Allexivirus pintoi

Symptoms of Allexivirus pintoi infection often manifest as leaf mosaicism, where alternating light and dark green patches appear on leaf blades. Deformation or curling of the leaves is frequently observed, which significantly affects the photosynthetic surface area.

Affected crops may exhibit general growth retardation, with plants appearing stunted compared to healthy specimens. In some cases, chlorosis is observed, starting from the leaf tips and gradually spreading across the entire blade.

For bulbous plants such as garlic, characteristic signs include striping patterns or spotting on the foliage during active vegetation. Often, external signs are subtle, making visual diagnosis difficult without laboratory confirmation.

During the flowering and bulb formation stages, premature yellowing and wilting of the lower part of the plants may occur, which is often confused with natural senescence or soil pest damage. This latent course of the disease makes visual monitoring insufficient.

With prolonged infection of the planting material, symptoms become more pronounced in each subsequent generation, leading to cultivar degeneration and a reduction in product quality.

The disease is caused by the Allexivirus pintoi virus, belonging to the genus Allexivirus, family Alphaflexiviridae. It is a phytopathogenic virus with a single-stranded RNA genome that primarily infects members of the Amaryllidaceae family, including various types of onion and garlic.

The virus is primarily transmitted through infected planting material, with the infection spreading systemically throughout all plant organs. Secondary transmission under field conditions often occurs via insect vectors, such as various mite species (specifically the garlic mite).

Mechanical transmission of the virus is possible during agronomic practices such as pruning, weeding, or harvesting when using contaminated tools. The presence of the virus in weeds of the same family can maintain the infectious background in the field.

The viral genome is characterized by relative stability, allowing it to survive for long periods in overwintering bulbs and vegetative parts of plants. Unlike some other viruses, it is not seed-transmitted but easily accumulates during clonal propagation.

Pathogen identification requires Enzyme-Linked Immunosorbent Assay (ELISA) or Polymerase Chain Reaction (PCR), as the morphology of viral particles is typical for the genus and does not allow for differentiation without specific antibodies.

Viral development is favored by conditions that promote the active reproduction of insect vectors, particularly warm and humid weather during the spring-summer period. Viral load accumulation occurs faster when monocultures are grown on the same site without proper crop rotation.

The spread of infection within a farm is often accelerated by the use of weak, initially infected planting material, which serves as a primary source of the virus for the entire population. Violation of phytosanitary rules in storage facilities also contributes to the transmission of the pathogen.

High planting density creates an optimal environment for virus transmission through contact between damaged leaves and insects moving from one plant to another. Stress factors, such as drought or micronutrient deficiencies, reduce the immune response of the crops.

Lack of control over weeds, which can act as reservoirs for the virus during the off-season, significantly complicates the epidemiological situation. Favorable conditions for mites feeding on bulbs accelerate the circulation of the pathogen in the soil and storage areas.

Agronomic practices involving mechanical damage to plant tissues create entry points for viral infection, especially if tools are not regularly disinfected.

The main harm consists of a significant reduction in yield, which can range from 10% to 50% depending on the cultivar and the degree of infection. Affected plants form smaller, lighter bulbs with low density.

The virus reduces product quality: organoleptic properties of garlic and onions deteriorate, the structure of the scales changes, making them unsuitable for long-term storage. The risk of secondary infection by bacterial and fungal rots increases through weakened tissues.

Economic damage is associated not only with the loss of crop mass but also with the inability to use the produce as high-quality seed material. This leads to the need for a complete replacement of the planting stock, requiring significant financial investments.

Accumulation of the virus in seed stocks over several years leads to the total degeneration of the crop on the plot. The progressive weakening of plants makes them less resistant to adverse weather conditions and other diseases.

Globally, the spread of Allexivirus pintoi limits export opportunities for producers, as many countries impose strict phytosanitary requirements regarding the absence of viral infections in imported materials.

The main protection strategy is based on the use of certified, virus-free planting material obtained through culture revitalization methods (meristem culture). This is the most effective way to prevent the spread of infection.

Strict adherence to crop rotation is necessary, avoiding the return of bulbous crops to the same location for at least 3–4 years. It is important to carry out timely destruction of weeds that may serve as natural reservoirs for the virus.

Control of insect vectors (primarily mites) is a mandatory component of protection. Both acaricides and preventive measures, such as thermal treatment of bulbs before planting, are employed.

Regular disinfection of agricultural tools with solutions that inactivate viruses (alcohol solutions, special disinfectants) during maintenance work significantly reduces the risk of mechanical transmission of infection from diseased to healthy plants.

• Utilization of cultivars with genetic resistance to viruses.
• Spatial isolation of crops from areas with a high probability of infection.
• Regular phytosanitary monitoring and culling of plants with suspected viral symptoms.