Morphological characterization and pathogenicity of Colletotrichum aenigma and C. siamense causing anthracnose on Euonymus japonicus in Beijing, China

Euonymus japonicus plays important roles in the process of urban landscape construction as an evergreen shrub. Anthracnose is an important limiting factor affecting the healthy growth of E. japonicus, seriously influencing improvement of urban landscape ecosystems. However, the Colletotrichum species associated with anthracnose on E. japonicus are unclear. In this study, diseased leaves of E. japonicus with typical anthracnose symptoms were collected in five nurseries in Beijing, China. Among 45 Colletotrichum isolates obtained, there were two distinct morphotypes, which were identified as C. aenigma or C. siamense by morphological characteristics and multilocus phylogenetic analysis. The growth rates of these two species were determined at different incubation temperatures, and the results showed that both species grew well at 10-35 degrees C, particularly at 25 or 30 degrees C, while C. aenigma isolates were adapted to high growth rates at a wider range of temperatures than C. siamense. Pathogenicity assays indicated that the two species showed varying degrees of pathogenicity on E. japonicus. Wounding was conducive to the pathogenicity of C. aenigma or C. siamense on E. japonicus either by inoculation with mycelial discs or conidial suspensions. This study presents the first report of C. aenigma causing anthracnose on E. japonicus worldwide and of C. siamense in north China causing anthracnose on E. japonicus. The morphological features of Colletotrichum spp. associated with anthracnose on E. japonicus were also compared in detail in this study. The findings provide a contribution to the prevention and control of anthracnose on E. japonicus by better understanding the species involved.

Automated summary

This study identified the Colletotrichum species causing anthracnose on Euonymus japonicus in Beijing, China. Two distinct species, C. aenigma and C. siamense, were found to have different growth characteristics and pathogenicity on E. japonicus. The study provides insights for the prevention and control of anthracnose on E. japonicus.