Silicon-Mediated Enhancement of Herbivore Resistance in Agricultural Crops

Abstract

Silicon (Si) is a beneficial mineral that enhances plant protection against abiotic and biotic stresses, including insect herbivores. Si increases mechanical and biochemical defenses in a variety of plant species. However, the use of Si in agriculture remains poorly adopted despite its widely documented benefits in plant health. In this study, we tested the effect of Si supplementation on the induction of plant resistance against a chewing herbivore in crops with differential ability to accumulate this element. Our model system comprised the generalist herbivore fall armyworm (FAW) Spodoptera frugiperda and three economically important plant species with differential ability to uptake silicon: tomato (non-Si accumulator), soybean, and maize (Si-accumulators). We investigated the effects of Si supply and insect herbivory on the induction of physical and biochemical plant defenses, and herbivore growth using potted plants in greenhouse conditions. Herbivory and Si supply increased peroxidase (POX) activity and trichome density in tomato, and the concentration of phenolics in soybean. Si supplementation increased leaf Si concentration in all plants. Previous herbivory affected FAW larval weight gain in all plants tested, and the Si treatment further reduced weight gain of larvae fed on Si accumulator plants. Notably, our results strongly suggest that non-glandular trichomes are important reservoirs of Si in maize and may increase plant resistance to chewing herbivores. We conclude that Si offers transient resistance to FAW in soybean, and a more lasting resistance in maize. Si supply is a promising strategy in management programs of chewing herbivores in Si-accumulator plants.

Silicon Fertilisation Affects Morphological and Immune Defences of an Insect Pest and Enhances Plant Compensatory Growth

“…We found that Si increased constitutive trichome density on leaves, which substantiates previous studies on grasses (Biru et al 2021;Johnson et al 2021) and other crops (Acevedo et al 2021). Interestingly, herbivory induced trichome production only on -Si plants, because + Si plants were already better defended with constitutively-produced silici ed trichomes, which were found to be essential for defence against chewing herbivores in rice (Andama et al 2020).…”

Siliceous and non‐nutritious: Nitrogen limitation increases anti‐herbivore silicon defences in a model grass

“…Si can be deposited within and between cells, at the leaf epidermis and within discrete structures including phytoliths, silica cells, prickle cells and trichomes/macro‐hairs (Hartley et al., 2015; Kumar et al., 2017). These structures are known to confer physical resistance to herbivory (Acevedo et al., 2021; Andama et al., 2020; Hall, Dagg, et al., 2020; Johnson, Hartley, Ryalls, et al., 2021). Strengthened and abrasive Si‐rich tissues can wear down mouthparts, lacerate herbivore organs and inhibit nutrient absorption once ingested (Massey et al., 2006; Massey & Hartley, 2009).…”

Detecting the Conspecific: Herbivory-Induced Olfactory Cues in the Fall Armyworm (Lepidoptera: Noctuidae)

“…The live and dry weight data were both fairly variable, and a larger sample size may have resulted in statistical significance. The availability of larval feeding data is similarly limited; however, Acevedo et al [28] recently reported that fall armyworm larvae that fed on corn plants with previous feeding damage gained less weight than larvae that fed on undamaged control plants [28]. Despite the dearth of current publications, the majority of…”

“…The live and dry weight data were both fairly variable, and a larger sample size may have resulted in statistical significance. The availability of larval feeding data is similarly limited; however, Acevedo et al [ 28 ] recently reported that fall armyworm larvae that fed on corn plants with previous feeding damage gained less weight than larvae that fed on undamaged control plants [ 28 ]. Despite the dearth of current publications, the majority of the data that are present in published studies indicate that the effects of conspecific feeding in fall armyworm populations is a subject matter that warrants further examination for the identification of alternative management tools for this damaging pest.…”