Calif. said source of global tree scourge

BERKELEY, Calif., Sept. 1 (UPI) -- Researchers say California is a prime suspect in a decades-long mystery of the source of a tree-killing fungus devastating six of the world's seven continents.

Genetic sleuthing by an international team of scientists has fingered the state as the source of the pathogen Seiridium cardinale, which causes cypress canker disease that in some parts of the world has killed as much as 95 percent of native trees in the cypress family, including junipers and some cedars.

S. cardinale was first identified in 1928 in California's San Joaquin Valley and has since made its way to Europe, Asia, New Zealand, Australia, South America and Africa.

"The fungus was likely introduced from California either into the South of France or in Central Italy 60 to 80 years ago, and that introduction resulted in a global pandemic that has devastated the region's iconic Italian cypress trees," Matteo Garbelotto, a professor of ecosystem sciences at the University of California, Berkeley, said in a university release Thursday.

The disease has left a swath of destruction throughout Southern Europe.

"Italian cypress trees are important to the ecosystem, but they are also considered the quintessential trees of the Mediterranean, the ones that dot the Tuscan countryside and that form the landscape of much of Greece, the South of France and Spain," said study lead author Gianni Della Rocca of the National Research Council in Florence, Italy. "It is difficult to put a price tag on the impact this pathogen has had. It's hard to imagine the Tuscan or Provence landscape without cypresses."

The researchers used modern DNA fingerprinting techniques to analyze diseased tree samples from seven Mediterranean countries, eight California counties, Chile and New Zealand.

The researchers found a variant of S. cardinale endemic to California is responsible for the epidemic of cypress canker in the Mediterranean, saying the fungi there all descended from a "founder" genotype that made its way to Europe.