Canadian Journal of Plant Science (2011) 91, 183-190

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S.F. Hwang, H.U. Ahmed, S.E. Strelkov, B.D. Gossen, G.D. Turnbull, G. Peng and R.J. Howard (2011)
Seedling age and inoculum density affect clubroot severity and seed yield in canola
Canadian Journal of Plant Science 91 (1), 183-190
Abstract: Clubroot, caused by Plasmodiophora brassicae, is a serious threat to canola (Brassica napus, B. rapa) production in western Canada because of its long-lived resting spores, high spore production potential, and negative impact on seed yield when inoculum pressure is high. The effect of inoculum density was studied by diluting heavily infested field soil with pathogen-free soil-less potting mix at seven increments, ranging from completely pathogen-free to 100% infested soil, and also by incorporating resting spores into the soil-less mix at concentrations of 1×105 to 1×108 spores cm−3, along with a non-inoculated control. Seed of the susceptible canola cultivar 34 SS 65 was planted in soil of each treatment, grown to maturity, and rated for plant height, seed yield, and clubroot severity (0-3 scale) at harvest. Clubroot severity increased and plant height and seed yield decreased with increasing inoculum density. To assess the effect of seedling age on reaction to clubroot, resting spores of P. brassicae were inoculated onto roots of 1-, 2-, 3- and 4-wk-old seedlings of 34 SS 65. In addition, seed (i.e., 0-wk-old seedlings) was sown into infested soil. Inoculation of young seedlings resulted in higher clubroot severity, shorter plants and lower yield than inoculation of older seedlings. These results indicate that seed treatment fungicides with a long residual period (4 wk or more) may be useful for the management of clubroot.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Stephen E. Strelkov, Gary Peng, Bruce D. Gossen

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Plasmodiophora brassicae Rape/canola (Brassica napus) Canada (west)