Jamaican Lion Shows Possible Tolerance to Hop Latent Viroid in Early Cannabis Research
A Jamaican Lion cannabis plant appeared unusually tolerant of hop latent viroid (HLVd) in experiments presented at CannMed23, raising the possibility that some cannabis genetics could help limit the pathogen’s damage. The plant also developed a purple coloration during the response—but researchers have not established that the color itself provides protection.
HLVd is a small, circular RNA pathogen associated with “dudding” disease in cannabis. Infected plants may show stunted growth, brittle stems, smaller flowers and fewer trichomes, with corresponding reductions in cannabinoid and terpene production. The pathogen was first reported in cannabis in California in 2019 and has since been detected in production systems across North America. A 2023 scientific review of HLVd describes the viroid’s biology, symptoms and potential economic impact.
Kevin McKernan of Medicinal Genomics presented the work, titled “Hop Latent Viroid Shares a 19 Nucleotide Sequence with Cannabis sativa COG7”. The study was released as a preprint and conference presentation rather than as a definitive, peer-reviewed demonstration of viroid resistance.
In the reported experiments, researchers attempted to infect Jamaican Lion plants through mechanical inoculation, including contact with infected material and injections. Across repeated tests, the plants did not show the same detectable infection pattern observed in a comparison variety. HLVd was detected in root tissue, but leaf and flower samples remained negative for much of the plant’s life cycle, including up to harvest in the reported observations.
Those findings suggest possible tolerance or tissue-specific restriction—not complete immunity. A negative test in one part of a plant does not necessarily prove that the viroid is absent elsewhere, and the experiment involved a limited number of plant genotypes. More controlled studies with larger sample sizes, repeated inoculations and quantitative yield measurements will be needed to determine whether Jamaican Lion consistently retains flower mass, cannabinoid content or trichome production after exposure to HLVd.
The researchers also observed that Jamaican Lion became increasingly purple. McKernan proposed that elevated anthocyanin production, which can create red, blue or purple pigmentation in plants, might be associated with the plant’s response to infection. That remains a hypothesis, however. The presentation did not show that anthocyanins caused the apparent tolerance, nor does purple coloration provide a reliable visual test for HLVd.
The preprint additionally reported a 19-nucleotide sequence shared by HLVd and the cannabis COG7 gene, which is involved in plant growth and meristem development. In a comparison between infected and uninfected plants, the researchers observed reduced COG7 expression in the infected sample. The result is biologically interesting but preliminary: the plants had different genetic backgrounds, and sequence matching alone does not prove that the viroid causes disease by silencing COG7.
For growers, sanitation and testing remain more practical defenses than selecting plants by color. HLVd can spread through infected cuttings and plant sap transferred by hands, tools and contaminated surfaces. The Oregon State University Extension guide to HLVd in hemp recommends using tested propagation material, removing infected plants and cleaning equipment that may have contacted infected sap. It also cautions that symptoms vary by genotype and environment, making visual diagnosis unreliable.
Breeding or selecting cultivars that maintain yield and potency despite HLVd could eventually become an important disease-management strategy. Jamaican Lion is therefore best viewed as a promising lead for further research—not yet as a proven viroid-resistant strain or evidence that purple cannabis plants are inherently protected.
