Shallot latent virus

Shallot latent virus (SLV) is a widespread plant pathogen belonging to the genus Carlavirus within the Betaflexiviridae family. As a systemic virus, it primarily affects crops in the Allium genus, including onions, shallots, and garlic, often causing asymptomatic or mild infections that still result in economic yield losses.

The virus is taxonomically classified as a member of the order Tymovirales. It is characterized by filamentous viral particles that infect the vascular system of the plant. While often latent, the presence of the virus can weaken the plant's physiological condition, making it more susceptible to environmental stressors and other secondary infections.

The transmission biology of SLV is primarily mediated by aphid vectors, such as Myzus persicae, in a non-persistent manner. The virus particles adhere to the stylets of the aphids during feeding on an infected plant and are subsequently inoculated into healthy tissues during short probing events, ensuring rapid spread within the field.

Environmental conditions that favor aphid population outbreaks significantly increase the incidence of SLV. Once a crop is infected, the virus becomes pervasive throughout the plant tissues, including the bulbs. Consequently, vegetative propagation remains the most critical pathway for the long-term spread of the pathogen in farming systems.

Effective management strategies center on integrated pest management (IPM). Key actions include:

• Sourcing certified virus-free planting material to prevent primary introduction.
• Maintaining robust weed control to eliminate alternative hosts for the virus.
• Applying targeted insecticides to reduce aphid vector populations during the peak growing season.
• Implementing appropriate spatial isolation between commercial onion fields and small-scale gardens.