Potato (Solanum tuberosum L.) cultivation is an important agricultural activity in the Andean region. The late blight Phytophthora infestans (Mont.) de Bary, considered one of the limiting diseases in production, represents a threat to food security and causes losses ranging from 30 to 100% of yield. This research evaluated the response to the disease in four commercial materials widely planted in the department of Narino. The evaluation was carried out under field conditions, in the municipality of Pasto, at AGROSAVIA's Obonuco research center, with natural inoculum, under a randomized complete block design with four replications. The response variables evaluated were incidence, severity, leaf area index and yield in the commercial categories. The ICA unica variety, reported as highly resistant in 2001, presented damage levels close to 75%, with a yield reduction of 49.88%, caused mainly by low yields of first category tubers, indicating a loss of its level of resistance, with damage levels similar to the highly susceptible control Diacol Capiro, which presented 100% of the area with symptoms of the disease and a reduction of 89% in yield. The genotypes Pastusa Suprema with disease tolerance characteristics and Superior showed the best performance with a severity level of 30% in each case and yield reductions of 30.5% and 40.92%, respectively. The results highlight the importance of these genotypes and their role as pillars in the integrated management of the disease through the planting of varieties with favorable behavior against the disease.
