**3. Discussion**

Plants are exposed to numerous biotic and abiotic stresses in their environment. Invasive plants may have evolved to adapt to these stresses and to fluctuating environmental conditions via plasticity in growth and development [6,28,70]. Studies investigating the molecular mechanisms responsible for invasion success are scarce in non-model plant species, but can now be investigated due to the availability of genomic technologies. In our study, we isolated partial gene sequences of key defense hormones in two non-model plant species (Table S6). These novel template gene sequences allowed us to investigate hormone signaling and their cross-talk within and between species to better understand the resistance of an invasive species to a globally distributed necrotrophic fungal pathogen. There were three major findings in our study: (1) *R. solani* successfully infected the invasive *A. philoxeroides* and its native congener *A. sessilis,* with disease development being much slower in *A. philoxeroides* compared to *A. sessilis*; (2) there were interspecific differences in hormone gene expression (including hormone

signaling and cross-talk) following inoculation by *R. solani*; and (3) there were differences in the hormone signaling and their cross-talk between infected local and the un-infected systemic leaves.
