Tabtoxin is a

Tabtoxin is a Pathotoxin.
A chemical of biological origin, other than an enzyme, that plays an important causal role in a plant disease is known as Pathotoxin.
Tabtoxin, also known as wildfire toxin, is a simple monobactam phytotoxin produced by Pseudomonas syringae. It is the precursor to the antibiotic tabtoxinine β-lactam (TBL).
Tabtoxin is a dipeptide precursor to the biologically active form of TBL, differing by having an extra threonine attached by a peptide bond to the C terminus. Tabtoxin is required by BR2(R) for both chlorosis and lesion formation on the bean.