Sulfometuron-resistant Amaranthus retroflexus: cross-resistance and molecular basis for resistance to acetolactate synthase-inhibiting herbicides |
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Authors: | M Sibony A Michel H U Haas B Rubin & K Hurle |
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Institution: | Institute of Plant Science and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel,;Institute of Phytomedicine, University of Hohenheim, Stuttgart, Germany |
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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 sulfometuron-methyl + 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 (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. |
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Keywords: | ALS inhibitors herbicide resistance cross-resistance Amaranthus retroflexus |
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