Product Code Database
Clubroot is a common disease of , broccoli, cauliflower, Brussels sprouts, , , Matthiola, Erysimum and other plants of the family Brassicaceae (Cruciferae). It is caused by Plasmodiophora brassicae, which was once considered a slime mold but is now put in the group Phytomyxea. It is the first phytomyxean for which the genome has been sequenced. It has as many as thirteen races. Gall formation or distortion takes place on latent roots and gives the shape of a club or spindle. In the cabbage such attacks on the roots cause undeveloped heads or a failure to head at all, followed often by decline in vigor or by death. It is an important disease, affecting an estimated 10% of the total cultured area worldwide.Christianson, J. (2008). Club Root of Crucifers. University of Nebraska-Lincoln. Retrieved from Mar 2012
Historical reports of clubroot date back to the 13th century in Europe. 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.
In 18th, 19th and early 20th century Britain clubroot was sometimes called finger and toe, fingers and toes, anbury, or ambury, these last two also meaning a soft tumor on a horse.
The potential of cultural practices to reduce crop losses due to clubroot is limited, and chemical treatments to control the disease are either banned due to environmental regulations or are not cost effective. Breeding of resistant cultivars therefore is a promising alternative. Hybrid Vegetable Development, by P. K. Singh (Ed.), S. K. Dasgupta (Ed.), S. K. Tripathi (Ed.), Haworth Press. NC State University Department of Plant Pathology [1] (accessed 27 October 2005) Clubroot in the cole crops: the interaction between Plasmodiophora brassicae and Brassica oleracea
Developing plants may not show any symptoms but as the plants get older they will start to show symptoms of chlorosis or yellowing, wilting during hot days, and exhibit stunted growth. Below ground, the roots experience cell proliferation due to increased auxin or growth hormone production from the plant as well as the pathogen. This causes the formation of galls that can grow big enough to restrict the xylem tissue inhibiting efficient water uptake by the plant. Galls appear like clubs or spindles on the roots. Eventually the roots will rot and the plant will die.
Although it is difficult to eradicate the pathogen once it is introduced to a field, there are several methods for its control. 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. Fumigation using metam sodium in a field containing diseased cabbages is yet another way to decrease the buildup of the pathogen. Control and management practices on already infected fields help to reduce the overall impact that P. brassicae has on a field of cabbage and other Brassicaceae plants, but it is extremely difficult to rid an individual plant of the disease once it is already infected.
In 2007, Alberta declared P. brassicae a pest via the foundation legislation in hopes to help contain spread of the disease.
The Pathotype 3, is the predominant source for Alberta outbreaks. Studies showed that out of the 13 strains of P. brassicae, the most virulent form is dominant in Alberta.
Studies have shown that infestation numbers are highest at common field entrances and decline as you move further into the field, away from the entrance. From these results, it was concluded that infested soil on farm machinery was increasing spread of the pathogen. Some natural field to field spread is starting to be seen
Liming has been an effective control measure to curb clubroot since the 19th century. This method does not eradicate clubroot but it will slow its development by creating unfavorable conditions. In addition, calcium and magnesium can be added to the nutrition profile of the soil to help control clubroot. To get efficient results the field soil, pH must be kept above 7.5. This takes massive applications to field soil in order to treat all of the soil where spores of clubroot are found. Combining lime with one other treatment has shown most effective.Kowata-Dresch, L.S., May-De Milo, L.L. (2012). Clubroot Management of Highly Infested Soils. "Crop Protection, 35, p47-52."
Several strains of canola have been tried, including European winter canola cv. Mendel ( Brassica napus), as a clubroot-resistant crop. It has been found that few cultivators exist. Specific genotypes do exist, of the Mendel strain, which could be a solution for canola crops in the Canadian prairies.Rahman, H., Shakir, A., Hasan, MJ. (2011). Breeding for clubroot resistant spring canola (Brassica napus L.) for the Canadian Prairies: Can the European winter canola cv. Mendel be used as a source for resistance. " Canadian Journal of Plant Science 91(3), p.447-458."
Crop rotation with non-host crops is another method to help prevent clubroot. The half life of P. brassicae is 3.6 years. Unfortunately, long rotations of approximately 20 years are required in order to be effective. This is very difficult with typical canola rotations not being more than three years. Canola crop brings in high revenue to farmers. This would also require complete removal of Cruciferae crops, such as wild radish and mustard.
Some fungicide has been found to help with clubroot but it is very pricey and would take huge amounts to saturate the soil. The best way to prevent contamination between fields is to clean agricultural equipment and vehicles which have come in contact with club root before moving to a new field. All contaminated soil, equipment and tools must not be moved to clean, disease-free fields. The best preventative method is field monitoring. Throughout the season, plants should be monitored for early symptoms of club root. More research is being conducted for early detection of club root in fall soils.Trembly, N., et al. (1999). Clubroot of Crucifiers: Control Strategies. "Agriculture and Agrifood Canada." Retrieved from http://publications.gc.ca/collections/Collection/A42-85-1999E.pdf March 2012.
|
|
