Poplar trees (Populus) provide vital ecosystem services for humans and are a critical species within their wide range of habitats. Our research goal was to investigate whether hybridization between Populus trichocharpa (Black Cottonwood) and P. balsamifera (Balsam Poplar) alters their resistance to a fungal pathogen Melampsora, or rust. Rust is apotential threat to proper development in many poplar species. Our garden is within a multi-institution poplar research project, consisting of 19 common gardens across North America with clones of 47 poplar genotypes. All genotypes exhibit a hybrid class, or percentage of DNA from the two focal species. Each garden collected general presence or absence of rust data. At our garden we conducted a detailed assessment of the proportion of leaves exhibiting rust damage. For our garden and across the larger project we used ANOVAs, linear models, and correlation tests to determine if there was a relationship between the presence of rust disease and genetic background. For both data sets, no significant relationships were found between rust presence and hybrid class. However, in the larger set, there was a significant relationship between rust and transect, or original location. Also, in our smaller set, rust was positively correlated with leaf area.
