Test of the Poisson model.

A test of the Poisson model, using the proportion of uninfected cells to predict the occurrence of mixed-variant infected cells.aΔ indicates whether the observed frequency of mixed-variant infected cells is greater than or less than the predicted value , if the difference is significant.bThe inoculated leaf.cSystemically infected leaf.dIn these cases pa is the mean qPCR-measured frequency, instead of being derived from the frequencies of infected cells, given that these data are not reported in the study.