Somatic mutation-mediated evolution of herbicide resistance in the non-indigenous invasive plant hydrilla (Hydrilla verticillata)

摘要

Hydrilla [Hydrilla verticillata (L.f.) Royle] was introduced in Florida lakes 50 years ago. This plant spread very rapidly through numerous mechanisms of vegetative reproduction and is now one of the most serious aquatic weed problems in the United States. Management of this weed has been achieved with the herbicide fluridone. Fluridone, the only herbicide approved by the USA-EPA for systemic treatment of large water bodies, has been used to manage hydrilla very successfully. However, a decrease in sensitivity to fluridone has been observed in some lakes. Analysis of hydrilla samples revealed that at least three fluridone-resistant biotypes of hydrilla have emerged in Florida lakes. Resistance is the result of one of three independent somatic mutations at the arginine 304 codon of the gene encoding phytoene desaturase, the target site of fluridone. While the specific activities of the three purified phytoene desaturase variants are similar to the wild-type enzyme, the mutant enzymes are more resistant to fluridone. This is the first known instance of evolution of resistance to phytoene desaturase inhibitors in higher plants. The resistant biotypes are expected to emerge in other locations and are likely to pose significant environmental challengesin the future.