Abstract
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.
Highlights
The highest root mass was observed in the landrace variety with Si application and without herbivory, and it was significantly lower when this maize genotype was under Si application and herbivory conditions (Table 1)
Our results showed that defense responses to Fall armyworm (FAW) were increased in maize plants by Si fertilization, which partially interacted with the effects of herbivory and were more specific to the landrace variety
The lower larval weight gain may have occurred because the larvae fed less on the landrace variety due to resistance induced by attacked plants under Si fertilization, which resulted in reduced injury to the plants
Summary
Smith) (Lepidoptera: Noctuidae) is considered the main insect pest of maize crop in Brazil (Cruz et al 2008; Lima Júnior 2012; Eghrari et al 2021) In recent years, it has become a new invasive species in West and Central Africa, where the first outbreaks were recorded in early 2016; the presence of distinct haplotypes collected from maize samples in Nigeria and São Tomé suggests FAW introduction to the African continent. It has become a new invasive species in West and Central Africa, where the first outbreaks were recorded in early 2016; the presence of distinct haplotypes collected from maize samples in Nigeria and São Tomé suggests FAW introduction to the African continent This pest has been reported more recently in Asian countries (Goergen et al 2016; Shylesha et al 2018; Jing et al 2019; Zhang et al 2019). FAW has become a pest that threatens food security in many developing countries worldwide and requires cost-effective control strategies
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