Field evaluations of hydroxamic acids as antibiosis factors in elite maize inbreds to the western corn rootworm (Coleoptera: Chrysomelidae)

The relationship between total hydroxamic acid content in roots of 9 inbreds of maize, Zea mays L., and root damage by western corn rootworm, Diabrotica virgifera virgifera LeConte, larvae was investigated. Measurements of root damage made just before adult rootworm emergence revealed a significant negative correlation between root damage rating and the logarithm of total hydroxamic acid content detected by high-pressure liquid chromatography. However, no correlation was found between these variables at the end of the growing season. Plant morphological factors, plant height, and total leaf count were not affected by infestation with western corn rootworm larvae and are therefore insensitive as measurements of plant damage. Generally, relative number of days to silk of susceptible inbreds was significantly increased with increasing infestation with western corn rootworm larvae, but remained unaffected in resistant inbreds. Inbreds containing high levels of root hydroxamates had significantly lower reductions in seed yield than inbreds containing low levels of root hydroxamates. It appears that resistance, in the form of antibiosis, is present in midwhorl maize inbreds to the western corn rootworm larvae and that root hydroxamic acid content may be contributing to this resistance