Herbicide Resistant Weeds

Rapid diagnosis of ALS/AHAS-resistant weeds.

Gerwick, B. C., L. C. Mireles, and R. J. Eilers. 1993. Rapid diagnosis of ALS/AHAS-resistant weeds. Weed Technology. 7: 519-524.

Laboratory experiments were conducted to rapidly identify acetolactate synthase/acetohydroxyacid synthase (ALS/AHAS)-resistant weeds. The technique used depended upon the differential accumulation of acetoin in the presence and absence of an ALS/AHAS inhibitor, imazaquin. Acetoin accumulation was induced by inhibition of ketol-acid reductoisomerase (KARI), the enzyme immediately following ALS/AHAS in the biosynthesis of branched-chain amino acids. Inhibition of ALS/AHAS prevented the build up of acetoin and formed the basis for distinguishing between sensitive and resistant biotypes. A new inhibitor of KARI, 1,1-cyclopropanedicarboxylic acid (CPCA), was found to cause acetoin accumulation in Abutilon theophrasti leaf discs at concn of 2-100 000 æM. In the presence of CPCA, a number of species (Xanthium strumarium, Amaranthus retroflexus, Chenopodium album and sorghum) that were important to monitor for ALS/AHAS resistance were found to accumulate acetoin at concn sufficient for resistance diagnosis in 2-8 h. In A. theophrasti, the youngest apical leaf was found to be the most active in acetoin accumulation. The resistance diagnosis method was validated by clearly distinguishing between imazaquin-sensitive and imazaquin-resistant X. strumarium biotypes.