First report of Fusarium verticillioides causing Momordica charantia fruit rot in Mexico

In July 2025, about 35% of Momordica charantia fruits developed rot symptoms in a 5‑ha commercial field in Sinaloa, Mexico (24°15'45.1"N, 107°12'00.4"W). Affected fruits exhibited dark necrotic lesions, tissue softening, epidermal collapse, and progressive decay, leading to substantial losses in commercial quality. For pathogen isolation, 25 symptomatic fruits were randomly collected, and a 1‑mm² tissue fragment was excised from the lesions of each fruit. The fragments were surface disinfected with 1% NaClO, rinsed twice for 1‑min with sterile distilled water, dried on sterile paper, and incubated on potato dextrose agar (PDA) with streptomycin sulfate (0.3 g L⁻¹) at 28°C for 7 days, placing 5 fragments per Petri dish. From the 5 isolates generated (1 per dish), 2 representative isolates, FUSAME10CULIASIN and FUSAME4CULIASIN were selected for identification. Cultures developed a pink and cottony surface, with a light pink coloration and some reddish areas on the reverse. Microconidia were hyaline, oval to ellipsoidal, with 0-2 septa, and measured 5.0-13.0 × 2.0-4.8 µm (n = 40). Macroconidia were slightly curved, with 3-5 septa, and measured 25.0–62.0 × 3.1–5.0 µm (n = 40). Chlamydospores were not observed. Based on these characteristics, isolates were identified as Fusarium verticillioides (Leslie and Summerell 2006). PCR analysis was performed using the primer pairs ITS1/ITS4 and EF1‑728F/EF1‑986R to amplify ITS region and part of the EF1‑α gene, following White et al. (1990) and Carbone and Kohn (1999), respectively. Sequences were deposited in GenBank under accession no. PX671477 and PX671478 for the ITS region, and PX677383 and PX677384 for the EF‑1α gene, corresponding to isolates FUSAME10CULIASIN and FUSAME4CULIASIN, respectively. BLAST analyses showed that ITS sequences PX671477 and PX671478 shared 100% identity (417/417 bp and 406/406 bp, respectively) with the reported F. verticillioides isolate PP783464. Likewise, EF‑1α gene sequences PX677383 and PX677384 showed 99.64% (549/551 bp) and 99.47% (561/564 bp) identity, respectively, with isolate PQ557397. Neighbor‑joining analysis of EF1‑α sequences (1,000 bootstraps, MEGA 11) produced a well‑supported clade grouping the isolates within F. verticillioides. Pathogenicity of both isolates was evaluated on healthy-surface sterilized fruits. For each isolate, 15 fruits were inoculated. Three superficial wounds, spaced 5 cm apart, were made on each fruit, and a 4 mm PDA plug with mycelium from 5‑day‑old cultures was placed over each wound. Additionally, 15 fruits per isolate served as controls and received PDA plugs without inoculum. Two weeks after inoculation, all inoculated fruits developed symptoms identical to those observed in the field, whereas control fruits remained asymptomatic. The pathogen was successfully reisolated and identified as F. verticillioides from symptomatic tissues, fulfilling Koch’s postulates. This species is a globally distributed phytopathogen of major economic relevance, associated with diseases affecting roots, stems, and fruits. It has been reported causing fruit rot in several crops such as Cucumis sativus (Cruz‑Lachica et al. 2022) and Mangifera indica (Goudarzi et al. 2021). To the best of our knowledge, this study represents the first worldwide report of F. verticillioides causing fruit rot in M. charantia. This finding expands the known fruit infecting host range of the species and supports future research on M. charantia fruit rot.