Focus Expansion in Plant Disease. IV: Expansion Rates in Mixtures of Resistant and Susceptible Hosts

(...) If the only difference between the cultivars is in their susceptibility to disease, theory predicts that the radial velocity of focus expansion increases linearly with the logarithm of the fraction of susceptible plants. This hypothesis was tested in the field by using the wheat-stripe rust pathosystem. The results of the experiment were generally consistent with the hypothesis, although minor deviations were present. There was an indication that in plots with a small fraction of susceptible plants, the velocity of focus expansion did not attain its final value