Occurrence, Characteristics, and qPCR-Based Identification of Causing Soft Rot of Chinese Cabbage in China.

is one of the most important genera of phytopathogenic bacteria. It can cause soft-rot diseases on a wide range of plant species across the world. In this study, three strains (KC01, KC02, and KC03) were isolated from soft-rotted Chinese cabbage in Beijing, China. These three strains were identified as based on phylogenetic analysis of 16S ribosomal RNA, , and 504 core genes, as well as a genomic average nucleotide identity analysis. Their biochemical characteristics were found to be similar to the type strain ICMP9168 but differed in response to citric acid, stachyose, D-glucuronic acid, dextrin, and N-acetyl-β-D-mannosamine. All of the tested strains showed different carbohydrate utilization abilities compared with and , particularly in their ability to utilize D-arabitol, L-rhamnose, and L-serine. Under laboratory conditions, the maceration ability of on Chinese cabbage was the highest at 28°C, compared with those at 13, 28, 23, and 33°C. Additionally, could infect all of the 17 known host plants, except for Welsh onion (). A SYBR Green quantitative PCR (qPCR) detection system was developed to distinguish from other soft-rot bacteria based on the combined performance of melting curve (with a single melting peak at around 85°C) and fluorescence curve (with cycle threshold <30) when the bacterial genomic DNA concentration was in the range of 10 pg/µl to 10 ng/µl. This study is the first to report the presence of on Chinese cabbage in China, as well as a specific and sensitive qPCR assay that can be used to quickly identify . The work contributes to a better understanding of and will facilitate the effective diagnosis of soft-rot disease, ultimately benefitting commercial crop production.