Virus

Begomovirus spp., Carlavirus spp., Comovirus spp., Crinivirus spp., Cucumovirus spp., Ipomovirus spp., Potyvirus spp., Tobamovirus spp., Torradovirus spp., Tospovirus spp. and others

1. Identification

Plant viruses constitute an extremely diverse group of pathogenic agents that affect agricultural, horticultural and ornamental crops as well as spontaneous species. Infections manifest as mosaics, chloroses, deformations, necroses, rings, reduced growth and significant productivity losses. Transmission occurs through vectors such as aphids, whiteflies, thrips, nematodes, seeds, pollen or mechanical contact. Among the most relevant viruses are representatives of several widely distributed genera of great economic impact.

2. Causal agent

The viruses belong to multiple families and genera, each with its own taxonomic and epidemiological characteristics.

• Begomovirus, described by Stanley et al. (2005), family Geminiviridae; includes DNA viruses transmitted by Bemisia tabaci, such as Tomato yellow leaf curl virus (TYLCV).
• Potyvirus, described by Adams et al. (2005), family Potyviridae; the largest group of plant viruses, including Potato virus Y (PVY) and Zucchini yellow mosaic virus (ZYMV).
• Tobamovirus, described by Adams et al. (2009), family Virgaviridae; very stable viruses transmitted mechanically, such as Tobacco mosaic virus (TMV) and Tomato brown rugose fruit virus (ToBRFV).
• Cucumovirus, described by Smith (1972), family Bromoviridae; includes Cucumber mosaic virus (CMV), with more than 1000 hosts.
• Tospovirus, described by Milne (1970), family Tospoviridae; transmitted by thrips, such as Tomato spotted wilt virus (TSWV).
• Crinivirus, described by Klaassen et al. (1994), family Closteroviridae; transmitted by whitefly, such as Tomato chlorosis virus (ToCV).
• Carlavirus, described by Adams et al. (2005), family Betaflexiviridae; includes Potato virus S (PVS).
• Comovirus, described by van Kammen & de Jager (1978), family Secoviridae; transmitted by nematodes, such as Bean pod mottle virus (BPMV).
• Ipomovirus, described by Fauquet et al. (2005), family Potyviridae; transmitted by whitefly, such as Sweet potato mild mottle virus (SPMMV).
• Torradovirus, described by Verbeek et al. (2007), family Secoviridae; transmitted by whitefly, such as Tomato torrado virus (ToTV).
• Other relevant genera include Luteovirus, Polerovirus, Nanovirus, Orthotospovirus and Alphaflexivirus.

3. Main hosts

• Solanaceae (tomato, pepper, potato).
• Cucurbits (cucumber, melon, squash, courgette).
• Legumes (bean, pea, lupin).
• Fruit trees (citrus, grapevine, banana).
• Ornamentals (chrysanthemums, gerberas, petunias, rose bushes).
• Spontaneous species that act as reservoirs.
• Young plants and tender tissues are generally more susceptible.

4. Symptoms

• Mosaics, chloroses and irregular patterns on the leaves.
• Leaf deformations, curling and blisters.
• Necroses, chlorotic rings and streaks.
• Reduced growth and dwarfism.
• Deformed, discoloured fruits or with irregular ripening.
• Significant losses of productivity and quality.

5. Disease cycle

• Survival in host, ornamental and weed plants.
• Transmission by specific vectors (aphids, whitefly, thrips, nematodes).
• Mechanical spread through tools or contact.
• Transmission by seeds or pollen in some viruses.
• Systemic replication after infection.
• Persistence in protected environments and mild climates.

6. Favourable conditions

• High vector density.
• Mild to warm temperatures.
• Presence of reservoir weeds.
• Continuous crops or overlapping cycles.
• Protected environments with high plant density.
• Mechanical wounds and frequent handling.

7. Disease management

• Removal of infected plants and elimination of alternative hosts.
• Vector control with cultural, biological or authorised methods.
• Use of resistant or tolerant varieties.
• Rigorous sanitation of tools and structures.
• Use of certified, virus-free plant material.
• Regular monitoring of symptoms and vectors.
• Physical barriers and insect-proof netting in greenhouses.
• Crop rotation and interruption of continuous cycles.

Bibliographic references

• Adams, M. J., Antoniw, J. F., & Fauquet, C. M. (2005). Molecular criteria for genus and species discrimination within the family Potyviridae. Archives of Virology, 150, 459–479.
• Adams, M. J. et al. (2009). Family Virgaviridae. ICTV Report.
• García‑Arenal, F., & Zerbini, F. M. (2019). Plant virus diversity and evolution. Annual Review of Phytopathology, 57, 113–132.
• Hull, R. (2014). Plant Virology. Academic Press.
• Jones, R. A. C. (2021). Global plant virus disease pandemics and epidemics. Plants, 10, 233.
• Klaassen, V. A. et al. (1994). Crinivirus: a new genus of whitefly‑transmitted plant viruses. Phytopathology, 84, 1068–1074.
• Milne, R. G. (1970). The classification of tospoviruses. Virology, 42, 256–259.
• Navas‑Castillo, J., Fiallo‑Olive, E., & Sanchez‑Campos, S. (2011). Emerging virus diseases transmitted by whiteflies. Annual Review of Phytopathology, 49, 219–248.
• Scholthof, K.-B. G. et al. (2011). Top 10 plant viruses in molecular plant pathology. Molecular Plant Pathology, 12, 938–954.
• Smith, K. M. (1972). Cucumovirus classification. Journal of General Virology, 14, 1–10.
• Stanley, J. et al. (2005). Revised taxonomy of the family Geminiviridae. Archives of Virology, 150, 821–837.
• van Kammen, A., & de Jager, C. P. (1978). The Comovirus group. Annual Review of Phytopathology, 16, 95–116.
• Verbeek, M. et al. (2007). Torradovirus: a new genus of plant viruses. Archives of Virology, 152, 1527–1532.