Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2001
Publication Date: 4/19/2001
Citation: DAYAN, F.E., MEAZZA, G., BETTARINI, F., SIGNORINI, E., PICCARDI, P., ROMAGNI, J.G., DUKE, S.O. SYNTHESIS, HERBICIDAL ACTIVITY AND MODE OF ACTION OF IR 5790. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY. 2001. v 49:2302-2307. Interpretive Summary: The manuscript describes the synthesis, herbicidal activity and mode of action of IR5790. This new herbicide has been developed to control weeds in rice and cereals and is active at very low concentration. IR 5790 inhibits the enzyme protoporphyrinogen oxidase, a target site considered by the EPA to be of reduced toxicological risk.
Technical Abstract: The arylthiadiazolone herbicide IR 5790 is structurally related to oxadiargyl and oxadiazon. Herbicidal activity and mode of action of IR 5790 were investigated. This herbicide has broad-spectrum preemergence activity against both dicotyledonous and monocotyledonous weeds. The phenotypic responses of sensitive plants, such as interruption of growth and light-dependent development of necrotic areas on the foliage, are consistent with those observed with protoporphyrinogen oxidase-inhibiting herbicides. Tissues exposed to IR 5790 in darkness accumulated protoporphyrin IX which led to a photodynamic loss of membrane integrity upon exposure to light. Consistent with these physiological symptoms, IR 5790 strongly inhibited protoporphyrinogen oxidase, with an I50 value of 3 nM. The presence of a sulfur atom did not significantly alter the molecular properties of the thiadiazolone ring, relative to the oxadiazolone ring of oxadiargyl, which explains why IR 5790 has the same mode of action as this herbicide.