Cultivar and other Brassica Host Evaluation to Manage Clubroot on Canola- 2021

Objective: To evaluate the resistance potential of commercial canola cultivars and other brassica hosts against the clubroot pathogen in field conditions.

Canola cultivars/varieties: Twelve commercial canola varieties along with other brassica hosts were planted to determine the level of resistance against clubroot (Table 1). The canola variety ‘DKL 30-42’ was used as the check.

Planted: First week of June (Hand planted after thorough tillage with a rototiller).

Field design: Randomized complete block design (RCBD) with four replications.

Plot size: 3 ft. x 5ft.

Clubroot Evaluated: Early August (59 days after planting).

Clubroot Disease Index (CRDI):

CRDI: <30% of Susceptible Check = Resistant (R)

CRDI: 30-69% = Intermediate (I)

CRDI: >70% = Susceptible (S)

Note: To validate a clubroot research trial, the susceptible check should have > 60% disease index.

Figure 1: Mean clubroot disease index (%) recorded on various commercial cultivars of canola, camelina, rutabaga, turnip and carinata tested in 2020.

Results: Canola cultivars 6076CR, 4187RR, InVigor L255PC, InVigor L234P, 45H33, 45CS40 CP955RR, CP9982RR and CS2600TFR showed resistance to clubroot and were significantly different from the other varieties tested.  Among the other brassica hosts tested, Camelina has the lowest CRDI followed by turnip.

Future research: Testing more commercial cultivars of canola will be helpful to growers and to monitor the clubroot resistance breakdown in commercially available resistant varieties.

Canola Council of Canada’s Monitoring Clubroot in Resistant Varieties:

“Growers using clubroot-resistant varieties in clubroot-infested fields may experience some infected plants, which can be attributed to susceptible volunteers and off-types. Volunteer canola seed can germinate many years after it was last grown, and if this comes from a susceptible canola crop, then the volunteers will be susceptible. Off-types are a normal part of hybrid canola production – no canola hybrid is 100% pure, so there may be a small proportion (1 to 4%) of the seed that is susceptible.

When scouting, if more than 10% of seeded plants (do not count volunteers) are infected, that may indicate that the clubroot resistance is no longer functional against the pathogen population in the field. These infected plants may be restricted to a small patch which indicates a recent pathogen change.”

Ideal Recommendation: Practice crop rotation (one canola crop using a clubroot resistant variety in three years in endemic areas).