根瘤蚜虫(2)

If correct, says Francois Delmotte, who works at INRAE's campus in Bordeaux and is one of the project's leaders, the finding fits with certain historical facts.
Though the Misisppi vlley was annexed from France by Britain and Spain in the mid- 18th century, and passed eventually to the United States, many French sttlers remained in the area and Franc New Orleans, for a long time.
Dr Delmotte says it would not be surprising if, in the 1gth. century age of steamships and naturalists, phylloxera survived on cuttings of V. riparia stored in a cool, dry hold to be brought to a botanical garden in France.
Or, even more ironicall, that it was imported with vines destined to cure their French cousins of an earlier imported blight powdery mildew The genetic diversity of European phylloxera is limited compared with that of its North American counterpart, says Dr Rispe.
That points to there having been only one or two introductions, with subsequent diffusion of the pest by people and their agricultural machines. However, another of the paper's authors, Astrid Forneck of the University of Natural Resources and Life Sciences in Vienna,
says it remains a possibility that a separate introduction infested eastern Europe, perhaps via the Austro-Hungarian empire's experimental vineyards at Klosterneuburg.
In America phylloxera attacks wild vines' leaves. It stimulates them to create galls in which it can live and feed, but which, from the plant's point of view, serve to isolate the problem. When it attacks cultivated vines, though, it goes for the roots.
These root galls open a plant to infection by bacteria and fungi, leading to its death. For a long time, researchers hunted for a single molecule, produced by the insect, that stimulated the growth of galls.
Blocking the action of this, they hoped, would phylloxera proof all vines. But here the sequencing project produced a disappointment. There is no such molecule. The researchers identified many genes-2,300 of them, more than a tenth of the that encode proteins which it secretes while feeding on the vine. These enable it to evade the plant's immune system while diverting resources from its host. The work now begins of teasing out what each of those genes does, and, ultimately, how phylloxera manipulates a plant and adapts to a new host.
This information may in turn generate new weapons against the creature. That could be valuable in parts of viticulture's New World, such as Australia, where vines remain ungrafted and phylloxera is still a problem.
It might also help if the insect ever evolves the ability to evade the natural resistance of American vine roots that currently stands between European growers and disaster. For Dr Forneck, this prospect is not outlandish.
The insect is already adapting to a warmer world, and shifting its range. Further shifs in its physiology are perfectly possible.