Pathogenicity of Colletotrichum species isolated from rotten fruit and asymptomatic flowers of loquat in Nagasaki Prefecture, Japan and characterization of C. nagasakiense Takata & Kyoko Watan. sp. nov

Abstract

Species of Colletotrichum are common pathogens that cause loquat fruit rot in Nagasaki Prefecture, Japan. For clarifying the site of infection and the Colletotrichum species responsible for anthracnose in loquat trees, fungi were isolated from asymptomatic flowers and rotten fruits and identified to the species rank based on morphological and molecular phylogenetic analyses. Nineteen isolates from 148 rotten fruits were identified as C. fioriniae (12 isolates), C. nymphaeae (2 isolates), C. gloeosporioides s. s. (1 isolate), and four unidentified species of Colletotrichum. From 900 asymptomatic flowers, C. fioriniae (5 isolates), C. gloeosporioides s. s. (1 isolate), C. siamense (2 isolates), an unknown species (11 isolates) belonging to the C. acutatum species complex, and 2 were Colletotrichum spp. All isolates were pathogenic on wounded leaves and fruits. These results imply that C. fioriniae and C. gloeosporioides s. s. infect flowers and cause loquat fruit rot after maturation. However, the pathogenicity of the other species remains unclear as does the reason for the differences in the composition and proportions of fungal species in fruits and flowers. Eleven isolates obtained from asymptomatic flowers that also cause anthracnose disease in loquat were identified as a novel species of Colletotrichum, which was named C. nagasakiense sp. nov.