ARS | Publication request: Detection of powdery scab on hairy nightshades

Submitted to: Potato Progress
Publication Type: Popular Publication
Publication Acceptance Date: July 15, 2008
Publication Date: September 2, 2008
Citation: Nitzan, N., Hamlin, L., Batchelor, D., Boydston, R.A., Brown, C.R. 2008. Detection of powdery scab on hairy nightshades. Potato Progress. VIII (14) p.1-3.

Technical Abstract: During the 2002 and 2003 growing seasons, powdery scab like root galls were detected on roots of hairynightshades (Solanum physalifolim, formerly S. sarrachoides) grown in potato fields where populations of the powdery scab pathogen were high. At the end of the 2007 growing season, hairy nightshades bearing root galls (Fig.3) were collected. To determine if the root galls were the outcome of infection by the powdery scab pathogen, potato cultivars susceptible to the disease, and hairy nightshade plants were inoculated separately with galls originating from potato or hairy nightshades. The results of this preliminary study are summarized in Table 1, indicating that 2 of 8 hairy nightshade plants that were artificially inoculated with potato inoculum had root galls. One of 7 hairy nightshade plants that were inoculated with hairy nightshade inoculum had root galls; and 5 of 6 potato plants that were inoculated with potato inoculum had root galls. None of the potato plants (0 of 7) that were inoculated with hairy nightshades inoculum had root galls, Detection of the powdery scab pathogen with molecular, PCR-based methods indicated that the root galls collected in the field from hairy nightshades were the out come of infection by the powdery scab pathogen. The present preliminary study indicated that the powdery scab pathogen, Spongospora subterranea, can infect and produce root galls on hairy nightshades. Also, powdery scab inoculum from potato or hairy nightshades can re-infect and develop root galls on hairy nightshades, but probably not on potato. Trials testing the infectivity of inoculum from hairy nightshades to potato are currently in progress.