ABSTRACT
BACKGROUND: Pinoxaden is a new cereal herbicide that provides outstanding levels of post-emergence activity against a broad spectrum of grass weed species for worldwide selective use in both wheat and barley. RESULTS: Factors influencing activity and tolerance to pinoxaden were in part linked to distinct structural parts of the active ingredient. Three complementary contributions that decisively impact upon the herbicidal potency against grasses were identified: a preferred 2,6-diethyl-4-methyl aromatic substitution pattern, a dione area suitable for proherbicide formation and beneficial adjuvant effects. The uptake and translocation pattern of pinoxaden when coapplied with its tailored adjuvant were analysed by autoradiography, indicating extensive and rapid penetration, followed by effective distribution throughout the plant. Crop injury reduction on incorporation of the [1,4,5]oxadiazepane ring into the aryldione template was reinforced with safener technology. Comparative studies on the behaviour of pinoxaden applied either alone or in combination with the safener cloquintocet-mexyl demonstrated that addition of the safener resulted in significant enhancement of metabolic degradation in wheat and barley, providing excellent crop tolerance and a substantial selectivity margin without adverse effects on weed control. CONCLUSION: The biological potential of pinoxaden and its active principle pinoxaden dione in terms of grass weed control and tolerance in cereals was fully exploited by inclusion of the safener cloquintocet-mexyl in the formulation in combination with a specific and tailor-made tank-mix adjuvant based on methylated rape seed oil.
Subject(s)
Herbicides/chemistry , Heterocyclic Compounds, 2-Ring/chemistry , Poaceae/drug effects , Quinolines/pharmacology , Adjuvants, Pharmaceutic/chemistry , Adjuvants, Pharmaceutic/pharmacology , Autoradiography , Crystallography, X-Ray , Herbicide Resistance , Herbicides/pharmacology , Heterocyclic Compounds, 2-Ring/pharmacology , Plant Weeds/drug effects , Structure-Activity Relationship , Weed ControlABSTRACT
Derivatives of the new class of 3-hydroxy-4-phenyl-5-oxo-pyrazolines were optimized towards both herbicidal activity on key annual grass weed species and selectivity in small grain cereal crops. The generic structure can be separated into three parts for the analysis of the structure-activity relationships, namely the aryl, the dione with its prodrug forms and the hydrazine moiety. Each area appears to play distinct and different roles in overall expression of biological performance which is further beneficially influenced by adjuvant response and safener action. Pinoxaden 6, a novel graminicide for use in wheat and barley incorporating a [1,4,5]oxadiazepane ring, eventually emerged as a development candidate from the discovery and optimization process.
