Resistance to ACCase‐inhibiting herbicides and isoproturon in UK populations of Lolium multiflorum: mechanisms of resistance and implications for control

Abstract

Herbicide-resistant Lolium multiflorum (Italian rye-grass) was first reported in the UK in 1993 and had been confirmed on 25 farms by 1999. In this study, resistance to five herbicides belonging to the aryloxyphenoxypropionate, cyclohexanedione and phenyl-urea classes was determined in six populations of L multiflorum from the UK under glasshouse and simulated field conditions. Glasshouse conditions tended to exaggerate the degree of resistance, but experiments performed in both environments detected resistance in four populations of L multiflorum. Four populations (Essex A1, Lincs A1, Wilts B1, Yorks A2) were resistant to diclofop-methyl, fluazifop-P-butyl, tralkoxydim and partially resistant to isoproturon, but only the population from Yorkshire (Yorks A2) showed resistance to cycloxydim. Biochemical analyses of acetyl coenzyme A carboxylase (ACCase) activity, oxygen consumption by thylakoids, diclofop metabolism and glutathione S-transferase activity showed that, in three of the resistant populations, an enhanced rate of herbicide metabolism conferred resistance. This is the first report world-wide of an enhanced metabolism mechanism of diclofop resistance in L multiflorum. In the Yorks A2 population, an insensitive ACCase was detected (target-site resistance) which also conferred cross-resistance to all of the other ACCase inhibitors investigated.

RNA-Seq transcriptome analysis of Amaranthus palmeri with differential tolerance to glufosinate herbicide

“…rigidum identified CYP72A genes to be involved in metabolic resistance to diclofop [ 37 ]. Non-target-site ACCase and ALS resistance in Alopecurus myosuroides [ 95 , 96 ], Stellaria media [ 105 ], Lolium [ 96 , 106 – 108 ], Sinapis arvensis [ 109 ], Echinochloa phyllopogon [ 110 ], and Digitaria sanguinalis [ 111 ] were reported previously to be facilitated by cytochrome P450 enzymes. Upregulation of CYP72A and CYP94A was reported in a multiple-herbicide-resistant E .…”

Genetic Resistance to Acetyl‐Coenzyme A Carboxylase‐Inhibiting Herbicides in Grain Sorghum

“…Trp-1999-Cys and Gly-2096-Ala were not good candidates since yeast-wheat chimeric protein studies reported reduced growth associated with these mutations (Liu et al,, 2007). Metabolism-based resistance seemed unlikely because the resistance factors observed were much higher than those reported for metabolism based resistance (Cocker et al, 2000(Cocker et al, , 2001Matthews et al, 2000). This was not surprising since the high levels of resistance observed in the dose-response e.xperiments suggested a target site mutation (Obermeier, 1998).…”

“…The question remained whether the gene was a mutant ACCase or a gene involved with metabolism. Metabolism-based resistance seemed unlikely because the resistance factors observed were much higher than those reported for metabolism based resistance (Cocker et al, 2000(Cocker et al, , 2001Matthews et al, 2000). Zero was set to 0.00011 for log-logistic plotting as directed in Seefeldt et al (1995).…”

Broad Resistance to ACCase Inhibiting Herbicides in a Ryegrass Population Is Due Only to a Cysteine to Arginine Mutation in the Target Enzyme

“…Additional non target site resistance in populations for which a target site mutation have been uncovered could also be inferred from large number of Lolium spp. samples from Greece [33], USA [34], UK [35] and Italy [10] on the basis of differential responses to metabolisable and non-metabolisable ACCase herbicides. Weed populations containing additional non target site resistance mechanisms are not restricted to grass weeds as these have recently been identified in broad leaved weed populations characterised by known ALS mutations [36].…”