Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/1999
Publication Date: N/A
Interpretive Summary: The fall armyworm is a major pest of late-planted corn in the South. Several corn germplasm lines with resistance to leaf feeding by fall armyworm have been developed and released by USDA-ARS scientists, and these lines are being used by commercial seed companies and international research centers to develop corn hybrids with resistance to fall armyworm. Growing hybrids with resistance is widely considered the most desirable way to reduce losses to this insect. A better understanding of the basis of this resistance is needed to more efficiently transfer it into high-yielding, agronomically acceptable hybrids. Larvae that are fed on tissue of resistant plants grow more slowly than those that are fed on tissue of susceptible plants. This investigation indicated that the reduced larval growth on resistant corn genotypes is greatest when larvae are fed on the yellow-green portions of developing leaves. No differences in larval growth were observed when larvae fed on tissue from the yellow tissue of the inner whorl. This indicates that the components responsible for resistance are present only in the more mature portions of the leaves.
Technical Abstract: The effect of diets prepared from whorl leaf tissue of fall armyworm resistant and susceptible corn genotypes on larval growth, development and physiology was analyzed. Larvae reared on lyophilized leaf tissue of resistant genotypes were smaller and had a longer developmental period that those reared on susceptible genotypes. Larvae reared on the green and yellow-green portions of whorl leaves of resistant plants were significantly smaller than those that were reared on the same portions of leaves of susceptible plants. When larvae were reared on the yellow tissue from the inner whorl, diferences in larval growth on tissue of susceptible and resistant genotypes were not significant. Larvae fed on resistant lyophilized leaf tissue not only grew more slowly, but also had a lower efficiency of conversion of ingested food to body substance. Differences in consumption index, approximate digestibility, and efficiency of conversion of digested food to body substance between larvae fed on tissue of susceptible and resistant genotypes were not significant. These results suggest that some components of the whorl tissue of resistant plants, especially the yellow-green portions of the leaf, inhibit food utilization in fall armyworm larvae.