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October, 2020
Clubroot lifecycle a plasmodium, a naked mass of protoplasm with many nuclei. The plasmodium eventually divides to form many secondary zoospores, which are then released into the soil. These second-generation zoospores re-infect the roots of the initial host or nearby plants. They then invade the cortex (interior) of the root. Once in the cortex, the amoeba-like cells multiply or join with others to form a secondary plasmodium. As this plasmodium develops, plant hormones are altered, which causes the infected cortical cells to swell. Clusters of these enlarged cells form “clubs� or galls. Clubroot galls are a nutrient sink. Severely infected roots of canola cannot transport sufficient water and nutrients for aboveground plant The life cycle of Plasmodiophora brassicae, the pathogen that causes parts. Symptoms will vary depending clubroot. (Source: Ohio State University). on the growth stage of the crop when infection occurs. Early infection at Resting spores germinate in the spring, producing the seedling stage can result in wilting, stunting and zoospores that swim very short distances in yellowing of canola plants in the late rosette to the soil water to root hairs. These resting spores are early podding stage. Clubroot infection that occurs exceptionally long-lived, with a half-life of about at later stages may not show plant wilting, stunting four years, but they can survive in the soil for up to or yellowing. However, infected plants may ripen 20 years. For example, Swedish research in clubroot- prematurely, and seeds will shrivel. Infected plants will infested spring rapeseed fields found that 17 years reduce the yield and quality (oil content) of the crop. were needed to reduce the infestation to nonRecipe for Clubroot Management (excerpts detectable limits. The longevity of the resting spores is a crucial factor contributing to the seriousness of the disease. A substance secreted from the roots of host plants stimulates resting spore germination. After the initial infection through root hairs or wounds, the pathogen forms an amoeba-like cell. This unusual cell multiplies and then joins with others to create
from clubroot.ca)
1. Vigilantly scout all canola fields (early) for symptoms, even if growing a CR (Clubroot Resistant) variety. Clubroot disease symptoms are most noticeable late in the season and remain visible during and after harvest. Producers are strongly encouraged to familiarize themselves with clubroot symptoms
