First report of bacterial soft rot of Konnyaku caused by Dickeya dadantii in China.
In 2011, there was a serious outbreak of Konnyaku (Amorphophallus rivieri) soft rot in Xuanwei District of Yunnan Province of China. The disease was characterized by partial or complete tuber rot. At its anaphase, the soft rot may move up the stem, causing the caudex to decay and the whole plant to collapse. If the stem is strong or big enough, the soft rot may develop on one side of the stem, leaving the other side healthy for several days. In this case, the stem does not collapse, and etiolation may be observed on the rotten tissue. In serious cases, up to 80% of the plants were infected. The disease is even more serious if Konnyaku is grown continuously in the same field for more than one year. At its worst, the disease can wipe out the whole crop. In 2012 and 2013, some 46 strains of bacteria were isolated from 60 Konnyaku tuber samples with soft rot symptoms from Xuanwei District. Based on morphological, biochemical, physiological, PCR assay and pathogenicity tests, the causal agent was identified as D. dadantii. This is thought to be the first report of Konnyaku soft rot caused by D. dadantii in China.