Enemy release after introduction of disease-resistant genotypes into plant-pathogen systems.

Predicting the magnitude of enemy release in host-pathogen systems after introduction of novel disease resistance genes has become a central problem in ecology. Here, we develop a general quantitative framework for predicting changes in realized niche size and intrinsic population growth rate after introgression of disease resistance genes into wild host populations. We then apply this framework to a model host-pathogen system targeted by genetically modified and conventionally bred disease-resistant host lines (Trifolium repens lines expressing resistance to Clover yellow vein potyvirus) and show that, under a range of ecologically realistic conditions, the introduction of novel pathogen resistance genes into host populations can pose a quantifiable risk to associated nontarget native plant communities. In the host-pathogen system studied, we predict that pathogen release could result in an increase in the intrinsic rate of population growth of up to 15% and the expansion of host populations into some marginal environments. This approach has general applicability to the ecological risk assessment of all novel disease-resistant plant genotypes that target coevolutionary host-pathogen systems for improvement of agricultural productivity.