First report of fruit rot on cranberry caused by <i>Neopestalotiopsis clavispora</i> in China

Cranberry (Vaccinium macrocarpon Ait.) is an economically important berry crop valued for its flavor and health benefits, widely processed into juice and dried products. Fuyuan City, Heilongjiang Province, has the largest cranberry cultivation base in Asia, covering 280 ha. In August 2025, fruit rot was observed on cranberry ‘Stevens’ at this base (47°25′30″N, 133°40′08″E), with approximately 20% fruit incidence. Symptoms began as small black spots that enlarged into rot lesions, leading to severe fruit decay and yield loss. Symptomatic fruit tissues (2 × 2 mm) from five fruits were surface sterilized in 5% NaClO and 75% ethanol, rinsed, and placed on potato dextrose agar (PDA) at 28°C for 5 days. Seven dominant fungal isolates with similar morphology were obtained via single spore purification (Liu et al. 2021). Colonies on PDA were white with cottony aerial mycelium at 7 days, and produced black acervular conidiomata by 10 days. Conidia were clavate to fusiform, four septate, 15.8–21.2 × 4.5–6.5 μm (n = 40), with three versicolored median cells and hyaline basal and apical cells. Each conidium had one basal appendage (4.5–5.5 μm) and three apical appendages (19.2–24.5 μm), matching Neopestalotiopsis spp. (Maharachchikumbura et al. 2012). Three representative isolates (MYM2, MYM3, MYM4) were sequenced for ITS, tef1-α, and tub2 using primers ITS1/ITS4, EF1-728F/EF1-986R, and Bt2a/Bt2b (Chaisiri et al. 2021). Sequences were deposited in GenBank (ITS: PX915794–PX915796; tef1-α: PX922708–PX922710; tub2: PX922711–PX922713). BLAST searches showed 99–100% identity with Neopestalotiopsis clavispora(GenBank: ITS: PV803238.1; tef1-α: PP957622.1; tub2: PV296041.1). Phylogenetic analysis using MEGA7 with the neighbor joining method confirmed placement within N. clavispora. Pathogenicity was tested on cranberry fruits with needle-pricked micro-wounds after 75% ethanol disinfection and spray inoculation. A conidial suspension (10⁶ spores/mL) was sprayed onto 15 detached fruits, while 15 control fruits received sterile water. Inoculated fruits were incubated at &gt;95% RH and 25°C for 48 h, then maintained at 25°C with a 12 h photoperiod for 5 days (Cao et al. 2019). Typical rot lesions developed on inoculated fruits within 5 days, whereas controls remained symptomless. The fungus was reisolated from symptomatic tissues and confirmed by morphology and molecular sequencing, fulfilling Koch’s postulates. Neopestalotiopsis clavispora is known to cause fruit rot on strawberry, blueberry, Syzygium cumini, and macadamia (Gilardi et al. 2019; Shi et al. 2022; Banerjee and Rana 2020; Qiu et al. 2020). To our knowledge, this is the first report of N. clavispora causing cranberry fruit rot globally. This study clarifies the pathogen of cranberry fruit rot in Fuyuan City. The results improve field disease diagnosis, and provide critical support for developing efficient management strategies to curb disease outbreaks and guarantee the sustainable development of the regional cranberry industry.