2006 Annual Report 4d.Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and WSU. Additional details of research can be found in the report for the parent project 5354-21000-002-00D, "Potato Variety Improvement Through Gene Transfer and Virological Studies (60%-301 and 40%-302)". This subordinate CRIS supports research of CRIS 5354-21220-008-00 entitled "Potato Variety Improvement through Gene Transfer and Virological Studies." This project is directed at screening for resistance to soil-borne pests and diseases common to the Columbia Basin. A disease called powdery scab, which despoils the tubers by inciting a scabrous type lesion on the tuber skin has emerged and during the last decade become widespread in the Columbia Basin. It is caused by the fungus Spongospora subterranea. The fungus propagates itself on the roots forming galls that consist of cystosori or collections of spores. These can be stored indefinitely in the soil or under the right conditions reproduction occurs rapidly. Inoculum can also be produced from the lesions which have spore generating capacity. Powdery scab occurs most intensively in well-water or over-watered fields in relatively cool temperatures (approximately 50 F). After three years of testing in Washington and Idaho sites (six tests) we have identified germplasm that appears to have substantial root galling resistance. These lines appear to be stably resistant over years and environments. A quantitative PCR test identifies and quantifies Spongospora DNA uniquely. Generally russet skin germplasm shows little or no lesion formation. Hence the focus on root galling is directed at remedy of the reduction of total yield and tuber size reduction due suppression of root development. The latter effect can impact prices which are highly sensitive to percentage of certain tuber sizes. A second organism of great concern for the Columbia Basin is the Black Dot organism (Colletotricum coccodes). It is associated with shortening the vegetative period. During the course of Spongospora screening we noted that some germplasm also showed resistance to black dot. We have found that development of plant disease is correlated with detectability at greater distance in stems from the soil level. Hence work continues to refine screening in the filed and greenhouse. Columbia root-knot nematode (M. chitwoodi) is a costly pest to control in the Columbia Basin. Resistance to this is controlled by a single gene. Nematode testing is quite laborious and subject to erratic results in the field and in pots. We have identified DNA fragments closely linked to the resistance gene that are derived from sequence close to the virus resistance N gene of tobacco. We have found several Sequence Tagged Sites primer sets that identify resistant segregants 100% of the time (i.e., without recombination). The test is a simple one only requiring amplification in PCR reaction and gel separation to identify.