Understand the biological transmission mechanisms of Hop Latent Viroid (HLVd) and implement essential tools to safeguard your cultivation facility.
What Is HLVd?
Hop Latent Viroid (HLVd) poses a serious risk to Cannabis cultivation, warranting a comprehensive understanding of its characteristics, implications, and preventing measures to reduce the infections (Buirs & Punja, 2024).
HLVd, belonging to the family Pospiviroidae, is a small, circular, single-stranded RNA pathogen known for its ability to infect a broad range of plant species, including Cannabis (Atallah et al., 2024).
How Does Infection Initiate and What Are the Symptoms?
In Cannabis, HLVd infections manifest through symptoms such as stunted growth, leaf distortion, chlorosis, reduced vigor, lower water intake, reduced flower mass and trichomes, and diminished cannabinoid production. Importantly, different Cannabis strains show different levels of subjectivity to HLVd infection and symptoms (Adkar-Purushothama et al., 2023; Buirs & Punja, 2024; Punja et al., 2024).
HLVd primarily spreads through vegetative propagation methods such as cloning and cuttings, where infected plant material serves as a reservoir for the viroid. Furthermore, mechanical transmission via contaminated tools or equipment further facilitates the rapid dissemination of HLVd within cultivation facilities (Buirs & Punja, 2024).
When spread through mechanical transmission, HLVd enters the plant’s phloem at the point of infection, travels to the roots, where it is replicated, and then moves systematically throughout the entire plant over a period of approximately 6 weeks (Atallah et al., 2024).
Once inside the cell, the viroid RNA hijacks the host cellular machinery to replicate itself. Unlike viruses, viroids lack a protein coat and rely solely on host machinery for replication. The viroid RNA serves as a template for the plant RNA polymerases to produce more copies of the viroid. As the viroid replicates, it can interfere with the normal gene expression of the host plant. Although the molecular mechanism behind HLVd infection symptoms have not been elucidated yet, recent evidence suggests that viroid RNA can interact with host proteins or RNA, disrupting normal cellular processes such as transcription, translation, and RNA processing. This interference can lead to the dysregulation of gene expression, affecting growth, development, and defense mechanisms (Adkar-Purushothama et al., 2023; Atallah et al., 2024; McKernan et al., 2022).
Besides, recent studies suggest that HLVd can also be transmitted by an infected plant to the seeds (Punja et al., 2024).
How to Prevent HLVd Infections?
The first line of defense against HLVd spreading is implementation of good growing practices and monitoring through molecular diagnostics.
Reverse Transcription Quantitative Polymerase Chain Reaction (RT-qPCR) is a sensitive molecular and diagnostics technique for the detection and quantification of RNA molecules. First, the reverse transcriptase converts RNA molecules into complementary DNA (cDNA). Then, target cDNAs are amplified and quantified during the qPCR step, using specific primers and fluorescent probes. Indeed, during amplification, the probes bind to the target DNA sequence, and upon amplification, the fluorescent signal emitted and increases proportionally to the amount of amplified DNA, allowing for real-time quantification of the target sequences. Notably, using multiple primers and probes conjugated to different fluorophores allows simultaneous identification of multiple targets in the same reaction. In other words, it is possible to check the presence of an internal control RNA, assuring the efficiency of RNA extraction, as well as a specific target, such as the viroid sequences, in the same tube.
More information about how qPCR is used in molecular diagnostics here.
In the context of HLVd, a RT-qPCR assay enables growers to accurately identify the presence of the viroid in plant samples with high specificity and sensitivity. Early detection through RT-qPCR empowers cultivators to enact timely management strategies, thereby curbing the spread of HLVd and mitigating crop losses (Adkar-Purushothama et al., 2023; Buirs & Punja, 2024).
Example of a HLVd RT-qPCR Detection Test result. The ‘S-shaped” curve indicates amplification, therefore infection. Molecular diagnostics of HLVd can be conducted at the cultivation site with the Cannabis qPCR Workstation.
How to implement HLVd Diagnostics in My Cannabis Cultivation?
When your harvest is on the line, accuracy is non-negotiable, yet the high cost and technical expertise required to build a diagnostic lab can feel out of reach. The Cannabis qPCR Workstation removes the barrier to entry. It’s an affordable, portable solution that includes every tool and training resource required to run your own diagnostics for HLVd, including the HLVd RT-qPCR Detection Test.
By understanding HLVd, its symptoms, and how it affects plant cells, we can better manage and protect plants from this disease-causing agent.
Related Resources
- Cannabis qPCR Workstation
- HLVd RT-qPCR Detection Test
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- qPCR validation Test 1
References
Adkar-Purushothama, C. R., Sano, T., & Perreault, J. P. (2023). Hop Latent Viroid: A Hidden Threat to the Cannabis Industry. In Viruses (Vol. 15, Issue 3). MDPI. https://doi.org/10.3390/v15030681
Atallah, O. O., Yassin, S. M., & Verchot, J. (2024). New Insights into Hop Latent Viroid Detection, Infectivity, Host Range, and Transmission. Viruses, 16(1). https://doi.org/10.3390/v16010030
Buirs, L., & Punja, Z. K. (2024). Integrated Management of Pathogens and Microbes in Cannabis sativa L. (Cannabis) under Greenhouse Conditions. Plants, 13(6), 786. https://doi.org/10.3390/plants13060786
McKernan, K., Kane, L., & McLaughlin, S. (2022). Hop Latent Viroid shares a 19 nucleotide sequence with Cannabis sativa COG7. https://doi.org/10.31219/osf.io/bwnmv
Punja, Z. K., Kahl, D., Reade, R., Xiang, Y., Munz, J., & Nachappa, P. (2024). Challenges to Cannabis sativa Production from Pathogens and Microbes—The Role of Molecular Diagnostics and Bioinformatics. International Journal of Molecular Sciences, 25(1). https://doi.org/10.3390/ijms25010014