Amaranthus hybridus populations resistant to triazine and acetolactate synthase-inhibiting herbicides

• Published in: Weed research Vol. 44; no. 1; pp. 21 - 26
• Main Authors: Maertens, K D, Sprague, C L, Tranel, P J, Hines, R A
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.02.2004; Blackwell Science
• Subjects: acetolactate synthase; Amaranthus hybridus; Biological and medical sciences; cross-resistance; Fundamental and applied biological sciences. Psychology; herbicide resistance; multiple resistance; Parasitic plants. Weeds; Phytopathology. Animal pests. Plant and forest protection; Oxo-acid-lyases; Carbon-carbon lyases; Amaranthus hybridus; multiple resistance; Enzyme; Weed science; Acetolactate synthase; Lyases; Cross resistance; cross-resistance; Pesticide resistance; herbicide resistance
• ISSN: 0043-1737; 1365-3180
• DOI: 10.1046/j.1365-3180.2003.00368.x

Summary Amaranthus hybridus L. populations (A, B and C) obtained from escapes in Massac County and Pope County fields in southern Illinois, USA were subjected to greenhouse and laboratory experiments to measure multiple resistance to triazine and acetolactate synthase (ALS)‐inhibiting herbicides and cross‐resistance between sulfonylurea and imidazolinone herbicides. Phytotoxicity responses of the three populations revealed that only population B exhibited multiple resistances to triazine and ALS‐inhibiting herbicides. This population was >167‐, >152‐ and >189‐fold resistant to atrazine, imazamox and thifensulfuron, respectively, at the whole plant level compared with the susceptible population. Population A was only resistant to triazines and population C was only resistant to ALS‐inhibiting herbicides. Results from in vivo ALS enzyme and chlorophyll fluorescence assays confirmed these findings and indicated that an altered site‐of‐action mediated resistance to both triazine and ALS‐inhibiting herbicides. Gene sequencing revealed that a glycine for serine substitution at residue 264 of the D1 protein, and a leucine for tryptophan substitution at residue 574 of ALS were the causes of resistance for the three populations.