Colletotrichum is the second most common pathogen that causes loquat fruit rot in Nagasaki prefecture, Japan. To clarify the anthracnose disease cycle in loquat trees, pathogens were isolated from collected asymptomatic flowers and rotten fruits. The isolates were identified at the species level based on morphological and molecular phylogenetic analyses. Nineteen isolates were obtained from 148 collected rotten fruits. The isolates were identified as C. fioriniae (12 isolates), C. nymphaeae (2 isolates), C. gloeosporioides (1 isolate), and four unidentified species. From 900 asymptomatic flowers, C. fioriniae (5 isolates), C. gloeosporioides (1 isolate), C. siamense (2 isolates), an unknown species (11 isolates) belonging to the acutatum species complex, and 2 were unidentified. All isolates exhibited pathogenic reactions to leaves and fruits. These results imply that C. fioriniae and C. gloeosporioides infect flowers and cause loquat fruit rot after maturation. However, those in other species remain unclear. We were unable to prove the reason for the differences in the composition of species in fruits and flowers and their proportions in this study. An isolate obtained from asymptomatic flowers that also cause anthracnose disease in loquat was identified as a novel species of Colletotrichum, and was named C. nagasakiense sp. nov.

No abstract

No abstract

Loquat fruit rot, caused by Pestalotiopsis sensu lato, is a key problem for loquat producers in Nagasaki Prefecture, the area with the highest loquat fruit production in Japan. In a previous study, it was postulated that fruit rot pathogens latently infect flowers, with the corresponding disease symptoms occurring in wounded fruits. To reveal whether the pathogens responsible for the development of fruit rot disease are found in the asymptomatic flowers and immature fruits of loquat trees, we sprayed a conidial suspension of nitrate-non-utilizing mutants, containing strains derived from pathogenic Neopestalotiopsis sp. (TAP18N004) and Pestalotiopsis sp. (TAP18N010), onto the flowers of “Mogi” and “Nagasaki-wase” trees. Both inoculated mutants were re-isolated using selective media (minimal media with chlorate) from the part of the asymptomatic immature fruit that includes the flower apex. Symptoms were observed in the mature fruits of both cultivars, and mutants were specifically detected in the symptomatic tissues of all rotted fruits. Additionally, all re-isolated mutants were reconfirmed by assessing corresponding nitrate auxotrophy characteristics. Consequently, it was revealed that both fruit rot pathogens that latently infect loquat flowers can cause fruit rot after maturation.