Fabavirus

Fabavirus is a genus of viruses in the family Secoviridae, which is part of the order Picornavirales. Viruses within this genus are known to infect a wide range of host plants, causing various diseases that can significantly impact agricultural productivity. The name Fabavirus is derived from the type species of the genus, Broad bean wilt virus 1 (BBWV-1), which primarily affects plants in the family Fabaceae, commonly known as legumes or pulses.

Characteristics

Fabaviruses are characterized by their bipartite, positive-sense, single-stranded RNA genomes. Each particle is encapsulated within an icosahedral capsid, which is not enveloped, measuring approximately 25-30 nm in diameter. The genome is divided into two segments, RNA1 and RNA2, each of which is separately encapsulated. These segments encode for the replication machinery and the structural proteins of the virus, respectively.

Genome Structure and Replication

The RNA1 segment of the fabavirus genome encodes for a large polyprotein that is post-translationally processed into the viral replicase and other non-structural proteins necessary for virus replication. RNA2, on the other hand, encodes for the structural proteins that make up the virus capsid. Replication of fabaviruses occurs in the cytoplasm of infected cells, where the viral RNA is used as a template for the synthesis of a complementary negative strand. This negative strand then serves as a template for the production of new positive-strand genomic RNA, as well as subgenomic RNAs that are used for the translation of viral proteins.

Host Range and Transmission

Fabaviruses have a broad host range, infecting various species within the families Fabaceae, Solanaceae, and others. Transmission of fabaviruses occurs primarily through aphids in a non-persistent manner. This means that the virus does not replicate within the aphid vector, and the aphid can only transmit the virus for a short period after acquiring it from an infected plant. Some fabaviruses can also be transmitted through seed, which can contribute to the spread of the virus across long distances.

Economic Impact

The economic impact of fabaviruses can be significant, particularly in crops of high economic value such as beans, peas, and lentils. Infection can lead to a range of symptoms including leaf mottling, yellowing, and wilting, which can result in reduced yield and quality of the harvested product. Management of fabavirus infections relies on the use of resistant plant varieties, control of aphid vectors, and the implementation of good agricultural practices to prevent the spread of the virus.

Notable Species

Some notable species within the Fabavirus genus include:

• Broad bean wilt virus 1 (BBWV-1)
• Broad bean wilt virus 2 (BBWV-2)
• Lamium mild mosaic virus
• Pea necrotic yellow dwarf virus

Research and Control

Research on fabaviruses focuses on understanding their molecular biology, host interactions, and mechanisms of disease in order to develop effective control strategies. This includes the development of resistant plant varieties through traditional breeding or genetic engineering, as well as the study of natural resistance mechanisms in plants. Integrated pest management strategies are also important for controlling the aphid vectors of fabaviruses.