An insidious disease is stalking the cannabis industry. Transmitted from plant to plant through cuttings with shared tools, and through seeds, the viroid can lay dormant and undetected. Over time, however, growers may notice changes in their grows: stunted growth, smaller flowers, yellowed leaves, limited cannabinoid and terpene production. Is this phenomenon – commonly referred to as ‘dudding’ – the sign of overstressed plants or the harbinger of something much worse?
The answer will have far ranging consequences and could cost cultivators millions in lost revenue.
Hop Latent Viroid (HLVd) is one of the biggest threats to the cannabis industry. The disease is difficult to identify and can rapidly spread undetected throughout a facility. According to MJBizDaily, California operators have lost 10-30% of their crop from the disease, and internal data shows infected plants can also suffer up to a 35% loss in cannabinoid content such as THC, and up to 70% reduction in yield.
The viroid mostly spreads through mechanical transmission, such as the sharing of tools between infected and uninfected plants. Because plants can remain asymptomatic for weeks, the threat continues to grow and does not appear to be waning any time soon. Growers turning to seed as a way to mitigate risk still need to contend with a seed transmission rate up to 8%. Without taking steps now to eradicate HLVd where it exists today, the viroid could cause significant supply chain disruptions for years to come.
Start Clean, Stay Clean: A Breakthrough in HLVd Eradication
At Front Range Biosciences, we undertook a year-long effort to develop and evaluate a method to effectively clean plants infected with HLVd as part of a broader strategy to mitigate risk throughout our facilities. Because of how easily transmissible HLVd can be, working with clean plant material in a sterile tissue culture environment is the ideal way to ensure a disease-free growing environment from the outset. Implementation of our Clean Stock® program starting with tissue culture guarantees clean, viroid-free plant stock for propagation. This approach of using tissue culture methods to eradicate HLVd from plant stock can mitigate the risk of costly cannabis crop failure, representing a huge win for the entire industry.
To remove HLVd from infected plants, we initiated material from six Cannabis sativa varieties that were confirmed HLVd positive into tissue culture. After letting the varieties grow, we culture indexed to identify any potential bacterial infections. Positive plants were removed and the remaining plant material (representing all varieties) was subjected to a proprietary thermotherapy method. This approach follows a similar methodology for destroying viroid diseases that has been successfully deployed in other cultivated crops such as strawberries. Meristems that came from plants that survived the thermotherapy treatment were isolated and transferred to a new medium to promote growth.
Once plants grew, they were individually tested for HLVd using an internally developed and validated assay. Plants testing positive were discarded, and the remaining healthy plants were maintained and re-tested 4-6 weeks later to confirm the absence of HLVd. Given the ability of HLVd to stay undetected, this secondary validation step was key to ensuring the cleaning process worked and that this new plant stock was indeed clean. With this new method to clean plants from HLVd infection now validated, we have a proven, proprietary process to produce and maintain HLVd-free lines in tissue culture.
Clean Stock, Clean Processes
Clean Stock® is only the first step. Employing an end-to-end approach of HLVd prevention, detection, and eradication can help the industry mitigate the HLVd problem by ensuring grows are populated with clean, high quality plants, generating a greater ROI for cultivators as well as a more consistent product for consumers.
Basic best operational practices can help prevent HLVd from spreading within a facility. Growers should minimize the number of people who has access to plants in mother stock and production rooms as well as maintain specific sanitation protocols for tools. Tools should not be shared between plants, greenhouses, or in sub-locations within a greenhouse. There should be strict protocols for cleaning tools, handling plants, cutting clones and even transferring plants between greenhouse locations.
Growers should create and maintain a separate mother stock area that is isolated and limits exposure to human and plant contact. This separate mother stock area should be continually replenished with HLVd-tested and certified clean replacements from tissue culture. Growers reliant on nursery stock should quarantine new plants from existing stock until the new plants are tested and verified as clean before introducing them into the system.
The presence of HLVd is best confirmed through molecular testing. Testing laboratories nationwide are rapidly scaling the capacity to test for HLVd. Expanded access to HLVd molecular testing will enable cultivators to continually monitor and assess the health of both mother and production stock. That said, testing is not a one-and-done proposition. Tests should be administered regularly, sampling varying parts of the plant canopy from top to bottom where possible.
Our ability to now collect, test, treat and cultivate via tissue culture is an important leap forward in eradicating not just HLVd, but any number of catastrophic diseases and infections that can impact cannabis cultivation. Starting plant stock with tissue culture-based closes provides benefits beyond the ability to clean infected plants. For example, in-vitro testing can be more effective at identifying pathogens versus in-vivo testing because there is less material to test, making it less likely that a pathogen is missed in sampling. More precise sampling and testing improves our ability to prevent spread and maintain clean material for plant propagation. Simply put, starting the cannabis supply chain with tissue culture, rather than the seed or cutting level, can help mitigate risk and ensure healthier plants.
Starting clean, preventative measures and testing vigilance, combined with the ability to clean infected plants, finally provides the industry with a full suite of tools needed to effectively eliminate HLVd – and whatever might come next. Growers implementing FRB’s Clean Stock® end-to-end approach can assuredly maintain high-quality, true-to-type plants that produce consistent terpene levels and high yields each and every harvest. To learn more, visit us at www.frontrangebio.com.
