Can wild species become problem weeds because of herbicide resistance? Brachypodium distachyon: a case study

Abstract

A purported drawback to the use of transgenic herbicide-resistant crops is the fear that the crop or interbreeding wild relatives will become weedy. It has been posited that a change even in a single trait can confer weediness. This hypothesis was tested with Brachypodium distachyon. This innocuous species came into contact with herbicides through the use of crushed rock from its habitat for road foundations. It evolved s-triazine resistance and developed as a monoculture. When true weeds later evolved simazine resistance, B. distachyon was partially competed from the ecosystem and then disappeared upon the use of non-triazine herbicides. Thus, this wild species remained a weed only until true weeds evolved resistance or until other herbicides were used. One gene mutation did not convert it into a weed, which implies that this will be equally improbable in other cases, when the gene codes for an otherwise neutral trait such as herbicide resistance.