Bean leaf beetle: Pathogens transmitted

Bean pod mottle virus (BPMV)
Comovirus particles: An electron micrograph of virus particles from the family Comoviridae. This virus family includes viruses such as bean pod mottle virus. This image is from the Virus Information Data Exchange.Comovirus particles: An electron micrograph of virus particles from the family Comoviridae. This virus family includes viruses such as bean pod mottle virus. This image is from the Virus Information Data Exchange.

This pathogen was first described from garden bean (Zaumeyer and Thomas 1948) and later discovered in soybean (Skotland 1958, Walters 1958). This virus is in the Comovirus group and is partly characterized by having two single stranded RNAs (ribonucleic acid) encapsulated by coat proteins that form an icosahedral structure (i.e., a polyhedron with 20 faces) (Matthews 1991, Šutić et al. 1999). Two subgroups of BPMV have been identified in nature (Ref Gu and Ghabrial). Although one subgroup (subgroup II) caused more severe symptoms, the two subgroups can reassort, recombine, or a single virus particle can contain RNA-1 from both subgroups (known as a partial diploid) (add references).

On soybeans, bean pod mottle virus may cause a severe systemic mottling with a puckering of leaflets and mottling of pods and seed coats (Stace-Smith 1981); however, symptomatic response varies by soybean variety (Walters 1970, Scott et al. 1974, Windham and Ross 1985) and soybean stage at inoculation (Windham and Ross 1985) and planting date (Giesler er al. 2002). Additionally, the foliar symptoms of bean pod mottle virus are masked by cool temperatures (Walters 1970).

There can be a reduction in yield in bean pod mottle virus-infected plants resulting from reduced seed size and pod set (Watlers 1970). This affect on soybean yield is most severe when soybeans are infected as seedlings (Demski and Kuhn 1989). Seed-infection either does not occur (Skotland 1958, Schwenk and Nickell 1980) or occurs at a very low infection-rate (Lin and Hill 1983), with virus usually present in the seed coat (Schwenk and Nickell 1980). Additionally, when present, bean pod mottle virus-symptoms can be difficult to distinguish from other viral symptoms, e.g., soybean mosaic virus, (Marking 2000).

The bean leaf beetle is the primary vector for bean pod mottle virus (Mueller and Haddox 1980). This virus is the most prevalent soybean viruses in the North Central states (Giesler er al. 2002). Possible sources of primary inocula include: soybean seed, overwintering bean leaf beetles, and perennial legumes (Krell et al. 2003, Bradshaw et al. 2007).

Other viruses transmitted by bean leaf beetles

Quail pea mosaic virus (QPMV)

Southern bean mosaic virus (SBMV)