infestans; the cultivars included in this study with their respective foliar and tuber ratings in parentheses were Jacqueline Lee [resistant (R), moderately resistant (MR); (Douches et al. 2001)] and Missaukee [R, intermediate (I); (Douches et al. 2010)]. Other cultivars used in this study were FL1879 [susceptible (S,S)], Russet Burbank

[moderately susceptible (MS),S], Red Norland find more (S,S) and Monticello (S,S) (Douches et al. 1997; Porter et al. 2004). Potato tubers were stored at 3°C in the dark at 90% relative humidity (RH) until used. Tubers were warmed to 15°C in incremental steps of 2°C for 7 days before inoculation. Tubers for the experiments were within the size grade range 50–150 mm diameter (any plane). Visual examination of a random sample of tubers from each entry for disease symptoms indicated that tubers were free from late blight. The samples were further tested with an ELISA immunodiagnostic for Phytophthora sp. (Alert Multiwell kit – Phytophthora sp. Neogen Corporation, Lansing, MI, USA) according to the manufacturer’s instructions; P. infestans was not detected in any of the see more tubers. Prior to inoculation, all tubers were washed with water to remove soil. The tubers were surface-disinfested by soaking in a 2% sodium hypochlorite solution for 30 min. Tubers were dried in a controlled environment chamber with continuous

airflow at 15°C in dry air (30% RH) for 4 h prior to inoculation. After inoculation, tubers were stored at 10°C and maintained for 30 days in the dark in a controlled environment chamber at 90% RH. Characteristics of the twelve different P. infestans isolates used in this study are summarized in Table 1. The selected Michigan

isolates were from the collection of W.W. Kirk (MSU, USA), US-8 and US-22 reference isolates were provided by Dr. W.E. Fry (Cornell University, USA), Colombian isolates were provided by Dr. Silvia Restrepo (LAMFU, Los Andes University, Colombia), and UK isolates were provided by Dr. David Cooke (The James Hutton Institute, Scotland, UK). For learn more lenticel infection experiment, isolates US-8F and Pi10-012 were selected due to their virulence on tuber tissue. The isolates were re-activated on inoculated leaf tissue and transferred into rye B media for 14 days in the dark at 18°C for sporangia production and transferred to the light for 2 days to encourage sporulation. Sporangia and mycelium were harvested by flooding with cold sterile water (4°C) and gentle scraping of the surface of the culture using a rubber policeman. The mycelium/sporangia suspension was stirred with a magnetic stirrer for 1 h. The suspension was strained through four layers of sterile cheesecloth, and the sporangia concentration was measured with a hemocytometer and adjusted to approximately 1 × 104 total sporangia/ml (discharged and non-discharged).