Role of maize kernels on the fitness of Spodoptera frugiperda (Lepidoptera: Noctuidae).

Recent outbreak of the fall armyworm, Spodoptera frugiperda (JE Smith), has caused considerable challenges to maize production, Zea mays L., in the world. Sustainable pest management through host plant resistance requires further confirmation of maize hybrids that reduce pest pressure during postflowering stage. In this study, the comparative resistance of kernels from 10 maize hybrids, including BC678, SC201, SC704, SC410, SC706, SC400, SC260, BK66, SC705, and BK65, was evaluated using the nutritional indices, demographic parameters, and enzymatic activities of Spodoptera frugiperda in relation to kernel biochemical traits. The selected hybrids are widely cultivated in Iran and represent the major maturity classes. Larvae fed on BC678 and SC705 exhibited lower efficiencies of conversion of ingested (ECI) and digested food (ECD), accompanied by higher relative metabolic rate and metabolic cost. In contrast, higher ECI and ECD values were observed on SC704 and SC400. The intrinsic rate of increase (r) ranged from 0.110 to 0.169 day-1 across treatments, with the lowest value recorded on SC705 and higher values on SC410 and SC706. Lower finite rate of increase (λ) and gross reproduction rate were also obtained on SC705. Decreased amylase activity was recorded on SC705. Moreover, larvae reared on SC705 displayed the highest peroxidase activity, while those reared on BC678 and SC705 showed increased superoxide dismutase activity. Variations in the concentrations of primary and secondary metabolites in the kernels significantly affected pest performance. The clustering results additionally classified SC705 as the least suitable hybrid for S. frugiperda, indicating its potential as a source of host plant resistance for maize breeding and as a component of integrated pest management programs to reduce insect damage during kernel development.