Fig. 1

From left to right: a Distribution of genomic relationships between pairs of pigs (kinship matrix). b Multidimensional scaling plot (n = 121). 0, non-carriers; 1, persistent carriers; PC, principal component. c Quantile-quantile plot. Black line, the expected distribution of association test statistics under the null hypothesis of no association is plotted against observed values. Any deviation from the X-Y line suggests a consistent difference between persistent carriers and non-carriers e.g., due to genetic confounding. At the extreme of the distribution, the observed chi-square values are higher than expected by chance which indicates true association. Red line, fitted slope