Is leaf or sheath antibiosis involved in the resistance of maize composite EPS12 to Sesamia nonagrioides?

AbstractThe pink stem borer (PSB) (Sesamia nonagrioidesLef?bvre, 1827; Lepidoptera: Noctuidae) is the main insect pest of maize (Zea maysL., Poaceae) in the Mediterranean area. Maize varieties partially resistant to PSB have been identified, but few studies have documented the mechanisms of resistance involved. The objectives of this research were to study the levels of leaf and sheath antibiosis of a maize population, EPS12, and determine whether antibiosis improved over the selection process for less stalk tunneling. A hybrid check and two Bacillus thuringiensis(Bt) hybrids were also examined. Several bioassays were carried out in a control chamber to evaluate antibiosis of maize leaves and sheaths against PSB larvae. Leaf antibiosis was significantly higher for EPS12 than for the hybrid check and sheath antibiosis was low for all non-Bt hybrids studied. We conclude that leaf and sheath antibiosis was not significantly improved during the selection process. Future efforts should look for other possible mechanisms of resistance, such as stem rind antibiosis.