The threat of emerging plant diseases has become more frequent as global warming and international trade are increasing. Blackleg and soft rot of potatoes caused by the group of bacteria in the family Pectobacteriaceae and the genera Dickeya and Pectobacterium are important diseases causing economic losses globally. In the European Union, they are regulated non-quarantine pests. Five species are commonly known to cause blackleg symptoms on potatoes indistinguishable from each other. For decades, P. atrosepticum has been the classic seed potato bacterial pathogen in cool temperate climates of Europe and North America, causing blackleg disease. However, recently several new species, unknown in Northern Europe, have emerged as virulent pathogens. One of these species is D. solani. In Finland, D. solani was first found in 2004 and has been the cause of major outbreaks of blackleg in Finland for more than a decade. Finland is one of the five countries in Europe (Germany, England, Ireland and the Azores Archipelago in Portugal) which are granted High-Grade status for seed potato production. The rationale of the High-Grade status is an obligation of applying stringent measures to keep the area clean from invasion by dangerous pests and pathogens of potatoes . Some of these measures include the controlled importation of seed potatoes to these areas, the use of high-class certified seeds for potato production in the zone and reducing the number of food potato fields (area) in the designated High-Grade localities.
The effective network and cooperation established between the Finnish seed potato importing and producing companies and those abroad exporting seed varieties to Finland played a vital regulatory system that helped to prevent the further spread of D. solani in Finland since generally free trade (import/export) is the main route of introduction of the blackleg Pectobacteriaceae to new territory.
Reference: Degefu, Y. (2024). Lesson from the emergence, spread and decline of Dickeya solani, the virulent potato blackleg and soft rot bacterial pathogen in Finland. Journal of Phytopathology, 172, e13282. https://doi.org/10.1111/jph.13282
