Identification, pathogenic mechanism and control of Aspergillus aculeatus causing postharvest fruit rot in Longan

Longan (Dimocarpus longan Lour) fruit rot is a severe post-harvest disease that significantly hampers the development of longan trade. In 2023, this disease was observed in Guangdong, China, with an incidence rate of approximately 25 %. Morphological and molecular identification confirmed it as Aspergillus aculeatus. To our knowledge, this is the first report of A. aculeatus causing longan fruit rot. The isolated strains maintained high pathogenicity. Infection by A. aculeatus increased the activities of polygalacturonase (PG), pectinase (PE), cellulase (CL), and β-galactosidase (β-Gal) in longan, accelerating the breakdown of cell wall materials (cell wall material, hemicellulose, cellulose, and pectin). This degradation leads to fruit decay, which is the primary cause of longan rot associated with this pathogen. A. aculeatus showed the highest sensitivity to fludioxonil, with an EC₅₀ value of 0.0170 ± 0.0006 µg/mL, and demonstrated good control efficacy in vivo (over 75 %). Therefore, fludioxonil is recommended as an effective fungicide for the management of A. aculeatus. In the future, effective resistance management should be implemented by rotating fungicides with distinct modes of action to mitigate resistance emergence and ensure the sustainable development of the fruit industry. This study provides a theoretical basis for the control of longan fruit rot.