Scientists identify a variety of cannabis resistant to HLVd

The Hop latent viroid (HLVd), a a viroid found worldwide in hops, but which, in recent years, has spread to cannabis and continues to threaten crops.

SFGate reports, however, that scientists from Medicinal Genomics, a Massachusetts-based company, has observed a cannabis strain called Jamaican Lion, which appears to be partially resistant to HLVd and turns purple when fighting the viroid.

Kevin McKernan, Scientific Director of Medicinal Genomics, presented the study « The Hop Latent Viroid Shares a 19-Nucleotide Sequence with Cannabis sativa COG7 »at the CannMed23 conference in Florida.".

The Jamaican Lion variety has thus proven to be resistant to the viroid and is turned a deeper shade of purple while it was fighting off the viroid. Jamaican Lion is a CBD-rich strain.

«We don’t know why [this is happening]. It could be an immune response, but we don’t see this [purple staining] increasing to the same extent in the uninfected control,» McKernan said.

Viroids can spread through biological pathways or be transmitted by growers via their hands or tools. Disinfection using a 10% bleach solution can reduce infection.

The scientists rubbed the viroid directly onto the plant’s cut leaves to infect them, and then injected the viroid into a plant. Six weeks later, the plant variety remained uninfected even after the test was repeated 57 times. Although the researchers were able to detect the HLVd In the plant's roots, the tissues of the leaves and flowers tested negative up until harvest.

Effects of the HLVd viroid on plants

HLVd produces smaller flowers and significantly less THC. When viewed under an electron microscope, the mature trichomes – where most of the THC is found – resemble a deflated balloon rather than a round ball. A study shows that 90% of California cannabis is infected with HLVd and that yield losses could reach $4 billion. While the viroid is bad news for cannabis, viroids only infect plants and therefore pose no physical danger to humans.

It is not yet clear why the plant was resistant to the viroid. McKernan explained that it had turned purple due to increased production of anthocyanin, a chemical that can cause plants to turn purple. The team believes that scientists should investigate whether there are more purple plants resistant to HLVd, as anthocyanin production is already linked to resistance against viroids.

«There are studies that link anthocyanin production to viroid infection. This applies to various plants and viroids, but these anthocyanins are a known immune response in plants,» said McKernan on SFGate.

Zamir K. Punja stated at the conference that HLVd should be considered a «major threat» to cannabis farms. Punja refers to HLVd as the «COVID of the cannabis world.» The findings suggest that THC yields in infected plants can drop by up to 40%.

The long-term solution to Medicinal Genomics One way to combat HLVd is to help breeders develop resistant cultivars—perhaps purple varieties—that do not suffer any loss in yield or potency.