Late blight field resistance in potatoes carrying Solanum americanum resistance genes (Rpi-amr3 and Rpi-amr1).

Potato (Solanum tuberosum L.) is an important global crop, but its production is severely impacted by late blight, caused by the pathogen Phytophthora infestans. The economic burden of this disease is significant, and current control strategies rely mainly on fungicides, which face increasing regulatory and environmental constraints. To address this challenge, potatoes with resistance genes from wild potato relatives offer a promising solution. This study evaluated field resistance to late blight in potato lines (Maris Piper) containing the Solanum americanum resistance genes Rpi-amr3 and Rpi-amr1 across three years (2018-2020) in Sweden. Field trials were conducted under natural infection conditions to assess disease resistance. Results showed that the transgenic lines conferred strong resistance to late blight compared to the susceptible control. However, slight late blight symptoms were observed in the transgenic lines. These results highlight the effectiveness of S. americanum resistance genes in providing strong resistance, and emphasize the potential of stacking multiple R genes, including these genes to maintain efficacy. This research supports the development of resistant potato varieties as a sustainable alternative to chemical control, promoting food security and environmentally friendly agriculture.