First report of Pseudomonas sp. as a new soft rot pathogen on sugar beet

Bacterial soft rots are among the most economically important diseases that cause significant yield losses in various crops. During 2022 and 2023, widespread occurrence of soft rot disease was observed in sugar beet fields in the Firuzan region, Hamedan Province, Iran. From the sugar beet plants with soft rot symptoms, a bacterial isolate was obtained that was obligately aerobic, negative for Gram, oxidase, levan, and arginine dihydrolase tests, and positive for pectinase, urease and hypersensitivity reaction on tobacco. Koch’s postulates confirmed its pathogenicity by developing soft rot symptoms in sugar beet plants. The 16SrRNA and rpoD sequences from this isolate were most closely related to Pseudomonas punonensis LMT03 with 99.8% and 94.7% identity, respectively and then to Pseudomonas argentinensis LMG22563 (= CH01) with 99.4% and 94.3% identity values. To our knowledge, this is the first report of a Pseudomonas sp. strain causing soft rot disease in sugar beet worldwide.