Plant materials and treatments applications
Two different maize inbred lines (PB130 and EP42) were used because they
were classified, at harvest, as partially resistant (PB130) and
susceptible (EP42) to MCB attack based on the length of tunnels made by
larvae in the stems; and differed for the early response to stem
tunneling by MCB larvae (Butron, Malvar, Cartea, Ordas & Velasco, 1999,
Butron, Malvar, Velasco, Revilla & Ordas, 1998, Rodriguez et
al. , 2012). Maize plants were individually grown in pots under
greenhouse conditions. Three consecutive sowings of 10 seeds per sowing
for each treatment-genotype combination were made; consecutive sowings
were separated by 10 days to guarantee that, during the bioassay, MCB
larvae were always fed with stems from plants around tasseling stage. In
the earliest sowing and within each genotype, 10 plants were infested
nine days before the establishment of the bioassay by placing two
2nd instar larvae between the stalk and the sheath of
basal leaves, 10 plants were infested 48 hours before and 10 plants were
left untreated (control). Infested pots were protected with nets to
avoid larval dispersion to non-infested pots. As stems to feed the
larvae were renewed during the bioassay, treatments were also done as
described in the second and third sowings to guarantee that stem
portions given to the larvae came from plants around the tasseling stage
pre-conditioned by larval feeding for 48 hours, nine days or
non-conditioned (control) [Figure S1].