Soybean defense induction to Spodoptera cosmioides herbivory is dependent on plant genotype and leaf position

Abstract

Plants have evolved a diverse array of defensive mechanisms against biotic and abiotic stresses, which can be either constitutive or inducible. Variation in plant-intrinsic factors such as the genotype and the leaf position coupled with insect herbivory can affect the expression of resistance to insects. We investigated if soybean defense induction triggered by Spodoptera cosmioides herbivory varies in function of the genotype and leaf position. This hypothesis was tested in two bioassays using leaf discs or entire leaflets collected from the upper and lower trifoliates of S. cosmioides-injured and uninjured V3-V4 soybean plants. We used one genotype that was constitutively resistant and one that was constitutively susceptible to S. cosmioides based on previous screening. Third-instar larvae were fed one of the treatments and assayed for leaf consumption, larval growth, and efficiency of conversion of ingested food. Genotype and leaf position significantly interacted with herbivory and affected soybean-induced resistance to S. cosmioides. Negative responses on S. cosmioides larvae consumption and growth rates were only observed when leaf material was originated from the upper soybean trifoliate. The susceptible soybean genotype did not exhibit induced resistance characteristics. Food offered as leaf disc was better at demonstrating induced resistance in previously injured soybean, whereas offering entire leaflet the induced effects were less pronounced. Here we provide new findings on soybean resistance by demonstrating that resistance induction to S. cosmioides herbivory is dependent on the plant genotype and leaf position where injury took place, with negative effects better evinced in bioassays using leaf discs than entire leaflets.

Maize resistance to Spodoptera frugiperda and its relationship to landrace variety, plant stage, and larval origin

“…In plants, factors such as genotype and phenology can influence resistance manifested against insect pests (Bowers & Stamp, 1993; de Freitas et al, 2018). However, insect symbiotic bacteria can also modulate plant defenses (Chung et al, 2013; Acevedo et al, 2017), and laboratory‐reared insects usually possess fewer and less‐diverse gut bacteria compared to their wild conspecifics.…”

Antibiosis to Spodoptera frugiperda (Lepidoptera: Noctuidae) in chickpea genotypes

“…The experiment was completely randomized with ten treatments (genotypes) and ten repetitions (individually separated larvae). The number of repetitions was based on previous studies (Freitas et al ., 2018; Queiroz et al ., 2020).…”

Protocol for assessing soybean antibiosis toChloridea virescens

“…The use of resistant cultivars is an important control tactic within a program of soybean integrated pest management, mainly because the adoption of this tactic contributes to reducing the use of insecticides in the crop. There have been several recent studies evaluating soybean cultivars for resistance to lepidopterans (Souza et al, 2014a,b; Boiça Júnior et al, 2015; Favetti et al, 2015; Wang et al, 2015; Chen et al, 2018; Freitas et al, 2018; Coelho et al, 2020; Queiroz et al, 2020), including C. virescens (Almeida et al, 2017a,b). However, studies aiming to develop an adequate, high‐throughput phenotyping protocol to evaluate soybean cultivars for resistance to lepidopterans are scarce in the literature (Eduardo et al, 2020), and to our knowledge, no studies have determined a protocol for antibiosis assays in soybean to lepidopterans.…”