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Background: Bacterial ring rot of potato (Solanum tuberosum) caused by the gram- positive coryneform bacterium Clavibacter sepedonicus is an important quarantine dis-ease threatening the potato industry around the globe. Since its original description in 1906 in Germany, management of ring rot has been a major problem due to the seed-borne nature (via seed tubers not true seeds) of the pathogen allowing the bacterium to be transmitted long distances via infected tubers.Disease symptoms: On growing potato plants: interveinal chlorosis on leaflets leading to necrotic areas and systemic wilt. On infected tubers: vascular tissues become yel-lowish brown with a cheesy texture due to bacterial colonization and decay.Host range: Potato is the main host of the pathogen, but natural infection also occurs on eggplant, tomato, and sugar beet.Taxonomic status of the pathogen: Class: Actinobacteria; Order: Actinomycetales; Family: Microbacteriaceae; Genus: Clavibacter; Species: Clavibacter sepedonicus(Spieckermann and Kotthoff 1914) Li et al. 2018.Synonyms (nonpreferred scientific names): Aplanobacter sepedonicus; Bacterium sepe-donicum; Corynebacterium sepedonicum; Corynebacterium michiganense pv. sepedoni-cum; Clavibacter michiganensis subsp. sepedonicus.Microbiological properties: Gram- positive, club-shaped cells with creamy to yellowish-cream colonies for which the optimal growth temperature is 20–23°C.Distribution: Asia (China, Japan, Kazakhstan, Nepal, North Korea, Pakistan, South Korea, Uzbekistan, the Asian part of Russia), Europe (Belarus, Bulgaria, Czech Republic, Estonia, Finland, Georgia, Germany, Greece, Hungary, Latvia, Lithuania, Norway, Poland, Romania, European part of Russia, Slovakia, Spain, Sweden, Turkey, Ukraine), and North America (Canada, Mexico, USA).Phytosanitary categorization: CORBSE: EPPO A2 list no. 51. EU; Annex designation I/A2.

Soft rot Pectobacteriaceae (SRP) are ubiquitous on earth as there are records of findings from all continents where host plants are grown. This chapter describes information on soft rot diseases on these continents. For some countries, detailed information is provided by local experts on the SRP present, their economic damage, and the management strategies applied for their control. The focus of the chapter is mainly on SRP as causative agents of potato blackleg, although in specific cases details are provided on SRP in other host plants. In Europe, the SRP cause important economic losses mainly on potato, with most species described in the literature being found. In Latin America significant losses are also reported due to potato diseases caused by various Dickeya and Pectobacterium species, while in Australia and Oceania, recent outbreaks of D. dianthicola in potato have resulted in high economic losses. In Asia, however, SRP cause economic losses mainly in vegetable crops other than potato, while in North America SRP cause diseases on a wide range of crops (including potato and ornamental plants) in both field and storage. In Africa SRP are only known to occur in 17 of the 54 African countries but where it is known, potato is the most affected crop.