Foliar resistance to the late blight pathogen Phytophthora infestans (Mont.) de Bary in a backcross of potato (Solanum tuberosum L.) cultivar Ando

Regardless of variable environmental conditions and changing pathogen populations, the Estonian potato cultivar (cv.) Ando has shown elevated field resistance to Phytophthora infestans for over 40 years. One of cv. Ando’s parents, the Latvian cultivar Agra, is considered a cultivar of medium to low resistance, the other parent, line 382-48, has a well-known source of resistance, Solanum demissum, in its pedigree. Segregation of late blight disease severity in a population of 95 hybrid plants from cv. Ando’s backcross to cv. Agra (cv. Ando x cv. Agra BC1) in field trials of three consecutive years (2013−2015) and in a test of a single pathogen isolate fits a model of additive action of multiple unlinked race-specific resistance genes responsible for the field resistance of cv. Ando. At least some of the resistance genes in cv. Ando’s genome do not function in juvenile plants and are developmentally upregulated.