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Title: Hairy Nightshade is an Alternative Host of Spongospora subterranea, the Potato Powdery Scab Pathogen

item NITZAN, NADAV - Washington State University
item Boydston, Rick
item BATCHELOR, DALLAS - Con Agra Foods, Inc
item Crosslin, James
item HAMLIN, LAUNA - Washington State University
item Brown, Charles - Chuck

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2009
Publication Date: 6/3/2009
Citation: Nitzan, N., Boydston, R.A., Batchelor, D., Crosslin, J., Hamlin, L., Brown, C.R. 2009. Hairy Nightshade is an Alternative Host of Spongospora subterranea, the Potato Powdery Scab Pathogen. American Journal of Potato Research. 86:297-303. DOI 10.1007/s12230-009-9083-1

Interpretive Summary: Powdery scab is a disease of potato that causes scab like lesions on potato tubers. The disease is difficult to control with crop rotation and commonly used crop protection chemicals. Some commonly used potato varieties, such as Shepody, are susceptible to large losses from powdery scab. Hairy nightshade is the most common annual nightshade species in the Pacific Northwest potato producing region and is a close relative of potato. As such, hairy nightshade is often reported as a host of potato nematode and insect pests and pathogens. Powdery scab galls were found in problem fields on hairy nightshade plants. Potato and hairy nightshade plants inoculated with spores from galls on hairy nightshade roots were infected with the disease and were able to produce new galls, providing evidence that the disease can complete its life cycle on hairy nightshade. Hairy nightshade likely contributes to powdery scab persistence in problem fields. Control of hairy nightshade should be part of an integrated approach to suppressing powdery scab disease.

Technical Abstract: Root galls possibly caused by Spongospora subterranea were observed on hairy nightshade (Solanum sarrachoide; HNS). HNS galls and galls from potato were used to artificially inoculate potato and HNS. Eighty-three and 52% potato and HNS plants inoculated with potato inoculum had root galls, respectively. Ten and 31% potato and HNS plants inoculated with HNS inoculum had root galls, respectively. A S. subterranea-specific PCR significantly correlated (P < 0.0001, Phi Coefficient = 0.69) with visual assessment of gall incidence in 34 of 40 samples. Five of 40 samples had no galls, but gave positive PCRs. One of 40 samples had root galls, but gave a negative PCR. More sporosori were produced on potato than on HNS. Therefore, the root galls on HNS were caused by S. subterranea that is able to complete its life cycle on HNS and produce new generations of sporosori that are infectious on potato.