The Guardian reports that these more resistant trees could potentially be used to breed down ash trees that could be used to repopulate the forests that have lost large portions of their native trees. There are drawbacks to this plan however. Although these English trees are more resistant to the fungus they are more susceptible to the emerald ash borer. Those working on slowing and controlling the spread of the fungal infection warn that care must be taken when selectively breeding tougher trees.
Map points are scaled by hue (high predicted damage scores in brown, low in green) and plotted according to the geographical origin of the parent trees of the British Screening Panel (n = 130) and the Danish Test Panel (n = 58).
I think this article and the research behind it highlight the benefit of the genetic diversity a single species across several geological locations can develop. Developing an ash tree with a resistance to both the fungal disease and emerald ash borer is the ultimate goal in this situation. If such a tree is created its introduction into the environment must be a careful undertaking. We could just as easily create a tree with a severe susceptibility to the next big disease or insect infestation.