Sulfometuron-resistant Amaranthus retroflexus: Cross-resistance and molecular basis for resistance to acetolactate synthase-inhibiting herbicides

M. Sibony, A. Michel, H. U. Haas, B. Rubin*, K. Hurle

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

87 Scopus citations

Abstract

A biotype of Amaranthus retroflexus L. is the first weed in Israel to develop resistance to acetolactate synthase (ALS)-inhibiting herbicides. The resistant biotype (Su-R) was collected from Ganot, a site that had been treated for more than 3 consecutive years with sulfometuronmethyl + simazine. On the whole-plant basis, the resistance ratio (ED50 Su-R)/(ED50 Su-S) was 6-127 for sulfonylureas, 4-63 for imidazolinones, 20-35 for triazolopyrimidines and 11 for pyrithiobac-sodium. Similar levels of resistance were found also when the herbicides were applied before emergence. Based on a root elongation bioassay, Su-R was 3240-fold more resistant to sulfometuron-methyl than Su-S. In vitro studies have shown that the Su-R biotype was resistant at the enzyme level to all ALS inhibitors tested. The nucleotide sequences of two amplified regions between the Su-S and the Su-R differed in only one nucleotide. One substitution has occurred in domain A, cytosine by thymine (CCC to CTC) at position 248, that confers an exchange of the amino acid proline in the susceptible to leucine in the Su-R. The proline to leucine change in domain A is the only difference in the amino acid primary structure of the regions sequenced, indicating that it is responsible for the ALS-inhibitor resistance observed.

Original languageAmerican English
Pages (from-to)509-522
Number of pages14
JournalWeed Research
Volume41
Issue number6
DOIs
StatePublished - 2001

Keywords

  • ALS inhibitors
  • Amaranthus retroflexus
  • Cross-resistance
  • Herbicide resistance

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