Matthew M Halldorson

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Scholarly Contributions

Journals/Publications

• Halldorson, M., & Keller, M. (2018). Grapevine leafroll disease alters leaf physiology but has little effect on plant cold hardiness. Planta, 248(5). doi:10.1007/s00425-018-2967-x
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  Main conclusion: Foliar sugar accumulation in grapevines with leafroll disease was correlated with lower photosynthesis, likely due to feedback inhibition. However, cold acclimation of dormant tissues remained unaffected by the virus status. Grapevine leafroll-associated viruses (GLRaV) contribute to losses in fruit yield and quality worldwide. Visually, leafroll disease symptoms appear similar to those associated with an imbalance in source/sink relations and a concomitant feedback inhibition of photosynthesis, which is often caused by an impasse in sugar translocation. In order to test this potential relationship and related physiological responses, leaf water status, gas exchange, non-structural carbohydrates, and dormant tissue cold hardiness were examined over 2 years in healthy and GLRaV-3-infected, field-grown Merlot grapevines. Diurnal and seasonal changes in leaf water status and gas exchange were dominated by variations in water availability, temperature, and leaf age, while GLRaV-3 infection contributed less to the overall variation. By contrast, foliar carbohydrates increased markedly in infected plants, with starch accumulating early in the growing season, followed by soluble sugar accumulation, leaf reddening, and declining gas exchange. Photosynthesis correlated negatively with leaf sugar content. However, dormant-season cold hardiness of buds and cane vascular tissues was similar in healthy and infected vines. These findings support the idea that visible symptoms of grapevine leafroll disease are a consequence of carbohydrate accumulation which, in turn, may lead to feedback inhibition of photosynthesis. In addition, this study provided evidence that GLRaV-3 infection is unlikely to alter the susceptibility to moderate water deficit and winter damage in mature Merlot grapevines.

Presentations

• Halldorson, M. M. (2024, August). Extension Work in Yavapai County. . “Dial the Dean”: Interview with Dean Burgess.. Zoom between Tucson and Prescott, AZ: College of Agriculture, Life & Veterinary Sciences & Cooperative Extension.
• Halldorson, M. M. (2024, July). Principles of Integrative Pest Management. Sonoita Vineyard Integrative Pest Management Workshop.. Sonoita, AZ: University of Arizona Cooperative Extension.
• Halldorson, M. M. (2024, June). Vineyard Pest Prevention Concepts. Verde Valley Vineyard Integrative Pest Management Workshop.. Clarkdale, AZ: University of Arizona Cooperative Extension.
• Halldorson, M. M. (2024, June). Vineyard Scouting. Vineyard Scouting, and Sampling Workshop. Clarkdale,.
• Halldorson, M. M. (2024, September). Incorporating Pesticides into a Successful IPM Program. . Arizona Community Tree Council Annual Meeting (IPM Workshop).. Camp Verde, AZ: Arizona Community Tree Council.
• Halldorson, M. M. (2023, April). A Year in the Life of a Washington Vineyard. Emerging Winemaker's Symposium. Clarkdale, Arizona: Yavapai College.
• Halldorson, M. M. (2023, December). Irrigation Strategies for Arizona Vineyards. Arizona Viticulture Symposium. Controlled Environment Agriculture Center, Tucson, AZ: University of Arizona Cooperative Extension/ Arizona Wine Growers Association.
• Halldorson, M. M. (2023, June). Irrigation Strategies and Cover Crop Use in Arizona Vineyards. Arizona Climate Smart Agriculture Workshop. Cornville, Arizona: Natural Resource Conservation Service.
• Halldorson, M. M. (2023, March). Arizona Viticulture Needs Assessment Results. Arizona Viticulture Symposium. Biosphere II: University of Arizona Cooperative Extension.
• Halldorson, M. M. (2023, September). Grape Integrated Pest Management. Arizona Community Tree Council. Camp Verde, Arizona.
• Halldorson, M. M. (2023, September). Urban Agriculture: Home Grapevine Production. Urban Ag Field Day. Prescott: USDA/NRCS/UA.

Poster Presentations

• Halldorson, M. M., Sherman, J. D., Weiss, J. L., & Rauluk, V. (2023, August). Arizona Statewide Commercial Viticulture Needs Assessment. University of Arizona Cooperative Extension Annual Conference. Tucson, Arizona: UA Cooperative Extension.

Other Teaching Materials

• Halldorson, M. M. (2023. Lecture Series: Botany, Climate, Irrigation, Soils, Veggies, Landscape Plants, Pest Management, Weeds and Disease. Yavapai County Home Horticulture Class (via Zoom).
• Halldorson, M. M., & Schalau, J. W. (2023. Master Gardener Training Program Lecture Series: Botany, Soils, Climate, Water, Orchard, and Integrated Pest Management.. Yavapai County Cooperative Extension.

Others

• Halldorson, M. M. (2023, June). Yavapai County Poultry Regulations by Community. Yavapai County Cooperative Extension.
• Halldorson, M. M. (2022, October). Laboratories Conducting Soil, Plant, Feed or Water Testing. UA Extension Bulletin. https://extension.arizona.edu/pubs/laboratories-conducting-soil-plant-feed-or-water-testing
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  This publication lists laboratories that provide soil, plant, feed, and water testing within the state of Arizona.