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

3.6.2 Experiment 2 – Shanghai pak choyBoth repetitions of this trial were conducted using the saturated techniqueemployed in the second repetition of Experiment 1. There was no repetition or repetitionx treatment interaction, so the data for the two repetitions were combined for analysis andpresentation. Clubroot incidence and severity were high in each of the treatments. Therewas a main effect of pathotype, with P3 consistently producing more severe clubroot thanP6 (74% DSI vs. 51% DSI), as observed on canola in Experiment 1. There were two-wayinteractions (soil x pathotype, soil x biofungicide, and biofungicide x pathotype) and athree-way interaction (growth medium x pathotype x biofungicide) for both incidenceand severity (Table 3.5). However, the three-way interaction made up only a smallproportion of the total variance and there was no clear pattern of response betweenpathotype and the other two factors across the experiments, as observed on canola inExperiment 1 (Table 3.4). Therefore, subsequent analysis focused on the interaction ofgrowth medium and biofungicide.There was a growth medium x biofungicide interaction for clubroot incidence andseverity, in addition to main effects for each variable (Table 3.5). Clubroot incidence was100% in the positive control, except in soil-less mix, where incidence was 81%. Severityamong treatments ranged from 42–85% DSI (Fig. 3.3). In the positive control, clubrootwas severe in the muck, sand and mineral soil treatments, with a maximum of 85% DSIin the sand. Clubroot level was moderate to high (81% CI and 42% DSI) in the soil-lessmix (Fig. 3.3 and Appendix 4, Table A3.9).89