Sensitivity to Tuber Necrosis Caused by Potato Mop-Top Virus in Advanced Potato (Solanum tuberosum L.) Breeding Selections

Potato mop-top virus (PMTV) is transmitted by the powdery scab pathogen (Spongospora subterranea f.sp. subterranea (Sss)) and no effective disease control methods are currently available for either pathogen. Eighty-one advanced breeding selections of potato (Solanum tuberosum L.) from different market classes and a broad genetic base were evaluated for sensitivity to PMTV-induced tuber necrosis in a field in North Dakota known to be infested with PMTV. Commercial cultivars, ranging from sensitive to tolerant in their reaction to PMTV-induced tuber necrosis incidence were included in each market class as internal controls. Results of tuber assessments revealed high variability in PMTV-induced tuber necrosis incidence and severity among selections. Based on PMTV-induced tuber necrosis incidence results over a two-year period, a total of 17 advanced selections were found to be tolerant, nine - moderately tolerant, eight - moderately sensitive, and six were found to be sensitive. The russet-skinned types had lower tuber necrosis incidence than the red-, white- and yellow-skinned types. Increases in the incidence of PMTV tuber necrosis during the storage period was influenced significantly by selection type and skin-color. Further studies are needed to investigate if tolerant selections are resistant to the virus to determine their suitability as parents in breeding programs to introduce PMTV resistance into commercial potato cultivars. In the short term, tolerant selections with other desirable agronomic characteristics could be released as commercial cultivars for growers to utilize as a means to limit the economic impact of PMTV-induced tuber necrosis.