ABSTRACT
An enrichment enzyme-linked immunosorbent assay (ELISA) using monoclonal antibody 4F6, which is specific for the lipopolysaccharide antigen of serogroup I strains of Erwinia carotovora subsp. atroseptica, was used to detect the blackleg pathogen in potato seed lots after having confirmed that this serogroup is still the predominant strain of the pathogen in Canada. E. carotovora subsp. atroseptica was detected on <6% of tubers in most seed lots, but the level of tuber contamination increased with the number of field generations. The incidence of E. carotovora subsp. atroseptica was generally greater in tissue taken from the stolon end of tubers than from peel samples, although there was a positive correlation between the bacterium's presence in the two sample types. The incidence of E. carotovora subsp. atroseptica in seed tuber lots was estimated from the results of tests on multiple composite samples, providing a cost effective approach for indexing seed lots for blackleg risk. The incidence of E. carotovora subsp. atroseptica was two and three times greater for both stolon end and peel samples, respectively, after harvest and storage of seed lots compared with tubers hand dug just before commercial harvesting, which suggests that the process whereby tubers become contaminated has both field and postharvest components.
