Characterization of priming,induced resistance,and tolerance to Spodoptera frugiperda by silicon fertilization in maize genotypes

Fall armyworm (FAW) Spodoptera frugiperda is considered the main defoliating insect pest of maize in many countries. Silicon (Si) applied to plants has been shown to increase the resistance to insects, especially in grasses such as maize. This study characterized the effects of Si fertilization regarding priming, induced resistance, and tolerance to FAW in a landrace variety and hybrid of maize. Si was applied in soil of potted-plants as H₄SiO₄ at 2 t ha^?1 when maize plants were at V2 stage, and when they reached V3 two FAW neonates were placed in the plant’s whorls to cause herbivory. FAW performance was evaluated on excised leaf sections in the laboratory and on plants with larvae infesting V4-stage plants in the greenhouse. Concentrations of H₂O₂, malondialdehyde, and Si, and the activities of antioxidant enzymes were recorded and correlated to Si-based responses on plant growth, and FAW injury and performance. As main results, there was reduced FAW injury and larval weight gain in Si-treated plants subjected to herbivory. Greater root dry mass was observed in the landrace variety with Si and without herbivory. Landrace plants showed higher shoot weights than the hybrid under FAW infestation. Si-fertilized plants showed higher H₂O₂ concentrations. The highest peroxidase activities occurred in Si-treated plants without herbivory, and the catalase and superoxide dismutase activities were highest in Si-treated plants without herbivory or herbivory-injured plants without Si. In conclusion, Si-based defense in maize to FAW involve mixed effects of priming and tolerance, and were more pronounced in the landrace variety.