Copy number variation of the CYP51 locus occurs frequently in E. necator and correlates with fungal growth under fungicide treatment. (A) Circular visualization of the allelic form (M = mutant, WT = wild type) and copy number of EnCYP51 in the 94 California isolates, and the fungicide spray regime of each collection site. At the center of the circular plot is a hierarchical clustering dendrogram determined by SSR marker-based fingerprinting (Additional file 3: Text S1). (B) Bar plots showing the proportion of wild type and mutant EnCYP51 alleles collected from sites sprayed or not sprayed with fungicides. Box plots showing (C) the distribution of EnCYP51 copy number in isolates containing the mutant allele compared to those with the wild type allele, and (D) box plots showing the distribution of copy numbers of the two genes that flank the conserved duplication boundaries observed in the individuals with multiple EnCYP51 copies. (E) Scatterplot shows the correlation between mean relative growth measured by qPCR and copy number estimates. The capability of isolates with different copy numbers of EnCYP51 to grow in the presence a DMI fungicide (Rally® 40WSP) was measured. To account for growth rate differences among isolates in absence of the fungicide, growth results in presence of the fungicide were calculated as a percentage of the fungal biomass accumulation in absence of the fungicide. Growth values are the mean of two separate assays, each run with three biological replicates.