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].