Graduate Thesis Or Dissertation
 

Efficacy of Cultural Practices for Mitigating the Negative Impacts of Grapevine Red Blotch Virus on Vine Physiology and Fruit Composition in Oregon Pinot Noir

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9c67wv41j

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  • The recently emerged Grapevine Red Botch Virus (GRBV) impedes proper berry ripening primarily by reducing sugar accumulation and color development in red-fruited Vitis vinifera L. cultivars. To date, there is no recommended management strategy for virus spread or the impacts of the disease beyond removal and replacement of infected vines. The present study investigates the potential of common vineyard cultural practices to dampen the effect of the disease on fruit composition and provide a lower-cost alternative to vine replacement while producing fruit of an acceptable quality for wine production. The responses of vine physiology, vegetative growth, disease severity, yield, and fruit composition in GRBV-infected Pinot noir vines to irrigation, fertilizer, and crop thinning treatments were observed over three years (2018-2020). In the first of two experiments, factorial combinations of grower control and supplemental (doubled) rates of irrigation and fertilizer were applied to infected vines. In the second experiment, treatments consisted of the previously described irrigation levels combined with either no thinning or thinning of fruit clusters; the treatment groups in the second experiment were duplicated on two rootstocks. In the first experiment, increasing irrigation significantly reduced disease severity in all three years, but the impact on fruit composition varied by year. In 2019 and 2020, increasing irrigation actually improved fruit ripening with regards to sugar accumulation, with an increase in total soluble solids of 1 and 3 °Brix in 2019 and 2020, respectively. Increasing applied fertilizer did not improve fruit composition in any of the years, which may be explained in part by few changes to vine nutrient status despite an increased fertilization. In the second experiment, thinning fruit clusters did not necessarily improve fruit ripening as a function of sugar accumulation. The increased berry size resulting from thinning may have reduced the concentration of desirable phenolic compounds. Additionally, thinning clusters increased disease severity in some years, suggesting that ripening dynamics of GRBV-infected vines is largely resistant to sink size manipulation. Increasing irrigation supplied to infected vines—in contrast to the routine practice of deficit irrigation—proved to be the most successful method for improving fruit ripening in infected vines. This is due largely to measured increases in carbon assimilation, canopy size, and vine water status, which likely facilitated both increased production and export of sugar. In addition to evaluating possible fruit quality mitigation strategies for GRBV-infected vines, this work helps to further elucidate the physiological dynamics of the disease related to carbon metabolism, source-sink relations, and vine water stress.
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  • Pending Publication
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  • 2021-04-28 to 2023-05-29

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