Potato Soft Rot Caused by Psychrotolerant Pseudomonas sp. from Subarctic Tundra Soil

Agricultural activities and the number of farms in the subarctic regions have been increasing annually after the coronavirus disease 2019 pandemic to achieve food self-sufficiency. Potatoes are vulnerable to soft rot bacteria at all stages of production, storage, and transportation. A novel bacterium, Pseudomonas sp. N3-W, isolated from Alaska tundra soil, grows at 5–25°C and produces extracellular protease(s). N3-W caused necrotic spots (hypersensitivity) in hot pepper leaves and soft rot disease (pathogenicity) in potato tubers. The psychrotolerant N3-W caused significant soft rot symptoms on potatoes at a broad temperature range (5°C, 15°C, and 25°C). In contrast, mesophilic Pectobacterium carotovorum KACC 16999 induced severe rotting symptoms in potatoes at their optimal growth temperature of 15°C and 25°C. However, it barely produced symptoms at 5°C, which is the appropriate storage and transportation temperature for potatoes. The results of pathogenicity testing imply that psychrotolerant soft rot pathogens from polar regions may cause severe soft rot not only during the crop growing season but also during storage and transportation. Our study indicates the possibility of new plant pathogen emergence and transmission due to the expansion of crop cultivation areas caused by permafrost thawing in response to recent polar warming.