Viruses leave no fossils. So, how can we reveal the history of a virus that was first found in Pinot Gris grapes just a decade ago, and which has already spread worldwide? To learn how its history was predicted, where it came from, when, and what may have affected its spread, read this pathogen profile.
Viruses are tiny microbes that infect almost all cellular organisms. Virus particles (virions) contain the genetic information of a virus and carry it from cell to cell and between host individuals. The sequence of nucleotides of viral genes determines the properties of a virus, and can be used, like a ‘bar code’, to identify it. Nowadays, gene sequencing is a routine and inexpensive procedure. The mechanisms in cells that reproduce genes are not perfect, leading to changes in the sequences of all genes over time in a clock-like manner. Therefore, gene sequences, if collected at different times, also contain information about time and enable ‘family trees’ (phylogenies) of viruses to be reconstructed and dated using new scientific methods called bioinformatics.
The base of the GPGV phylogeny was that of isolates from China and northeast Asia. The oldest branch, dated 3500 years ago, carries isolates from ‘Crimson Glory Vine’ (Vitis coignetiae) growing in Japan. This species is native to northeast Asia; however, since the late 19th century, it has grown worldwide as an ornamental species. All the other GPGV isolates were obtained from Vitis vinifera grapevines, which were domesticated in Europe and taken to China c. 2000 years ago. The phylogeny indicates that GPGV in V. vinifera arrived in Europe, probably Germany, around 1800 CE, and later spread from Europe to other world regions.
Branches appeared unevenly in the phylogeny, and these were linked with historical events and revealed an increase of spread with the arrival of the phylloxera root-feeding hemipteran from North America around 1875 that destroyed all European vine crops until they had been transferred from their own roots to resistant root-stocks; the other periods coincided with post-war restoration and expansion of vine growth, or varietal changes associated with ‘alcohol prohibition’ in the USA. These periods of increased spread indicate the major influence humans have on the spread of the virus.
Ben Mansour, K., Gibbs, A.J., Meßmer, N., Fuchs, R., Wetzel, T. and Winterhagen, P., published this study in Plant Pathology Journal:
TITLE IMAGE: Graph showing three flattenings of the ‘node date curve’ for GPGV which were observed around 1870 CE – 1880 CE, 1920 CE – 1930 CE, and around 1950 CE, and corresponding to marked historical events that affected grapevine production and the occurrence of GPGV. (Pictures from Wikimedia)