Professor Carlo Leifert: "An important breakthrough"
Scientists at the University of Newcastle have discovered the variety does not need to be treated with fungicide to fight off the disease.
This could help organic farmers who see crops worth millions of pounds destroyed by blight every year.
The potatoes are thriving in a remote agricultural research station in Northumberland - which is nicknamed "The Purple Patch".
While plots with other potatoes are wilting under attack from the blight, the purple vegetable which hails from Hungary has suffered only a few small marks.
'Extremely promising'
Professor Carlo Leifert, from the University of Newcastle, said: "This is extremely promising for organic farmers and consumers.
"A potato which can be grown commercially without using chemicals would be an important breakthrough for the organic movement worldwide.
"The tiny lesions on the leaves are particularly encouraging because they show that the blight is present but not progressing.
"This suggests that the plants have a high level of durable resistance which is preventing the blight from reaching the potatoes underground.
"In England and all other countries, the supply of organically-grown potatoes does not meet demand from consumers because blight is so prevalent.
"It destroys crops worth millions of pounds each year and deters many farmers from growing potatoes because the risks are so high.
"That is why supermarkets have a very limited supply of organically-grown potatoes.
"There is little choice of variety and stocks frequently run out."
The potato trials at Close House research station, near the village of Heddon-on-the-Wall, are England's contribution to a £3.5m European Union research programme called Blight-Mop, in which many new varieties of potato are tested for blight control.
But, of course, the next big test for the potato is on the palate.
A source at the university said: "Some of the researchers have had a nibble and they said it tastes fine."