Genetic Nature of the Concentration of 2,4‐dihydroxy‐7‐methoxy 2H‐l,4‐benzoxazin‐ 3(4H)‐one and Resistance to the European Corn Borer in a Diallel Set of Eleven Maize Inbreds 1

A diallel set of 11 inbreds of maize, Zea mays L., was used to study the concentration of 2,4‐dihydroxy‐7‐methoxy‐ 2 H ‐l,4‐benzoxazin‐3 (4 H )‐one (DIMBOA) in the whorl tissue and the resistance to leaf feeding by firstbrood European corn borers, Ostrinia nubilalis (Hubner). The correlation between concentration of the chemical in the plant tissues and level of resistance to leaf feeding by the first‐brood borer was highly significant statistically for the inbreds (r = −0.89**) and the single crosses (r = −0.74**). Also, effects due to general and specific combining ability were highly significant for both traits, but general combining ability accounted for 84% of the variation in the resistance ratings and for 91% of the variation due to concentration of DIMBOA. These results provide further evidence that DIMBOA is a chemical factor in the resistance of maize to the European corn borer and that an objective chemical analysis for DIMBOA in the whorl portion of the maize plant can serve as an indicator of resistance to leaf feeding by the first‐brood European corn borer and possibly eliminate the visual resistance ratings.