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Article

Impact of Maize Nutrient Composition on the Developmental Defects of Spodoptera frugiperda

by
Wenjie Zhang
1,
Haolin Li
1,
Cuifang Zhang
2,
Jiangan Hou
1,
Xiaxia Guo
1,
Dengfeng Dong
3 and
Xuesheng Li
1,*
1
Guangxi Key Laboratory of Agric-Environment and Agric-Products Safety, College of Agriculture, Guangxi University, Nanning 530004, China
2
Dongguan Houjie Town Agricultural Technology Service Center, Dongguan 523086, China
3
College of Agriculture, Guangxi University, Nanning 530004, China
*
Author to whom correspondence should be addressed.
Agronomy 2024, 14(8), 1690; https://doi.org/10.3390/agronomy14081690
Submission received: 20 June 2024 / Revised: 21 July 2024 / Accepted: 30 July 2024 / Published: 31 July 2024
(This article belongs to the Section Pest and Disease Management)
Browse Figures
Versions Notes

Abstract

:
Spodoptera frugiperda (J.E. Smith) is a crucial agricultural pest owing to its global impact on >300 crops. Among these, the corn strain of S. frugiperda causes significant damage to maize (Zea mays L.). However, limited research exists on the influence of maize nutrients on the metamorphosis of S. frugiperda and the underlying mechanisms. In this study, the effects of different growth stages of maize leaves, namely, tender leaves (tender) and mature leaves (mature), on various aspects of larval development, including body weight, body length, developmental age, pupation rate, and eclosion rate, were investigated. Additionally, we measured the levels of 20-hydroxyecdysone (20E) and three types of juvenile hormone (JH; i.e., JH I–III) in S. frugiperda larvae fed on tender or mature. The results revealed that larvae fed on Tender exhibited significantly prolonged instar duration, reduced body weight and length, and decreased pupation and eclosion rates, with the emergence of abnormal adults. Analysis of nutritional components in maize leaves revealed significantly higher levels of amino acids, soluble sugars, and sterols in mature than in tender. Hormone analysis in S. frugiperda larvae revealed higher 20E titers in individuals feeding on mature during prepupal and pupal stages. We demonstrated the crucial role of sterols in regulating the level of 20E and pupation rate of S. frugiperda. Based on these findings, we propose that isoleucine, arginine, glutamic acid, sucrose, campesterol, and β-sitosterol serve as key nutrients influencing the development of S. frugiperda. Moreover, β-sitosterol is a significant factor influencing the interaction between maize leaves and S. frugiperda. Our research results provide a reference for the control strategy of S. frugiperda based on breeding insect-resistant varieties by altering host nutrition.

Graphical Abstract

1. Introduction

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a phytophagous insect [1,2] that can be categorized into two strains based on its preferred host plant: rice strain and corn strain [3,4,5]. The rice strain of S. frugiperda primarily feeds on rice, while the corn strain mainly feeds on corn. Originating from the Americas, this pest has caused significant economic damage to global agriculture. Particularly in maize-growing areas, the larvae of these pests cause extensive damage to maize, leading to stunted growth and reduced yields [6,7,8]. The strain of S. frugiperda that has invaded China is the corn strain, and its rapid spread poses a serious threat to maize safety and production stability, presenting a major challenge to Chinese agriculture [6,9,10].
Host plants play a crucial role in the growth and development of herbivorous insects by providing essential nutrients, such as nitrogenous compounds, carbohydrates, and sterols [1,11,12]. Nitrogen, an essential element, is vital for protein synthesis and nucleic acid synthesis [13]. Free amino acids, nitrogen-containing compounds, serve as crucial nutrients for insects [14,15]. Carbohydrates, particularly sugars, are also important for the survival, growth, development, flight migration, reproduction, and other vital processes of insects [16,17]. For example, insects rely on sugars as a rapid energy source during take-off or short-distance flight [13].
As arthropods, insects lack the ability to synthesize cholesterol de novo owing to the absence of multiple enzymes involved in the cholesterol synthesis pathway [18,19,20]. Therefore, phytophagous insects must acquire sterols from plants to meet their growth and development requirements [21]. Sterols, which are important constituents of cell membranes, maintain membrane fluidity and integrity [19]. Additionally, sterols act as precursors for sterol hormones, such as ecdysone, with 20-hydroxyecdysone (20E) being the primary form in insects, which plays a crucial role in insect molting and metamorphosis as well as other physiological processes across various organisms [22,23].
The growth and development of insects are regulated by the interplay between juvenile hormones (JHs) and 20E [24]. JH primarily facilitates larval growth and prevents larvae from transitioning into pupae and adults [25], whereas 20E mainly regulates larval molting and metamorphosis [26]. Most insects exclusively biosynthesize JH III [23,25], whereas S. frugiperda, similar to other lepidopteran insects, produces JH I, JH II, and JH III during larval and adult stages [27,28]. The combined action of JH I–III and 20E hormones orchestrates the metamorphosis of S. frugiperda. The nutritional quality of the diet significantly influences the syntheses of JH and 20E, thereby impacting insect growth and development [29,30].
These findings demonstrate that nutrients from host plants regulate the synthesis of JHs and 20E, thereby influencing the growth and development of insects. S. frugiperda primarily relies on maize as its main food source and exhibits rapid reproductive rates, indicating its reliance on maize for essential nutrients [1]. However, there is limited research on how maize nutrients specifically regulate JHs and 20E and consequently affect the growth and development of S. frugiperda. If these relationships can be clarified, future studies could potentially decrease the content of certain nutrients in maize leaves through breeding. This could in turn affect the levels of JH and 20E within S. frugiperda, aiming to inhibit their growth and development. This will provide a theoretical foundation for the control of S. frugiperda.
With more than half of the one million known insect species being herbivorous [31], there exist countless opportunities for novel interactions between insects and plants [32]. Sitobion avenae contains pectinases that induce wheat (Triticum aestivum) to release volatiles, enhancing the plant’s attraction to Aphidius avenae [33]. However, infestation by Ostrinia nubilalis triggers maize to produce large quantities of diterpenoid compounds called kauralexins, which have antifeedant effects against Ostrinia nubilalis [34,35]. Similarly, by understanding the interactions between S. frugiperda and maize, and identifying key influential factors, we can contribute to the control of S. frugiperda.
The feeding behavior of S. frugiperda is quite complex. Early-stage larvae prefer tender leaves. However, our previous research found that if larvae only feed on tender leaves during their larvae stages, their development slows down, the pupation rate is low, and abnormal pupae and adults appear.
Aim to study how the different nutritional components in leaves of varying maturity levels affect the metamorphosis and pupation of S. frugiperda. In this study, we investigated the growth and development of S. frugiperda by feeding maize leaves of the same variety at two different growth stages. The changes in 20E, JH I, JH II, and JH III titers in S. frugiperda were monitored, and the nutritional components of maize leaves were compared between the two stages. This study aimed to determine the impact of nutrients on the growth and development of S. frugiperda, identify its essential nutritional requirements, and investigate the impact of nutritional components on the interaction between maize and S. frugiperda. Provide empirical evidence and a theoretical foundation for the prevention of pests and the screening of resistant maize varieties.

