[2] Clavibacter michiganensis, also known as Ring Rot, is an unusual genus of phytopathogenic bacteria in that it is gram-positive and does not have a type three secretion system.
[3] Clavibacter michiganensis infects the primary host in one of three ways: wounds, hydathodes, or by contaminated seed.
To this end, strains of a phytopathogenic bacteria, called pathovars, are distinguished by cultural (selective media), physiological, biochemical (e.g. secreted enzymes the chemical responses of the plant), or pathological characteristics (including the range of susceptible hosts).
[3] When the infection occurs in an early stage of the tomato plant there may be wilting on leaves because Clavibacter michiganensis subsp.
The host may look like it was rubbed with cornmeal or coarse flour but it is actually a series of blisters that me be raised or sunken and appear white to pale orange.
Fruits may develop "bird's eye" spotting, which are pale green to white raised pustules that have a brown center and chlorotic halo.
The virulent and avirulent strains produced the same amount of exopolysaccharides, suggesting that EPS does not play a significant role in pathogenicity.
[7] The causal agent of bacterial wilt and canker of tomato survives in or on seeds for up to 8 months[6] but occasionally also in plant refuse in the soil.
[8] The risk of spreading the bacteria to healthy tomato plants is greatest during transplanting, tying, and suckering or any time when the host may be wounded.
What is known is that Cmm can use hydrolysis products as carbon and energy sources by means of a number of ATP-binding cassette transporters and α- and β-glucosidases.
[11] Also lacking in the Cmm genome are genes for assimilatory sulfate reduction, which is associated with an auxotrophy for methionine – one of two amino acids that contain sulphur.
[11] Cmm has a pathogenicity island (PI) that is encoded in the chromosome and is probably associated with colonization and plant defense evasion or suppression.
Serine proteases of the families S1A, Ppa, and PpA-E are encoded in the chp subregion as well as subtilase SbtA.
[3] Warm temperature in the range of 23–28 °C (73–82 °F) and the high relative humidity (>80%) are optimal environments for Clavibacter michiganesis subsp.
[12] In humid or wet weather, slimy masses of bacteria ooze through the cracks to the surface of the stem, from which they are spread to leaves and fruits and cause secondary infections[9] Infected host plants will show severe symptoms on hot days when there is a high transpiration rate since the bacteria may plug the xylem vessels.
In addition, using chemical treatments such as copper hydroxide[13] or streptomycin in the seed bed,[9] removing or isolating diseased crops can be helpful to reduce the rate of infection.