Seeds Carrying HLVd? Why Breeders and Growers Are Racing to Stay Ahead

The Silent Threat to Cannabis Cultivation

One of the most pressing challenges in cannabis cultivation today is the spread of plant diseases—especially Hop Latent Viroid (HLVd). This highly transmissible pathogen can devastate crops, leading to stunted plants, reduced yields, and substantial financial losses. Growers and breeders are actively searching for ways to prevent HLVd contamination and ensure their seeds and clones are clean. Still, without proactive measures, the industry risks losing not only valuable genetics but also long-term customer trust.

What Is HLVd and Why Is It So Dangerous?

Hop Latent Viroid is an RNA-based pathogen that infects cannabis plants, often without immediate symptoms. When they do appear, symptoms include weak yield, brittle stems, and a drop in cannabinoid production by up to 50-70% (Adkar-Purushothama et al., 2023). Unfortunately, with its latent tendency, growers often unknowingly cultivate infected plants only to see poor yield and dead plants down the line. The pathogen is currently estimated to cause $4 billion in losses annually and is present in an average of 25% of cannabis operations in Canada (Punja et al., 2023). With so much shared genetics, it is likely even higher in the United States.

HLVd spreads through cloning, water systems, and contaminated tools or PPE, but its recent discovery in seeds has raised new concerns. A 2024 study found that infected cannabis flowers resulted in HLVd-positive seeds, which in turn created HLV-positive seedlings (Punjab et al., 2024). Not only does HLVd infection in the flowers cause increased seed abortion, but it also decreases seed weight, resulting in fewer and lower-quality seeds. It is a lose-lose situation for both cultivators and breeders alike. With seeds as a vector of transmission, the viroid can easily be introduced into previously clean grow environments at the start of every grow cycle. Once established, eradicating HLVd is nearly impossible without completely overhauling an operation or performing costly remedial treatments. New tools are needed to prevent contamination in the first place.

Seed Certification: A Standard in Other Industries

The cannabis industry is still catching up, but seed certification has long been the norm in other agricultural industries (commercial vegetable, grain, and fruit production) to ensure that seeds are free from pathogens and meet strict quality standards. These programs exist because farmers cannot afford to take risks on seed stock that could introduce disease into their operations or result in poor performance.

If cannabis cultivators are expected to invest in high-quality genetics, they should also have proof that those genetics are disease-free. Some are now pushing for industry-wide certification standards to protect growers from unknowingly purchasing infected seeds. That’s why LeafWorks and forward-thinking breeders like Purple Caper Seeds are teaming up to bring scientifically backed seed certification programs into standard operations.

The Science Behind LeafWorks’ HLVd-Free Certification

One of the biggest challenges in cannabis testing is ensuring statistical accuracy. Many a la carte HLVd tests on the market rely on small, unsystematic sampling, which doesn’t always reflect the health of an entire batch—testing just a few seeds from a large lot isn’t enough to confidently declare an entire batch free from HLVd.

The issue prompted LeafWorks to partner with a statistician who specializes in predictive statistics and genomics to develop a rigorous testing process. The result is a certification designed using epidemiological principles, meaning:

It accounts for batch size by testing a statistically significant number of seeds to provide an accurate representation of the entire lot.

It offers true scientific validation of the lot instead of a superficial test of a handful of seeds.

It allows breeders to make valid and defensible claims that their seed lots are free from HLVd.

It takes variability in viral load into account. Seeds have shown a positive HLVd signal as long as two years with highly variable viral loads among seeds (Punja et al. 2024).

It prioritizes robustness. Common assays like LAMP techniques run the risk of cross-contamination, carry-over contamination, and off-target amplification, resulting in false positives. This is why LeafWorks uses qPCR as the chosen genetic method for the certification.

This overall approach ensures that certified seeds aren’t just assumed to be clean—they are proven to be clean based on real scientific data.

Why Breeders and Seed Sellers Are Starting to Certify

For breeders and seed sellers in a competitive market, trust is everything. Seed companies that unknowingly sell infected seeds risk losing customer confidence, damaging their brand, and facing potential legal issues.

This need for trust and transparency is why industry leaders are increasingly focused on preventative measures. More breeders are implementing strict testing protocols and advocating for seed lot testing to ensure their products are clean. As noted above, respected breeder Purple Caper Seeds is among those taking action. They recently began certifying their seed lots as HLVd-free with LeafWorks to emphasize the importance of clean genetics.

“Clean seed is vital to a farmer’s success. Moving forward, viroid testing should be the standard to ensure bountiful harvests and a sustainable future.”

— Purple Caper Seeds

Their decision reflects a growing movement within the cannabis industry: breeders who recognize that scientifically validated seed testing is key to preserving both their own genetics and the larger cultivation ecosystem.

The Stakes for Farmers and Cultivators

For cultivators—whether large-scale commercial growers or home gardeners—purchasing infected seeds can mean disaster. With testing technology now available, farmers deserve proof that the seeds they are buying are clean, and many are willing to pay a premium for verified pathogen-free genetics. The push for better testing and certification isn’t just about protecting individual grows—it’s about ensuring the long-term health and stability of the cannabis industry as a whole.

Proactive prevention is the only real defense. That means regular and rigorous testing of mother plants, seeds and clones, and adopting better biosecurity measures such as sterilizing tools and monitoring water systems while demanding transparency from seed suppliers and prioritizing clean, tested genetics.

By staying ahead of HLVd through science-backed practices, operators can avoid costly outbreaks, protect prized genetics, and ensure strong, high-yielding plants they expect. As cannabis continues to evolve, so must the standards for seed quality. The fight against HLVd is just beginning, but with vigilance and the right tools, growers and breeders can safeguard the future of their harvests.

References:

Adkar-Purushothama CR, Sano T, Perreault JP. Hop Latent Viroid: A Hidden Threat to the Cannabis Industry. Viruses. 2023 Mar 4;15(3):681. doi: 10.3390/v15030681. PMID: 36992390; PMCID: PMC10053334.

Punja ZK, Kahl D, Reade R, Xiang Y, Munz J, Nachappa P. Challenges to Cannabis sativa Production from Pathogens and Microbes—The Role of Molecular Diagnostics and Bioinformatics. International Journal of Molecular Sciences. 2024; 25(1):14. https://doi.org/10.3390/ijms25010014

Punja, Z. K., Wang, K., Lung, S., & Buirs, L. (2023). Symptomology, prevalence, and impact of Hop latent viroid on greenhouse-grown cannabis (Cannabis sativa L.) plants in Canada. Canadian Journal of Plant Pathology, 46(2), 174–197. https://doi.org/10.1080/07060661.2023.2279184

 

Kerin Law is the Chief Scientific Officer of LeafWorks Inc.