Characterization of a Potato Soft Rot Pseudomonas Strain and Its Potential Threat to Greenland Farmlands

Abstract

Rapid global warming is causing Arctic permafrost to melt, expanding arable land and potentially exposing dormant soilborne plant pathogens to crops. However, research on bacterial plant pathogens emerging from these newly available farmlands remains limited. In this study, Pseudomonas sp. strain G2-4, isolated from the rhizosphere soil of Oxyria digyna in Northern Greenland, was characterized as a potent soft rot pathogen capable of producing black pigment, though its role in pathogenicity remains unclear. G2-4 exhibited strong extracellular protease activity, demonstrated by the formation of clear zones on skim milk agar plates, but showed no cellulolytic and pectinolytic activities. This proteolytic activity suggests a potential mechanism for degrading plant cell wall-associated proteins (structural or signaling proteins), which might be the key mechanism in soft rot pathogenesis by G2-4. The strain induced bacterial soft rot on potato tubers across a temperature range of 5°C to 25°C, with maximal pathogenicity at 15°C. Antibiotic susceptibility testing revealed resistance to four antibiotics―ampicillin, cefotaxime, ciprofloxacin, and vancomycin―while the wellknown Korean soft rot pathogen Pectobacterium carotovorum KACC (Korean Agricultural Culture Collection) 16999 was resistant only to vancomycin. These findings underscore the importance of monitoring potentially harmful plant pathogens emerging from Arctic permafrost due to rapid soil warming.