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- Title
Glyphosate, paraquat and ACCase multiple herbicide resistance evolved in a Lolium rigidum biotype.
- Authors
Yu, Qin; Cairns, Andrew; Powles, Stephen
- Abstract
Glyphosate is the world’s most widely used herbicide. A potential substitute for glyphosate in some use patterns is the herbicide paraquat. Following many years of successful use, neither glyphosate nor paraquat could control a biotype of the widespread annual ryegrass ( Lolium rigidum), and here the world’s first case of multiple resistance to glyphosate and paraquat is confirmed. Dose–response experiments established that the glyphosate rate causing 50% mortality (LD50) for the resistant (R) biotype is 14 times greater than for the susceptible (S) biotype. Similarly, the paraquat LD50 for the R biotype is 32 times greater than for the S biotype. Thus, based on the LD50 R/S ratio, this R biotype of L. rigidum is 14-fold resistant to glyphosate and 32-fold resistant to paraquat. This R biotype also has evolved resistance to the acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides. The mechanism of paraquat resistance in this biotype was determined as restricted paraquat translocation. Resistance to ACCase-inhibiting herbicides was determined as due to an insensitive ACCase. Two mechanisms endowing glyphosate resistance were established: firstly, a point mutation in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, resulting in an amino acid substitution of proline to alanine at position 106; secondly, reduced glyphosate translocation was found in this R biotype, indicating a co-occurrence of two distinct glyphosate resistance mechanisms within the R population. In total, this R biotype displays at least four co-existing resistance mechanisms, endowing multiple resistance to glyphosate, paraquat and ACCase herbicides. This alarming case in the history of herbicide resistance evolution represents a serious challenge for the sustainable use of the precious agrochemical resources such as glyphosate and paraquat.
- Publication
Planta: An International Journal of Plant Biology, 2006, Vol 225, Issue 2, p499
- ISSN
0032-0935
- Publication type
Academic Journal
- DOI
10.1007/s00425-006-0364-3