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Evaluation of chemical soil treatment and cultivar on the incidence of powdery scab and Potato mop-top virus in potato

Ana Cristina Fulladolsa: Colorado State University

<div><em>Potato mop-top virus</em> (PMTV) is a necrotic virus of potato and an emerging threat to North American potato production. The powdery scab pathogen <em>Spongospora subterranea</em> f. sp. <em>subterranea</em> (Sss) is the vector of PMTV and has been found in most potato producing regions of the U.S. Sss resting spores, which may harbor PMTV, survive in the soil for many years, even without potato. Neither Sss nor PMTV can be cultured in a laboratory in the absence of a plant host. As a result, there has been relatively little progress in understanding these pathogens and their interactions, and growers have few available management options. We evaluated the effects of two chemical soil treatments on the incidence and severity of Sss and PMTV in six potato cultivars, and on the reduction of Sss soil inoculum. We collected soil samples pre-planting and prior to harvest in each soil treatment block and quantified Sss resting spores using a real-time PCR assay. There was no significant difference of the treatments on the amount of Sss resting spores in the soil, indicating that the efficacy of the soil treatments was low. The variability among samples collected prior to harvest, within each soil treatment, was higher than among those collected pre-planting. This may be due to a differential response of the pathogen to the presence of its host or the cultivar planted in the sampling location. A 50-tuber sample per cultivar-treatment combination was collected at harvest and stored for 90 days at 55 °F. We will determine the incidence and severity of powdery scab on the tubers, and the incidence of PMTV. The information generated through this work will improve our understanding of Sss, its role as a vector of PMTV and will aid the development of improved management practices.</div>