Changes in frequency of virulent <i>avrLm7</i> isolates in <i>Leptosphaeria maculans</i> populations before and during exposure to the <i>Rlm7</i> selection in a field experiment at Grignon and control plots at Grignon and Versailles.

aThe field experiment was established in autumn 2004 and the first samples from it were in autumn 2006. brlm7 (without the Rlm7 gene) plants were sown and used as trap cultivars to estimate the proportion of virulent isolates present in the air and landing on the crop at each site in each year. cValues in square brackets represent the exact confidence interval of the percentages at a 95% confidence level based on the total number of isolates and the percentage of virulent isolates in the sampling; values in brackets indicate the total number of isolates analysed for each sampling. dna, not applicable (the resistance gene was not yet released); nd, not determined.