|Marshall-Farrar, K - UNIVERSITY OF WI|
|MCGRATH, J MITCHELL|
|James, R - UNIVERSITY OF WI|
|Steverson, W - UNIVERSITY OF WI|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 27, 1997
Publication Date: N/A
Interpretive Summary: Late blight is one of the most devastating diseases of potato and was a major cause of the Irish potato famine in the last century. In the United States, late blight has occasionally been a problem but careful cultural practices and the use of a very effective fungicide has kept blight in check. In 1994, these measures failed and many growers were severely impacted. Characterization of the late blight fungus isolated in 1994 using fungicide sensitivity tests, protein markers and genetic crosses showed that it was a strain not seen before in Wisconsin. The new strain was shown to be resistant to the fungicide normally applied for late blight control. Recognition of this new strain allowed alternative control measures to be developed which limited the economic impact of late blight disease in 1995.
Technical Abstract: Late blight of potato (Solanum tuberosum), caused by Phytophthora infestans, recently reappeared in Wisconsin and was a significant production problem in 1994. P infestans isolates colleted in Wisconsin from 1993 to 1995 were characterized for the following traits: mating type, sensitivity to metalaxyl, and allozyme genotype for Glucose-6- phosphate isomerase (Gpi). Characterization of these isolates revealed that a new, more aggressive population (A2 mating type, metalaxyl resistant, and Gpi genotype 100/111/122) is displacing the old population (A1 mating type, metalaxyl sensitive, and Gpi genotype 86/100) in Wisconsin.