Rhynchosia rugose mosaic

Pathogen and disease type. Rhynchosia rugose mosaic is a viral condition caused by the Begomovirus rhynchosiarugosi. As a member of the Geminiviridae family, this virus possesses a single-stranded circular DNA genome. It is classified as an insect-transmitted virus, where the primary vector is the whitefly (Bemisia tabaci), which facilitates the spread of the disease through persistent transmission.

Susceptible crops. This virus primarily affects members of the Fabaceae family. It poses a significant threat to legume crops, including common beans (Phaseolus vulgaris) and soybeans. The wild plant Rhynchosia minima serves as a critical alternate host, acting as a primary reservoir from which the virus jumps to commercial crop fields.

Symptoms and signs. Clinical signs of the infection typically include severe mosaic patterns, chlorosis, and crinkling or curling of the leaf tissues. Infected plants exhibit stunted growth and shortened internodes, leading to a bushier, abnormal appearance. Reproductive structures are often impacted, with flowers failing to set pods or producing underdeveloped, shriveled beans.

Development and severity. The disease spread is highly dependent on the lifecycle of its whitefly vector, which thrives in tropical and subtropical climates. Under high temperatures, the whitefly population can explode, accelerating the transmission rate. The damage is considered severe because infected plants suffer from reduced photosynthetic activity and systemic necrosis, leading to massive crop failure if left unmanaged.

Prevention and management measures. Managing this begomovirus requires a holistic approach focused on vector control and host sanitation:

• Eliminating wild host plants like Rhynchosia minima from the vicinity of fields.
• Monitoring and managing whitefly populations using targeted insecticides or physical barriers.
• Implementing integrated pest management (IPM) to reduce reliance on chemicals while controlling vectors.
• Selecting cultivars with demonstrated resistance or tolerance to local viral strains.