Genetic Effects Conditioning Resistance to Earworm in Maize1

Abstract

Eleven sweet and 11 dent maize, Zea mays L., inbreds were tested for the types of genetic effects which condition resistance to ear‐feeding injury by the corn earworm, Heliothis zea (Boddie). Parental, F1, F2, and backcross populations were rated to obtain generation means. Variability among means was partitioned by least squares procedures into portions attributable to additive, dominance, and epistatic genetic effects.Additive, dominance, and epistatic sources of variability among generation means were found to be significant with both the sweet and dent corn crosses tested. R2 values, indicating the proportion of variability attributable to various genetic effects, suggested a preponderance of additive effects among sweet corn crosses and dominance effects among dent corn crosses. A comparison of F1 and F2 within plot variances, and the observance of some large parental variances, indicated that earworm injury measurements of individual plants for some generations had a substantial error component. Broad‐sense heritability estimates, on an individual plant basis, of 29% were obtained for both sweet and dent groups. Increasing the general level of resistance within the two population groups tested, and particularly hi the sweet group, should be possible with any of several progeny selection regimes.