Complex genetic control of non-target-site-based resistance to herbicides inhibiting acetyl-coenzyme A carboxylase and acetolactate-synthase in Alopecurus myosuroides Huds.
Résumé
The genetic control of non-target-site-based resistance (NTSR) to three herbicides inhibiting acetyl-coenzyme A carboxylase (ACCase) and one inhibiting acetolactate-synthase (ALS) was investigated in Alopecurus myosuroides (black-grass). Hundred controlled pairings were used to determine the minimum number of loci involved in NTSR to each herbicide and their associated resistance pattern. Resistant parental plants survived herbicide doses ranging from 1 to 12 times the field rate. In a single plant, NTSR to a given herbicide involved at least one to three dominant loci or one recessive locus. Accumulation of up to at least three NTSR loci in a single plant could be necessary to confer resistance. Most NTSR loci endowing resistance to one herbicide did not confer detectable resistance to any other herbicide assayed. This is the first study demonstrating that NTSR is a quantitative trait. It also revealed three nested levels of complexity in NTSR: the loci, which can confer resistance at the whole plant level depending on the herbicide and on the dose used; the individual plants, which can accumulate various sets of NTSR loci via sexual reproduction; and the populations, which are made of various frequencies of genotypes each containing different numbers and combinations of NTSR loci.