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Scientists sequence Strawberry mottle virus


Researchers have sequenced the genome of Strawberry mottle virus, the most widespread virus that affects strawberry plants worldwide. Infected plants are less vigorous and produce fewer strawberries than normal. The virus attacks the foliage of the plants and causes scattered, inconspicuous spots on the leaves. Symptoms vary seasonally, even though some strawberry species do not show the typical mottling at all. The sequencing of Strawberry mottle virus (SMoV) could lead to new methods for detecting viruses in strawberry plants.

Strawberry plant infected with Strawberry mottle virus. View larger

The sequencing revealed that the genome of Strawberry mottle virus consists of two genomic components, RNA1 and RNA2. The researchers found that the general genome organization is most similar to Satsuma dwarf virus (SDV), a tentative member of a group called nepoviruses—plant viruses containing multicomponent single-stranded RNA.

Given the similarity to Satsuma dwarf virus and the bipartite genomic structure, Strawberry mottle virus seems to belong to the group of nepoviruses. The fact, however, that the virus is transmitted by aphids—the strawberry aphid Chaetosiphon fragaefolii is a very pale, almost translucent insect that lives on the plant—suggests otherwise.

Strawberry aphids.

"The most outstanding feature of SMoV, based on its nepovirus-like organization, is that it is aphid-transmissible," the researchers write in The Journal of General Virology. The team included scientists of the German Institut für Pflanzenschutz im Obstbau, Dossenheim and Plant Research International in Wageningen, The Netherlands.

The researchers propose that Strawberry mottle virus is a tentative member of a new family of bipartite picorna-like viruses. Picornaviruses are single-stranded RNA viruses, and the name 'picorna' comes from 'PICO' meaning small and 'RNA'. "The close identity of SMoV and SDV-like viruses with the aphid-transmissible RTSV [Rice tungro spherical virus] suggests that these viruses form a new group," the researchers conclude in their paper.

The study is part of a joint European Community project to develop methods for detecting strawberry viruses transmitted by aphids. Aphids are a major threat to the strawberry industry because they can transmit several viruses. Mixed virus infections by aphids can cause yield losses of 30 percent and more.

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Thompson, J.R. et al. Characterization and complete nucleotide sequence of Strawberry mottle virus: a tentative member of a new family of bipartite plant picorna-like viruses. J Gen Virol 83, 229-239 (January 2002).

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