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. KEYWORDS: Seed potato, Bacterial wilt, Ralstonia solanacearum, Quarantine pest, Rsol_fliC

Highlights

  • Bacterial wilt of potato is considered as one of the most destructive diseases of potato

  • The DNA-based detection method was applied to screen imported seed potato to get an idea about the probability of entrance of R. solanacearum into Sri Lanka through seed potatoes

  • Two tested seed potato samples imported in 2015/2016 season; and three tested samples imported in 2016/2017 season were found to be infected by the bacterium

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Summary

Introduction

Bacterial wilt of potato is considered as one of the most destructive diseases of potato. In Sri Lanka potato is considered as an economically important vegetable crop. Bacterial wilt caused by R. solanacearum is a major problem confronted by the potato farmers in Sri Lanka. According to the Plant Protection Act No 35 (Ministry of Agriculture, 1999), R. solanacearum is considered as a quarantine pest in Sri Lanka, since some of the strains of this species have not yet been reported, the existing strains have a restricted distribution (Bandara, 1983; Kelaniyangoda, 1995) and the disease is officially controlled in the country. Introduction of the unavailable strains of R. solanacearum into the country may cause major outbreaks of diseases in potato and in other crops in family Solanaceae and Musaceae, causing huge economic losses

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