Role of Infected Seed Potato Tuber in Contamination of Land and Clean Potato Stocks with Common Scab

The objective of this study was to assess the role of scab-infected seed tubers in contamination of land and progeny of clean potato stock with common scab. The experiment was conducted over two consecutive years using the white-skinned cultivar ‘Diamant’ and the red-skinned ‘Pekaro’. They were planted in separate plots as contaminated and clean seed tubers, respectively, or mixed along the same ridge in an alternating pattern of contaminated and clean seed stocks of the two potato cultivars. In both seasons, scabby seed tubers produced significantly the highest infection levels in the progeny tubers (34% and 41.7%, respectively). In comparison with the clean control, the progeny of the clean stock in the mixed treatment developed significantly higher common scab (17.3% and 30.3% in the two seasons, respectively). The abundance of scab on progeny tubers was also significantly different between the various treatments and followed the same trends as above. The disease development was significantly greater on tubers harvested twelve weeks after planting compared to earlier harvest. Thus the seed-borne scab inoculum appeared to play a profound role in contamination of land and consequentially a significant infection of clean potato stocks.