First Report of Mango Stem-end Rot caused by <i>Diaporthe garethjonesii</i> in Yunnan Province, China

Stem-End Rot (SER) is a postharvest disease of mango fruit causing heavy losses in storage. On August 16, 2025, 12 apparently healthy mango fruits (cv. SanNian) at 70‑80% maturity stage were harvested from an orchard in Xishuangbanna (21°08′N 101°50') and placed at room temperature (25-28℃). After 5-7 d, 8 fruits showed typical SER symptoms. Originally, small brown-black spots appeared around the peduncle of fruits, and then quickly expanded and merged. After sterilization with 75 % C2H6O for 3 min and 3% NaClO for 30 s, rinsing with sterile water and air-drying, fruit tissue pieces around 0.5 cm × 0.5 cm were aseptically cut from the lesion margins. Tissues pieces were placed on PDA plates and cultured in darkness at 28°C for 7 d (Tovar-Pedraza et al. 2020). Three isolates with similar morphology (BNSN-1, BNSN-2, and BNSN-3) were obtained via the single-spore isolation method, and the most virulent strain, BNSN-3, was used for further analysis after preliminary pathogenicity assays. Colonies covered the whole plate and appeared distinctive zonation appearance with irregular edges after 7 d incubation at 28 °C in the dark. The front of the colony was off-white to light grayish-white, while the reverse side was dark brown to grayish-brown with lighter periphery. Within 15 to 30 d, pycnidia appeared, growing in clusters, with a white-gray color and covered with velvety hyphae on the surface. Alpha conidia, 5.54~7.81×1.64~2.96 µm (n=30), were aseptate, transparent, glabrous, guttulate, fusiform to elliptical, tapering toward both ends, straight with obtuse apexes . Beta conidia, 19.05~29.41×1.37~1.98 µm (n=30) and less numeous than alpha conidia, were hyaline, smooth, straight, bent or hamular. These characteristics corresponded to the original descriptions of Diaporthe garethjonesii (Kytövuori 2016). The ITS (the internal transcribed spacer region), tef1-α (translation elongation factor 1-alpha), CAL (calmodulin), HIS (histone), and β-TUB (beta-tubulin) gene sequences of BNSN-3 were amplified, sequenced and submitted to GenBank (ITS: PX781187, tef1-α: PX789849, CAL: PX789851, HIS: PX789850, β-TUB: PX789852). BNSN-3 clustered with the type strain D. garethjonesii MFLUCC 120542aT (ITS: KT459423, tef1-α: KT459457, CAL: KT459470, β-TUB: KT459441) using maximum likelihood analysis by MEGA 7.0.21 (Norphanphoun et al. 2022). Based on morphological and molecular identification, BNSN-3 was definitively identified as D. garethjonesii. Pathogenicity assays were conducted on 15 healthy mango fruits (cv. Golek) by inoculating mycelial plugs onto needle-punctured wounds at the peduncle and equatorial regions according to Feng et al. (2023). Control fruits were treated identically, except that sterile PDA plugs were used instead of mycelial plugs. Three replicate fruits were used per each treatment and the experiment was performed three times. Typical SER symptoms appeared on inoculated mango fruits 7 days post-inoculation (dpi) after incubation at 28 ℃ and 95% ± 3% relative humidity, whereas the controls remained asymptomatic. The isolates obtained from symptomatic artificially inoculated fruits were identified as D. garethjonesii through ITS, tef1-α, CAL, HIS, and β-TUB gene sequencing, thus fulfilling Koch's postulates. To date, there is no reported case of plant disease including SER, induced by D. garethjonesii. This study extends the known host range of D. garethjonesii and is conducive to developing targeted control measures for mango SER.