Clavibacter insidiosus

• Comment: still needs revision -- too much of an essay DGG ( talk ) 03:37, 3 June 2021 (UTC)

• Comment: needs ck for copypaste, and finishing. DGG ( talk ) 04:47, 9 June 2020 (UTC)

---

---

Alfalfa root infected with Clavibacter michiganensis subsp. insidiosus

Alfalfa with bacteria wilt caused by Clavibacter michiganensis subsp. insidiosus

Clavibacter michiganensis subsp. insidiosus causes bacterial wilt with its most notable host being Medicago sativa (alfalfa). Other species in the Medicago genus are also known to be hosts such as Medicago falcata. Additionally, Lotus corni-culatus, Melilotus alba, Onobrychis viciifolia, and Trifolium sp. are known hosts³. Plants like alfalfa are often mowed, and thisz causes cut stems. The cut stems increase disease susceptibility be providing wounds for the bacteria to enter⁴. Clavibacter michiganensis subsp. insidiosus causes a systemic disease: the leaflets curl up, an indicative symptom of this disease³. Occasionally, it causes necrosis of the leaflets⁴. Yellowing of the plant and yellow-brown roots often occurs. This disease is either fatal or causes severe damage to the host with the bacteria leading to stunted growth⁴. Clavibacter michiganensis subsp. insidiosus needs to be cultured from the infected plant tissues and PCR-tests must be run to confirm a diagnosis⁴.

Clavibacter michiganensis subsp. insidiosus is typically dispersed by the moving of hay between different agricultural sites. Farm equipment that is not properly sanitized can also spread the pathogen. Water is known to move the bacterium²; if an area in not irrigated and there is low rainfall, the disease will usually not be present⁴. Plant wounds, specifically on the stem or roots, increase disease susceptibility² (because there is now wound for the bacteria to enter⁴) and are often made by mowing, nematodes, or insects. Stem nematodes often act as a vector. They can carry the bacteria on their surface². If the plant is infected by root-knot nematodes, bacterial wilt is more likely and typically more severe⁴. Infested soil can additionally cause disease⁵. A small number of diseased plants (about 6.3-7.7%) can transmit the bacterium to their seeds⁶.

Disease management of bacterial wilt is critical. One crucial way to control the disease is plant resistance. Finding and then growing only resistant plants will limit the bacterium’s ability to spread¹. Plants that can winter well tend to be more resistant⁵. If susceptible plants are grown, there should be a two-year crop rotation with cultivation⁵ (cultural management) and herbicide⁴ (chemical management). There are many methods of cultural management to control bacterial wilt. Some countries require crop inspection in order for seed to be moved⁴. Additionally, it is important to keep seeds with the pathogen away from areas where bacterial wilt is not present5. The bacterium can be transferred on a variety of farm equipment so the equipment should be cleaned very regularly⁴. If plants need to be cut, they should do so when they are dry because the bacterium moves in water. Furthermore, plants that are younger and/or resistant should be cut prior to the plants that are older and/or susceptible to prevent disease. Due to the bacterium’s affinity for water, any irrigation used should be carefully monitored to prevent any excess water⁵. This all helps to prevent the epiphytic phase of the bacterium.

References

1. CABI, and EPPO. “Clavibacter Michiganensis Subsp. Insidiosus.” EPPO Global Database, gd.eppo.int/taxon/CORBIN/documents. 2. EFSA. “Scientific Opinion on the Pest Categorisation of Clavibacter Michiganensis Subsp. Insidiosus (McCulloch) Davis Et Al.” EFSA, John Wiley & Sons, Ltd, 11 Dec. 2014, efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2014.3910. 3. “PM 7/99 (1): Clavibacter Michiganensis Subsp. Insidiosus.” Wiley Online Library, John Wiley & Sons, Ltd (10.1111), 15 Nov. 2010, onlinelibrary.wiley.com/doi/epdf/10.1111/j.1365-2338.2010.02408.x. 4. Rhodes, Landon H, and William o Lamp. “Bacterial WiltLa.” Compendium of Alfalfa Diseases and Pests, by Deborah A. Samac, third ed., American Phytopathological Society, 2015, pp. 62–63. 5. Samac, D. A., et al. “CHAPTER 16: Detection of Clavibacter Michiganensis Subsp. Insidiosus in Alfalfa Seeds.” Detection of Plant-Pathogenic Bacteria in Seed and Other Planting Material, Second Edition, 2017, pp. 103–107., doi:10.1094/9780890545416.016. 6. Samac, Deborah A, et al. “Transmission Frequency of Clavibacter Michiganensis Subsp. Insidiosus to Alfalfa Seed and Identification of the Bacterium by PCR.” Plant Disease , vol. 82, no. 12, Dec. 1998, pp. 1362–1367., doi:10.1094.