Identification ofColletotrichum siamensecausing litchi pepper spot disease in mainland China

Abstract

Litchi (Litchi chinensis) pepper spot disease results in black spotting symptoms on litchi fruits. This disease was first observed on litchi cultivar Guiwei, in Guangzhou, China, in 2009, and then found widespread in other litchi‐growing regions of China.Colletotrichumisolates were consistently recovered from typical black spot lesions of diseased fruits with frequency ranging from 83% to 100%. Three representativeColletotrichumisolates from Maoming, Guangzhou and Shenzhen were selected for identification and pathogenicity testing in the field. Based on morphology and phylogenetic analysis using the ribosomal internal transcribed spacer region (ITS), glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), calmodulin (CAL), actin (ACT), β‐tubulin (TUB2) and glutamine synthetase (GS) gene sequences, the three isolates were identified asC. siamense. In the pathogenicity experiments, typical symptoms appeared on the inoculated litchi fruits, including black spots and green patches around these black spots. These symptoms were consistent with the symptoms originally observed in the field.Colletotrichum siamensewas successfully reisolated from the typical black spot lesions of the inoculated litchi fruits. To the authors' knowledge, this is the first report on characterization ofC. siamenseas the causal agent of litchi pepper spot disease in mainland China by successful inoculation on fruits under field conditions.