Resistance to Southwestern Corn Borer in Corn after Anthesis

Abstract

Southwestern corn borer, Diatraea grandiosella Dyar, is an important pest of corn, Zea mays L., in the southern USA and Mexico. Germplasm with resistance to attack by southwestern corn borer in the vegetative stages has been released; however, resistance to attack after anthesis has not yet been identified. The objectives of this investigation were to evaluate a diallel cross among a group of inbred lines, some of which appeared to exhibit resistance in laboratory and preliminary field tests, and to evaluate the effectiveness of visual ratings of leaf sheath and husk damage in identifying resistant hybrids. The nine‐parent diallel cross was grown for 2 yr and plants were infested with southwestern corn borer larvae 7 d after anthesis. Leaf sheaths and husks were visually rated and larvae recovered, counted, and weighed 14 d after infestation. Husks were also collected from an additional planting of the diallel cross within 3 d after silk emergence, lyophilized, and used in preparation of laboratory diets. Larvae were fed on the diets for 21 d and then weighed. Leaf sheath and husk ratings were not significant among hybrids; however, differences in number of larvae, mean larval weight, and total weight of larvae collected from a plant in the field test and mean larval weight in the laboratory among hybrids were significant. General combining ability (GCA) was a significant source of variation among hybrids for all traits. Estimates of general combining ability effects indicated that the parental inbreds, Mp305 and SC213, contributed to resistance of their hybrids.