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Exploring the hemp virome and assessing hemp germplasm for resistance to emerging pathogens

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dc.contributor.authorHackenberg, Laine, author
dc.contributor.authorNachappa, Punya, advisor
dc.contributor.authorRoberts, Robyn, committee member
dc.contributor.authorStenglein, Mark, committee member
dc.date.accessioned2024-05-27T10:31:58Z
dc.date.available2024-05-27T10:31:58Z
dc.date.issued2024
dc.description.abstractHemp (Cannabis sativa L.), commonly grown for its seeds, fiber, and non-psychoactive cannabinoids, has been experiencing a resurgence in the United States with its recent legalization. While farmers across the nation have readily adopted this crop, resources for pest management are still lacking, particularly regarding the diversity and distribution of pathogens. As production increases and the crop diversifies, the emergence and spread of these pathogens are certain. To circumvent loss due to disease, research is needed understand the threats and to identify sustainable management options. The goal of this study is to describe the diversity and distribution of viruses/viroids infecting hemp in Colorado and to determine if there is genetic resistance to pathogens in hemp. The objectives of this study are to 1) characterize the virome of different hemp cultivars throughout the growing season across different locations and 2) screen a panel of genetically unique genotypes of hemp for resistance to emerging viruses/viroids of hemp. Throughout 2021 and 2022, the hemp virome was examined in four major hemp producing regions of Colorado. In total, nine fields were sampled, and each field was visited during three phenological stages (early vegetative, late vegetative, and mature flowering) in order to characterize the virome throughout the growing season. Leaf tissue samples were collected from two cultivars of hemp from each field site. These tissue samples were submitted for High Throughput Sequencing (HTS) and upon bioinformatic analysis, candidate virus/viroid sequences were validated. Across both years, a total of seven viruses were identified: Alfalfa mosaic virus (AMV), Beet curly top virus (BCTV), Cannabis cryptic virus (CanCV), Cannabis sativa mitovirus (CasaMV1), Grapevine line pattern virus (GLPV), Opuntia umbra-like virus (OULV), and Tomato bushy stunt virus (TBSV). All viruses identified had >97% nucleotide identity to the nearest GenBank accession. Between individual cultivars isolated from the same field, both similar and unique viromes were observed. Viral diversity and incidence increased as the growing season progressed for both years. The three viruses that were most commonly found across all regions were CasaMV1, GLPV, and BCTV. Dominating the virome in viral load were CasaMV1 and GLPV. Given the prevalence of BCTV in the virome, in addition to its prevalence in hemp across the western United States, 13 genotypes of hemp were screened for resistance to this pathogen. These genotypes of hemp are genetically diverse, which will aide in the discovery of candidate genes involved with resistance. BCTV is the causal agent of curly top disease which can have drastic symptomology in hemp plants, causing malformed growth, stunted plants, and crop loss up to 100%. Varying BCTV copy number was observed across the hemp genotypes. Additionally, percent disease index (PDI) was analyzed to determine the frequency of infection of individual genotypes. Two of the genotypes were observed to have a lower PDI than the others, 4587 and 4710. Hop latent viroid (HLVd) has been emerging as a threat to the cannabis industry. It has been described across North America but is believed to be worldwide due to its global distribution in hops. HLVd has been documented to cause drastic reduction in cannabinoid content in mature inflorescences and therefore has the potential for substantial economic losses. Although not identified within the 2021 or 2022 virome, HLVd was determined to be an important threat facing hemp production therefore it was included in the screening. Similarly to BCTV, a panel of 14 genetically unique genotypes of hemp were analyzed for resistance to HLVd. Resistance was identified in a single genotype, 517, which had a lower frequency of infection than the others. However, no varying viroidal loads were observed between genotypes. Throughout this study, viruses associated with hemp were described as well as the identification of genetic resistance to emerging pathogens. This work will help to further integrated pest management strategies and promote sustainable agriculture.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.identifierHackenberg_colostate_0053N_18268.pdf
dc.identifier.urihttps://hdl.handle.net/10217/238398
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2020-
dc.rightsCopyright 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.
dc.subjecthemp
dc.subjectvirome
dc.subjecthop latent viroid
dc.subjectbeet curly top virus
dc.titleExploring the hemp virome and assessing hemp germplasm for resistance to emerging pathogens
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineAgricultural Biology
thesis.degree.grantorColorado State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)

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