Five new potato breeding lines are being tested by Agricultural Research Service (ARS) scientists and collaborators to resist powdery scab and black dot diseases, caused by the fungi Spongospora subterranea and Colletotrichum coccodes, respectively.
These fungi often occur together in the same soil, attacking the potato plant's roots, tubers or stems. Outbreaks can cause yield losses of up to 25 percent and prevent tubers from reaching the sizes needed by the french fry and fast-food industry. Of the two fungi, only black dot can be chemically controlled with fungicides; however, multiple applications are needed, ratcheting up production costs to prohibitive levels. A more sustainable alternative is genetic resistance, according to geneticist Chuck Brown, with the ARS Vegetable and Forage Crops Production Research Laboratory in Prosser, Wash.