The aim of this study was to identify pathogenic isolates of Fusarium in fruits of yellow pitahaya affected by basal rot. Molecular characterization was performed on seventeen isolates associated with the disease, collected in yellow pitahaya producing areas of Valle del Cauca, Risaralda, Boyacá, and Cundinamarca in Colombia. PCR with primers ITS1 - ITS4 and TEF1α was used. The sequences of the PCR products were compared with the ones registered in National Center for Biotechnology Information (NCBI) and were aligned using Clustal W2 program, the phylogenetic relationships were built with MEGA6 program with the coefficient of maximum likelihood. The sequencing results for the markers showed that pathogenic isolates were F. oxysporum. Phylogenetic concept confirmed that basal rot of yellow pitahaya was caused by F. oxysporum. A species of Fusarium not reported in GenBank was also identified.

Keywords: phylogeny, rot of the fruit, etiology.