Purple Cannabis Strain Shows Resistance to HLVd Virus

Virus-Resistant Purple Cannabis Plant (HLVd)

Cannabis plants are sensitive to pathogens. Many cannabis growers suffer crop failure due to diseases that destroy cannabis plants. A recent scientific breakthrough seems to change that.

Scientists have discovered a purple strain of cannabis that appears to combat the widespread plant disease Hop Latent Viroid (HLVd). HLVd damages cannabis plants and significantly reduces their value by reducing the amount of active compounds the plant produces.

Resistant cannabis plant

But two weeks ago, a group of scientists at Medicinal Genomics, a Massachusetts-based company, announced that they had accidentally discovered that one of their cannabis plants appears to be partially resistant to HLVd. The scientists also noticed that the plant turned purple while fighting the disease.

Cannabis plants can sometimes change from green to other colors, such as red, blue, or purple, due to genetic or environmental factors. Purple plants have long been valued in the cannabis community, with prized strains such as Granddaddy Purple, Mendocino Purps and Purple Haze.

Kevin McKernan, chief scientific officer of Medicinal Genomics, announced his company’s findings at a conference in Florida earlier this month. McKernan said the plant was significantly more purple than a second plant that had the same genetics but had not been exposed to the viroid. “We don’t know why this is happening. This could be an immune response.”

Threat to cannabis growers

Zamir K. Punja, a Canadian professor of plant biology, said at the same conference that he sees HLVd as a major threat to cannabis farms. His research has shown that infected plants can reduce their THC production by 40%, causing serious economic damage to a farm.

It is extremely difficult to get rid of the pathogen because HLVd spreads easily between plants, attaches to used materials, and circulates in a cannabis farm’s water supply. In addition, an infected plant is more susceptible to other diseases.

The good news is that HLVd poses no health risk to humans, as it only affects plants. Punja added that there is evidence that some strains of cannabis are much more resistant to the effects of HLVd.

Super plant

McKernan said his company initially didn’t realize it had a plant with a unique response to HLVd. The scientists deliberately infected the plants with HLVd to try to understand how the disease changes infected plants. They rubbed the viroid directly onto the cut leaves of the plant. What resulted? One of their specimens, a cannabis variety they call Jamaican Lion, was resistant.

The team repeatedly exposed the plant to HLVd for six weeks, but the plant never tested positive for the virus. In the end, the scientists injected the viroid directly into the plant’s stem, but even then, the disease only seemed to infect the plant’s roots and not the leaves.

The team noticed that the leaves and flowers of the infected plant turned purple, but a second uninfected version of the same plant did not change color. They continued to test the plant for HLVd, but 57 of 57 purple plant tissue tests were negative. The only leaves that tested positive for the virus were green leaves. The good news is that HLVd poses no health risk to humans because it only affects plants, Punja said. He added that there is evidence that some strains of cannabis are much more resistant to the effects of HLVd.


It is unclear why purple plant material is associated with fighting disease. McKernan attributed the color change to “increased” production of anthocyanin, a plant compound that can turn cannabis purple. McKernan said it is worth investigating more purple plants to see if they are tolerant to HLVd, since anthocyanin production is already associated with fighting viroids.

McKernan added that his company is conducting new experiments on this particular plant to better understand how the strain fights HLVd. Cannabis growers are currently fighting HLVd with a combination of cleaning techniques and testing, hoping to be able to eliminate infected plants and reduce the spread. Will this new discovery save cannabis growers from crop failure?

Source: sfgate.com (EN)

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