Figure 2
Competitive success of virulent isolates in field experiments. Mean (± S.E.) frequencies of vir9 (a), vir4 and vir6 (b) isolates relative to their corresponding avirulent (Avir) isolates, as determined in pairwise competition experiments. Competing pairs (A-J) of virulent (vir) and avirulent (Avir) isolates (i1–i16) were started at an initial 50:50 ratio and the relative frequency of the vir isolate measured at the end of the growing season. Each point represents the means and S.E. calculated over 2 years and 2 host cultivars. For all 10 pairs, final frequencies were significantly different from the initial 50:50 ratio (t7 > 3.49; p < 0.0101).