Scientists root out wine blight genome sequence
In the mid-19th century almost half of France’s vineyards were destroyed in the great French wine blight.
The previously unknown phylloxera insect, an almost microscopic aphid-like creature, went on to decimate vines across Europe before spreading to Australia, South Africa and elsewhere. It is long thought to have come from North America via steamships crossing the Atlantic.
Now, French and US scientists have identified the genome sequence that holds the secret of where the phylloxera originated and how it came to spread.
In a paper published in BMC Biology, the researchers say they compared the genetics of individual European phylloxera insects with those found in wild Vitis riparia vines along the upper Mississippi, once French territory.
The paper’s lead authors, Claude Rispe and Fabrice Legeai of the French National Research Institute for Agriculture Food and the Environment (INRAE), say the study identified the existence of a new family of 2,300 genes – the biggest identified to date – representing 10% of the entire phylloxera genome.
“These genes are believed to be essential to interactions between phylloxera and grapevines. They code for small secreted proteins, called ‘effectors’, which are thought to intervene in deactivating the basic defences of the plant,” the study states.
Researchers have identified Vitis riparia as the phylloxera’s original host and say it came to Europe from the upper midwest in the US – mainly Wisconsin and Illinois – though they are continuing their research along the Mississippi valley. The identified area was originally colonised by France, which held the territory until the mid-18th century when it became part of the US. The number of French settlers meant it retained important trading links with France.
While now controlled in Europe, the study says phylloxera is “ever present and little known”. In wild vines in its native US, it attacks the leaves but does not kill the plant. In cultivated vines previously planted in Europe, it attacks and damages the roots leaving the plants open to fungus and bacteria that eventually kill them.
Over a period of 15 years from when it was thought to have arrived in France via steamship in 1858 – it was first officially identified in the country in 1863 – it devastated vines and the French wine economy.
The problem was solved by grafting European vines on to wild American vine roots that had a resistance to the insect, but it took another 30 years for the French wine industry to recover. The grafting of European vines on to American roots is a process still used today, but phylloxera is still a threat especially in Australia, and there are fears that the North American rootstocks are losing their resistance to the pest.
Scientists are working on finding out what each gene does to establish how the insect affects and lives off a new host. This they hope will enable vineyards to fight the problem.
They say: “This new knowledge also serves to improve our understanding of biological invasions and their potentially disastrous consequences on agriculture and therefore on society and the economy.”