Hema Kasinathan Thesis May 1 2012.pdf - Atrium - University of ...

2.3 Materials and methods2.3.1 GeneralTwo companion studies on canola were conducted to assess clubroot developmentat the two infection phases of the pathogen lifecycle; i) infection and pathogendevelopment in root hairs were assessed in seedlings (root hair infection trial), and ii)secondary infection and symptom development were assessed in older plants (symptomdevelopment trial). The plants for both studies were seeded and transplanted on the sameday, and the environmental conditions, growth media, cultivar, pathogen source, andinoculation were identical between the two studies to facilitate comparisons between thestudies. Both studies were arranged in a split-plot design with two factors: temperature(main plot) and pH (subplot), and three replications. Both studies were repeated withslight modification.Air temperature was recorded in each growth cabinet using HOBO temperaturesensors (ProSeries Temp RH 2009 ONSET Computer Corporation, MA) to quantifyfluctuations. The recorded temperatures were generally close to the target temperatures(data not shown). Variation from the target temperature was less than 1°C, except in therepetition of the studies at 20°C, which had slightly higher mean temperature thantargeted (21.2°C). Therefore, the target temperatures were used in the regressionanalyses.2.3.2 Plant cultureSeeds of the clubroot-susceptible canola cv. 46A76 (Pioneer Hi-Bred, Chatham,ON, Canada) were sown in moist sand in Petri dishes at 20°C with 16-h photoperiod.36