Page 223 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

for optimized uses of resistant canola cultivars, and this Avr profiling for each crop district will aid in
regional recommendations for cultivars carrying effective R genes, as well as in the selection of new R
genes for blackleg resistance breeding.

[P39] EFFECT OF DIFFERENT SOILLESS MIXES ON DEVELOPMENT OF CLUBROOT
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(PLASMODIOPHORA BRASSICAE). Komathy Prapagar , Shauna Chesney , Bruce D. Gossen , Merek
Wigness , and Mary Ruth McDonald 1. 1 Department of Plant Agriculture, University of Guelph, Guelph, ON
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N1G 2W1, Canada; and Agriculture and Agri-Food Canada, Saskatoon Research and Development
Centre, Saskatoon, SK S7N 0X2, Canada
Correspondence to: kprapaga@uoguelph.ca

Clubroot, caused by the soil-borne pathogen Plasmodiophora brassicae, can result in severe damage on
canola (Brassica napus) and Brassica vegetables. Controlled environment studies are often part of
research on the biology of P. brassicae. Occasionally no disease develops, even when viable inoculum is
applied to a susceptible crop under optimum conditions for infection. A growth room study was conducted
to assess the effect of two soilless mixtures on clubroot symptom development in canola. The growth
room was set to 24°/21°C day/night cycle, 17-hour photoperiod and 50% humidity. The soilless mixes
(Sunshine mix L4A from Sungro and BM6 HP from Berger) were assessed at three levels of inoculum
concentration (0, 1x10 , 1x10 spores/mL) and two levels of moisture (wet or dry mix), which had
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previously been shown to affect compaction of soilless mix. The experimental design was a three-way
factorial in a complete block design with four replicates and 10 plants per experimental unit. The
experiment was repeated. Seven and 12 days after seeding, the plants were inoculated with 5 mL of
resting spores of pathotype 2. Roots were assessed for clubroot symptoms 6 weeks after inoculation and
assigned to classes using a standard 0–3 scale where: 0 = no clubbing and 3 = clubs on > 2/3 of the root;
a disease severity index was calculated. Fresh and dry weights of above-ground plant material were also
assessed at 6 weeks. Severe clubroot developed in L4A mix at both inoculum concentrations, but there
was little to no clubroot in BM6 and none in the non-inoculated control. Soil moisture at the time of
compaction had no effect on any variable. Inoculation reduced plant fresh and dry weight; dry weight was
lower on plants in LA4 soilless mix treatments than in the BM6, associated with higher clubroot severity.
Sunshine LA4 mix is recommended for clubroot research. The reason for the variation in clubroot severity
in the mixes is not known but could be related to characteristics of the peat moss or the surfactant
component of the soilless mix.

*[P40] BEAUVERIA BASSIANA: A PROMISING FUNGAL ENDOPHYTE AGAINST CLUBROOT ON
CABBAGE 2023. Kelly Ruigrok , B. D. Gossen , and M. R. McDonald . Department of Plant Agriculture,
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University of Guelph, 50 Stone Road E, Guelph, ON; and Saskatoon Research and Development
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Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2 Canada
Correspondence to: kruigrok@uoguelph.ca

Clubroot, caused by the soil-borne chromist Plasmodiophora brassicae Wor., is a constraint to production
of brassica crops worldwide. Host resistance is generally not durable and management options are
limited. The fungus Beauveria bassiana (Balsamo) Vuillemin is a well-known entomopathogen; several
commercial formulations are available for management of insect pests. Beauveria bassiana is also
reported to be endophytic, with beneficial effects on disease resistance and plant growth. A growth room
study was conducted to assess its effect on cabbage transplants inoculated with P. brassica. The
clubroot-susceptible cabbage (Brassica oleracea L.) cv. Bronco was seeded in plug trays. At the
cotyledon stage, one Beauveria product (BioCeres @ 10 mL/L or Botanigard @ 8 mL/L) was applied as a
foliar drench at 500 mL per tray. The hypothesis was that early application would maximize root
colonization prior to inoculation of P . brassicae, mimicking cabbage seedlings being transplanted into an
infested field. Plants were transplanted into pots 6 weeks after seeding and inoculated with 5 mL per
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seedling of resting spore suspension at 1 x10 , 10 or 10 spores of P . brassicae per mL. The study was
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laid out in a randomized complete block design with four replicates; controls with no B. bassiana or no P.
brassicae were included. Clubroot severity was assessed at 6 weeks after inoculation with P. brassicae.
Severity in the absence of B. bassiana was 23, 58 and 87 DSI (disease severity index) for plants
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inoculated with 10 , 10 and 10 spores of P . brassicae; application of Botanigard reduced DSI to 7, 14
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