Screening for resistance to powdery scab disease of potatoes.

Abstract

Powdery scab disease of potatoes, caused by the fungus Spongospora subterranea, has developed as an important disease of potatoes in Victoria because of changes in agronomic practices, such as increased supplementary irrigation, earlier planting and increased use of the highly susceptible cultivar Kennebec. Different reactions to the disease between potato cultivars and breeding lines were found in trials on a commercial potato property and at a trial site inoculated with the causal organism. In the commercial field trial 96% of tubers of the cultivar Nooksack had no powdery scab compared with 1% of scab-free tubers for Kennebec. Of the 24 potato lines tested in the inoculated trial, two had more than half of their produce free of scab while Kennebec had 1.6% of produce in the scab-free category. Kennebec, the cultivar most commonly grown in Victoria, was the most susceptible cultivar tested in the inoculated trial. Results from these trials show the potential for selecting potato lines that are resistant to S. subterranea.