Technical Abstract: Powdery scab is a serious disease of potato that is among the most damaging emerging potato pathogens throughout the world. Twenty years ago it was rarity in the Columbia Basin but today it is widespread, damaging and a threat to the profitability of the industry. Flagellated zoospores which swim in soil water constitute a part of the lifecycle. The resting spore, the cystosorus, is very durable, meaning that fields maintain inoculum for up to six years and survive passage through animal digestive tracts. Given good conditions, abundant soil moisture and temperatures at 11-18° C, zoospores from multiple cycles continue the infection process throughout the growing season. Unfortunately no soil or plant treatment has an economically beneficial effect on the level of damage. Although the fungus causes damage on the skin of certain varieties, (i.e., Shepody), the tubers of russeted skin varieties are seldom damaged. Damage is caused, however, by means of root suppression and yield loss in total tonnage and tonnage of large sized tubers. The fungus is also the vector for Potato Mop-Top Virus, a quarantine virus in the United States. Resistance to the fungus could raise the profitability of the potato crop. Over three years of testing at two locations a subsection of the powdery scab germplasm has proved to be durably resistance. The genetic source of resistance appears to be a breeding line, which now has been named Summit Russet, appearing in the ancestry of clones Summit Russet has the highest level of resistance to root galling that has been tested. In addition resistance to powdery scab has been found in pedigrees with Solanum hougasii in the background.