Clubroot

Clubroot is a common disease of cabbages, broccoli, cauliflower, Brussels sprouts, radishes, turnips, stocks, wallflowers and other plants of the family Brassicaceae (Cruciferae).

Gall formation or distortion takes place on latent roots and gives the shape of a club or spindle.

In the late 19th century, a severe epidemic of clubroot destroyed large proportions of the cabbage crop in St. Petersburg.

The Russian scientist Mikhail Woronin eventually identified the cause of clubroot as a "plasmodiophorous organism" in 1875, and gave it the name Plasmodiophora brassicae.

Below ground, the roots experience cell proliferation due to increased auxin or growth hormone production from the plant as well as the pathogen.

[10] This causes the formation of galls that can grow big enough to restrict the xylem tissue inhibiting efficient water uptake by the plant.

These zoospores swim through the moist soil and enter host plants through wounds or root hairs.

The secondary plasmodium forms the overwintering resting spores which get released into the soil as the “clubs” rot and disintegrate.

These resting spores can live in the soil for up to 20 years while they wait for a root tip to come in close proximity for them to infect.

Good sanitation practice is important with regard to the use of tools and machinery in order to prevent the introduction of the pathogen to a disease-free field.

It is not uncommon for an inattentive farmer or gardener to unknowingly carry in the pathogen after being previously exposed to it at a different time.

Keeping the soil at a slightly basic pH of 7.1–7.2 by the addition of agricultural lime as well as the integration of crop rotation will reduce the occurrence of cabbage clubroot in already infected fields.

P. brassicae is able to infect 300 species of cruciferous plants, making this disease a recurring problem even with crop rotation.

Additionally, cabbage clubroot may be a stubborn disease due to its ability to form a microbial cyst as an overwintering structure.

[14] These cysts may last many years in the soil until it comes into contact with a suitable host, making it difficult to entirely avoid the introduction of the disease.

These formations impede nutrient and water uptake and can cause plant death, wiping out important money generating canola crops.

Specific genotypes do exist, of the Mendel strain, which could be a solution for canola crops in the Canadian prairies.