2. Materials and Methods

2.1. Planting of Maize Leaves

The maize variety was Yuebainuo-6, and the seeds were purchased from the Chunmanyuan Seed Industry. The test plants were cultured in the net room without pesticide treatment, and the maize leaves with growth stages of 10 days and 60 days were selected for the test. In this experiment, the maize row spacing was 60 cm, and the plant spacing was 25 cm. Urea, ammonium dihydrogen phosphate, and potassium chloride were applied as fertilizers twice throughout the growing season. Half of the total nitrogen fertilizer was used as the base fertilizer and applied to the soil before the maize was sown. Based on the first day of the feeding experiment, the maize planting schedule was as follows: the first batch of maize seeds was sown 60 days before the start of the experiment (60-day maize plants, mature leaves), and the second batch of maize seeds was sown 10 days before the start of the experiment (10-day maize plants, tender leaves). Maize plants that were in 10-day growth stages typically had 4–5 leaves, while maize plants that were in 60-day growth stages generally had 10–15 leaves. On the first day of the experiment, the 2nd to 4th leaves were harvested from both the 60-day and 10-day growth stages of maize plants. The leaves from the two different growth stages were placed into separate sealed bags and stored at 4 °C, serving as a food source for S. frugiperda. From the first day of the feeding experiment, two different leaves were taken out daily and fed to the larvae of S. frugiperda.

2.2. Rearing of S. frugiperda

S. frugiperda (corn strain) was collected from maize fields in Xixiangtang District, Nanning City, China. After 10 generations of artificial feed at (26 ± 1) °C, relative humidity (75 ± 5)%, and photoperiod 16 L/8 D in a greenhouse, larvae of S. frugiperda were individually placed into enclosed round pudding containers (6 cm × 2 cm: diameter × height) and fed maize leaves (with a growth stage of 30–40 days), with fresh maize leaves replaced daily. The container lids were punctured with small holes (approximately 1 mm in diameter) to allow for air exchange. Filter paper (6 cm in diameter) was placed at the bottom of the containers as bedding. Within 24 h after emergence, healthy first-emergence female and male moths were selected and placed into disposable plastic cups (500 mL), maintaining a 1:1 ratio of females to males. The mouths of the plastic cups were covered with sterile gauze for oviposition, and the moths were fed 10% honey water. The gauze was replaced daily. The newly hatched larvae were selected for the feeding experiment.

2.3. Chemicals and Reagents

Juvenile hormone and ecdysone: JH I, JH II, JH III, and β-hydroxyecdysone(20E). 21 amino acids (AA): Aspartic acid (Asp), Glutamic acid (Glu), Asparagine (Asn), Serine (Ser), Glutamine (Gln), Histidine (His), Glycine (Gly), Argnine (Arg), Threonine (Thr), Alanine (Ala), γ-aminobutyric acid (GABA), Proline (Pro), Theanine (The), Cysteine (Cys), Tyrosine (Tyr), Valine (Val), Methionine (Met), Lysine (Lys), Isoleucine (Ile), Leucine (Leu), Phenylalanine (Phe). Four soluble sugars: glucose, fructose, sucrose, and maltose. Four sterols: stigmasterol, β-sitosterol, campesterol, and stigmastanol. N-methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA), N, N-dimethylformamide (DMF), 6-Aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC), and the details of these standards are listed in Table S1 of the Supporting Information.
Acetonitrile (HPLC grade) was purchased from Merck (Darmstadt, Germany). Analytical-grade methanol, n-hexane, and isooctane were purchased from Chengdu Kelong Chemical Reagents (Chengdu, China). Ultrapure water was obtained using a Milli-Q treatment system (Millipore, Billerica, MA, USA).

2.4. The Feeding Experiment of S. frugiperda Larvae

Two experimental groups were established, with tender and mature leaves provided as dietary treatments. Three replicates were established for each experimental group, with a total of 300 S. frugiperda larvae in each replicate. Each larva was individually reared under consistent feeding conditions, as described in Section 2.2.
Each treatment was meticulously monitored and documented, commencing from the newly hatched larvae, with daily inspections to ensure timely food replacement.
Additionally, our previous research revealed that larvae younger than the 3rd instar cannot feed on mature leaves and have a high mortality rate. This may be because the hardness of mature leaves makes it difficult for 1st and 2nd instar larvae to consume. Hence, we chose 3rd instar larvae for our experiments.
From the 3rd instar stage onwards, each larva was individually fed. To facilitate feeding, the maize leaves were cut into 1 cm × 1 cm pieces, and a sufficient amount of maize leaves was provided to the larvae daily. S. frugiperda, which feeds on mature maize leaves, is referred to as MSF, while the one that feeds on tender maize leaves is known as TSF. The growth of 3rd to 6th instar larvae was documented, encompassing daily measurements of larval weight and length (all taken within 12 h after molting), as well as calculations for larval duration, pupal weight, pupal stage, pupation rate, eclosion rate, and teratological rate. Male and female individuals of MSF are referred to as M-male and M-female, respectively. Male and female individuals of TSF are referred to as T-male and T-female, respectively (Figure 1).

2.5. Determination of 20E, JH I, JH II, and JH III in S. frugiperda

The analytical methods developed by Yi et al. [36] and Fang et al. [37] were refined for the quantification of 20E, JH I, JH II, and JH III in S. frugiperda.
About 0.1 to 0.5 g of S. frugiperda was weighed and placed into a 10 mL centrifuge tube, followed by the addition of eight small steel balls, 50 mg of anhydrous magnesium sulfate, and 3 mL of ethanol. The mixture was then ground at 60 Hz for 2 min using a grinding instrument, oscillated for three minutes, and finally centrifuged at 4000 r min−1 for 5 min. The supernatant was transferred and extracted twice.
Two milliliters of a mixed solution containing 0.9% sodium chloride and acetonitrile in a ratio of 1:1 was added, followed by the addition of 3 mL of n-hexane. The solution was shaken for three minutes before centrifuging at 4000 r min−1 for five minutes. The supernatant was transferred to another container, and 3 mL of n-hexane was added. This extraction process was repeated twice before combining all four supernatants obtained. The resulting mixture was then dried using the nitrogen blow dry method, after which ethanol was added to achieve a constant volume of 0.2 mL. The sample was filtered through a nylon syringe filter with a pore size of 0.22 μm before being transferred into an inner tube for analysis using UPLC-MS/MS.
An ultra-performance liquid chromatography (UPLC) system with an autosampler (Waters, Milford, CT, USA) coupled with an electrospray ionization tandem mass spectrometer (API 4000, AB SCIEX Instruments, Redwood City, CA, USA) was used for analysis. Target chemicals were measured using multiple reaction monitoring (MRM) in the positive and negative modes. The MRM and other mass spectrometric parameters (i.e., theoretical mass, quantifying ions, qualitative ions, cone voltages, and collision energies) are shown in Table 1. The temperature of the MS source, nebulous gas, and heating gas was 550 °C, and the pressure was 50 psi. The ion spray voltage was optimized at 5500 eV for positive ionization. Data were acquired and analyzed using Analyst v.1.6.2 (Applied Biosystems/MDS SCIEX Instruments). The samples (15 μL) were injected and separated at 30 °C at a flow rate of 0.5 mL min−1. In this study, four analytes (JH I, JH II, JH III, and 20E) were separated on an Agilent ZORBAX StableBond SB-C18 column (100 mm × 2.1 mm, 1.8 μm, Santa Clara, CA, USA). The mobile phase consisted of 0.1% formic acid in ultrapure water (solvent A) and 0.1% formic acid in ACN (solvent B) with the following gradient: 0 min, 85% solvent A, held for 1 min, 1–5 min linear gradient, 85–0% solvent A, held for 2 min, and 7–9 min linear gradient, 0–85% solvent A, held for 1 min. The total elution time was 10 min, and all analytes were separated within 6 min.

