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 t's
no secret that Phytophthora infestans has long been a term of unremitting
dread to the Irish and their descendants since the days of the Great
Famine.
Phytophthora
what...?
Okay, the potato
blight. The disease that wiped out the potato crops that caused
the Great Famine, which killed over a million Irish peasants and
drove another million plus into exile. Phytophthora infestans has
long been considered the culprit, because until now genetic testing
relied on DNA from modern-day late-blight outbreaks, and scientists
assumed it was the same. Russia is suffering the worst attack, although
smaller blights continue to ravage Ireland, Mexico, Ecuador, and
the United States.
But according
to new DNA evidence published in last week's issue of Nature
— Phytophthora infestans wasn't the culprit in Ireland after all.
North Carolina State University plant pathologist Dr. Jean Beagle
Ristaino and her team analyzed the DNA of 150-year old Irish potato
leaves kept from the famine preserved in the British Royal Botanic
Gardens in Kew, England. "Our data emphasize the importance
of using actual historical specimens,". she said. Her study
is the first ever to isolate and analyze mitochondrial DNA from
historic specimens.
Ristaino expected
to find traces of the 1b haplotype, or strain, of late-blight Phytophthora
infestans. Instead, she found one of three other late-blight candidates.
No traces of Phytophthora infestans.
Why is this
important? After all, it's not like this is really going to change
the history books or make the Irish feel any better. (On the other
hand — some of the Irish Famine memorials built around the world
may need some touching up.)
Ristaino said,
"Identifying the geographic center of origin for late blight
is important, because that's where you're most likely to find host
resistance — potato plants that have developed natural resistance
to the pathogen — that can be used to breed new, more resistant
potato varieties for widespread use."
According to
her team's paper, the pathogen may have originated in South America
rather than Mexico where it was believed to originate. But Ristaino
concedes that much more research is needed before scientists can
be certain "...because the South American collections are not
as complete or well-studied as they should be."
Knowing how
the pathogen has spread, and how it has mutated or evolved over
the years, would be helpful, according to Ristaino, because it could
aid scientists in developing better control measures to prevent
future epidemics.
Doesn't it
figure? Not being able to stop the Famine from killing so many peasants,
some enterprising English scientists figured, "What the hell,
we may as well collect some of the deadly leaves for posterity."
And only now they turn out to be truly helpful!
That's the
luck of the Irish for you.
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