Résumé
The increase in human-mediated introduction of plant species to new regions due to global travel and globalization has resulted in a rise of invasive exotic plants (IEPs) that can have significant effects on biodiversity, ecosystem processes, and food production. The introduction of IEPs to new regions often occurs through seed dispersal, and most pathogens are not vertically transmitted, leading to low viral loads in these plants. Also, most pathogens are not evenly distributed across the Earth, meaning that IEPs colonizing a new territory are unlikely to encounter pathogens from their native range. This situation, referred to as the "enemy-release hypothesis" suggests that decreased pathogen-mediated selective pressures on IEPs in colonized territories will result in increased IEP populations, densities, and geographical distributions. To test the enemy-release hypothesis, the virome of an invasive cane bluestem (Bothriochloa barbinodis) was compared to that of four or more indigenous grass species in both naturalized and native ranges. The results showed that the IEPs had lower viral infection loads than the native grasses, providing evidence that supports the enemy release hypothesis. Novel viruses associated with Bothriochloa barbinodis were further partially or fully sequenced and the phylogenetic relationships of these viral sequences and representative sequences of corresponding virus families were analyzed.