2.6. Determination of 21 Amino Acids Content in Maize Leaves

The analytical method developed by GB/T 30987-2020 [38] was refined for the quantification of 21 amino acids in maize leaves.
Five grams of maize leaves was precisely weighed and placed into a 250 mL conical flask. Then, 200 mL of boiling water was added to the mixture, which was heated in a 95 °C water bath. The solution was mixed every 5 min, extracted for 10 min, and filtered while still hot. After cooling to room temperature, pure water was added until the volume reached a constant value of 10 mL. After agitation, the sample solution was filtered through a 0.45 μm membrane filter. A clean 150 μL glass tube was used to dispense 10 μL of the prepared sample or standard working solution, followed by the addition of 70 μL of derivative buffer solution and the subsequent addition of 20 μL of derivative reagent. The mixture was vortexed for 10 s, sealed in an injection vial, and allowed to stand at room temperature for one minute before being transferred to a preheated oven at 55 °C for 10 min. After cooling to room temperature, the mixture was subjected to HPLC analysis.

2.7. Determination of 4 Soluble Sugars Content in Maize Leaves

The analytical method developed by Gailing et al. [39] was refined for the quantification of 4 soluble sugars content in maize leaves.
Two grams of crushed maize leaves was weighed and placed in a 50 mL centrifuge tube, followed by the addition of 40 mL of ultrapure water. The mixture was vigorously shaken and subjected to ultrasonic cleaning for 40 min before being centrifuged at a speed of 4000 r min−1 for 10 min. The supernatant was then carefully removed, with only 10 mL transferred into a clean and dry volumetric flask with a capacity of 100 mL. After dilution with ultrapure water, the solution was thoroughly mixed, filtered through a membrane with a pore size of 0.45 μm, and finally analyzed using ion chromatography.

2.8. Determination of 4 Sterols Content in Maize Leaves

The analytical method developed by Asl et al. [40] was refined for the quantification of 4 sterols in maize leaves.
Maize leaf samples were freeze-dried, crushed, and passed through a 40-mesh sieve. A precisely weighed 100 mg sample was placed in a 4 mL centrifuge tube and extracted with 1.5 mL of n-hexane using ultrasonication for 10 min. The mixture was then centrifuged at 6000 r min−1 for 5 min.
Five hundred microliters of the sample was transferred into a chromatographic injection bottle, followed by the addition of 50 μL of derivatization reagent (MSTFA/DMF, volume ratio 1:1). The mixture was subjected to a derivatization reaction at 40 °C for 50 min in a water bath. After cooling down to room temperature and passing through a nylon syringe filter with a pore size of 0.22 μm, the samples were analyzed using GC-MS/MS.

2.9. Data Analysis

Pairwise comparisons, e.g., TSF versus MSF (Figures 3 and 4, Tables 4 and 5), tender versus mature (Figure 5), and CK versus treatment (Figure 7c), were analyzed for significance with Student’s t-test (p < 0.05). ANOVA was performed for multiple comparisons. In investigating the effects of sterols on the growth and development of S. frugiperda larvae, we selected three different sterols, each tested at five distinct concentrations. Significant differences were observed both between the various concentrations of the same sterol and among the different sterols. Consequently, we employed ANOVA for the analysis (Table 5, Figure 7a). Significant treatment effects were investigated when the main ANOVA effects were significant (p < 0.05).

3. Results

3.1. Method Validation

The results showed that S. frugiperda exhibits matrix effects on 20E and JHs, necessitating the use of a matrix standard curve to ensure linearity in the analysis. Table 2 presents the calibration curves, correlation coefficients, linear ranges of the curves, limits of detection (LOD) and quantification (LOQ), as well as matrix effects for 20E and JHs from S. frugiperda. A linear range of 1–200 ng mL−1 was examined for the JHs, while a linear range of 1–4000 ng mL−1 was examined for the 20E. The linearity range and correlation coefficients were obtained from matrix-matched calibration curves. The correlation coefficients of the calibration curves were all >0.99, and the linear range was also favorable for detecting low titers of 20E and JHs. The recovery rates were 75–88% at 1–10 ng mL−1 and 83–95% at >10 ng mL−1, and the RSD of the overall data was <15%, as shown in Table 3. The matrix effect was calculated from a calibration curve, although the results showed a weakening effect overall; the LOD and LOQ were 0.04–0.30 and 0.12–0.90 ng mL−1, respectively. Thus, the 20E and JHs that needed to be measured still met the accuracy requirements defined by the validation (Table 2).
Table 2 lists the linear ranges and linear equations of the 21 amino acids, including the standard curves, correlation coefficients, linear ranges, LOD, and LOQ. The results demonstrate that a linearity range of 50–10,000 ng mL−1 was observed for the 21 amino acids. All the standard curves exhibited correlation coefficients greater than 0.99, indicating a favorable linear range for detecting the content of these amino acids in maize leaves. The LOD and LOQ values were determined to be 0.45–15.12 and 1.35–45.36 ng mL−1, respectively. Therefore, the measurements of the 21 amino acids complied with the accuracy requirements as defined by the validation (Table 2).
Similarly, Table 2 also provides the linear ranges and linear equations for the 4 soluble sugars, including the standard curves, correlation coefficients, linear ranges, LOD, and LOQ. The investigation revealed a linear range of 100–5000 ng mL−1 for the 4 soluble sugars. The standard curves exhibited correlation coefficients greater than 0.99, indicating a favorable linear range for detecting the content of these sugars in maize leaves. The LOD and LOQ values were determined to be 12.36–33.25 and 37.08–92.22 ng mL−1, respectively. Hence, the measurements of the 4 soluble sugars fulfilled the accuracy requirements as defined by the validation (Table 2).
Furthermore, Table 2 lists the linear ranges and linear equations for the 4 sterols, including the standard curves, correlation coefficients, linear ranges, LOD, and LOQ. The analysis demonstrated a linear range of 50–5000 ng mL−1 for the 4 sterols. All the standard curves exhibited correlation coefficients greater than 0.99, indicating a favorable linear range for detecting the content of these sterols in maize leaves. The LOD and LOQ values were determined to be 9.69–15.47 and 29.07–46.41 ng mL−1, respectively. Therefore, the measurements of the 4 sterols satisfied the accuracy requirements as defined by the validation (Table 2).

