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

Stem-End Rot (SER) of mango is a devastating postharvest disease, often results in soft rot around the peduncle with consequent heavy losses in fruit yield and quality. On July 18, 2025, a total of 40 intact mango fruits (cv. Jinghuang) at the 70-80% ripening stage were collected from orchards in Xishuangbanna(21°08′N 101°50'), Yunnan Province, China and stored at room temperature (25-28℃). After 7 days, 28 fruits exhibited typical SER symptoms. Initially, small brown-black lesions appeared at the stem end and then rapidly spreaded through the pulp tissues. After disinfecting with 75% alcohol for 3 min and 3% NaClO for 30 s, rinsing with sterile water and air-drying, fruit tissues (0.5 × 0.5 cm) were excised from the edge of the lesions. These tissues were placed on potato dextrose agar (PDA) and incubated in the dark at 28°C for 7 days (Tovar-Pedraza et al.,2020). Pure cultures were obtained through single-spore isolation. Twenty-seven isolates exhibiting three distinct morphologies on PDA were preliminarily identified as Diaporthe hubeiensis (n=5), Botryosphaeria dothidea (n=14), and Neofusicoccum parvum (n=8) based on internal transcribed spacer (ITS) region sequences. Among them, D. hubeiensis, an uncommon SER pathogen, exhibited white, velvety mycelia with sparse aerial hyphae on PDA, the reverse of colony was dark brown to black. Within 15 to 30 days, clusters of gray-black pycnidia developed. Pycnidia contained α-conidia, 5.43-7.49×2.36-3.22 μm (n=30), aseptate, transparent, ellipsoidal to cylindrical, biguttulate, blunt at both ends. These characteristics corresponded to the original descriptions of D. hubeiensis (Manawasinghe et al.,2019). Following a preliminary pathogenicity test, the most virulent strain of D. hubeiensis, BNJH-2, was used for DNA-based identification. The ITS, tef1-α (translation elongation factor 1-alpha), CAL (calmodulin), HIS (histone), and β-TUB (beta-tubulin) gene sequences of BNJH-2 were amplified, sequenced and submitted to GenBank (ITS: PX464957, tef1-α: PX503229, CAL: PX503227, HIS: PX503228, β-TUB: PX503230). BNJH-2 clustered with the type strain D. hubeiensis JZB320123T (ITS: MK335809, tef1-α: MK523570, CAL:MK500235, β-TUB: MK500147) using maximum likelihood analysis by MEGA 7.0.21 (Norphanphoun et al.,2022). Based on morphological and molecular identification, BNJH-2 was definitively identified as D. hubeiensis. Fifteen healthy mango fruits (cv. San Nian ) inoculated with mycelial plugs were used to evaluate the pathogenicity by needle-inoculation following Feng et al. (Feng et al.,2023). Five mangoes mock-inoculated with sterile PDA plugs were used as controls. Mangoes were maintained at 28 °C and 90% ± 3% relative humidity, and the experiment was repeated three times. SER symptoms were observed 7 days post-inoculation on the treated group, whereas the controls remained asymptomatic. Strains re-isolated from symptomatic tissues were identified as D. hubeiensis based on morphology and DNA sequence fulfilling Koch's postulates. Previous studies indicate that D. hubeiensis infects citrus and grape (Manawasinghe et al.,2019, Yang et al.,2021), and that several Diaporthe species, such as D. pseudomangiferae, and D. pseudophoenicicola, are pathogens of mango SER (Lim et al.,2019, Benatar et al.,2023). To our knowledge, this is the first report of D. hubeiensis causing mango SER in China. This study provides scientific basis for developing targeted control measures for mango SER.