The fungal strains were subjected to increasing concentrations of
natamycin based on the method of Schroeder and Bullerman (1985),
who used this method for studying the tolerance of fungi against sor-
bate. This procedure has been dubbed “training”. For the first step of
this procedure, agar media were prepared with natamycin concen-
trations of 10% of the M.I.C. as assessed for each of the strains, corre-
sponding to 120 nM to 1.1 μM (since the M.I.C.s varied between 1.2
and 11 μM). To ensure an equal distribution of the compound
through the agar, the natamycin stock was diluted in a relatively
large volume of warmed sterilized water (50–55 °C) that was
mixed with an equal volume of hand-warm double strength MEA
medium. The plates were stored in the dark before use. Growth of
the strains at 10% of the M.I.C. was assessed in triplicate after
3 days of incubation at 24 °C.