The first report of rot disease of onion occurred by Pseudomonas kitaguniensis, causing severe rot symptoms at lower temperatures.

Abstract In early spring of 2020–2022, rot symptoms were observed on onion growing in Iwate and Akita Prefectures. The symptoms exhibited water-soaking rot on leaves, or light brown soft rot on leaf sheaths and bulbs, bringing death of whole plants. From lesions, LOPAT group IVa bacteria were isolated. Based on pathogenicity, bacteriological properties, and sequences of 16S rRNA and housekeeping genes, isolates were identified as Pseudomonas kitaguniensis. This is the first report of bacterial rot of onion caused by P. kitaguniensis. P. kitaguniensis caused strong rot on onion bulbs at 15–25 ºC than 30 ºC, different from other closely related species.