Introducing the PhytoX Assay!
June 16, 2022
By Shaun Stice, PhD
Today, microbial threats wipe out as much as 30% of potential Cannabis and Hemp crop yield, a risk to grows that can’t be ignored. PhytoX from PathogenDx let’s labs help growers with quicker results, and take fast action to remove infected plants before viruses spread and impact potency and growth. The easy-to-use RT-PCR microarray assay detects nine plant viruses driving Cannabis, Hemp, and other agriculture yield losses, all in a single test.
9 plant viruses, 1 easy test.
Hop latent viroid (HLVd) – HLVd is a circular, single stranded RNA viroid in the Cocadviroid genus 1. It was first described and named by Puchta et al. 1998 where they determined that most hop cultivars are infected with HLVd but lacked any symptoms, thus the term ‘latent’ was applied 2. More recently in Cannabis spp. HLVd has been described as causing significant damage resulting in “dudding” disease and stunting of plants 3,4. HLVd is transmitted primarily through clonal propagation and mechanical transmission, which is why disinfecting cutting instruments is important when trimming and pruning plants.
Lettuce chlorosis virus (LCV) – LCV is a linear single stranded positive-sense RNA virus in the Crinivirus genus. It was first described and named by Duffes et al. in 1996 where they identified interveinal yellowing, stunting, and leaf rolling in lettuce and sugar beets grown in the southwest desert regions of California5. In Cannabis sativa an outbreak of LCV was described by Hadad et al. in Israel 6. Symptoms of LCV in Cannabis spp. included chlorotic foliage, and leaf yellowing these symptoms are similar to nutrient deprivation making testing of mother plants critical 6. LCV is transmitted primarily through clonal propagation and insect transmission. White fly (family Aleyrodidae) and the only known insect vector of LCV currently making insect control important for grows where there is an outdoor component to the growing operation.
Cannabis cryptic virus (CanCV) – CanCV is a linear double-stranded bipartite RNA virus in the Betapartitivirus genus. It was inadvertently isolated by Ziegler et al. in 2012 when they were studying HLVd in cannabis 7. More recently Righetti et al. conducted RNA-seq analysis of hemp plants exhibiting symptoms of the so-called hemp streak disease. They identified CanCV in both symptomatic and asymptomatic plants and were unable to establish CanCV as the causative agent of hemp streak symptoms 8. CanCV appears to primarily be transmitted clonally from infected mother plants to cuttings. Experimental mechanical transmission was unsuccessful. Related Betapartitivirus can be efficiently transmitted vertically to seeds as well 9.
Beet curly top virus (BCTV) – BCTV is a circular single-stranded positive-sense RNA virus in the Curtovirus family and can infect more than 300 plant species10 . BCTV was originally described in beets and causes characteristic curling of upper leaves on the plants. In Cannabis spp. BCTV has become a major issue for operations that include an outdoor grow 11,12. Industrial hemp infected with BCTV had diminished crop yield, low quality flowers, and overall stunted growth 13. BCTV is transmitted by leafhopper insects that may carry the virus between crops and weeds. Control of insect and weed populations is important to mitigate the impact of this virus.
Tobacco streak virus (TSV) – TSV is a linear double-stranded positive-sense RNA virus in the Ilarvirus genus. TSV was first identified in tobacco and is known to cause severe diseases in more than 80 plant species including tomato plants14. TSV was reported to infect cannabis spp. in 1971 and symptoms were described as stunting and mosaic leaf pattern 15. Recently in Colorado TSV was identified through sequencing in industrial hemp plants grown outdoors 13. TSV is transmitted through clonal propagation, pollen, and seeds. Outdoor growing operations are more at risk for this virus.
Arabis mosaic virus (ArMV) – ArMV is a linear single-stranded positive-sense RNA virus in the Nepovirus family. ArMV has a relatively wide host range of around 90 species, most notably strawberries, hops, hemp, grapes, and raspberries 16. Symptoms of ArMV include stunting, chlorotic mottling, and vein yellowing. ArMV is transmitted by nematodes, small, microscopic worms in the soil that feed on plant roots. ArMV can also be transmitted mechanically, clonally, through seed, and pollen. To control ArMV start with clean steam-sterilized soil or other matrices. Proper sanitation of cutting instruments is also important to prevent mechanical transmission.
Alfalfa mosaic virus (AMV) – AMV is a linear single stranded positive-sense RNA virus in the Alfamovirus genus. AMV was first identified in 1931 as an economically important disease in alfalfa. AMV has a wide host range and can infect many field crops including potato, tomato, and beans. AMV has been reported to infect industrial hemp in Europe17. Symptoms of this virus include distinct yellow or whitish mosaic patterns on leaves, fruits and flowers may be stunted or misshapen, impacting yield significantly. AMV is transmitted by Aphid insects. It can also be transmitted clonally, by pollen, and by seed. To mitigate AMV virus infection in your grow control aphid insects and clean cutting instruments between each plant.
Tobacco mosaic virus (TMV) – Tobacco mosaic virus is a single stranded positive-sense RNA virus in the Tobamovirus family. TMV is one of the most well studied viruses in the world and was the first pathogen to be identified as a virus in 1930. TMV has a wide host range including many vegetables and ornamental plants. In Cannabis spp. TMV symptoms include mosaic leaf pattern, yellow veins, small curled or wrinkled leaves, decreased yield and stunted growth. TMV is incredibly transmissible via mechanical transmission, for example if one handles tobacco products like cigarettes it is possible to transmit the virus to plants by handling them after handling the cigarette18. This makes sanitation extra important. Clean cutting instruments, wear and change gloves frequently when handling plants to prevent mechanical transmission from occurring.
