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ARS Home » Pacific West Area » Aberdeen, Idaho » Small Grains and Potato Germplasm Research » Research » Publications at this Location » Publication #410293
Research Project: Genetic Improvement of Potato for Sustainable Production and Enhanced Tuber Qualities for the Western United States

Location: Small Grains and Potato Germplasm Research

Title: Powdery scab of potato: a diagnostic guide

Author
item BALENDRES, MARK - De La Salle University
item WOODHALL, JAMES - University Of Idaho
item Whitworth, Jonathan
item CUMAGUN, CHRISTIAN J - University Of Idaho

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2024
Publication Date: 5/15/2024
Citation: Balendres, M.A., Woodhall, J., Whitworth, J.L., Cumagun, C. 2024. Powdery scab of potato: a diagnostic guide. Plant Health Progress. 1535-1025. https://doi.org/10.1094/PHP-11-23-0097-DG.
DOI: https://doi.org/10.1094/PHP-11-23-0097-DG

Interpretive Summary: Powdery scab is a disease in potato that is caused by the pathogen Spongospora subterranea. S. subterranea is a plasmodiophore that was previously classified as a fungus. The pathogen is soil born and long lived in the soil through spore balls (or sporosori). The resulting scab lesions on the tubers can make them unmarketable for eating and for use as seed potatoes. Detection of the pathogen is important as tuber symptoms are hard to distinguish from common scab, which is caused by the bacteria, Streptomyces scabiei, which is also soil born. The pathogen can also be infected with Potato mop-top virus which can cause internal dead tissue in tubers in the form of necrotic arcs known as spraing. This disease can also render tubers unmarketable. Diagnostic methods for detecting the pathogen are given as well as field sampling methods to allow for archiving and using the pathogen for further studies.

Technical Abstract: Powdery scab on potato is caused by the plasmodiophorid pathogen Spongospora subterranea f. sp. subterranea (Wallroth) Lagerheim, herein referred to as S. subterranea. The pathogen causes symptoms on tubers and roots of potato, its primary host plant. The economic impact of S. subterranea scab lesions on potato tubers rendering them unmarketable for eating or seed. S. subterranea is a vector of Potato mop-top virus (PMTV). PMTV is the causal agent of spraing in potato tubers which is discolored rings or arcs in the tuber flesh further reducing marketability. Powdery scab tuber symptoms start as small, purple-brown, pimple-like swellings, which increase and rupture the tuber periderm upon maturity. Powdery scab symptoms may be confused with common scab (caused by Streptomyces scabiei ) and potato wart (caused by Synchytrium endobioticum). Root galling is the result of the rapid proliferation of sporosori in the pathogen’s life cycle. Galls are produced on root hairs and root epidermis. Spongospora subterranea has been reported on every continent and is considered to have a worldwide distribution wherever potatoes are grown. Information on pathogen detection by visual and microscopy, plant-baiting or bioassay, serology, and molecular approaches is given. Field sampling strategies and preparation of infested soil samples is given for preservation of the pathogen for future study and inoculations.