3.2. Effects of Feeding on Maize Leaves at Different Growth Stages on the Growth and Development of S. frugiperda

The growth and development of S. frugiperda were examined by feeding them with tender and mature maize leaves separately. The results revealed that, except for the adult stage, MSF had a shorter instar duration than TSF (Table 4). The adult stage of MSF was significantly longer than that of TSF (p ≤ 0.01; Table 4). Additionally, the 1st and 4th instar duration as well as the total instar duration of MSF were shorter than those of TSF (p ≤ 0.05; Table 4). During the larval stage (1st–6th instars), the length of MSF instars was significantly shorter than that of TSF instars (p ≤ 0.01; Table 4). The pupation and eclosion rates of TSF were lower than those of MSF (p ≤ 0.01), whereas the adult teratological rate was higher in TSF than in MSF (p ≤ 0.01; Figure 1; Table 5). Significant differences were observed in the phenotype, weight, and length of TSF and MSF. Until the 10th day, the weight and length of MSF were higher than those of TSF (Figure 2a,b and Figure 3). On the 11th day, the weight and length of MSF started to decrease after entering the prepupal stage, whereas TSF remained in the larval stage on this day (Figure 3).

3.3. Effects of Feeding on Maize Leaves at Different Growth Stages on the Levels of 20E, JH I, JH II, and JH III in S. frugiperda

In order to clarify the impact of nutritional components on endogenous hormone levels during the larval and adult stages of S. frugiperda, we measured the titers of 20E, JH I, JH II, and JH III in larvae and adults of S. frugiperda that fed on tender and mature leaves. The 20E titer in S. frugiperda was initially low during the larval stage but began to increase from the prepupal stage. The peak titer of 20E was observed in the middle of the pupal stage, which then decreased gradually. The 20E titer in MSF started to increase on the 11th day, whereas that in TSF began increasing on the 13th day. Consequently, MSF entered the prepupal stage earlier than TSF. The 20E titer in MSF reached its highest value (5969.5 ng g−1) on the 13th day, whereas that in TSF reached its highest value (472.3 ng g−1) on the 15th day. The 20E titer in MSF was 12.6-fold higher than that in TSF. The 20E titer in M-female decreased to 34.6 ng g−1 during early adulthood, whereas the 20E titers in M-male, T-female, and T-male were ≤0.36 ng g−1 (Figure 4a and Figure S1a).
The titers of JH I and JH II exhibited a decreasing trend with the progression of larval instars, ultimately reaching ≤0.05 and 0.06 ng g−1 during the pupal stage, respectively. JH I and JH II were exclusively detected in adult males, with M-male (18.7 ng g−1) exhibiting a 4.16-fold higher titer of JH I than T-male (4.5 ng g−1). Additionally, M-male (40.2 ng g−1) exhibited a 2.15-fold higher titer of JH II than T-male (18.7 ng g−1) (Figure 4b,c and Figure S1b,c). The titer of JH II in S. frugiperda was generally low and exhibited no discernible pattern. The titers of JH III in M-male and M-female were 1.2 and 1.1 ng g−1, respectively, whereas those in T-male and T-female were ≤0.08 ng g−1 (Figure 4d and Figure S1d).
Overall, the titers of JH I, JH II, and 20E showed significant changes during the developmental stages of S. frugiperda. A marked increase in 20E titer was noted during the prepupal stage, although JH I and JH II titers were not detectable. Conversely, in the adult stage, the titers of JH I and JH II significantly increased, but no detectable titers of 20E were noted. Moreover, no discernible trend in JH III titer was noted. During metamorphosis development, compared with TSF fed on tender leaves, MFS fed on mature leaves exhibited an initial increase in 20E titer during the pupal stage, followed by a rise in JH I and JH II titers during adulthood. This finding provides a plausible explanation for the earlier pupation and emergence of MSF fed on mature leaves.

3.4. Differences in the Levels of 21 Amino Acids in Maize Leaves at Different Growth Stages

Amino acids play a crucial role in insect growth and development, and they can be classified into essential and nonessential amino acids. Essential amino acids are vital for insect development but cannot be synthesized by insects themselves, necessitating their supply through food. We determined the levels of 21 amino acids, including 9 essential amino acids, in tender and mature leaves. The levels of essential amino acids, including His (9.6 μg g−1), Arg (1.29 μg g−1), Thr (9.1 μg g−1), Val (29.8 μg g−1), Lys (19.8 μg g−1), Ile (11.6 μg g−1), Leu (21.1 μg g−1), and Phe (8.4 μg g−1), were higher in mature leaves than in tender leaves. Notably, Arg and Ile were only detected in mature leaves. Several amino acids, including Glu, Asn, Pro, and Cys, exhibited significantly higher levels in mature leaves than in tender leaves (p ≤ 0.05). Furthermore, the levels of Ser, Gln, Gly, Arg, Thr, GABA, Tyr, Val, Lys, Ile, Leu, and Phe were significantly higher in mature leaves than in tender leaves (p ≤ 0.01). The three most abundant amino acids in mature leaves were Ser (138.0 μg g−1), Gly (77.4 μg g−1), and Ala (75.6 μg g−1), with their levels being 5.4-, 5.3-, and 1.6-fold higher than those in tender leaves, respectively (Figure 5a).

3.5. Differences in the Levels of Four Soluble Sugars in Maize Leaves at Different Growth Stages

Sugars serve as a crucial energy source for insect growth and development and are also converted into fat stores. Certain sugars, including glucose, maltose, sucrose, and fructose, are readily utilized by insects owing to their stimulant properties. The levels of four soluble sugars in tender and mature leaves were analyzed.
The results revealed the presence of three soluble sugars, namely, glucose, fructose, and sucrose, in mature leaves, whereas only glucose and fructose were detected in tender leaves. Moreover, the levels of glucose and fructose were significantly higher in mature leaves than in tender leaves (p ≤ 0.01; Figure 5b). Mature leaves exhibited elevated levels of glucose (709.9 μg g−1) and fructose (738.2 μg g−1), representing a 5.8- and 3.7-fold increase compared with those in tender leaves, respectively. Notably, sucrose was only synthesized in mature leaves (Figure 5b).

