Identification and genomic characterization of <i>Sphingomonas parapaucimobilis</i> causing leaf edge wilt in Chinese cabbage

A new disease of Chinese cabbage that occurs in autumn was recently found. During the early stage of this disease, most leaves begin to exhibit parching from the leaf edge. As the disease worsens, the parched leaves spread inward from the leaf edge, causing most parts of the plant to dry up. Once this disease occurs, the yield of Chinese cabbage will be reduced, seriously threatening the production of Chinese cabbage and causing its quality to decline. Consequently, production costs increase, resulting in economic loss among crop growers. To date, no relevant literature has identified the pathogen of this disease. In the current study, a strain of pathogenic bacteria isolated from disease samples with bacterial wilt was preliminary identified as Sphingomonas sp. by using physiological and biochemical identification techniques. This strain is traditionally named YK209. Molecular identification of the YK209 strain was performed, and phylogenetic trees were drawn to analyze the phylogenetic relationships and evolution of this strain with other Sphingomonas species. Through bacterial genome sequencing, YK209 was identified as Sphingomonas parapaucimobilis, and its pathogenic mechanism was analyzed. A study on the physiological and biochemical characteristics and genetic diversity of the pathogen will provide a theoretical basis for the breeding of leaves that are resistant to leaf edge wilt, the search for resistance genes, the identification of the pathogenic mechanism of the pathogen, and ways to control this disease.