Field Response of Commercial Potato Genotypes to Globodera pallida Under Natural Infestation in Two Andean Environments of Southern Colombia

Potato cyst nematodes are persistent soilborne pathogens that constrain potato production in the Andean region. This study compared ten commercial potato genotypes under natural infestation by Globodera pallida in Pupiales and Ospina, Nariño, Colombia. A randomized complete block design with four blocks per location was used. Cyst and second-stage juvenile (J2) densities were assessed at 20, 60, and 120 days after planting (DAP), immature females attached to roots at 60, 90, and 120 DAP, and the reproduction factor (Rf) from final cyst density and the site-level initial population estimate. Each variable and sampling time was analyzed using a combined model including location, block nested within location, genotype, and location × genotype; Fisher’s protected least significant difference test was used following a significant genotype effect. Genotype effects on cyst and J2 densities were detected at 120 DAP, but not at 20 or 60 DAP. Betina had the lowest numerical final cyst density, final J2 density, and Rf in both locations, whereas Rubí had the highest final cyst density and Rf. The location × genotype interaction was not significant for final cyst or J2 density, but immature-female counts showed a more location- and time-dependent response. Previous morphological and molecular reports from Nariño, including Ospina and Pupiales, support attribution to G. pallida, although the experimental populations were not molecularly confirmed. Betina therefore represents a candidate with reduced observed host suitability under the evaluated conditions. Controlled assays with plot-specific initial populations and molecularly characterized nematodes, followed by additional locations and seasons, are required before confirming resistance or broad stability.