Fall 2009

On Henry Mall

Blight Future

Gene sequence may offer new hints for combating plant pathogen.

As farmers and gardeners battled with an outbreak of late blight this summer, scientists were taking on the disease on another front: its genetics. An international team of researchers announced completion of the genome of Phytophthora infestans, the organism that causes the disease, potentially pointing to more effective ways to deal with the pathogen.

Best known as the cause of the 19th century crop failure that sparked the Irish Potato Famine, late blight remains a serious threat to potato and tomato crops. This summer’s outbreak—the first in Wisconsin since 2002—was contained quickly, but only after farmers spent time and money on treatments to ward off the disease.

The sequencing project found that the mold responsible for late blight contains almost four times as many genes as close relatives, which may be key to its lethal capacity. “This pathogen has an exquisite ability to adapt and change, and that’s what makes it so dangerous,” says Chad Nusbaum, an MIT scientist who led the study. Much of the extra material comprises repeated strings of DNA, allowing the pathogen to pick up and lose traits quickly, he says.

Helping unravel all of that DNA was David Schwartz, a UW-Madison professor of chemistry and genetics and the inventor of optical mapping sequencing technology. Optical mapping complements traditional, letter-by-letter sequencing by providing a broader view of how segments of DNA fit together in a full genome.

“We now have a comprehensive view of (the pathogen’s) genome, revealing the unusual properties that drive its remarkable adaptability,” says Nusbaum. “Hopefully, this knowledge can foster novel approaches to diagnose and respond to outbreaks.”

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