A viroid is an infectious, single-stranded circular RNA molecule, usually about 246-401 nucleotides long, that causes disease in plants. Unlike a virus it has no protein coat and does not code for any proteins. It relies entirely on host enzymes to copy itself, and disrupts the plant's gene regulation as it does. The best-known example in cannabis is hop latent viroid (HLVd).
In practice
Viroids are very stable and spread mainly mechanically: on cutting tools, hands, grafts and propagation material, and in some cases via seed or pollen. Common alcohol wipes are not reliable against them; growers use disinfectants with documented efficacy, such as diluted sodium hypochlorite (bleach) solutions, between plantsbeing reviewed. Viroids cannot be treated with any spray. Testing by RT-PCR and discarding infected stock are the only reliable controls, with tissue culture to recover clean lines.
Don't confuse with
- Plant virus: has a protein coat and genes; often spread by insects.
- Prion: a misfolded protein in animals, nothing to do with plants.
- Bacteria: living cells that can be cultured; viroids cannot.
An infectious particle of nucleic acid in a protein coat that replicates inside plant cells; on cannabis, often insect-spread and incurable once infected.A gene is a stretch of DNA that carries the instructions for one functional product, usually a protein such as an enzyme, and is the basic unit of inheritance.HLVd, a small infectious RNA that spreads through sap and tools, causing stunting, brittle stems, small loose buds and reduced resin in cannabis; called dudding.Photon efficacy is how many micromoles of PAR photons a fixture produces per joule of electricity (µmol/J); higher means more light for the same power bill and heat.Sodium (Na) is not essential for cannabis; it enters through water, softeners and some inputs, and at high levels causes salt stress and crowds out potassium and calcium.Free chlorine is the disinfectant (hypochlorous acid and hypochlorite) added to many tap waters; it dissipates from standing or aerated water within about a day.Tissue culture is growing small pieces of a plant on sterile nutrient gel in a sealed vessel, used to multiply, clean up and store cannabis genotypes.Cleaning and disinfecting rooms, tools, containers, irrigation and people's clothing so that pests and pathogens are not carried from plant to plant or crop to crop.Holding incoming plants, clones or seeds apart from the main grow, under observation and sometimes treatment, until they are shown to be free of pests and disease.
