Pectobacterium spp. and Dickeya spp. cause Blackleg on potato worldwide (Charkowski, 2018). Potato plants (cv. Innovator V4 or Favorita) with blackleg symptoms (vascular browning of crown stems or curled leaves, Fig. S1) were observed in the field in Xilingol League, Inner Mongolia in 2018, and in Chengdu, Sichuan Province in 2020, in China. The disease incidence were around 10% and 20% in Xilingol League (20 ha) and Chengdu (40 ha), respectively. Diseased plants (5 from Xilingol League, and 2 from Chengdu) were collected to isolate the pathogen. Blackleg symptomatic stems were soaked in 75% ethanol for 2 min, rinsed and ground in sterile distilled water. Serial tenfold dilutions of the above solution were plated onto the crystal violet pectate agar (CVP) plate (Ge et al., 2018). Two to 3 days after incubation at 28°C, the bacterial colonies which digested pectin from the media and developed pit on CVP plates were purified and sequenced for identification using the universal 16S rRNA gene primer set 27F/1492R (Monciardini et al., 2002). Three colony sequences that showed more than 99% sequence identity to Pectobacterium polaris type strain NIBIO1392 (NR_159086.1) were submitted to the GenBank ( accession numbers: MT242579, MT242580, and MZ489432). Additionally, six housekeeping genes proA (MZ39581–MZ395583), gyrA (MZ395569–MZ395571), icdA (MZ395572–MZ39574), mdh (MZ395575–MZ395577), gapA (MZ395578– MZ395580), and rpoS (MZ39584–MZ395586) of these three isolates were amplified and sequenced (Ma et al., 2007, Waleron et al., 2008). All strains show 99% to 100% identity with Pectobacterium polaris strain NIBIO1392. Phylogenetic trees based on 16S rRNA gene sequences (Fig. S2) and concatenated sequences of the housekeeping genes (Fig. S3) of the 3 isolates were constructed using MEGA 6.0 software (Tamura et al., 2013). Koch’s postulate was performed on potato seedlings (cv. Favorita) by injecting 100 μl bacterial suspension (107 CFU/ml) or sterile phosphate-buffered solution into the crown area of the stems and kept at 80% humidity and 21°C for 2 days. Seven days after inoculation, the infected area of the inoculated seedlings rotten and turned black or even lodged, while the controls were symptomless (Fig. S4). It was observed that isolate MZ489432 from Chengdu, Sichuan Province was more virulent than the isolates from Xilingol League (Fig. S4). Bacterial colonies were reisolated from these symptomatic seedlings and identified using the same methods described above. Blackleg on potato plants has been reported to be caused by Pectobacterium atrosepticum, Pectobacterium carotovorum subsp. carotovorum, Pectobacterium carotovorum subsp. brasiliense, and Pectobacterium parmentieri in China (Zhao et al., 2018; Cao et al., 2021). To our knowledge, this is the first report of blackleg of potato caused by Pectobacterium polaris in China. We believe that this report will draw attention to the management of this pathogen in China.