Vegetative phase change in maize and its association with resistance to fall armyworm

Vegetative development in maize can be divided into juvenile and adult phases. Each phase is characterized by distinctive morphology and physiology. 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 armyworn 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. When using leaves collected at different vegetative stages of plant development and lyophylized for artificial diet bioassays, fall armyworm resistance was highly correlated with juvenile-adult phase transition.