Sweetpotato severe mosaic disease

Sweetpotato severe mosaic disease is a viral infection caused by the Sweetpotato severe mosaic virus (SPdSMV), a member of the Potyvirus genus. This disease primarily affects sweet potatoes (Ipomoea batatas), causing systemic infection that disrupts plant development and significantly hampers the plant's ability to produce high-quality storage roots.

Symptoms of the disease are characterized by distinct mosaic patterns on leaves, featuring a mix of yellow, light green, and dark green spots. Infected plants often show stunted growth, leaf deformation, and an overall loss of vigor. In severe cases, the foliage may curl or become crinkled, which leads to a reduced photosynthetic area and reduced energy production for the plant.

The virus is primarily transmitted by aphids in a non-persistent manner, meaning the insect acquires the virus after very short feeding times and transmits it immediately to healthy plants. Another crucial pathway for the spread of the disease is the use of infected vegetative cuttings (vines). Because the virus colonizes the entire plant, any propagule taken from an infected mother plant will harbor the virus, leading to new outbreaks.

The economic impact of this disease is significant, as it can cause substantial yield losses and degradation of tuber quality. Yield reduction is usually directly proportional to the stage of growth at which infection occurred. Early-season infections often result in almost no marketable yield, while late-season infections can still affect the marketability and size of the harvested roots.

Preventive strategies are essential for managing sweetpotato severe mosaic disease since there is no direct chemical cure for viral infections once a plant is infected. Effective control measures include:

• Using only certified virus-free planting material for every season.
• Implementing rigorous aphid control programs during the early stages of plant growth.
• Rogueing or removing infected plants as soon as they are identified to limit the local spread.
• Sanitizing agricultural tools regularly to prevent mechanical transmission.
• Rotating crops and maintaining weed-free fields to eliminate secondary hosts for the virus.