Emergence of bacterial soft rot in calla lily caused by Pectobacterium aroidearum in China.

Bacterial soft rot is a destructive disease affecting calla lily production, and it is mainly caused by Pectobacterium carotovorum (Pc). In 2019, this destructive disease was observed in the Shandong and Jiangsu Provinces of China and resulted in serious economic losses for commercial greenhouse producers of ornamental plants. The disease symptoms on leaves and stems were yellow and dark brown patches, and then water-soaked lesions that turned to wet rot occurred on the stems. In total, we obtained twenty-eight calla lily soft rot samples collected from Shandong and Jiangsu. Fifteen colonies on LB medium were milky white, nearly round, with a smooth surface and neat edges. The soft rot symptoms in calla lily caused by artificial inoculation were the same as the natural symptoms in the field. Based on the phenotypic properties determined by morphological, biochemical and physiological analyses, 16S ribosomal DNA gene sequence analysis, and multilocus sequence analysis, the pathogen was identified as P. aroidearum. In addition, all P. aroidearum strains exhibited high virulence and a wide host range on monocotyledonous and dicotyledonous plants. This study is the first official report of P. aroidearum causing calla lily soft rot in China, and the results contribute to a better understanding of the disease. • This is the first report of bacterial soft rot of calla lily caused by Pectobacterium aroidearum in China. • P. aroidearum strains exhibited high virulence to calla lily and fulfilled Koch's postulate. • P. aroidearum is a broad host range bacterial pathogen, which causes soft rot of monocotyledonous and dicotyledonous plants. • The identity of these isolates was molecularly confirmed by multilocus sequence analysis. [ABSTRACT FROM AUTHOR]