AN ABSTRACT OF THE THESIS OF Justin Litwin for the degree of Master of Science in Horticulture presented on May 4, 2020. Title: Assessment of Grapevine Red Blotch Virus Impacts on Physiology, Productivity, and Fruit Composition of ‘Pinot noir’ Grown in Oregon’s Willamette Valley Abstract approved: ______________________________________________________ Patricia Skinkis Grapevine red blotch disease (GRBD) is caused by Grapevine Red Blotch Virus, a virus in the Geminiviridae family. Observable symptoms can manifest in red cultivars, such as leaf blades that are partially to fully red, red veins, and different combinations of the two. Previous research has shown evidence of reduced total soluble solids, anthocyanins, and phenolic compounds in GRBD infected vines. In cool regions, such as Oregon’s Willamette Valley, GRBD could have a significant effect on fruit ripeness and wine quality. Most research on this disease to date has been conducted in New York and California. To understand the impacts of vine physiology, productivity, and fruit quality from GRBD in a cool climate, a field study was conducted in Oregon’s Willamette Valley from 2017 to 2019. A commercial Pinot noir vineyard containing both GRBD+ and GRBD- vines, including GRBD+ vines that were either symptomatic or asymptomatic was selected for this research. Vines were monitored through each growing season for visual disease symptoms and physiological measures. Visual symptoms began to appear on leaves at véraison in the basal portion of the shoots and continued acropetally as the season progressed. No consistent differences were observed in the physiological measures of photoassimilation, stomatal conductance, or leaf greenness. Véraison nutrient testing in all three years revealed a consistent magnesium deficiency in petioles of symptomatic GRBD+ vines compared to asymptomatic GRBD+ vines. Yield and berries per cluster did not differ between healthy and GRBD+ vines at harvest in any year, but cluster and berry weight were lower in symptomatic GRBD+ compared to asymptomatic GRBD- in 2017 and 2018. Fruit at harvest did not differ in total soluble solids in any year between healthy and GRBD+ vines. However, during 2018 and 2019 pH was higher and titratable acidity was lower in 2019 in symptomatic GRBD+ vines compared to asymptomatic GRBD+ vines. No consistent differences in total anthocyanin, total phenolic, or total tannins were measured based on virus or symptom status. This study suggests that there are few impacts of GRBD for Pinot noir grown under the cool climate conditions of Oregon’s Willamette Valley. ©Copyright by Justin Litwin May 4, 2020 All Rights Reserved Assessment of Grapevine Red Blotch Virus Impacts on Physiology, Productivity, and Fruit Composition of ‘Pinot noir’ Grown in Oregon’s Willamette Valley by Justin Litwin A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented May 4, 2020 Commencement June 2020 Master of Science thesis of Justin Litwin presented on May 4, 2020 APPROVED: Major Professor, representing Horticulture Head of the Department of Horticulture Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Justin Litwin, Author ACKNOWLEDGEMENTS I would like to thank Dr. Patty Skinkis for her continued support and mentorship. I began this journey as an undergraduate with little experience in research and have been allowed to explore curiosities and gain knowledge on my way to this goal. I would also like to acknowledge the other members of my committee, including Dr. Jay Pscheidt and Dr. Alec Levin for their involvement in my education and helping me pursue answers that moved me forward. All of the members the Skinkis Lab are also to thank for their comradeship and guidance on issues pertinent to the day to day, as well as always being warm and inviting. Finally, I would like to thank all of my friends and family for their support over these past years. It was not always easy, but without you I could not have completed this. CONTRIBUTION OF AUTHORS Dr. Patrcia Skinkis was the principal investigator and served as major professor. Dr. Robert Martin assisted with collection of virus samples and performed virus testing. TABLE OF CONTENTS Page Chapter 1: Introduction ................................................................................................. 1 Literature Cited .......................................................................................................... 6 Chapter 2: Assessment of Grapevine Red Blotch Virus Impacts on Physiology, Productivity, and Fruit Composition of ‘Pinot noir’ Grown in Oregon’s Willamette Valley .......................................................................................................................... 11 Introduction ............................................................................................................. 11 Materials and Methods ............................................................................................ 12 Symptom Evaluations .......................................................................................... 15 Vine growth and production ................................................................................. 15 Leaf Gas Exchange............................................................................................... 16 Vine nutrient status............................................................................................... 16 Yield parameters and fruit composition ............................................................... 17 Statistical Analysis ............................................................................................... 18 Results ..................................................................................................................... 18 Seasonal climate data ........................................................................................... 18 Disease symptoms. ............................................................................................... 19 Leaf gas exchange and leaf greenness.................................................................. 20 Vine nutrient status............................................................................................... 21 Vine growth and productivity .............................................................................. 22 Fruit composition ................................................................................................. 22 Discussion ................................................................................................................ 23 Conclusion ............................................................................................................... 27 Literature Cited ........................................................................................................ 28 Figures ..................................................................................................................... 34 Tables....................................................................................................................... 39 2 TABLE OF CONTENTS (Continued) Page Chapter 3: Conclusions ............................................................................................... 45 Literature Cited ........................................................................................................... 47 LIST OF FIGURES Figure Page 1. Grapevine red blotch disease symptomatic leaves found …..…………………….34 on a ‘Pinot noir’ grapevine that tested positive for the virus in a vineyard in Amity, OR. 2. Progression of ‘Pinot noir’ grapevine red blotch disease ...……………………...35 symptom incidence in the canopy of individual grapevines from the first symptom onset at late véraison to post- harvest for a vineyard in Amity, OR during 2019. 3. Symptomatic grapevine red blotch virus positive ‘Pinot noir’……………………36 vine next to an asymptomatic healthy (grapevine red blotch virus negative) ‘Pinot noir’ vine in a vineyard in Amity, OR. 4. Mean (+SE) single leaf photoassimilation from the upper……………………….37 positions of ‘Pinot noir’ vines in 2017, 2018, and 2019. 5. Mean (+SE) single leaf stomatal conductance from the………………………….38 upper canopy positions of ‘Pinot noir’ vines in 2017, 2018, and 2019. 2 LIST OF TABLES Table Page 1. Weather data for the north Willamette Valley of Oregon…………………………39 during three growing seasons (2017-2019) during which grapevine red blotch research was conducted. 2. Mean (+SE) véraison nutrient concentration of ‘Pinot noir’..………………….…40 grapevines in Amity, OR. 3. Mean (+SE) véraison micronutrient concentration of ‘Pinot……..…………….…41 noir’ grapevines in Amity, OR. 4. Mean (+SE) growth and crop load measures of ‘Pinot noir’ ……….……..……..42 grapevines in Amity, OR. 5. Mean (+SE) harvest yield and cluster components of ‘Pinot ………….…………43 noir’ grapevines in Amity, OR. 6. Mean (+SE) berry composition at harvest of ‘Pinot noir’….…………………….44 grapevines in Amity, OR. Chapter 1: Introduction Grapevine red blotch disease (GRBD) has become an important concern among the Oregon wine industry, with reports coming from California producers and some local information indicating the potential for reduced fruit and wine quality. Grapevine red blotch disease is a relatively new disease and the need for more research in Oregon