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

Svante Resjö Iqra, Nam P Kieu, Muhammad Awais Zahid, Marit Lenman, Björn Andersson

 & Erik Andreasson

GM Crops & Food; Pages 263-271; Published online: 23 Mar 2025

ABSTRACT

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.

See https://www.tandfonline.com/doi/full/10.1080/21645698.2025.2479913?src=exp-la

Figure 1. (a) Visual assessment of transgenic lines (Rpi-amr3_5C, Rpi-amr1D_15A, Rpi-amr1D_15B) and Maris Piper (control) with late blight of potato. The x-axis indicates the days after planting. The recordings for the transgenic lines Rpi-amr3_5C, Rpi-amr1D_15A and Rpi-amr1D_15B are overlapping in the graph. The y-axis indicates the disease severity of late blight symptoms in percentage. (b) The area under disease progress curve (AUDPC) is shown for each genotype in field trial year 2018. The x-axis indicates the tested genotypes in three consecutive year. The y-axis indicates the mean values for disease progression curve. N = 2. (c) Minimum spanning network (MSN) of P. infestans using Bruvo’s distance for samples collected in 2018 in this field. MSN is based on 12 SSR markers and each circle represents a unique multilocus genotype. Branch thickness represents genetic relatedness. Circle size displays the number of samples of each MLG. Circles in red represent unidentified genotypes, while the circle in blue represents a genotype previously characterized by the Euroblight network (www.Euroblight.net).