Late blight resistant potatoes – a sustainable solution for disease control

Potato late blight is a devastating disease caused by an oomycete, Phytophthora infestans. It can result in 100% yield losses in unprotected potato and tomato plantations, and it is a major challenge for organic cultivation of these crops. In high-input agriculture, late blight control requires intensive chemical protection which increases the financial and environmental cost of potato and tomato production. A sustainable, alternative solution for disease control is growing late blight resistant cultivars. The goals of this work were to: i) find new sources of resistance to late blight among wild potato relatives, ii) introduce new late blight resistance (Rpi) genes in potato breeding, and iii) investigate distribution and diversity of Rpi genes among existing potato cultivars. Using Diversity Array Technology, detached leaflet infection assays and genetic mapping, several Rpi genes have been discovered in wild potato relatives, including Rpi-phu1 from Solanum phureja, Rpi-rzc1 from S. ruiz-ceballosii and Rpi-mch1 from S. michoacanum. Through crossing at diploid level and marker-assisted selection (MAS), the Rpi-phu1 gene was pyramided with resistance of cv. Sárpo Mira, resulting in a new late blight resistant cultivar Gardena registered in Poland. MAS was also used to pyramid the Rpi-phu1 and Rpi-rzc1 genes in potato breeding lines.