Improving genomic resources for the study of invasiveness in Eurasian watermilofil (Myriophyllum spicatum) and their hybrids

Abstract

Genomics has revolutionized the way biologists ask fundamental questions about evolution. The thousands to tens of thousands of molecular markers generated through modern genomics increase the likelihood of detecting traits associated with a phenotype of interest. While genomics provides ever increasing evidence detecting these traits, they must be developed in each new system. Myriophyllum spicatum L. (Eurasian watermilfoil, EWM) and their hybrids with native Myriophyllum sibiricum Komorov (northern watermilfoil, NWM) are heavily managed aquatic plants in the United States. Genotypes both within and across these taxa and their hybrids can differ in their growth and herbicide response, prompting interest in determining which specific genotypes and genes will respond best to specific control tactics. However, because genotypes are unable to be distinguished by morphology, distinguishing genotypes requires molecular markers. EWM, NWM, and their hybrid are hexaploid (2n=6x=42) and developing these molecular markers requires accurately genotyping in a hexaploid with unknown chromosomal inheritance. The first manuscript of this dissertation empirically tested the genotyping information obtained from three commonly used molecular marker types, AFLPs, microsatellites, and GBS data. We found that while GBS markers have the lowest error rate, all molecular marker types provide the same genotype information. In the second chapter we used a mapping population, GBS data, and likelihood models to determine if watermilfoil was an allohexaploid, autohexaploid, or a mix between them. We found overwhelming evidence that watermilfoil is an allohexaploid across the genome. Finally, using the characteristics of each molecular marker type, the third chapter developed a cost-effective and information dense panel of microhaplotypes to genotype in watermilfoil. Microhaplotyping data can be shared across laboratories and promotes collaboration with weed managers by informing management with genetic information. Together, the work in this dissertation provides diploidized molecular markers and polyploid mode of inheritance to begin to connect genotype to herbicide response traits in watermilfoil.