An additional point of worry is that it seems to have affected varieties which were not previously known to be susceptible and the infestation seems to be increasing over the last 3 years
we are a recently formed research group under the leadership of Dr Diane Saunders at the John Innes Centre/TGAC in Norwich working on wheat yellow rust genomics (http://yellowrust.com/). Your post is a bit old already, but if you still need help we could maybe work something out. We have the necessary skills to process and analyze YSR samples, so we might be able to find out were the resistance you describe originates from. Let me know if you are interested.