In the United States, hops (Humulus lupulus L.) are grown mainly in the Pacific Northwest (PNW). For this reason, most cultural information is based on the growing conditions of the PNW. Growing conditions in Virginia differ drastically and present unique disease and production challenges. Three studies were conducted with the intent of increasing hop cultivation knowledge for Virginia growers. For the first study, 13 cultivars of hops grown at the Virginia Tech hop yard were compared for growth, yield, and quality. Mean cone fresh weight per plant ranged from 12.00 g for Mt. Hood to 1002.87 g for Crystal in 2016 and from 97.98 g for Mt. Hood to 900.33 g for Cascade in 2017. In 2016, only Alpharoma, Cascade, Mt. Rainier, and Southern Cross had alpha acid levels, an indicator of cone quality, within the accepted range. In 2017, Alpharoma, Centennial, Mt. Rainier, and Nugget had alpha acid levels within the expected range. Three cultivars (Cascade, Crystal, and Ultra) were above the expected alpha acid range, which indicates more bittering potential for beer brewers.
In a nutrient deficiency study, hop plants were grown in hydroponic solutions, and deficiencies were induced for nitrogen (N), phosphorus (P), and potassium (K). After visual deficiency symptoms had been induced, leaf tissue samples were taken and analyzed for nutrient content. Images were taken at each deficiency stage. For N, incipient deficiency symptoms were observed at a mean of 3.18% dry weight in leaf tissue samples. Visual symptoms included a chlorotic appearance, undersized leaves, and red petioles. Incipient symptoms for P were observed at a mean of 0.307% dry weight in leaf tissue samples. Necrotic spots, leaf cupping, and undersized leaves were apparent with this deficiency. Incipient symptoms for K were observed at a mean of 1.21% dry weight in leaf tissue samples. Symptoms included rounded leaf tips, blue veins, and marginal scorch. In the third study, a whole leaf powdery mildew (Podosphaera macularis) assay was developed and tested using five hop cultivars, Alpharoma, Cascade, Comet, Sorachi Ace, and Tahoma. Leaves were inoculated with powdery mildew (PM) using a settling tower. This method was used to rapidly assess the resistance of cultivars. Leaves were successfully inoculated and PM colonies were allowed to grow for two weeks. Images of the PM colony development on inoculated leaves were compared using ImageJ to determine percentage of coverage. Tahoma was the only cultivar found to produce a significantly different mean percent coverage (19.5%) compared with the resistant cultivars Cascade and Comet (<1%). / Master of Science in Life Sciences / Hops (Humulus lupulus) were first grown in the United States in Massachusetts in the early 1600s. Production of this crop eventually spread throughout the Northeastern US. By the mid-1800s, commercial production spread to southern states such as Virginia. Infestation of pests, e.g., hop aphid and diseases such as downy mildew in eastern states, and prohibition on the production of alcohol caused a significant shift in hop production, which favored the Pacific Northwest (PNW). As a result, in Virginia specific knowledge of hop cultivation is now lacking. Three studies were conducted to increase our knowledge of hop cultivation for the region. For the first study, 13 cultivars grown at the Virginia Tech hop yard were compared for growth, yield, and quality. The cultivars Cascade and Alpharoma had alpha acid levels equal to or higher than expected for the 2016 and 2017 seasons. The alpha acid levels are an indicator of the hop quality from the Cascade and Alpharoma cultivars. Cascade was also a top producer of hop cones with a mean fresh weight of 989.67 g and 900.33 g in 2016 and 2017, respectively. In a nutrient deficiency study, plants were grown in Hoagland hydroponic solutions, which contain all essential nutrients needed for plant growth. This was done to provide photographic documentation to assist local growers with deficiency identification. Deficiencies were induced for nitrogen (N), phosphorus (P), and potassium (K) by removing each of the specific nutrient of interest from each treatment solution. After deficiency symptoms were induced, leaf tissue samples were taken and analyzed for nutrient content. Nutrient deficiencies were documented using photographs. For N, visual symptoms included a chlorotic appearance, undersized leaves, and red petioles. Incipient symptoms for P included necrotic spots, leaf cupping, and undersized leaves. For K, leaf cupping, blue green veins, marginal scorch, and rounded leaf tips. Disease resistance of cultivars is important information for growers and can heavily influence hop yard planning. As such, in another study, an assay for powdery mildew (Podosphaera macularis) was developed that allows for rapid low cost testing of hop cultivars. The assay was tested on the following cultivars: Alpharoma, Cascade, Comet, Sorachi Ace, and Tahoma. Leaves were inoculated with powdery mildew (PM) using a settling tower. Powdery mildew colonies were allowed to grow for two weeks and were then analyzed using ImageJ software to determine percent coverage. At the end of the experiment, Tahoma had significantly greater PM coverage compared to the other cultivars, indicating that Tahoma is less resistant to the specific PM strain. / Hops (Humulus lupulus) were first grown in the United States in Massachusetts in the early 1600s. Production of this crop eventually spread throughout the Northeastern US. By the mid-1800s, commercial production spread to southern states such as Virginia. Infestation of pests, e.g., hop aphid and diseases such as downy mildew in eastern states, and prohibition on the production of alcohol caused a significant shift in hop production, which favored the Pacific Northwest (PNW). As a result, in Virginia specific knowledge of hop cultivation is now lacking. Three studies were conducted to increase our knowledge of hop cultivation for the region. For the first study, 13 cultivars grown at the Virginia Tech hop yard were compared for growth, yield, and quality. The cultivars Cascade and Alpharoma had alpha acid levels equal to or higher than expected for the 2016 and 2017 seasons. The alpha acid levels are an indicator of the hop quality from the Cascade and Alpharoma cultivars. Cascade was also a top producer of hop cones with a mean fresh weight of 989.67 g and 900.33 g in 2016 and 2017, respectively. In a nutrient deficiency study, plants were grown in Hoagland hydroponic solutions, which contain all essential nutrients needed for plant growth. This was done to provide photographic documentation to assist local growers with deficiency identification. Deficiencies were induced for nitrogen (N), phosphorus (P), and potassium (K) by removing each of the specific nutrient of interest from each treatment solution. After deficiency symptoms were induced, leaf tissue samples were taken and analyzed for nutrient content. Nutrient deficiencies were documented using photographs. For N, visual symptoms included a chlorotic appearance, undersized leaves, and red petioles. Incipient symptoms for P included necrotic spots, leaf cupping, and undersized leaves. For K, leaf cupping, blue green veins, marginal scorch, and rounded leaf tips. Disease resistance of cultivars is important information for growers and can heavily influence hop yard planning. As such, in another study, an assay for powdery mildew (Podosphaera macularis) was developed that allows for rapid low cost testing of hop cultivars. The assay was tested on the following cultivars: Alpharoma, Cascade, Comet, Sorachi Ace, and Tahoma. Leaves were inoculated with powdery mildew (PM) using a settling tower. Powdery mildew colonies were allowed to grow for two weeks and were then analyzed using ImageJ software to determine percent coverage. At the end of the experiment, Tahoma had significantly greater PM coverage compared to the other cultivars, indicating that Tahoma is less resistant to the specific PM strain.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/86196 |
| Date | 29 November 2018 |
| Creators | Judd, Barslund Duane |
| Contributors | Horticulture, Scoggins, Holly L., Brewster, Carlyle C., Owen, James Stetter |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Coverage | Virginia, United States |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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