Genetic Resistance of Tropical Corn Inbreds to Second-Generation European Corn Borer (Lepidoptera: Pyralidae)

Abstract

<p>Diallel crossesamong five resistant (Tzi4, Narin 0330, Hi34, Hi29, Ant.C5) and four susceptible (Hi32, Tx601, B73, Oh43) maize, <em>Zea mays</em> L., inbreds were used to determine the genetic control of resistance to damage by second-generation European corn borer, <em>Ostrinia nubilalis</em> Hübner. The nine parents and their 36 crosseseach received 10 applications of 50 larvae (500 larvae per plant). Six replications of five plants per plot were infested at anthesis. Visual ratings were taken of sheath and collar tissue 50 to 60 d after infestation based on a nine-point rating scale (1, no damage to 9, severe damage). Significant differences for resistance were observed among the nine parents and the 36 crosses.Ratings of individual crosses varied significantly and averaged 3.7 with range of 1.8 (Tzi4 × Narin0330) to 5.3 (B73 × Oh43). Heterotic effects for resistance of the 36 crossesaveraged -19.5%, which was equivalent to a difference of 1.78 on the rating scale. General (GCA) and specificcombining ability (SCA)mean squares were significant with GCA accounting for 82 and SCAfor 18% of the total variation among crosses.Among the nine parents, four (Tzi4, Narino330, Hi34, Ant.C5) showed greater GCA effects for resistance.</p>