Begomoviruses

Begomoviruses are a genus of plant viruses in the family Geminiviridae. They are circular single-stranded DNA viruses transmitted by whiteflies, mainly Bemisia tabaci, in a persistent, circulative manner. Begomoviruses infect a wide range of dicotyledonous plants and are responsible for important crop diseases in tropical and subtropical regions.

Most begomoviruses have either bipartite or monopartite genomes. Bipartite begomoviruses carry two circular DNA components, DNA-A and DNA-B, each about 2.6–2.8 kilobases in length. DNA-A encodes replication-associated protein (AC1/Rep), transcription activator protein (AC2/TrAP), a replication enhancer (AC3), and the coat protein (AV1). DNA-B encodes the nuclear shuttle protein (BV1) and the movement protein (BC1), which facilitate intercellular spread within the plant. Monopartite begomoviruses possess a single DNA-A–like component and often rely on associated satellites for symptom development or replication assistance. Betasatellites and alphasatellites may accompany begomoviruses, modulating replication and pathogenicity.

Transmission and biology: Whiteflies acquire begomoviruses during feeding, and the viruses circulate within the insect before being transmitted to new plants. In the plant, begomoviruses replicate in the nucleus and move systemically with the help of viral movement proteins and host factors. Recombination and component exchange among begomoviruses contribute to rapid genetic diversification.

Impact and management: Begomoviruses cause symptoms such as leaf curling, mosaic or yellowing, vein clearing, and stunting, leading to yield losses in crops like tomato, cassava, and cotton. Management focuses on controlling whitefly populations, using resistant plant varieties, deploying clean planting material, and implementing integrated pest and crop-management strategies. Diagnostics rely on PCR, rolling-circle amplification, and sequencing.