Amorphophallus konjac anthracnose caused by Colletotrichum siamense in China.

AIMS: Amorphophallus konjac is an important commercial crop grown in China because it is the only plant species which is rich in glucomannan concentration. Recently, an outbreak of anthracnose (incidence ranging from 10-15%) was observed in a field survey conducted from June to August 2018. This study aims to identify the causal agent of A. konjac anthracnose. METHODS AND RESULTS: The pathogen was isolated on potato dextrose agar (PDA) medium. The fungal colony on PDA was greyish to dark grey. Conidia were falcate, one-celled and hyaline. Based on the micro-morphological and cultural characteristics, the pathogen was identified as Colletotrichum sp. blast search and phylogenetic analysis of the ITS, GAPDH, CHS1, ACT, CAL and TUB2 genes revealed the pathogen as Colletotrichum siamense. Koch's postulates were conducted on 2-month konjac leaves with conidial suspension. Development of typical anthracnose disease was recorded 5 days after inoculation and the pathogen's identity was confirmed by re-isolation and molecular identification. CONCLUSIONS: Amorphophallus konjac anthracnose was caused by C. siamense in China. SIGNIFICANCE AND IMPACT OF THE STUDY: Identification of causal agent of A. konjac anthracnose will be helpful in designing effective disease control strategies.