Cucumber mosaic virus (CMV) – Cucumber mosaic virus is a single stranded positive-sense RNA virus in the Cucumovirus family. CMV has a wide host range infecting mostly vegetables 19. Symptoms of this virus include yellow patches, downward pointing and distorted leaves, reduction in yields and distorted flowers and fruit. CMV is transmitted clonally, mechanically, and by aphid insects. Proper control of insect populations in your grow as well as instrument sanitation will reduce the risk of a CMV outbreak occurring.
- Lavagi, I., Matoušek, J., and Vidalakis, G. (2017). Other Cocadviroids. In Viroids and Satellites (Elsevier), pp. 275–287. 10.1016/B978-0-12-801498-1.00026-7.
- Puchta, H., Ramm, K., and Sänger, H.L. (1988). The molecular structure of hop latent viroid (HLV), a new viroid occurring worldwide in hops. Nucleic Acids Res 16, 4197–4216. 10.1093/nar/16.10.4197.
- Bektaş, A., Hardwick, K.M., Waterman, K., and Kristof, J. (2019). Occurrence of Hop Latent Viroid in Cannabis sativa with Symptoms of Cannabis Stunting Disease in California. Plant Dis 103, 2699. 10.1094/PDIS-03-19-0459-PDN.
- Warren, J.G., Mercado, J., and Grace, D. (2019). Occurrence of Hop Latent Viroid Causing Disease in Cannabis sativa in California. Plant Dis 103, 2699–2699. 10.1094/PDIS-03-19-0530-PDN.
- Duffus, J.E., Liu, H.-Y., Wisler, G.C., and Li, R. (1996). Lettuce chlorosis virus — A new whitefly-transmitted closterovirus. Eur J Plant Pathol 102, 591–596. 10.1007/BF01877027.
- Hadad, Luria, Smith, Sela, Lachman, and Dombrovsky (2019). Lettuce Chlorosis Virus Disease: A New Threat to Cannabis Production. Viruses 11, 802. 10.3390/v11090802.
- Ziegler, A., Matoušek, J., Steger, G., and Schubert, J. (2012). Complete sequence of a cryptic virus from hemp (Cannabis sativa). Arch Virol 157, 383–385. 10.1007/s00705-011-1168-8.
- Righetti, L., Paris, R., Ratti, C., Calassanzio, M., Onofri, C., Calzolari, D., Menzel, W., Knierim, D., Magagnini, G., Pacifico, D., et al. (2018). Not the one, but the only one: about Cannabis cryptic virus in plants showing ‘hemp streak’ disease symptoms. Eur J Plant Pathol 150, 575–588. 10.1007/s10658-017-1301-y.
- Martin, R.R., Zhou, J., and Tzanetakis, I.E. (2011). Blueberry latent virus: An amalgam of the Partitiviridae and Totiviridae. Virus Res 155, 175–180. 10.1016/j.virusres.2010.09.020.
- Stanley, J. (2008). Beet Curly Top Virus. In Encyclopedia of Virology (Elsevier), pp. 301–307. 10.1016/B978-012374410-4.00696-8.
- Hu, J., Masson, R., and Dickey, L. (2021). First Report of Beet curly top virus Infecting Industrial Hemp (Cannabis sativa) in Arizona. Plant Dis 105, 1233–1233. 10.1094/PDIS-11-20-2330-PDN.
- Melgarejo, T.A., Chen, L.-F., Rojas, M.J., Schilder, A., and Gilbertson, R. (2022). Curly top disease of hemp (Cannabis sativa) in California is caused by mild-type strains of beet curly top virus often in mixed infection. Plant Dis. 10.1094/PDIS-04-22-0856-SC.
- Chiginsky, J., Langemeier, K., MacWilliams, J., Albrecht, T., Cranshaw, W., Fulladolsa, A.C., Kapuscinski, M., Stenglein, M., and Nachappa, P. (2021). First Insights Into the Virus and Viroid Communities in Hemp (Cannabis sativa). Frontiers in Agronomy 3. 10.3389/fagro.2021.778433.
- Tomassoli, L., Tiberini, A., and Vetten, H.-J. (2012). Viruses of Asparagus. In, pp. 345–365. 10.1016/B978-0-12-394314-9.00010-5.
- Hartowicz, L., Knutson, H., Paulsen, A., Eatton, B., and Eshbaugh, E. (1971). Possible biocontrol of wild hemp. North Central Weed Control Conference, Proceedings 26, 69.
- Scientific opinion on the risk to plant health posed by Arabis mosaic virus, Raspberry ringspot virus, Strawberry latent ringspot virus and Tomato black ring virus to the EU territory with the identification and evaluation of risk reduction options (2013). EFSA Journal 11. 10.2903/j.efsa.2013.3377.
- Kegler, H., and Spaar, D. (1997). Zur virusanfälligkeit von hanfsorten ( Cannabis sativa L.). Archives Of Phytopathology And Plant Protection 30, 457–464. 10.1080/03235409709383198.
- Iftikhar, Y., Vadamalai, G., Sajid, A., Mubeen, M., and Ullah, M.I. (2018). Wilting of Bean Plants from Tobacco Mosaic Virus from Smoking Tobacco in Pakistan. Asian J Biol Life Sci 7, 77–80. 10.5530/ajbls.2018.7.8.
- García-Arenal, F., and Palukaitis, P. (2008). Cucumber Mosaic Virus. In Encyclopedia of Virology (Elsevier), pp. 614–619. 10.1016/B978-012374410-4.00640-3.