Pea seed-borne mosaic virus

The virus consists of flexuous rod-shaped particles containing single-stranded RNA. Its defining characteristic is seed transmission, meaning the pathogen is introduced into fields directly through infected planting stock.

Secondary spread occurs via aphids in a non-persistent manner. More than 20 aphid species, including the pea aphid (Acyrthosiphon pisum), are known to act as vectors, acquiring the virus in seconds from infected plants.

Environmental factors significantly influence the development of the disease. While the virus can survive in wild legumes and plant debris, its rapid multiplication is favored by warm weather and high population levels of aphid vectors.

The virus has a wide host range within the Fabaceae family. Its ability to persist in seeds makes it a major concern for international trade of agricultural commodities and seed production systems.

PSbMV causes systemic infection, which severely affects the physiological development of the plant. Infected plants show stunted growth, reduced biomass, and diminished yield potential of both fodder and grain.

The quality of the harvest is heavily compromised. Seeds produced from infected plants are often deformed, shriveled, and exhibit poor germination rates, making them unsuitable for subsequent sowing.

Economic losses are cumulative, arising from reduced yield, lower seed quality, and the necessity of discarding infected seed lots. Early infection by the virus can lead to near-total crop failure in susceptible varieties.

Beyond grain production, the presence of the virus negatively impacts the photosynthetic efficiency of the crop. This makes the plants more susceptible to abiotic stresses like drought or heat.

The infection significantly alters the appearance of the seeds, which may carry visible symptoms, leading to downgrading of the product in commercial markets and potential financial losses for farmers.

Symptoms of PSbMV can vary depending on the genotype of the plant and the environment. The most common sign is a mosaic pattern on the leaves, characterized by light and dark green areas.

Severe infections lead to leaf malformation, where leaves become narrow, twisted, and exhibit curled margins. In some cases, systemic chlorosis or yellowing of the veins is clearly observable.

Stunting is a hallmark of this disease. Plants infected early remain significantly shorter than healthy counterparts, with shorter internodes and a rosette-like appearance of the terminal shoots.

Reproductive organs are also affected. The formation of flowers and pods is often delayed, and the pods themselves may be deformed, containing fewer and smaller seeds than healthy pods.

• Mosaic pattern and mottling on foliage.
• Leaf curling, twisting, and deformation.
• Stunting of the entire plant.
• Reduced pod size and seed count.
• Seed coat cracking or "zipper" markings on the seed surface.

The primary control strategy for PSbMV is the use of certified, virus-free seeds. Routine testing of seed batches using ELISA (Enzyme-Linked Immunosorbent Assay) is essential for seed producers.

Agronomic management should include spatial isolation of seed production fields from commercial legume crops. Eliminating weeds that can serve as alternative hosts is vital to minimize inoculum pressure.

While insecticide applications can reduce aphid populations, they have limited success in preventing the initial spread of the virus due to the rapid, non-persistent transmission mechanism of aphids.

The adoption of resistant or tolerant cultivars is the most effective long-term solution. Breeding programs are currently focused on introducing specific resistance genes to protect crops against PSbMV.

Good agricultural practices, such as strictly adhering to crop rotation schedules (leaving 3-4 years between legume plantings), help reduce the survival of the pathogen in the local environment and protect future crops.