Soilborne mosaic

Soilborne mosaic is a significant viral disease primarily affecting winter cereals, including wheat, rye, and barley. It is caused by the Soil-borne wheat mosaic virus (SBWMV), which belongs to the Furovirus genus. This disease is characterized by its reliance on soil vectors for transmission, making it a persistent challenge in specific geographical regions with suitable soil conditions.

The primary vector for the virus is the soil-dwelling plasmodiophorid fungus Polymyxa graminis. The virus particles are encapsulated within the resting spores of this fungus, which can survive in the soil for several years. Infection occurs when the motile zoospores of the fungus infect the roots of susceptible host plants, effectively inoculating the crop with the viral pathogen during the seedling stage.

The diagnostic symptoms appear in early spring, shortly after the crop resumes growth. Affected plants display a characteristic mosaic pattern on the foliage, consisting of yellow-green spots, stripes, or mottling. In severe cases, the disease causes significant stunting, reduced tiller production, and general chlorosis, which often leads to a substantial reduction in the overall biomass and grain yield.

Disease development is heavily influenced by environmental factors, particularly soil moisture and temperature. Cool, wet autumns are critical, as they promote the activity of Polymyxa graminis and the subsequent infection of root systems. Poorly drained, low-lying fields or heavy clay soils are prone to high disease incidence due to the water-dependent nature of the fungal vector.

Management strategies focus on long-term prevention rather than direct curative action. Key practices include:

• planting resistant or tolerant cultivars;
• employing long-term crop rotation to reduce the population density of the fungal vector;
• improving field drainage to prevent water stagnation;
• delaying sowing dates to avoid the peak infection window during the autumn cooling period.