Ginger (Zingiber officinale Roscoe) is a crop of economic importance; its rhizomes are used medicinally and in Mexican cuisine. Puebla is the main producing state in Mexico, with Xicotepec as the top producing municipality (SIAP 2025). In September 2024, a random field sampling of 1000 plants over 300 000 m2 was conducted in San Pedro, Xicotepec (20°16'11.1"N, 97°55'52.4"W), Puebla, Mexico, where 150-day-old ginger plants exhibited basal stem, root, and rhizome rot, with 45% incidence and 50% severity in infected rhizomes. Symptoms included yellowing and general wilting of foliage, soft rot and constriction at the base of the stem, and root rot. Rhizomes showed necrosis, soft rot, and abundant brown mycelium. Tissues from 45 symptomatic rhizomes were cut into 5 mm pieces, sterilized with 3% sodium hypochlorite for one minute, rinsed with sterile distilled water, and plated on Petri dishes containing potato dextrose agar. The cultures were incubated in the dark for 7 days at 28 °C. Colonies resembling Rhizoctonia were consistently obtained, with one isolate per diseased rhizome obtained using the hyphal tip method. After 7 days, colonies formed abundant aerial mycelium, initially white, turning brown with age. Septate hyphae (n=50) measuring 4.6 to 7.8 µm in width were observed with right-angled branching and constrictions at the branch origin. Microscopic examination by Safranin-O staining showed two nuclei per cell in the 45 isolates. The morphological characteristics of the isolates resembled those of Ceratobasidium (Sneh et al. 1991). Two isolates were identified molecularly by genomic DNA extracted using the CTAB protocol (Dar et al. 2025) and amplification and sequencing of the internal transcriber spacer (ITS) region by primers ITS1/ITS4 (White et al. 1990; Zhou et al. 2017). Sequences of isolates CZo3 and CZo5 were deposited in GenBank (PV194990, PV197090). BLAST analysis of the partial ITS sequences (CZo3: 600 bp and CZo5: 600 bp) showed both isolates had 99.83% identity with Ceratobasidium sp. AG-R isolate (GenBank: KY880973) (Zhou et al. 2017). Phylogenetic analysis grouped isolates CZo3 and CZo5 within the AG-R clade of Ceratobasidium sp. Pathogenicity was confirmed by inoculating 20 detached healthy rhizomes from 150-day-old ginger plants cultivated in 8-inch pots with sterilized soil. A portion of mycelium from a 7-day-old isolate CZo3 was inserted into each rhizome at a depth of 5 mm using a colonized wooden toothpick. For controls, a sterile wooden toothpick was inserted into 10 healthy rhizomes (Terrones et al. 2023). The rhizomes were placed in a humidity chamber with 3 cm of water at the bottom and covered with a plastic sheet to maintain a 90% relative humidity to 28°C and darkness. After 11 days, the inoculated rhizomes showed necrosis and soft rot with abundant brown mycelium, while no symptoms were observed in the controls. The fungus was re-isolated from the inoculated rhizomes and characterized morphologically and molecularly, yielding identical results as previously described, and was identified as Ceratobasidium sp. AG-R, fulfilling Koch’s postulates. Pathogenicity tests were repeated three times. Ceratobasidium sp. has been reported to cause root rot and stem canker in Phaseolus vulgaris in Sinaloa, Mexico (Rabago et al. 2023). This is the first known report of Ceratobasidium sp. AG-R causing root, and rhizome rot in ginger in Mexico. This research is crucial for developing integrated management strategies for this disease.
Arenas et al. (Sat,) studied this question.