To determine evidence of fitness penalty on Snn1 wheat, we used a digital PCR approach to compare the DNA biomass of SN15 (+) and (-) during infection of Snn1 (H086, H336 and H091) and snn1 (H213 and H324) wheat varieties deriving from the CxW population that lacked Tox3 and Tox2A sensitivity (Fig 5). The gene discussed is TOX3; the disease is infection.