Hop latent viroid (HLVd) Information

Hop latent viroid (HLVd) is found all over the world in hops, but in the past few years, it has moved to cannabis, causing big drops in yield, cannabinoid concentrations, and earnings in the US and Canada. Some experts have started calling HLVd "the COVID of cannabis."

HLVd is a single-stranded, viral RNA that is in a circle. Like viruses, viroids cannot reproduce without the biology of the plant they live in. But unlike viruses, viroids don't have a layer of protection like a protein coat. In fact, viroids are about 40nm in size and are the smallest known plant diseases.

How Common Is the Hop Latent Virus?

One study says that up to 90% of the weed in California is infected with HLVd, which costs the state nearly $4 billion in lost yields. In another study, Dr. Zamir Punja of Simon Fraser University found that HLVd was present in 40% of the cannabis flower sold in Canadian shops. Humans are not hurt by the HLVd, which is good news.

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How do you know if you have Hop Latent Viroid?

Depending on what stage of growth the plant is in when it gets infected with HLVd, the signs are very different.

Stage of spreading

Clones made from HLVd-infected mother plants have much shorter roots and less root growth. This slows down root growth, which makes clones grow more slowly and makes rooted cuts of lower quality. Pathogens that attack roots, like fusarium and pythium, may be able to attack plants more easily when their roots don't grow as much.

Vegetative Stage 

When HLVd infects a plant during its growing stage, it often stunts its growth, which can be seen in the following ways:

  • Branches on the side 

  • Cracked stems 

  • Less wide and smaller leaves 

  • leaves with wrong colors and shapes

  • Less space between the nodes

  • Odor similar to burning leaves

  • Stage of flowering

Infected plants often show the most signs of HLVd when they are blooming. In fact, there are more detectable viroid when the plant is blooming than when it is growing. Researchers still don't know why HLVd levels go up when plants bloom, but it may have something to do with the plants being under more stress.  

Just like when they were growing, HLVd-infected plants that are blooming will look smaller than healthy plants, and the leaves near the bud sites may suddenly turn yellow, like in the picture below.

How does the Hop Latent Virus get around?

HLVd can spread through a building in many different ways. Most of the time, HLVd is spread by tools, equipment, and people who have worked with sick plants. Before working on a new plant, people who grow plants should always use a 10% bleach solution to clean their tools, equipment, and hands.

When cuts are taken from a mother who has HLVd, the virus can also spread through cloning. And because the signs of HLVd aren't always clear when the plant is still growing, it can be hard to tell which mother plants are affected. This is especially true if the plant gets sick later in its life, when the reduced growth won't be as obvious. Before getting new cuttings, growers should test the mother plants to make sure that they are making clean clones.

Roots have a lot of HLVd, so it can spread through the water in hydroponic systems. Even if the roots of the plants don't touch, healthy plants that share water with sick plants can get the virus.

Experiments have shown that HLVd can be passed on through seeds when infected males mate with healthy females or when healthy males mate with infected females. HLVd was found on the seed coat and inside the seed in both cases.

How does Hop Latent Viroid infect and spread through cannabis plants?

HLVd has figured out how to take over the host plant's Rolling Circle Amplification (RCA) and RNA ligase. When RNA or DNA molecules are round, they can be copied like a wheel, which 

becomes a pattern that can be used over and over again. This makes long pieces of the viroid DNA called concatemers. After that, these concateners are cut into 256 base pieces that have the same Ribozyme activity as the original double-stranded viroid. Once the genome is cut up, plant RNA ligases put it back together in many rings so the process can be done again. is a good place to start. This tool compares the different parts of your HpLVd genome to the Jamaican Lion transcriptome. This lets you see which parts of the Viroid are similar to the weed mRNAs.

Is Hop Viroid Latent Systemic?

HLVd moves through the plant in a planned way through the phloem over a time of about 6 weeks. At the place of infection, HLVd gets into the plant's phloem, where it travels to the roots and then all over the plant.

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