Submitted to: Maydica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/1999
Publication Date: N/A
Interpretive Summary: Vegetative development of the corn plant can be divided into two phases, juvenile and adult. Each stage is characterized by distinct differences in morphology and physiology. One of the most obvious differences is in the appearance of juvenile and adult leaves. Because of unique waxes on the leaf surface, juvenile leaves have a bluish appearance while adult leaves appear shiny green. Differences among varieties occur in timing of transition from the juvenile to adult phase. In this investigation, corn hybrids with resistance to leaf feeding by fall armyworm completed the transition from juvenile to adult earlier than susceptible hybrids. In laboratory experiments, fall armyworm larvae that fed on leaves of the resistant hybrids grew more slowly than those that fed on leaves of susceptible hybrids. Larvae that fed on adult leaves of a given hybrid, whether resistant or susceptible, weighed less than those fed on juvenile leaves of the same hybrid. Fall armyworm damage to late-planted corn in the South is a serious problem for corn producers. The association between earlier transition and resistance to fall armyworm means that plant breeders should be able to increase resistance to fall armyworm in corn by selecting for an earlier transition from juvenile to adult phase.
Technical Abstract: Vegetative development in maize can be divided into juvenile and adult phases. Each phase is characterized by distinctive morphology and physiology. Epicuticular waxes on juvenile leaves are bluish in appearance; adult leaves are shiny green in appearance. Two maize hybrids with resistance to fall armyworm feeding, two susceptible hybrids, and a hybrid with an intermediate level of resistance were evaluated for the timing of juvenile-adult phase transition and duration of transition period. The fall armyworm resistant hybrids completed the phase transition earlier than the susceptible hybrids. Earlier phase change was highly correlated with resistance to fall armyworm as indicated by reduced plant damage and lower larval weights in the field and laboratory bioassays.