Comparison of molecular markers to distinguish genotypes of Eurasian watermilfoil, northern watermilfoil, and their hybrids

摘要

Managed aquatic plant taxa can exhibit genetic variation that is relevant to their growth, impacts, and control efficacy. For example, genotypes of hydrilla {Hydrilla verticillata L.f. Royle) differ in their degree of sensitivity to fluridone (Michelet al. 2004), and genetic screening of hydrilla populations can therefore be used to predict whether fluridone treatment will be efficacious on the specific genotypes present in a water body (Benoit and Les 2013). For most species, where, when, and how genetic variation will be important for management decisions and outcomes is still unknown. However, molecular markers can be used to quantify and monitor genetic variation across space and time, which holds potential to identify specific genotypes of interest (e.g., putatively herbicide-resistant genotypes) or changes in genetic variation that could signal important changes in population-level responses to management.Invasive Eurasian watermilfoil (Myriophyllum spicatnm L.; EWM) is a highly managed aquatic plant in the United States. EWM hybridizes with native northern watermilfoil (Myriophyllum sibiricum Komarov; NWM), and EWM and hybrid genotypes can differ in their growth and herbicide response (Berger et al. 2012, 2015, Thum et al. 2012, LaRue et al. 2013, Netherland and Willey 2017, Taylor et al. 2017), prompting interest in determining which specific genotypes will respond best to specific control tactics. However, because genotypes are unable to be distinguished by morphology, distinguishing genotypes requires molecular markers.Previous studies of genetic variation in EWM, NWM, and hybrid watermilfoil have used amplified fragment length polymorphisms (AFLPs) and microsatellite markers. AFLPs have been used to identify hybridization and demonstrate genetic diversity in EWM, NWM,and hybrids (Zuellig and Thum 2012, LaRue et al. 2013). AFLPs are relatively cheap, but they have limited precision to distinguish closely related genotypes from sequencing or scoring errors.