Rathayibacter toxicus is a phytopathogenic bacterium known for causing annual ryegrass toxicity (ARGT) commonly found in South and Western Australia.

[5][6][8] In 1956, the first reported livestock deaths due to annual ryegrass toxicity (ARGT) were found in the "wheat-sheep belt" in Black Springs, South Australia.

[4] The identification of the bacterium as "Corynebacterium rathayi" was insufficiently supported, and transfer into the genus Clavibacter was urged by Davis et al.. in 1984 after the peptidoglycan layer of the cell wall was found to have 2,4-diaminobutyric acid (DAB).

[5][11] In 1987, Riley found that the bacteria associated with ARGT were distinguishable from not only Corynebacterium rathayi but other phytopathogenic coryneforms through immunological assays.

[5][13] Due to differences in serology, allozyme analysis, bacteriophage susceptibility, vector adhesion, and biochemical properties that distinguished the new Clavibacter sp.

[5] It possesses a capsule around the cell that is 0.08-0.2 μm thick, allowing the microorganism to survive hot and arid conditions during the summer or in the absence of a host plant.

[5][1] The generation time of R. toxicus is approximately 18 hours in 523M broth at 25 °C (77 °F) based on optical density measurements via a spectrophotometer.

[3] Initially, ISSRs were used to track the ecological distribution of a Southern Turkish relative species, Clavibacter michiganensis.

[3] The PCR products were analyzed using agarose gels and the SimQual program identified and designated Jaccard similarity values for 94 ISSR loci of R. toxicus isolates.

[3] The analyzed MLST genes, involved in antibiotic resistance, chromosome replication, and biosynthetic pathways, served to distinguish the various locations of R. toxicus isolates.

[3] The Geneious software, Primer3 suite, and whole genome of R. toxicus allowed for creation of PCR primers R16sF1 and R16sR1 to amplify a 1110 bp 16S rDNA gene fragment.

[3] The ISSR markers that were generated, along with the MLST results confirmed the presence of three distinct populations of Rathayibacter toxicus, RT-I, RT-II, and RT-III.

[1] ARGT is a neurological disorder caused by R. toxicus’ secretion of a lethal glycolipid toxin (structurally similar to tunicamycin) in infected livestock.

[3][9] The toxin induces convulsions and/or development of unusual gait which typically ends in death of cattle and sheep grazing on infected plants.

[18][19] Many other organisms have shown vulnerability including horses, pigs, and “other laboratory animals” with sheep having a 90% mortality rate and death occurring within 24 hours of poisoning.