Rhynchosia Havana begomovirus

Pathogen and disease type
The Rhynchosia Havana begomovirus (Rhynchosia golden mosaic Havana virus) belongs to the genus Begomovirus within the family Geminiviridae. This pathogen consists of a single-stranded circular DNA genome and causes systemic viral infections in host plants. By interfering with the plant's hormonal and photosynthetic pathways, it causes chronic debilitating diseases that significantly reduce agricultural yields.

Affected crops
The primary hosts of this virus are members of the Fabaceae family, particularly the Rhynchosia genus. However, the virus exhibits a broad host range, allowing it to colonize various legume species often found in agricultural settings. The potential for the virus to jump to other related crops makes it a significant concern for tropical and subtropical farming systems.

Symptoms and signs of infection
Typical symptoms include the development of bright golden mosaic patterns on the leaves, coupled with severe leaf curling and crinkling. Affected plants display stunting, reduced branching, and reduced pod set. The foliage often appears chlorotic, indicating a significant decrease in chlorophyll levels due to the viral infection, which severely inhibits the plant's capacity for carbon assimilation.

Conditions for development and spread
The virus is primarily transmitted by the whitefly Bemisia tabaci in a circulative, non-propagative manner. The insect acquires the virus while feeding on infected sap and retains the ability to inoculate healthy plants throughout its lifespan. Warm, humid environmental conditions facilitate both the movement of whiteflies and their population growth, leading to rapid disease spread within a field.

Damage and control measures
The economic impact of this begomovirus is substantial, leading to severe yield losses and degraded crop quality. Management strategies must include:

• Applying insecticides to manage the whitefly vector population.
• Eliminating alternative host weeds within and around the field.
• Utilizing resistant or tolerant crop varieties where available.
• Maintaining field hygiene through the early removal of symptomatic plants.