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Sulfometuron‐resistant Amaranthus retroflexus : cross‐resistance and molecular basis for resistance to acetolactate synthase‐inhibiting herbicides
Author(s) -
Sibony M,
Michel A,
Haas H U,
Rubin B,
Hurle K
Publication year - 2001
Publication title -
weed research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 74
eISSN - 1365-3180
pISSN - 0043-1737
DOI - 10.1046/j.1365-3180.2001.00254.x
Subject(s) - acetolactate synthase , proline , biology , cross resistance , leucine , cytosine , weed , amino acid , microbiology and biotechnology , enzyme , stereochemistry , biochemistry , chemistry , botany , genetics , gene
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 sulfometuron‐methyl + simazine. On the whole‐plant basis, the resistance ratio ( ED 50 Su‐R)/( ED 50 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 (C C C to C T C) 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.