First report of <i>Lasiodiplodia pseudotheobromae</i> causing shoot blight on <i>Annona atemoya</i> in China

Sugar apple (Annona atemoya) is an important economic fruit crop and widely planted in Guangxi Province, China. In July 2024, shoot blight symptoms were observed in a plantation located in Chongzuo County, Guangxi, China(22°20′17.1″N, 106°47′19.1″E), affecting over 80% of plants across a 15 ha area. The disease predominantly targets tender shoots, characterized by browning, necrosis, or rotting of young buds and leaves. Subsequently, affected tissues desiccate and exhibit pronounced contraction. A total of eight symptomatic shoots were collected and typical lesions were cut into small pieces (5 × 5 mm), disinfected with 75% ethanol for 30 s and 0.1% HgCl₂ for 1 min, rinsed three times with sterile distilled water, and cultured on potato dextrose agar (PDA) at 28°C in the dark for 7 days. Ten isolates were obtained through single-spore isolation. Isolate FLZSK3 was selected as a representative for further analysis. Mycelia grew with an average rate of 4.02 cm/day. Hyphae were highly aerial and initially white and then turned dark gray. Subsequently, pycnidia formed and secreted black cirri on the PDA medium after 15 days. Immature conidia were hyaline, ellipsoid, and aseptate. Mature conidia were dark brown, one-septate, and exhibited longitudinal striations, and length × width of 20.6 to 31.8 × 10.7 to 16.4 μm (n = 50). FLZSK3 colony morphology was consistent with Lasiodiplodia pseudotheobromae (Phillips et al., 2013). For molecular identification, the internal transcribed spacer (ITS) region, translation elongation factor 1-alpha (TEF1-α), tubulin beta (TUB) and the second largest RNA polymerase subunit (RPB2) were amplified with the primers ITS1/ITS4 (White et al. 1990), EF1-688F/EF1-1251R primers (Alves et al. 2008), βT2a/βT2b (Glass and Donaldson, 1995) and RPB2-LasF/RPB2-LasR (CruywagenElsie et al. 2017). The resulting sequences were deposited in GenBank (ITS, PX410285; TEF1-α, PX422682; TUB, PX422684; RPB2, PX422683). The reconstructed maximum likelihood tree showed that the FLZSK3 clustered with the L. pseudotheobromae type strain CBS 116459. Pathogenicity tests were conducted on seven-year-old plants with healthy shoots (Annona atemoya). Five surface-sterilized and wounded shoots were inoculated with mycelial plugs (5 mm) from 2-day-old colonies. For the control, five shoots were inoculated using PDA agar plugs. All tested shoots were enclosed in plastic bags, and plants were maintained at 30°C and 80% relative humidity in a greenhouse. The pathogenicity test was performed three times. After 2 days, all inoculated shoots displayed blight symptoms resembling those observed in the plantation, whereas control shoots remained symptomless. The inoculated fungus was reisolated and confirmed as L. pseudotheobromae by morphological characteristics. L. pseudotheobromae is a well-known plant pathogen that infects a wide range of host species, including strawberry, Hylocereus spp., blueberry, citrus, and several other economically important plants (Zhang et al., 2024; Khadija et al., 2024). To our knowledge, this is the first report of L. pseudotheobromae causing shoot blight on Annona atemoya in China. This finding provides a foundation for future research on disease management and fungal biology.