Mutations of the ALS gene endowing resistance to ALS-inhibiting herbicides in Lolium rigidum populations |
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| Authors: | Yu Qin Han Heping Powles Stephen B |
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| Institution: | Western Australian Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, Crawley, WA, Australia. |
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| Abstract: | BACKGROUND: In the important grass weed Lolium rigidum (Gaud.), resistance to ALS‐inhibiting herbicides has evolved widely in Australia. The authors have previously characterised the biochemical basis of ALS herbicide resistance in a number of L. rigidum biotypes and established that resistance can be due to a resistant ALS and/or enhanced herbicide metabolism. The purpose of this study was to identify specific resistance‐endowing ALS gene mutation(s) in four resistant populations and to develop PCR‐based molecular markers. RESULTS: Six resistance‐conferring ALS mutations were identified: Pro‐197‐Ala, Pro‐197‐Arg, Pro‐197‐Gln, Pro‐197‐Leu, Pro‐197‐Ser and Trp‐574‐Leu. All six mutations were found in one population (WLR1). Each Pro‐197 mutation conferred resistance to the sulfonylurea (SU) herbicide sulfometuron, whereas the Trp‐574‐Leu mutation conferred resistance to both sulfometuron and the imidazolinone (IMS) herbicide imazapyr. A derived cleaved amplified polymorphic sequences (dCAPS) marker was developed for detecting resistance mutations at Pro‐197. Furthermore, cleaved amplified polymorphic sequences (CAPS) markers were developed for detecting each of the six mutant resistant alleles. Using these markers, the authors revealed diverse ALS‐resistant alleles and genotypes in these populations and related them directly to phenotypic resistance to ALS‐inhibiting herbicides. CONCLUSION: This study established the existence of a diversity of ALS gene mutations endowing resistance in L. rigidum populations: 1–6 different mutations were found within single populations. At field herbicide rates, resistance profiles were determined more by the specific mutation than by whether plants were homo‐ or heterozygous for the mutation. Copyright © 2008 Society of Chemical Industry |
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| Keywords: | acetolactate synthase (ALS) ALS mutation (d)CAPS Lolium rigidum herbicide resistance imazapyr sulfometuron |
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