Grad student’s find sheds light on disease spread

PULLMAN – Washington’s peppermint producers can make better informed decisions about what to plant and how to rotate their crops, thanks to a discovery by graduate student Jeremiah Dung. The state’s peppermint industry was valued at $36.6 million in 2009.
Dung, who is pursuing his Ph.D. in plant pathology, earned first place in a graduate student paper contest at the Pacific division of the American Phytopathological Society last summer for his work regarding a soil-borne fungus called Verticillium dahliae. He also presented his findings at the regional meeting.
The Pacific division is the largest in the APS and includes members from 13 states.
“Jeremiah’s research is increasing our understanding of the nature of resistance in mint to the Verticillium wilt pathogen and of the population dynamics of Verticillium dahliae,” said Dennis Johnson, Dung’s major professor. “Knowledge in both of these aspects is needed to economically manage diseases caused by this wide spread and destructive plant pathogen.”
Dung’s research began while he was on a class trip in July 2008 for a field plant pathology class taught by Gary Grove and Lindsey du Toit. He noticed that plants wilting and dying in an organic skullcap field looked similar to potato and mint crops suffering from a disease.
Skullcap is a native North American herb in the mint family that is grown commercially for its reputed medicinal properties.
Du Toit, assistant professor of plant pathology, worked with Dung and fellow doctoral student Emily Gatch to isolate Verticillium dahliae as the cause of what Dung observed in the skullcap field. The team determined it was the first report of Verticillum wilt affecting skullcap.
They also demonstrated that the pathogen can be carried in infected stems or seeds used for planting new fields.
In addition, Johnson demonstrated that fungus isolates collected from either skullcap or peppermint produced severe symptoms on both hosts.