Potato cultivars ‘Desiree’, ‘Russet Burbank’ and ‘Shepody’ were maintained as tissue cultured plants (Tegg et al. 2008). Pathogenic Streptomyces scabiei isolates #32 and #20, were obtained from diseased potato tubers from NW Tasmania and maintained on ISP2 slopes (Tegg et al. 2008). For all experiments, 2-week-old potato plantlets were transplanted into the hydroponic system (maintained ALK inhibitor at 20–25°C), which utilized a nutrient film technique (NFT) with recirculated nutrient solution (Yang 2004; Fig. 1). Optimal nutrient solution parameters including

pH, Electrical Conductivity and pumping rate during plant establishment were consistent with those identified by Yang (2004). Plant development and growth were regularly monitored and tuber initiation was defined as when the stolon tip swelled to more than twice its usual diameter (Lapwood et al. 1970). Short stolons were removed to encourage subsequent stolon growth and tuberization and achieve

40–50 tubers of similar-age per bench (replicate). A preliminary experiment was established to test the ability of two inoculation techniques to induce disease in three potato varieties (Desiree, Russet Burbank, and Shepody) in the hydroponic growth system. Eighteen plantlets of each variety were established on 22nd February 2006. A few days prior to tuber inoculation, developing stolons and tubers were selected and positioned in Petri plates with dry matting underneath. Each plate contained 1–3 initiating buy Ulixertinib tubers and they were grouped to allow 10 tubers per treatment. Nutrient flow rate was reduced from 120 down to 60 ± 5 ml/min, for the duration of the experiment to induce drier conditions favourable for disease development. Inoculum was freshly prepared on each treatment day. Spores were harvested from six sporulating slopes of S. scabiei isolate #32 (2–3 weeks old) and suspended in 250 ml this website of distilled water. The spore suspension was thoroughly mixed and constantly agitated prior to application. Three sets of treatments were applied to individual groups

of ten tubers at 5 day intervals, 5, 10 and 15 days after tuber initiation (DAT) by two methods. The first applied the suspension as a fine spray mist with a hand held sprayer until tubers were fully wetted. The second method applied suspension directly to tubers as a droplet (100 μl) with a micropipette. Control treatments of water only were included at each inoculation date. Paper was placed around the treated tubers to prevent inoculum drift. Treated tubers were harvested at plant senescence and presence of any disease lesions noted. Following confirmation of the ability to achieve infection in hydroponically produced tubers, two main experiments were established to assess the period of susceptibility to infection of developing tubers. In these experiments, cv.