CONICET | Buscador de Institutos y Recursos Humanos

Predictions based on evolutionary theory suggest that the adaptive value of evolvedherbicide resistance alleles may be compromised by the existence of fitness costs.There have beenmany studies quantifying the fitness costs associated with novel herbicideresistance alleles, reflecting the importance of fitness costs in determining theevolutionary dynamics of resistance. However, many of these studies have incorrectlydefined resistance or used inappropriate plant material and methods to measure fitness.This review has two major objectives. First, to propose a methodological frameworkthat establishes experimental criteria to unequivocally evaluate fitness costs.Second, to present a comprehensive analysis of the literature on fitness costs associatedwith herbicide resistance alleles. This analysis reveals unquestionable evidencethat some herbicide resistance alleles are associatedwith pleiotropic effects that resultin plant fitness costs.Observed costs are evident from herbicide resistance-endowingamino acid substitutions in proteins involved in amino acid, fatty acid, auxin and cellulosebiosynthesis, as well as enzymes involved in herbicide metabolism. However,these resistance fitness costs are not universal and their expression depends on particularplant alleles and mutations. The findings of this review are discussed within thecontext of the plant defence trade-off theory and herbicide resistance evolution.