Yam mosaic virus

Yam mosaic virus (Potyvirus yamtesselati) is a significant plant pathogen classified within the Potyvirus genus. It poses a substantial threat to yam production worldwide, as it can drastically reduce both the quality and quantity of harvested tubers, leading to serious economic losses for farmers.

This virus primarily infects various species of the genus Dioscorea (yam). Due to its nature, the virus establishes a systemic infection, meaning it propagates through the plant's vascular system, ensuring that once an individual plant is infected, the entire plant remains a source of inoculum for the rest of its lifespan.

Symptoms of the disease are typically observed on the foliage, manifesting as intricate mosaic patterns, mottling, and yellowing (chlorosis). In severe cases, the infected leaves may become stunted, crinkled, or distorted, resulting in a diminished photosynthetic capacity that directly restricts tuber development and enlargement.

The transmission of this virus occurs mainly through aphid vectors in a non-persistent manner. Insects acquire the virus by probing infected plants and transmit it rapidly to healthy ones. Another major factor contributing to the spread is the recycling of infected tubers as planting material, which ensures the virus persists from one season to the next.

Effective prevention and control of Yam mosaic virus require an integrated approach:

• Sourcing certified virus-free planting material from reputable nurseries.
• Implementing roguing practices to remove and destroy symptomatic plants early in the season.
• Managing populations of aphid vectors using appropriate insecticidal regimes.
• Maintaining field hygiene and ensuring isolation from other potentially infected yam plots.
• Utilizing biotechnological methods like meristem culture to produce clean planting stock.