First Report of Strawberry ( Fragaria × ananassa ) Fruit Rot Caused by Alternaria angustiovoidea in China

Strawberry (Fragaria × ananassa) is economically important in the global berry industry (Resende Filho et al. 2019). In January 2024, typical fruit rot symptoms were observed on diseased ‘Benihoppe’ strawberries from Golden Manor Agricultural Products Co., Ltd., Nanjing, China (31.74°N, 119.07°E). Diseased fruit exhibited small grayish-brown blurred-margin spots, which expanded into sunken brown regular-edged lesions and were finally covered with a dense grayish-brown mold layer. Lesion edge tissues were surface-sterilized by soaking in 75% ethanol for 30 seconds, rinsing three times with sterile water (30 seconds each time), dried with sterile filter paper, placed onto potato dextrose agar (PDA), and incubated at 28℃ for 7 days. Hyphal tips were subcultured 3 times to obtain uniform pure colonies, and the strain was named FA.010. Healthy, uniform strawberries were surface-sterilized with sterile water, and then air-dried. Surface-sterilized fruits were wounded (≤1 mm depth) on the equator, inoculated with 10 μL of 1×10⁶ spores/mL conidial suspension (n=10). Controls received sterile water. Inoculated fruit initially developed small gray-brown spots at the wounds, and lesions expanded slowly and eventually molds covered sunken lesions. No symptoms developed on the fruit in the control. The pathogen was re-isolated, fulfilling Koch’s postulates. The pathogenicity test was performed in three independent biological replicates. Morphological traits of FA.010 and the re-isolated strain were observed and compared with the classic taxonomic description of A. angustiovoidea (Zhang et al. 2025; Shu et al. 2019; Dhara et al. 2025). Colonies were circular, black-centered with gradually lighter margins, with a diameter of 53.87 ± 0.36 mm. Conidia were ovoid or elliptical, containing 1-4 septa, measuring 10.5 to 12 μm in length and 5 to 6.5 μm in width (n=50). Cryo-SEM showed uniformly linear hyphae with smooth conidia, which were typically ellipsoid-pyriform with obtuse bases. Conidial surfaces had fine verrucous protrusions and arranged in chains. All morphological traits of both strains matched the classic records of A. angustiovoidea. Molecular identification used ITS1/ITS4 (for ITS) (Sundaresan et al. 2019) and Alternaria-gapdh-F/R (for GAPDH) (Lawrence et al. 2013; Woudenberg et al. 2014) primers. Sequences were deposited in GenBank (PX473016, PX504214). The phylogenetic analysis included the ex-type strain of Alternaria angustiovoidea (CBS 195.86) for accurate species identification. Neighbor-joining trees (MEGA 11) confirmed the species: the ITS tree placed FA.010 with A. angustiovoidea CBS 195.86 (MH861939.1) and SP004 (OK447928.1), while the GAPDH tree grouped FA.010 into a well-supported clade with A. angustiovoidea D53 (PV130456.1), D59 (PV130455.1) and SP004 (OL754646.1). Combined morphological and molecular data identified FA.010 as Alternaria angustiovoidea. This disease is not limited to the Golden Manor Agricultural Products Co., Ltd.; it has not been reported elsewhere due to lack of targeted investigation. Alternaria angustiovoidea has been reported on Abelmoschus esculentus and apples. (Dhara et al. 2025; Elfar et al. 2018). To the best of our knowledge, this is the first report of its pathogenicity to strawberries, providing key data for disease management.