3.6. Differences in the Levels of Four Sterols in Maize Leaves at Different Growth Stages

Sterols are essential nutrients for the growth, development, and reproduction of insects. Although some insect species can acquire these nutrients from symbionts, most of them rely on dietary sources or convert plant sterols present in their food into cholesterol. Sterols play a crucial role in the formation of insect tissue structure and serve as raw materials for ecdysone synthesis.
The levels of four sterols were analyzed in tender and mature leaves, and detectable levels of these sterols were found in both leaf types. Furthermore, the levels of stigmasterol, β-sitosterol, and campesterol were significantly higher in mature leaves than in tender leaves (p ≤ 0.01). However, there was no significant difference in the level of stigmasterol between tender and mature leaves. Notably, the level of campesterol was the highest among the sterols, with mature leaves (138.8 μg g−1) exhibiting a 2.7-fold increase in campesterol level compared with tender leaves (Figure 5c).

3.7. Effects of Different Sterol Levels on S. frugiperda

Studies have shown that phytophagous insects cannot synthesize cholesterol from carbohydrates or lipids, thus relying on sterols obtained from plants, which are converted into cholesterol to support normal growth and reproduction. Cholesterol serves as a precursor for insect ecdysone (Figure 6). The results revealed significant differences in the levels of stigmasterol, β-sitosterol, and campesterol between the two maize leaf types (Figure 4c).
To investigate the impact of these sterols on the 20E titer of S. frugiperda, we supplemented the 6th instar larvae with different levels of β-sitosterol, campesterol, and stigmasterol (Figure 7a). Supplementation with these sterols at levels of 50, 100, and 500 μg head−1, respectively, significantly increased the 20E titer compared with the control group (p ≤ 0.01; Figure 7a). The 20E titer exhibited an initial increase and then decreased, with the highest 20E titers being observed with the abovementioned supplementation levels of β-sitosterol, campesterol, and stigmasterol (Figure 7b). Notably, through a regulatory mechanism, the 6th instar larvae of S. frugiperda maintained the highest 20E titer, which remained stable at 389.7–521.9 ng g−1 and did not increase linearly with rising sterol levels.
Compared with the control group, supplementation with sterols, specifically 100 μg head−1 of β-sitosterol and campesterol (p ≤ 0.01) and 1000 μg head−1 of stigmasterol (p ≤ 0.05), significantly increased the pupation rate of S. frugiperda. However, there was no significant difference in the eclosion rate between S. frugiperda treated with sterols and those in the control group. In summary, an increase in the level of the three sterols in mature leaves was crucial for ensuring the normal pupation of S. frugiperda larvae (Table 6).

3.8. Defense Response of Maize Leaves

The nutritional composition of maize leaves exerts a significant influence on the growth and development of S. frugiperda, with sterols directly impacting the titer of 20E in these insects. The observation prompted us to investigate potential modifications in the nutritional composition of maize leaves following damage caused by S. frugiperda. Therefore, we quantified the sterol contents of maize leaves that were either undamaged or damaged by S. frugiperda (Figure 8). The results of our study revealed a significantly higher β-sitosterol content in damaged leaves compared to undamaged ones (p ≤ 0.05), while no significant differences were observed for the other three types of sterols (Figure 7c). Notably, β-sitosterol exhibited the highest conversion efficiency with the lowest required amount for achieving maximum titers of 20E in S. frugiperda (Figure 7b).

4. Discussion

In this study, the growth of S. frugiperda was monitored by feeding the pest species with either tender or mature maize leaves. We revealed that the total larval stage duration of S. frugiperda fed on mature leaves was shorter than that of S. frugiperda fed on tender leaves, and significant differences were observed in the weight, length, pupation rate, eclosion rate, and abnormal adults between S. frugiperda fed on tender and mature leaves. Analysis of 20E, JH I, JH II, and JH III levels in S. frugiperda indicated that JH I and JH II exhibited antagonistic effects with 20E, whereas the relationship between JH III and 20E was less apparent.
Research on the nutrient composition of maize leaves at different growth stages is limited. This study analyzed maize leaves harvested at 10-day and 60-day growth stages, finding that longer growth periods resulted in higher nutrient content in the leaves, indicating greater maturity. Nutrients such as sugars, amino acids, and sterols are crucial for the growth and development of insects. Previous studies have shown that the nutritional conditions required by insects determine their body size, development, and reproductive processes. Inadequate fats, amino acids, and carbohydrates can hinder cell growth and reproduction in insects [42,43]. The amino acid, sugar, and sterol levels of tender and mature leaves were determined. The results revealed that mature leaves contained a greater variety and abundance of amino acids than tender leaves. Previous studies have shown that Ile is an essential amino acid for insect growth [44,45,46,47]. It plays a crucial role in various physiological processes, including promoting protein synthesis, inhibiting protein degradation, and facilitating the biosynthesis of hormones and enzymes (e.g., insulin and growth hormone). Additionally, Ile serves as a precursor for glutamine synthesis, modulating amino acid metabolism, and providing energy to the body [48]. Gan et al. [49] demonstrated that Ile deficiency can significantly impair the growth performance of grass carp, whereas an increase in dietary Ile level leads to greater protein and fat deposition in muscle tissue. In the present study, Ile was only detected in mature maize leaves, suggesting that inadequate Ile intake contributes to the developmental retardation observed in S. frugiperda feeding on tender maize leaves.
Wang et al. [50] reported that Arg and Glu play distinct roles in regulating cell fate during different developmental stages in Helicoverpa armigera. Arg promotes cell proliferation during the larval stage, whereas Glu facilitates imaginal disc growth during the pupa-to-adult transition. Our findings revealed significantly higher levels of Glu in mature maize leaves than in tender leaves, and Arg was only detected in mature leaves. Therefore, inadequate intake of Arg may contribute to the low pupation rate observed in S. frugiperda larvae feeding on tender maize leaves, and insufficient Glu intake may lead to morphological abnormalities in adult moths.
Numerous studies have highlighted the crucial role of sugars in insect development and reproduction. Sugars serve as the primary carbohydrates consumed by larvae, providing energy for their vital activities [16,51,52,53]. Indeed, Vera et al. [54] found that increasing sugar levels enhanced larval survival rates. Moreover, the larval diet significantly influences the development and behavior of adult insects, particularly in terms of reproductive and flight performance [41,55].
Experiments on Adalia bipunctata L. have indicated that adding sucrose to the diet significantly increases larval survival rates [56]. Our findings revealed that the profile of soluble sugars was more diverse and abundant in mature leaves than in tender leaves. Notably, sucrose was exclusively detected in mature leaves. Su et al. [16] showed that the pupal weight of Grapholita molesta is significantly influenced by sucrose level, with higher sucrose levels facilitating the development of strong flight ability. Williams et al. [57] demonstrated that sucrose administration enhances the survival rate of female Psyttalia lounsburyi. Overall, our findings highlight the importance of sugar, particularly sucrose, as a major determinant of S. frugiperda growth and development.
S. frugiperda, a holometabolous insect, regulates various developmental processes, including egg production, larval tissue growth and apoptosis during metamorphosis, and tissue remodeling during the transition from pupae to adults, through changes in the levels of two major endocrine hormones: JH and 20E [58,59,60]. Therefore, we analyzed the changes in the levels of 20E, JH I, JH II, and JH III in S. frugiperda fed on tender and mature leaves, revealing significant differences (p < 0.05 or p < 0.01) in the level of these hormones between insects fed on the two maize leaf types. These findings align with the observed low pupation rate of S. frugiperda larvae fed on tender maize leaves.
We also investigated the differences in sterol level and species between tender and mature leaves, revealing significantly higher levels of stigmasterol, β-sitosterol, and campesterol in mature leaves than in tender leaves (p < 0.01). To evaluate the effects of these sterols, the 6th instar larvae of S. frugiperda were fed with three sterols, and the changes in 20E, JH I, JH II, and JH III levels were monitored. The results revealed a significantly higher 20E titer in S. frugiperda fed on different levels of sterols than in the control group. We found that the 20E titer in S. frugiperda reached 389.7–521.9 ng g−1 during the 6th instar and prepupal stage, and further increases in sterol levels led to a decline in 20E titer, indicating the initiation of the inactivation pathway. The highest 20E titer was observed with β-sitosterol, campesterol, and stigmasterol supplementation at doses of 50, 100, and 500 μg head−1, respectively. Stigmasterol required the highest replenishment, possibly because its conversion pathway involves an additional step compared with the pathways of β-sitosterol and campesterol. Specifically, stigmasterol is first converted into 22E-cholesta-5,22,24-trien-3b-ol before being transformed into desmosterol, a key precursor in cholesterol synthesis [61,62] (Figure 6).
Following sterol supplementation, the pupation rate of S. frugiperda significantly increased compared with that of the control group. However, it did not reach the pupation rate (88.33%) observed in S. frugiperda fed on mature leaves, suggesting that multiple factors influence the pupation of this species. There was no significant increase in the eclosion rate of S. frugiperda following sterol supplementation, indicating that sterols are not the key factors regulating the species’ successful emergence. The accumulation of substances and energy necessary for the successful emergence of S. frugiperda may originate from lower larval stages.
In order to comprehend the role of sterols in the interaction between maize leaves and S. frugiperda, we also investigated the alterations in sterol content within maize leaves subsequent to S. frugiperda infestation. Our research findings indicate a significant increase in β-sitosterol content in maize leaves following S. frugiperda infestation, while other sterols remained unchanged. Our study also demonstrated that β-sitosterol exhibits the highest efficiency in converting into 20E. Insects undergo metamorphosis through the antagonistic effects of 20E and JH [24], with 20E titers being regulated within a specific range to prevent exceeding maximum values. Our research findings support this observation. The increase in β-sitosterol content may serve as a defensive response to leaf damage in maize, while S. frugiperda may counteract this defense mechanism by deactivating 20E. While Su et al. [63] also demonstrated that TYLCV infection in tomato plants leads to elevated concentrations of sugars and amino acids in the phloem sap, a similar trend was observed in squash plants infected with papaya ringspot virus, which resulted in increased levels of various free essential and nonessential amino acids as reported by Gadhave et al. [64]. These findings suggest that plant nutrition plays a significant role in influencing interactions between plants and insects [32].

