Hop Latent Viroid (HLVd) Background
Professor DeBacco

Research Article
Adkar-Purushothama, C. R., Sano, T., & Perreault, J. P. (2023). Hop Latent Viroid: A Hidden Threat to the Cannabis Industry. Viruses, 15(3), 681.
https://www.mdpi.com/1999-4915/15/3/681

First Found in Hops in 1987
Viruses (and viroids) often get their name connected with the plant species for which it was first identified in.
However this does not mean it only infects this plant, it only signifies the plant tissue it was first found in.
In 1987, Pallas et al. reported the presence of viroid-like RNA in nucleic acid preparations from two of the three commercial hop varieties (Humulus lupulus L., family, Cannabaceae) grown in the León region of Spain.

“Duds” or “Dudding Disease”
Initially detected in 2019 in California

Early on it was called the “Duds” or “Dudding Disease” of cannabis which later turned out to be hop latent viroid (HLVd).

Currently, HLVd has become the most devastating cannabis disease (syn. Hemp) (Cannabis sativa, Cannabis indica, Cannabis ruderalis) in cannabis-growing areas.
Wider Spread Than Most Realize
A survey conducted in 2021 by the Dark Heart Nursery Research that involved 200,000 tissue tests concluded that 90% of cannabis– growing facilities in California were contaminated with HLVd.

HLVd has been detected throughout the cannabis-growing facilities of North America
Why is HLVd of Concern?
Infected crops could suffer anywhere from a 50%–70% loss in tetrahydrocannabinol (THC) content, thus considerably lowering their commercial value (Adkar-Purushothama, 2023).

A survey conducted in 2021 revealed that approximately 90% of all cannabis-growing facilities in California tested positive for HLVd, and 30% of the plants in each facility showed symptoms of the viroid’s infection (Adkar-Purushothama, 2023).

Why “Latent” Viriod?
Originally it was tentatively “hop viroid-like RNA fast” (HV-f) since it was similar to avocado sunblotch viroid (ASBVd), but had different physical and biological properties with faster electrophoretic mobility than the hop stunt viroid.

However, since HV-f did not induce any visible disease symptoms in hops, it was tentatively named “hop latent viroid” (HLVd).
The Hidden Disease
Although HLVd-infected hop plants are symptomless, infection significantly reduces market value.
Via yield and either the alpha-bitter acid or the essential oil content in the hop cone.

Subsequently, HLVd has been detected in 90% to 100% of the tested hop germplasms in European countries
What Does This Mean?
When it was first being discovered (in hops) there was no found effect, which means it was present, but was not causing a noticeable problem.
In this case latent is referring to being asymptomatic, meaning it is present but not noticeable.

Asymptomatic
It is there, but there are no issues… well, not exactly…
Even though this is the name given even in hops it can cause issue with oil and acid levels.
Also, depending on the cultivar of hops the degree to which it has an impact can vary.
*In cannabis this virod is NOT asymptomatic

HLVd Infection… Secondary Impacts
When a plant is infected it can also become more susceptible to other diseases (Ex. Fusarium wilt and Powdery Mildew)
Seems to be Stable
Overall the genetic screening seem to be showing minimum variability across geographic regions.

Considering the small number of nucleotides this is a good thing as changes (mutations) could quickly occur.
Other viroids do show changes (mutations) in sequences when there is a host change

Sequence Variation
*Only the full-length sequence (256-nt) was considered for the analysis
Can1 and Can2
Two distinct HLVd isolates:
Can1 (GenBank Acc. No.: MK876285)
100% sequence similarity with the HLVd-type species
Can2 (GenBank Acc. No.: MK876286)
One mismatch (point mutation) at the nucleotide 225 with the Uracil mutated to Adnine as compared to the HLVd-type species, refered to as U225A.
Can2 isolate was 100% identical to an HLVd isolate retrived from a commercial hop garden in China (GenBank Acc. No.: EF613183).
Where Have These Isolates Been Found in the USA?
HLVd reported from Delta county (CO, USA) was found to be 100% similar to the Can1 isolate.
The Can2 isolate matched with an HLVd isolated from both Santa Barbara (CA, USA) and Boulder counties (CO, USA).
This indicates the presence of at least two HLVd sequence variants infecting cannabis
U225A
The single nucleotide change (U225A) did not affect the structure of the Can2 isolate as compared to that of the type species.
Note: This change is located within the lower pathogenicity domain

Link to Lecture Slides: https://drive.google.com/file/d/1H4So...

*Due to the description character limit the full work cited for "Hop Latent Viroid HLVd Background" can be viewed at.. https://docs.google.com/document/d/1g...