Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/10/2008
Publication Date: 1/27/2009
Citation: Driscoll, J., Coombs, J., Hammerschmidt, R., Kirk, W., Wanner, L.A., Douches, D. 2009. Greenhouse and Field Nursery Evaluation for Potato Common Scab Tolerance in a Tetraploid Population. American Journal of Potato Research. 86:96-101. Interpretive Summary: Common scab disease is a serious problem for potato growers, reducing the quality and market value of the crop. Hence, USDA is developing disease-resistant potato plants. Evaluating disease resistance in potatoes requires a good understanding of the genetics of resistance in potatoes and an accurate and reproducible test for resistance. In this study, common scab resistance was examined in a family of potato plants obtained by crossing parents different in their common scab resistance. The results of two years of field studies showed that resistance must be complex, with more plants susceptible than resistant. The most and least resistant plants from field studies were studied again in a greenhouse test, which gave similar results. This genetic and testing information will be used by breeders in developing disease-resistant potato varieties.
Technical Abstract: Potato common scab (Streptomyces scabies (Thaxt.) Waksman & Henrici) is a major disease of potato (Solanum tuberosum L.), due to the unmarketability of affected tubers. For identification of the most common scab-tolerant material, and for developing molecular markers for common scab tolerance, more information is needed on the genetic basis of common scab tolerance. Phenotyping common scab susceptibility is difficult because of the large variability in disease symptoms among tubers from a single plant, ranging from no common scab to severe pits. Two years of field data were collected for scab reaction on a segregating tetraploid population (MSL603, 160 individuals). Continuous variation in common scab susceptibility phenotype was observed among the progeny, with a normal distribution suggesting common scab disease phenotype is a genetically complex trait. Transgressive segregants were also observed, but they are skewed toward susceptibility. A greenhouse-based screening procedure was evaluated to discern tolerant from susceptible potato lines. A subset of ten individuals from this population were selected (five resistant, five susceptible). For the greenhouse study, soil was inoculated with a pathogenic S. scabies strain MSDPZ at a concentration of 3 X 108 CFU/ml. This greenhouse assay effectively discerned tolerant and susceptible individuals. There was a moderate correlation between the greenhouse study and the field trial. The greenhouse assay may provide information that would complement field data in identifying resistant clones.