Page 207 - PC2019 Program & Proceedings

PLANT CANADA 2019

S199. Assessment of fruit and foliage resistance to bacterial spot (Xanthomonas gardneri) in
commercial processing tomatoes (Solanum lycopersicum L)
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Simonton, T. ; C. Trueman ; D. Robinson ; C. Gillard ; K. Jordan
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1 University of Guelph, Ridgetown Campus
2 University of Guelph
Bacterial spot (Xanthomonas gardneri) is a major production issue in Ontario field tomatoes. The
traditional focus on breeding for host resistance is on foliar symptoms. To investigate anecdotal reports of
differences in foliar and fruit resistance, nine commercial cultivars were inoculated at the Ridgetown
Campus, University of Guelph at the vegetative (foliar experiment) or reproductive (fruit experiment)
stage from 2016-2018. In the foliar experiments, symptoms appeared in ‘CC337’ four days later than
‘TSH18’, but no differences were observed in growth room trials. The standardized area under the disease
progress curve for defoliation was 51 to 54% higher for ‘TSH18’ than ‘H9706’, ‘Hypeel 696’ and
‘H3406’, but equivalent to ‘CC337’. Fruit incidence was 49 and 47% lower for ‘CC337’ than ‘TSH18’
and ‘H9706’, but equivalent to ‘H3406’ and ‘Hypeel 696’. Fruit severity was 63 and 60% lower for
‘CC337’ than ‘H9706’ and ‘H3406’, respectively but equivalent to ‘TSH18’ and ‘Hypeel 696’. In the
fruit experiment, fruit incidence was equivalent among cultivars in randomly sampled fruit, while the
disease severity index for ‘H9706’ (3.4) was higher than ‘Hypeel 696’ (0.7). The observation that
‘H9706’ was less susceptible to defoliation than ‘TSH18’ but had equivalent fruit incidence and severity
to ‘TSH18’ suggests differences in resistance among plant organs. Mechanisms of fruit symptom
development require further investigation and fruit susceptibility should be considered in breeding
programs.

Tina Simonton (simontot@uoguelph.ca)

S200. Management of crown and root rot, caused by Fusarium oxysporum, and powdery mildew,
caused by Golovinomyces cichoracearum on Cannabis sativa
Scott, C. ; Z. Punja
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Simon Fraser University

Fusarium oxysporum, which causes crown rot, root rot and damping-off, and Golovinomyces
cichoracearum, which causes powdery mildew, can affect cannabis plants at all stages of growth,
reducing overall quality and yield. To investigate powdery mildew control, cuttings of a mildew-
susceptible strain ‘Copenhagen Kush’ were potted in a 75% coir, 25% perlite mix. They were incubated
for 14 days inside a humidity dome and then placed under two 54watt 6400K T5H0 lights with a 24 h
photoperiod. Natural inoculum of G. cichoracearum caused mildew development. Treatments included
Actinovate , MilStop , Neem oil, Regalia Maxx , Rhapsody ASO and ZeroTol . Plants, in groups of
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four, received weekly sprays and disease assessments over five weeks. Assessments of disease severity
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(percentage of leaf area infected) were converted to AUDPC values. MilStop and Regalia provided
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significantly (p<0.05) lower AUDPC values compared to the control. Rhapsody ASO, ZeroTol , Neem,
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and Actinovate were less effective but still had significantly lower AUDPC values than the control
(p<0.05). A group of eight plants was exposed daily for 3-5 sec to UV-C light from a CleanLight Pro unit
to test the effects on mildew development. Results showed a disease reduction of 45.2 %. For
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management of damping-off on cuttings caused by F. oxysporum, treatments including Rhapsody ASO,
Prestop , RootShield Plus WP, Regalia and Karanja oil are being evaluated in a hydroponic system.
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Experiments are currently in progress
Cameron Scott (cameron_scott_2@sfu.ca)
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