Assessment of Resistance to Late Blight (Phytophthora infestans (Mont.) de Bary) in Chilean Native Potatoes (Solanum tuberosum Chilotanum group)

Phytophthora infestans (Mont.) de Bary is a highly destructive oomycete in potato crops, and managing its impact is crucial. Host plant resistance plays a pivotal role in disease management. This study aimed to evaluate the resistance to late blight in nine preselected Chilean native potato genotypes through field and laboratory experiments, comparing them with the moderately susceptible control cultivar Désirée. The field trial spanned two seasons (2017/2018 and 2018/2019) at the same location in Southern Chile. Foliar damage percentage caused by natural infection was measured, and the relative area under the disease progress curve (rAUDPC) was calculated. The laboratory experiments included a detached leaflet assay and a tuber assay in 2019. The results indicated that seven genotypes, Azul (0.10), SN-1 (0.10), Chilca-1 (0.11), Azul Casposa (0.07), Corahila Reina (0.16), Piku (0.17) and Murta (0.24), exhibited partial resistance with significantly lower rAUDPC values than the control cultivar across both seasons. Moreover, the detached leaflets assay in 2019 highlighted four genotypes with substantially lower damage percentages: Azul Casposa (0.11%), Chilca-1 (0.64%), Piku (1.11%) and SN-1 (3.16%). The tuber assay conducted in 2019 revealed that five of the foliar-resistant genotypes, Azul (43.98%), SN-1 (38.06%), Chilca-1 (41.54%), Corahila Reina (45.5%) and Murta (39.11%), exhibited low to medium resistance also in tubers. This study successfully identified favourable variation for Phytophthora infestans resistance, indicating the potential suitability of given Chilean native potato germplasm as donors in potato breeding programs.