Fitness costs linked to dinitroaniline resistance mutation in Setaria

Abstract

A mutant Thr-239-Ileu at the a2-tubulin gene was found to confer resistance to dinitroanilines, a family of mitosisdisrupting herbicides. However, mutations affecting microtubule polymerization and cell division are expected to impact growth and reproduction, that is, the fitness of a resistant weed or the yield of a tolerant crop, although it has not been demonstrated yet. This study was designed to test this hypothesis for the growth and reproduction of nearisogenic resistant and susceptible materials that were created in F 2 and F 3 generations after a Setaria viridis x S. italica cross. Differential growth was noticeable at the very onset of seedling growth. The homozygous resistant plants, grown both in a greenhouse cabinet and in the field, were smaller and had lower 1000-grain weight and therefore a lower yield. This fitness penalty is certainly due to modified cell division kinetics. Although the presence of the mutant allele accounted for 20% yield losses, there were also measurable benefits of dinitroaniline resistance, and these benefits are discussed.

Biotechnological aspects of cytoskeletal regulation in plants

“…This is probably related to the fitness cost of tubulin-linked acquired dinitroaniline resistance, since at least in apicomplexan parasites, dinitroaniline-resistant tubulin mutations are associated with aberrant microtubular structure and compromised function (Ma et al, 2007). Indeed a survey of dinitroaniline resistance in green foxtail (i.e., S. viridis), showed that the substitution of T239 of α-tubulin by isoleucine (T239I) conferring resistance to trifluralin was associated with a fitness penalty negatively affecting vegetative plant size and reducing overall reproductive yield (Darmency et al, 2011). Two other amino acid substitutions have been correlated with weed dinitroaniline resistance and include M268 which is replaced by threonine in dinitroaniline-resistant biotypes (M268T) and L136 which is replaced by phenylalanine (L136F; Délye et al, 2004).…”

Pleiotropic effects of herbicide-resistance genes on crop yield: a review

“…In another instance, the resistance allele was transferred by sexual cross between green foxtail and foxtail millet. F 2 and F 3 descendants of crosses between susceptible varieties and resistant ones bearing the mutation Thr‐239‐Ileu of the α2‐tubulin gene have shown differences in juvenile growth, plant size, and grain size, which led to 20% less yield in the resistant plant . The resistance cost may be due to the conformational changes that prohibit the herbicide from attaching and slow the tubulin polymerisation, which results in modified cell division kinetics.…”

The red queen in the corn: agricultural weeds as models of rapid adaptive evolution

“…Herbicide resistance has likely evolved de novo in other weeds due to the fitness cost associated with resistance when herbicide selection is not present. Examples include waterhemp (Duff et al, 2009) and foxtail grass (Darmency et al, 2011).…”