ANATOMICAL CHARACTERISTICS OF MAIZE RESISTANT TO LEAF FEEDING BY SOUTHWESTERN CORN-BORER (LEPIDOPTERA, PYRALIDAE) AND FALL ARMYWORM (LEPIDOPTERA, NOCTUIDAE)

Maize, Zea mays L., inbred lines with resistance to leaf feeding by the larvae of the southwestern corn borer. Diatraea grandiosella Dyar, and the fall armyworm, Spodoptera frugiperda (J. E. Smith) have been released. The mechanisms of resistance are larval antibiosis and nonpreference; however, the factor or factors causing the resistance are not fully understood. In this study, selected anatomical characters of inner whorl tissue of several leaf feeding susceptible and resistant maize inbreds were compared. For both insect species, correlations were calculated between the anatomical characters and leaf feeding damage scores and between the anatomical characters and weights of larvae. Significant differences were detected between several anatomical characters of the resistant and susceptible inbreds. The most striking and consistent difference between the resistant and susceptible inbreds was the thickness of the cuticle and the epidermal cell wall (cell wall complex). The cell wall complex of the resistant inbreds was 1.7x thicker than that of the susceptible inbreds. Significant correlations existed between anatomical characters of the inner whorl and both leaf feeding damage scores and larval weights. The characters most closely associated with leaf feeding damage and larval weights were the upper and lower cell wall complexes. The inner whorl tissue from the resistant inbreds tended to be tougher than comparable tissue of the susceptible inbreds.