The selection of reference genotypes with well-known reaction to the pathogen strains under study is a crucial step in any phenotyping trial. A differential set of banana genotypes with resistant, susceptible and also an intermediate response to the target Foc strains need to be carefully selected for both greenhouse and field conditions.

Some may consider that including three reference genotypes is excessive but the importance of doing so cannot be overstated. When interpreting the results of the trial, it is not so much the absolute amount of disease suffered by the varieties under test but the comparison of their disease response relative to the reference genotypes. Disease levels may vary from one trial to another due to effective inoculum density and climatic variables in particular, but by the inclusion of those genotypes with well-known disease reactions, these factors are taken into account.