Abstract:
Potato is an economically important crop among vegetables grown in Sri Lanka that mainly relies on
healthy seed potatoes. About 40% of the annual seed potato requirement is fulfilled by the import of
seed potatoes from Netherland, USA, Germany and France. Import of seed potatoes makes possibilities
to enter plant pathogenic pests and diseases to Sri Lanka. Bacterial wilt is one of the most destructive
diseases of potato. Ralstonia solanacearum, which causes bacterial wilt of potato, is considered as an
important quarantine significant plant pathogen in Sri Lanka. The currently available conventional
methods such as culture methods, biochemical methods are time consuming, very laborious and not
sensitive for the detection of R. solanacearum in imported seed potatoes. Although immunodiagnostic
methods are rapid, the sensitivity is not enough to detect the bacterium in asymptomatic or latently
infected seed potatoes. In this study, a DNA-based detection method was applied to screen seed
potatoes imported into Sri Lanka and 5 out of 30 tested samples (17%) were positive for R.
solanacearum. The seed potato samples detected as infected with R. solanacearum were further studied
and it revealed that the Asian phylotype I and the American phylotype II were detected from seed potato
samples imported to the country. Phylotype II (Race 3/biovar 2) was detected in seed potatoes imported
from USA and France and both phylotype I and phylotype II (Race 3/biovar 2) were detected in seed
potatoes imported from Netherland from where majority of seed potatoes are imported into the country.
The quarantine measures should be strictly followed to avoid the spread and establishment of phylotype
II, Race 3/biovar 2 strains within the country, as it is the extremely destructive potato pathogen which
have a restricted distribution in higher elevations of Sri Lanka. Further, the DNA-based method can be
used to identify the pathogen to avoid the introduction or entry of R. solanacearum into the country for
the betterment of potato cultivation in Sri Lanka
