Target-site resistance to als-inhibiting herbicides in silky bent grass (apera spica-venti l. beauv.) populations is conferred by documented and previously unknown mutations
- Publication Type
- Journal contribution
- Authors
- Dario Massa and Björn Krenz and Roland Gerhards
- Year of publication
- 2011
- Published in
- Weed Research
- Band/Volume
- 51/3
- DOI
- 10.1111/j.1365-3180.2011.00843.x
- Page (from - to)
- 294-303
In this study, whole-plant bioassays were performed on 72 Apera spica-venti populations that have survived application of acetolactate synthase (ALS)-inhibiting herbicides in recent years. Molecular genetic analysis of the ALS gene revealed a Thr mutation at Pro197 within 67 populations. Sequencing of the whole ALS gene from wild-type and resistant plants not carrying the above-mentioned mutation revealed the presence of a Leu mutation at Trp574 within two populations and an Asn mutation at Pro197 within two populations. As the Pro197-Asn amino acid substitution is reported for the first time in a field-selected weed population, a Cleaved Amplified Polymorphic Sequences (CAPS) marker was developed for its quick detection. In addition, one novel mutation was found within a population that coded for a His substitution at Arg377. Enzyme assays confirmed a significant reduction in inhibition of ALS activity compared with the wild type. This population showed resistance to sulfonylureas (SUs) and cross-resistance to sulfonylaminocarbonyltriazolinones (SCTs) and triazolopyrimidines (TPs) within the whole-plant bioassays. ALS protein sequence alignments from weedy and cultural plants revealed that the Arg377 is highly conserved among known wild-type enzymes. In agreement with existing literature concerning the structure and mechanisms of inhibition of plant ALS, this mutation is probably involved in target-site resistance to ALS inhibitors. Our results suggest that further single-nucleotide polymorphisms impairing proper herbicide performance might be selected within field populations in the near future, making the short- and long-range evolution of target-site resistance difficult to predict depending solely on herbicide use history.
Keywords: acetolactate synthase, acetolactate synthase-inhibitors, loose silky-bent, target-site resistance, single-nucleotide polymorphisms, sequencing