Resistance in maize hybrids and inbreds to first-generation southwestern corn borer, Diatraea grandiosella (Dyar) and sugarcane borer, Diatraea saccharalis Fabricius

The mechanisms of resistance in three maize hybrids and five CIMMYT maize lines (CML) to southwestern corn borer (SWCB) Diatraea grandiosella Dyar (Lepidoptera: Pyralidae) and sugarcane borer (SCB) Diatraea saccharalis Fab. (Lepidoptera: Pyralidae) were studied in the field and laboratory. The SWCB infests maize in the high latitude and mid-altitude areas and SCB infests maize in the lowland tropical areas in Mexico. The hybrids tested were Ki3 X CML131, CML67 X 135 and CML139 X 135, and the inbreds tested were Ki3, CML67, CML131, CML135 and CML139. Nonpreference and/or antibiosis were the mechanisms of resistance expressed by the hybrids CML67 X 135 and CML139 X 135 grown in the fields as indicated by the low leaf feeding damage, low larval survival of the two species. The resistance in the two resistant hybrids evidently came from the resistant inbreds CML67 and CML139 because the parameters measured for non-preference and antibiosis were also very low in these resistant inbreds in comparison to CML131, Ki3 and CML135. Laboratory studies also indicated that feeding nonpreference and/or antibiosis was the first line of defence in the resistant hybrids (CML67 X 135 and CML 139 X 135) and inbreds (CML67 and 139) against the attack of stem borers. The survival and growth of the larvae were then adversely affected because of antibiosis in resistant plants to two species of borers. Because of non-preference and antibiosis mechanisms of resistance, the hybrids CML67 X 135 and CML139 X 135 suffered little from leaf and stalk damage, and thus lost little grain yield (3-4%) in comparison to the susceptible hybrid Ki3 X CML131 (35-40%) under heavy infestation by the SWCB and SCB in the fields. These resistant hybrids can be readily used in the integrated pest management (IPM) programs under subsistence farming conditions in the subtropical and tropical environments to reduce yield reductions and increase food production, if grain color, texture, taste and grain quality are acceptable.