Sorghum mosaic

The virus consists of flexuous, filamentous particles containing single-stranded RNA. Due to its high genetic diversity, different strains of the virus exist, which complicates the development of universally resistant sorghum cultivars.

In the field, the virus persists in perennial grasses and overwintering host plants, acting as a bridge between growing seasons. It is important to note that this virus is not seed-transmitted.

The transmission of the virus is primarily mediated by aphids, which acquire the virus while feeding on infected plants and transmit it to healthy ones in a non-persistent manner during short probing sessions.

Mechanical transmission also plays a role in the field, as the virus can be spread by the movement of farm equipment, leaf-to-leaf contact during windy conditions, or through insect-induced wounds on the foliage.

The primary hosts of the virus are varieties of sorghum, including grain, sweet, and forage sorghum. The virus can also infect corn and sugarcane, which can serve as alternative hosts and reservoirs for the disease.

Significant damage occurs when young plants are infected early in the season, leading to systemic infection that severely stunts plant growth and drastically reduces the potential yield of grain or biomass.

The infection negatively impacts the plant's metabolic efficiency, resulting in lower sugar accumulation and reduced nutritional quality of the forage, which is a major concern for the livestock industry.

Plants infected with the virus show reduced tolerance to environmental stressors, such as drought, making them more vulnerable to secondary infections and unfavorable weather conditions.

Economic losses arise not only from reduced crop yields but also from increased management costs associated with monitoring and chemical control of insect vectors in the affected areas.

Initial signs of the infection appear as light green or chlorotic patches on the younger leaves, which gradually develop into a characteristic mosaic pattern with alternating light and dark green areas.

As the disease progresses, the chlorosis may become more pronounced, and the leaf surface can become crinkled or distorted, indicating a severe systemic infection within the plant tissues.

Infected plants typically exhibit significant stunting compared to healthy ones, with shorter internodes and smaller leaf areas, which leads to a patchy and uneven appearance across the field.

Reproductive development is often compromised; plants may show delayed flowering or produce small, deformed panicles with poor grain set, ultimately impacting the final harvest quantity.

Visual identification can sometimes be confused with nutrient deficiencies, requiring confirmation through diagnostic techniques like ELISA or PCR to accurately distinguish the viral mosaic from other physiological issues.

Effective management begins with controlling aphid populations during the early stages of crop growth, as these insects are the primary vectors responsible for the initial spread of the virus.

Sanitation practices, such as removing weeds from fields and surrounding areas, are critical to eliminating alternative host plants that harbor the virus during the off-season.

Planting resistant or tolerant sorghum cultivars remains the most sustainable and efficient strategy to mitigate the impact of the disease, reducing the need for intensive chemical applications.

Maintaining spatial separation between sorghum fields and other susceptible crops like sugarcane or corn can help reduce the influx of viruliferous insects into the sorghum plots.

Adjusting planting dates to ensure that plants reach a more mature stage before peak aphid activity can significantly lower the rate of infection and minimize damage in sensitive areas.