5. Conclusions

In summary, the present findings provide valuable insights into the essential nutritional factors required for the growth and development of S. frugiperda and elucidate the impact of sterols on the interaction between maize leaves and S. frugiperda, providing data to support the development of effective prevention and control measures against this pest. Our results suggest that Ile, Arg, Glu, sucrose, campesterol, and β-sitosterol in maize leaves are critical factors influencing the growth and development of S. frugiperda. Campesterol and β-sitosterol, the predominant sterols in maize leaves, can enhance the species’ pupation rate. This finding offers an alternative perspective to explain the feeding preference of S. frugiperda toward maize. In the meantime, it has been determined that β-sitosterol is a significant factor influencing the interaction between maize leaves and S. frugiperda. This means that we can interfere with the synthesis of β-sitosterol in plants to breed maize varieties with low β-sitosterol content or disrupt the absorption and utilization of β-sitosterol by S. frugiperda, making S. frugiperda unable to complete pupation, which provides a new idea for the prevention and control of S. frugiperda.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy14081690/s1, Figure S1: Trends of 20E, JH I, JH II, and JH III of S. frugiperda; Table S1: Detailed information of standards used in this study.

Author Contributions

X.L. and W.Z. conceived the study; X.L., D.D. and W.Z. designed the experiments; W.Z. and H.L. performed experiments; W.Z., C.Z., J.H. and X.G. analyzed data; X.L. and W.Z. wrote the initial draft, and all authors contributed to its final version. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Special Fund for Innovation-driven Development of Guangxi under grant number GuiKe AA 17204043.

Data Availability Statement

Data are contained within the article or Supplementary Materials.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Abbreviations

Juvenile hormone (JH), β-hydroxyecdysone(20E), Aspartic acid (Asp), Glutamic acid (Glu), Asparagine (Asn), Serine (Ser), Glutamine (Gln), Histidine (His), Glycine (Gly), Argnine (Arg), Threonine (Thr), Alanine (Ala), γ-aminobutyric acid (GABA), Proline (Pro), Theanine (The), Cysteine (Cys), Tyrosine (Tyr), Valine (Val), Methionine (Met), Lysine (Lys), Isoleucine (Ile), Leucine (Leu), Phenylalanine (Phe). The maize leaves with growth stages of 60 days (mature), the maize leaves with growth stages of 10 days (tender). S. frugiperda that feeds on mature maize leaves (MSF), S. frugiperda that feeds on tender maize leaves (TSF). Male individuals of MSF (M-male), female individuals of MSF (M-female). Male individuals of TSF (T-male), female individuals of TSF (T-female).

