Sunday, November 30, 2008

Study suggests Potyvirus lineage carried to Australia by Austronesians

A new study suggests that the bean common mosaic virus, which is commonly transmitted to crops and wild plants by aphids, originated in "south-east and East Asia, Oceania or Australia" and diverged about 3,580 years ago.

The authors suggest that one sub-lineage of the seven lineages studied was carried by Austronesian seafarers to Australia about 2,005 years ago.

The bean common mosaic virus belongs to the genus Potyvirus; the latter suggested in one study to have diverged about 6,600 years ago with the early spread of agriculture.

Arch Virol. 2008 Nov 22. [Epub ahead of print]Click here to read

The bean common mosaic virus lineage of potyviruses: where did it arise and when?

, 7 Hutt St, Yarralumla, Canberra, ACT, 2600, Australia,

There are more than 30 species in the bean common mosaic virus lineage of the genus Potyvirus. We have used their partial coat protein gene sequences to infer their phylogenies and have compared these with host and provenance information. Members of six species of the lineage have been isolated from crops distributed around the world, but three of these show clear links with South and East Asia. Members of the remaining species have been found in wild plants, minor crop species or ornamentals, and the majority of these have only been found in south-east and East Asia, Oceania or Australia. This phylogeographic pattern suggests that the bean common mosaic virus lineage arose in that region. Maximum-likelihood trees of the sequences were dated using the report that the initial major radiation of all potyviruses was 6,600 years ago. In this way, the bean common mosaic virus lineage was found to have first diverged 3,580 years ago, and one sub-lineage of seven species, found only in Australia, probably diverged there 2005 years ago. We discuss the ways in which the viruses could have moved from south-east Asia to Australia and note that their movement coincided with the spread of the Austronesian sea-faring/farming culture from China/Taiwan throughout the islands of the southern and eastern Pacific Ocean. Our study shows that virus isolates from wild or minimally domesticated plants, and from islands, are probably more useful indicators of the origins of viruses than those from widely grown well-travelled crop species.