards.
Developing a Spray-Induced Gene Silencing (SIGS) method for the control of Grape Powdery Mildew (Erysiphe necator)
Powdery Mildew development in vineyards in the Pacific Northwest is one of the greatest impacts to grape and wine quality and the economic health of a grape grower is severely impacted by the number of sprays required to control the disease or loss in fruit sales if a severe infection develops. In high wine-producing regions, Grape Powdery Mildew (GPM) accounts for 75% of total pesticide use applications. If the grapevines are not properly treated until harvest, the presence of GPM in harvest grape clusters substantially depreciates the value of the entire crop. This project aims to develop a methodology to turn off specific grapevine genes (susceptibility genes [MLO]) and Powdery Mildew-related genes essential for the pathogen’s life cycle.
Inducement of malolactic fermentation using Lactobacillus plantarum in musts and wines from the Pacific Northwest.
The completion of both alcoholic and malolactic fermentation (MLF) in red wine are essential to the quality and stability of red wine and to its commercial success in the market. In this study, alcoholic and malolactic fermentations were induced in low and high nitrogen-containing Cabernet Sauvignon musts by adding both yeast (Saccharomyces cerevisiae) and bacteria (Oenococcus oeni or Lactobacillus plantarum) at the same time. While O. oeni was able to complete MLF in the high nitrogen fermentations, only one of the three strains of Lb. plantarum was able to convert the majority of malic acid to lactic acid (<0.5 g/L residual malic acid). Under low nitrogen conditions, neither alcoholic or malolactic fermentation finished in any of the wines. Subsequent fermentations using a synthetic grape juice medium yielded poor growth of bacteria whether inoculated subsequently or concurrently with S. cerevisiae. Additional studies with Lb. plantarum are required to fully evaluate their potential usefulness to Pacific Northwest winemakers.
Botrytis Bunch Rot: Where, When, and What to use
From 2020-2022, eleven sites from nine different vineyards in Oregon, and four in Washington were surveyed for Botrytis by sampling grape inflorescence and developing fruits, vineyard floor debris (prior year grape rachis), and nuisance blackberries. Botrytis on grape inflorescence and fruits varied from site to site and year to year likely due to yearly disease pressure differences and unique site microclimates. Prior year dead grape rachis on the vineyard floor with sporulating Botrytis infestations varied from year to year as well, but generally declined as the season progressed. Incidence of Botrytis on vineyard floor debris in all but one site in 2021 was over 75% in late April and all sites sampled decreased over time to under 25% by September. Wild nuisance blackberry flowers and fruits adjacent to the vineyard were also found to be potential sources of Botrytis inoculum throughout the season. Inoculum estimation from historical spore trap DNA samples originally taken to monitor powdery mildew in the Willamette Valley were re- assayed for Botrytis inoculum.