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Figure 1. The feeding experiment of S. frugiperda.
Figure 1. The feeding experiment of S. frugiperda.
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Figure 2. Developmental stages of S. frugiperda. (Note: Spodoptera frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF. (a) TSF and MSF on the 8th day, with MSF being larger in size. (b) TSF and MSF in the pupal stage, with MSF being larger in size. (c) Comparison of successful and unsuccessful pupation of TSF during the prepupal stage, with the four S. frugiperda on the right failing to pupate. (d) Deformed TSF after emergence in the adult stage).
Figure 2. Developmental stages of S. frugiperda. (Note: Spodoptera frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF. (a) TSF and MSF on the 8th day, with MSF being larger in size. (b) TSF and MSF in the pupal stage, with MSF being larger in size. (c) Comparison of successful and unsuccessful pupation of TSF during the prepupal stage, with the four S. frugiperda on the right failing to pupate. (d) Deformed TSF after emergence in the adult stage).
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Figure 3. Effects of feeding on maize leaves at different growth stages on the weight and length of S. frugiperda. (a) The weight of TSF and MSF. (b) The lenght of TSF and MSF. (Note: Data are presented as the mean ± standard error of the mean (SEM) of three replicates. Significant differences are indicated by asterisks. Significantly different at (*) the 0.05 level and (**) 0.01 level (Student’s t-test). Spodoptera frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF.).
Figure 3. Effects of feeding on maize leaves at different growth stages on the weight and length of S. frugiperda. (a) The weight of TSF and MSF. (b) The lenght of TSF and MSF. (Note: Data are presented as the mean ± standard error of the mean (SEM) of three replicates. Significant differences are indicated by asterisks. Significantly different at (*) the 0.05 level and (**) 0.01 level (Student’s t-test). Spodoptera frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF.).
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Figure 4. Effects of feeding on maize leaves at different growth stages on the levels of 20E (a), JH I (b), JH II (c), and JH III (d) in S. frugiperda. Note: Spodoptera frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF. (1) MSF and TSF entered the prepupal stage on the 11th and 13th days, respectively. (2) S. frugiperda were sampled at 24, 48, 72, and 120 h during the pupal stage. (3) Adults of MSF and TSF emerged on the 17th and 19th days, respectively. (4) Male and female individuals of MSF are referred to as M-male and M-female, respectively. (5) Male and female individuals of TSF are referred to as T-male and T-female, respectively. (6) Data are presented as the mean ± SEM of three replicates. Significant differences are indicated by asterisks. Significantly different at (*) the 0.05 level and (**) 0.01 level (Student’s t-test).
Figure 4. Effects of feeding on maize leaves at different growth stages on the levels of 20E (a), JH I (b), JH II (c), and JH III (d) in S. frugiperda. Note: Spodoptera frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF. (1) MSF and TSF entered the prepupal stage on the 11th and 13th days, respectively. (2) S. frugiperda were sampled at 24, 48, 72, and 120 h during the pupal stage. (3) Adults of MSF and TSF emerged on the 17th and 19th days, respectively. (4) Male and female individuals of MSF are referred to as M-male and M-female, respectively. (5) Male and female individuals of TSF are referred to as T-male and T-female, respectively. (6) Data are presented as the mean ± SEM of three replicates. Significant differences are indicated by asterisks. Significantly different at (*) the 0.05 level and (**) 0.01 level (Student’s t-test).
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Figure 5. Comparison of the types and levels of (a) 21 amino acids, (b) 4 soluble sugars, and (c) 4 sterols in maize leaves at different growth stages. Note: S. frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF. Data are presented as the mean ± SEM of three replicates. Significant differences are indicated by asterisks. Significantly different at (*) the 0.05 level and (**) 0.01 level (Student’s t-test).
Figure 5. Comparison of the types and levels of (a) 21 amino acids, (b) 4 soluble sugars, and (c) 4 sterols in maize leaves at different growth stages. Note: S. frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF. Data are presented as the mean ± SEM of three replicates. Significant differences are indicated by asterisks. Significantly different at (*) the 0.05 level and (**) 0.01 level (Student’s t-test).
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Figure 6. Sterol synthesis pathway leading to the formation of 20E in insects. Refer to Svoboda and Weirich [41].
Figure 6. Sterol synthesis pathway leading to the formation of 20E in insects. Refer to Svoboda and Weirich [41].
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Figure 7. Role of sterols in the interaction between maize leaves and S. frugiperda. (a) Effects of different sterols on the 20E titer of S. frugiperda. Different letters in the bar chart indicate significant differences between samples. Different lowercase letters differed significantly (p < 0.05); different capital letters differed significantly (p < 0.01, ANOVA). N-hexane was used as the control. (b) The correlation between the content of various sterols and the trend in 20E titer changes. (c) The alteration in sterol content in maize leaves following infestation by S. frugiperda. The maize leaves affected by S. frugiperda were designated as the treatment group. Significantly different at (*) the 0.05 level (Student’s t-test).
Figure 7. Role of sterols in the interaction between maize leaves and S. frugiperda. (a) Effects of different sterols on the 20E titer of S. frugiperda. Different letters in the bar chart indicate significant differences between samples. Different lowercase letters differed significantly (p < 0.05); different capital letters differed significantly (p < 0.01, ANOVA). N-hexane was used as the control. (b) The correlation between the content of various sterols and the trend in 20E titer changes. (c) The alteration in sterol content in maize leaves following infestation by S. frugiperda. The maize leaves affected by S. frugiperda were designated as the treatment group. Significantly different at (*) the 0.05 level (Student’s t-test).
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Figure 8. Experiment of S. frugiperda damaging maize leaves. (a) The S. frugiperda larvae were introduced onto intact, healthy maize leaves, with two 5th instar larvae placed on each individual maize plant. The white arrow indicates S. frugiperda. (b) The maize plants should be individually wrapped with gauze. (c) The maize leaves display damage inflicted by S. frugiperda within a 12 h timeframe.
