Background/Objective.

The cultivation of pitahaya (Selenicereus undatus) has expanded in recent years in Mexico. In 2023, symptoms of stem rot were observed in commercial pitahaya orchards in the state of Puebla. The objective was to characterize and identify the causal agent of stem rot, evaluate the pathogenicity of the causal agent in different pitahaya species as well as other plant species, and assess its in vitro sensitivity to commercial bactericide formulations.

Materials and Methods.

Ten rotten stems from Huitziltepec, Puebla, were analyzed. Tissue samples from each stem were disinfected and macerated in 500 µL of sterile distilled water; from there, 100 µL were seeded in Wilbrink's and King's B culture media. From the bacterial growth, strain CPHU23 was biochemically characterized and identified by multilocus sequence analysis (MLSA) and phylogenetic analysis of the rpoB, gyrB, leuS, and fusA genes. The pathogenicity of CPHU23 was evaluated by infiltration of 3 × 10⁸ CFU mL⁻¹ in five species of the genus Selenicereus:

S. ocamponis, S. purpusi, Selenicereus sp. “Golden,” Selenicereus sp. “Solferina” and S. undatus, as well as in Agave cupreata, A. angustifolia, Aloe vera, Allium cepa, Solanum lycopersicum, and Capsicum annuum. In vitro sensitivity was determined by the disk diffusion method with 10 commercial bactericide formulations.

Results.

Three bacterial morphotypes were isolated from the 10 stems. The CPHU23 morphotype was the most common, with yellow, round colonies with smooth edges and a mucoid appearance. Biochemical characterization of the CPHU23 strain showed 93% similarity to Pantoea vagans. MLSA analysis phylogenetically grouped the CPHU23 isolate within the Pantoea vagans clade, phylogenetically related to the type strains of P. vagans LMG 24199, YI-1, and MA I6050 with bootstrap support greater than 85%. Inoculation with P. vagans CPHU23 caused stem rot in the five species of the genus Selenicereus, in leaves of A. cupreata and A. vera, but not in bulbs of A. cepa and fruits of S. lycopersicum and C. annuum. Pantoea vagans CPHU23 was sensitive in vitro to copper oxychloride, gentamicin sulfate, oxytetracycline hydrochloride, and streptomycin, but resistant to kasugamycin.

Conclusion.

Pantoea vagans is the causal agent of stem rot in pitahaya in Puebla. All five pitahaya varieties are susceptible to stem rot. Agave cupreata and Aloe vera could be potential hosts for P. vagans. The use of copper oxychloride may be an efficient management strategy for P. vagans in pitahaya cultivation in Mexico.

        · resumen en Español     · texto en Español | Inglés     · Español ( pdf ) | Inglés ( pdf )