Plant Nutrition Influences Resistant Maize Defense Responses to the Fall Armyworm (Spodoptera frugiperda)

Abstract

Plants are often confronted by different groups of herbivores, which threaten their growth and reproduction. However, they are capable of mounting defenses against would-be attackers which may be heightened upon attack. Resistance to insects often varies among plant species, with different genotypes exhibiting unique patterns of chemical and physical defenses. Within this framework, plant access to nutrients may be critical for maximal functioning of resistance mechanisms and are likely to differ among plant genotypes. In this study, we aimed to test the hypothesis that access to nutrition would alter the expression of plant resistance to insects and alter insect performance in a manner consistent with fertilization regime. We used two maize (Zea mays) genotypes possessing different levels of resistance and the fall armyworm (Spodoptera frugiperda) as model systems. Plants were subjected to three fertilization regimes prior to assessing insect-mediated responses. Upon reaching V4 stage, maize plants were separated into two groups, one of which was infested with fall armyworm larvae to induce plant defenses. Plant tissue was collected and used in insect bioassays and to measure the expression of defense-related genes and proteins. Insect performance differed between the two plant genotypes substantially. For each genotype, fertilization altered larval performance, where lower fertilization rates hindered larval growth. Induction of plant defenses by prior herbivory substantially reduced naïve fall armyworm growth in both genotypes. The effects between fertilization and induced defenses were complex, with low fertilization reducing induced defenses in the resistant maize. Gene and protein expression patterns differed between the genotypes, with herbivory often increasing expression, but differing between fertilization levels. The soluble protein concentrations did not change across fertilization levels but was higher in the susceptible maize genotype. These results demonstrate the malleability of plant defenses and the cascading effects of plant nutrition on insect herbivory.

Effects of plant-beneficial fungi on plant growth and herbivore resistance under contrasting fertilizer conditions

“…Fertilization enhanced basal transcript levels (expression levels in absence of herbivory) of SA-dependent defenses, while no effect was found on JA-dependent signaling. The latter is in agreement with previous research reporting no effect of fertilization on constitutive proteinase inhibitor activity or total JA-production in the absence of herbivory (Chen et al 2008;Mason et al 2022;Stout et al 1998). Furthermore, in inoculated plants stink bug feeding generally induced higher expression of SA-and JA-dependent defenses.…”

Nutrition vs association: plant defenses are altered by arbuscular mycorrhizal fungi association not by nutritional provisioning alone

“…Studies have shown that feeding by FAW, as well as FAW saliva and frass, elicit changes in expression of genes along both the JA and SA pathways [42][43][44]. It has also been shown that maize defense compounds are altered by AMF colonization of plant roots [45][46][47] and by plant fertilization [48][49][50]. Furthermore, soil legacies left behind by different cover crop species have been shown to differentially alter plant nutrition, AMF colonization, and regulation in JA and SA defense genes in subsequent maize plants, as well as alter the feeding and behavior of FAW larvae toward those maize plants [51].…”

Development of a polyphagous leaf beetle on different host plant species and its detoxification of glucosinolates

“…In contrast, polyphagous herbivores have to deal with a broad range of defences of plants belonging to different taxa (Halon et al, 2015;Katsanis et al, 2016). The nutritional quality and composition of natural products of the host plants influence the development and population dynamics of herbivores (Mason et al, 2022). Their behavioural, physiological and biochemical adaptations determine how herbivores develop on these plants and how they deal with the plant chemistry (Després et al, 2007;Beran and Petschenka, 2022).…”