Deyle, Luke, authorNachappa, Punya, advisorNalam, Vamsi, committee memberPrenni, Jessica, committee memberUchanski, Mark, committee member2024-12-232024-12-232024https://hdl.handle.net/10217/239805The emergence of hop latent viroid (HLVd) in the hemp (Cannabis sativa L. <0.3% THC) and marijuana (C. sativa >0.3% THC) industries poses a significant threat to agricultural production. Since its first identification in California in 2019, HLVd has spread across the U.S. and Canada, causing substantial yield losses due to its ability to severely disrupt crop development. Mechanically transmitted through propagation, pollen, seed, and water, HLVd is challenging to control; and its impact on emerging crops like hemp is of particular concern. The overarching goal of this thesis was to determine the impact of HLVd on hemp quality and yield and to apply new knowledge and practices to manage HLVd, reducing losses in the hemp and marijuana industries in the U.S. and worldwide. Two objectives achieved this goal: 1) assess the impact of HLVd on the growth and yield of two hemp cultivars, NWG 2463 (dual-purpose fiber grain) and Unicorn (CBD), and 2) determine the effect of chemical elicitors in reducing HLVd infection levels and symptom development. HLVd infection did not impact overall yield metrics—such as biomass, flower, or seed yield—in either the dual-purpose cultivar NWG 2463 or the CBD cultivar Unicorn under the conditions of this study. However, HLVd-symptomatic plants in the CBD Unicorn cultivar exhibited significant reductions in cannabinoid levels, specifically THCA and CBLA: CBCA. These findings highlight the critical risks that HLVd presents to producers relying on consistent cannabinoid profiles. RT-qPCR analysis indicated that specific chemical elicitors may reduce HLVd levels in the CBD Unicorn cultivar, with 1-Triacontanol (TRIA) showing a marginally significant reduction in viroid titers compared to its ethanol (EtOH) control (p = 0.07), and Kinetin demonstrating a trend toward significance against its potassium hydroxide (KOH) control (p = 0.08). Beyond potential viroid reduction, chemical elicitors such as salicylic acid (SA), brassinolides (BR), and 6-benzylaminopurine (BAP) significantly increased biomass and flower production in the CBD Unicorn cultivar infected with HLVd. However, SA, BR, TRIA, chlormequat chloride (CCC), and methyl jasmonate (MeJA) also reduced key cannabinoid levels, notably THC and CBD, highlighting the complexity of using chemical elicitors in viroid-infected plants. The observed trade-off between enhanced plant growth and reduced cannabinoid content suggests that, although chemical elicitors may offer potential as part of an integrated management strategy, their application must be carefully optimized to avoid unintended crop losses. This research provides critical insights into the broader agricultural implications of HLVd on hemp production and highlights the need for refined viroid management practices. The potential impact of HLVd on hemp emphasizes the urgency of developing targeted strategies that balance yield improvement with cannabinoid preservation, thereby safeguarding the financial viability of hemp cultivation in the face of viroid challenges.born digitalmasters thesesengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Cannabis sativahop latent viroid (HLVd)plant defense mechanismschemical elicitorscannabinoid biosynthesisintegrated pest management (IPM)Text