Background

Potato (Solanum tuberosum L.) is one of the most important non-cereal food crops in terms of food and nutritional value (Zhang et al., 2017). Late blight of potato caused by the oomycete pathogen P. infestans is one of the most devastating potato diseases in the world and is the most important yield-limiting factor in potato production (Haverkort et al., 2008 and 2016; Fisher et al., 2012). Breeding for late blight resistance is considered an important factor to fight against this disease. For this purpose, identification of novel sources of resistance in the available germplasm is a crucial step. Several testing methods such as field tests, whole plant assays, and detached leaf assays (DLA) have been developed. DLA provides increased infection and potato leaves showing more susceptibility to P. infestans than the field and whole plant assays (Stewart, 1990; Vleeshouwers et al., 1999; Vossen et al., 2016). Since the genotype of the host and pathogen are generally static in infection assays, observed differences in susceptibility among testing methods are likely due to variation in environmental conditions. DLA is suited for identification of qualitative resistance available in the germplasm which is typically a qualitative trait governed by a single or a few disease resistant (R) genes.