Figure 8. Experiment of S. frugiperda damaging maize leaves. (a) The S. frugiperda larvae were introduced onto intact, healthy maize leaves, with two 5th instar larvae placed on each individual maize plant. The white arrow indicates S. frugiperda. (b) The maize plants should be individually wrapped with gauze. (c) The maize leaves display damage inflicted by S. frugiperda within a 12 h timeframe.
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Table 1. Mass spectrometer parameters and ions (m/z) used for MRM of 4 target analytes.
Table 1. Mass spectrometer parameters and ions (m/z) used for MRM of 4 target analytes.
AnalytesESI ModeRt (min)TM (m/z)CV (V)Quantifying IonCE (eV)Qualitative IonCE (eV)
JH Ipositive5.72295.345.0263.310295.317
JH IIpositive5.51281.340.0249.2957.140
JH IIIpositive5.27267.355.0235.28147.316
20Epositive2.67481.281.5445.219371.224
Table 2. Validation parameters—linearity range, correlation coefficient (r), limit of detection (LOD), limit of qualification (LOQ), and matrix effect.
Table 2. Validation parameters—linearity range, correlation coefficient (r), limit of detection (LOD), limit of qualification (LOQ), and matrix effect.
MatrixAnalytesStandard CurveCalibration CurveLinearity Range (ng mL−1)LOD (ng mL−1)LOQ (ng mL−1)Matrix Effect
EquationrEquationr
SpodopterafrugiperdaJH Iy = 7079.5 x − 49,2730.9992y = 5101.2 x − 11,454.40.99951–2000.050.150.72
JH IIy = 2938.1 x − 11,233.50.9989y = 2069.9 x − 9409.40.99911–2000.040.120.70
JH IIIy = 2997.7 x − 51,902.10.9992y = 1916.6 x – 29,367.10.99871–2000.070.210.64
20Ey = 2943.2 x − 3244.60.9995y = 1644.8 x − 3547.40.99911–40000.300.900.56
Maize leavesAspy = 456,614 x + 361,7500.9977——50–10,00010.0330.09—
Gluy = 324,736 x + 184,0750.9998——50–10,0007.5422.62—
Asny = 456,201 x + 385,9340.9971——50–10,0004.6513.95—
Sery = 986,938 x + 56,1290.9999——50–10,0005.2115.63—
Glny = 189,5451 x − 25,3231.0000——50–10,0002.878.61—
Hisy = 1,991,836 x + 75,7981.0000——50–10,0004.6513.95—
Glyy = 1,666,200 x + 151,0591.0000——50–10,0002.146.42—
Argy = 1,779,518 x + 155,5621.0000——50–10,0007.0321.09—
Thry = 1,802,003 x + 517,7830.9999——50–10,0002.688.04—
Alay = 1,433,572 x + 620,8120.9999——50–10,0001.043.12—
GABAy = 1,077,132 x + 749,9420.9988——50–10,0001.685.04—
Proy = 660,450 x + 132,9511.0000——50–10,0004.7814.34—
They = 1,259,897 x + 221,5180.9999——50–10,0003.4710.41—
Cysy = 1,549,093 x + 150,9320.9998——50–10,00015.1245.36—
Tyry = 343,025 x + 33,0850.9998——50–10,0003.4110.23—
Valy = 2,484,236 x + 420,3721.0000——50–10,0001.584.74—
Mety = 1,631,826 x − 31,9750.9994——50–10,0003.4310.29—
Lysy = 2,943,732 x + 504,1760.9999——50–10,0002.336.99—
Iley = 950,400 x + 878,6100.9987——50–10,0000.782.34—
Leuy = 3,098,555 x + 1,750,3751.0000——50–10,0000.591.77—
Phey = 4,524,886 x + 682,1010.9996——50–10,0000.451.35—
Glucosey = 2.9232 x + 0.27180.9998——100–500012.3637.08—
Fructosey = 1.4463 x + 0.22550.9995——100–500033.2599.75—
Sucrosey = 0.9074 x + 0.36960.9957——100–500026.3278.96—
Maltosey = 1.1931 x + 0.25240.9993——100–500030.7492.22—
Stigmasteroly = 56,689 x − 76660.9911——50–500010.3931.17—
β-sitosteroly = 805,511 x − 105,0480.9943——50–500015.4746.41—
Campesteroly = 47,850 x − 47990.9941——50–500013.5640.68—
Stigmastanoly = 58,737 x − 83480.9926——50–50009.6929.07—
Note: Matrix effect = B/A, A: slope of the standard curve, B: slope of the calibration curve.
Table 3. Average recoveries and RSD of 20E and JHs from Spodoptera frugiperda when spiked at three different levels.
Table 3. Average recoveries and RSD of 20E and JHs from Spodoptera frugiperda when spiked at three different levels.
MatrixAnalytesSpiked (ng g−1)
110100
S. frugiperdaJH I85 (8) a87 (11)95 (10)
JH II81 (9)88 (7)91 (12)
JH III88 (11)85 (9)83 (14)
20E75 (10)80 (13)89 (12)
Note: a e.g., 85 (8) indicates that the average recovery of JH I from S. frugiperda is 85% and the RSD is 8% when spiked at a level of 1 ng g−1, n = 5. The remaining data are presented similarly.
Table 4. Age and developmental process of S. frugiperda that fed on maize leaves at different growth stages.
Table 4. Age and developmental process of S. frugiperda that fed on maize leaves at different growth stages.
StageDevelopmental Duration (d)
TSFMSF
1st instar2.11 ± 0.19 a1.33 ± 0.33 b
2nd instar2.11 ± 0.19 a2 ± 0.33 a
3rd instar2.33 ± 0.33 a1.78 ± 0.19 a
4th instar2.11 ± 0.19 a1.33 ± 0.33 b
5th instar2 ± 0.33 a1.89 ± 0.19 a
6th instar1.89 ± 0.19 a1.89 ± 0.19 a
Larval stage (1st–6th instars)12.56 ± 0.19 A10.22 ± 0.19 B
Prepupal stage1.33 ± 0.00 a1.11 ± 0.19 a
Pupal stage6.44 ± 0.38 a6 ± 0.33 a
Adult stage6.11 ± 0.19 A7.33 ± 0.33 B
Total instars (larva adult)26.44 ± 0.19 a24.67 ± 0.67 b
Note: Different letters in the table indicate significant differences between samples. S. frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF. Data in the same row followed by different lowercase letters differed significantly (p < 0.05); data in the same row followed by different capital letters differed significantly (p < 0.01, Student’s t-test).
Table 5. Pupation rate, eclosion rate, and teratological rate of S. frugiperda that fed on maize leaves at different growth stages.
Table 5. Pupation rate, eclosion rate, and teratological rate of S. frugiperda that fed on maize leaves at different growth stages.
RateTSF (%)MSF (%)
Pupation rate55.74 ± 1.70 A88.33 ± 0.56 B
Eclosion rate32.05 ± 0.77 A49.64 ± 1.11 B
Teratological rate of eclosion33.40 ± 1.07 A0.00 ± 0.00 B
Note: Different letters in the table indicate significant differences between samples. Spodoptera frugiperda feeding on mature maize leaves are referred to as MSF, whereas those feeding on tender maize leaves are known as TSF. Data in the same row followed by different capital letters differed significantly (p < 0.01, Student’s t-test).
Table 6. Pupation and eclosion rates of S. frugiperda that fed on different types and levels of sterols.
Table 6. Pupation and eclosion rates of S. frugiperda that fed on different types and levels of sterols.
RateSterolQuality (μg/Head)
0 (Control)10501005001000
Pupation rate (%)β-sitosterol52.78 ± 2.78 Bc55.56 ± 2.78 ABbc66.67 ± 4.81 ABab69.44 ± 2.78 Aa66.67 ± 4.81 ABab66.67 ± 4.81 ABab
campesterol58.33 ± 4.81 ABabc66.67 ± 4.81 ABab69.44 ± 2.78 Aa66.67 ± 4.81 ABab63.89 ± 2.78
ABabc
stigmasterol58.33 ± 4.81 ABabc61.11 ± 2.78 ABabc63.89 ± 7.35 ABabc61.11 ± 2.78 ABabc66.67 ± 4.81 ABab
Eclosion rate (%)β-sitosterol33.33 ± 4.81 Aa30.56 ± 2.78 Aa36.11 ± 2.78 Aa30.56 ± 2.78 Aa36.11 ± 2.78 Aa36.11 ± 2.78 Aa
campesterol30.56 ± 2.78 Aa36.11 ± 2.78 Aa36.11 ± 2.78 Aa36.11 ± 2.78 Aa33.33 ± 4.81 Aa
stigmasterol30.56 ± 2.78 Aa33.33 ± 9.62 Aa33.33 ± 4.81 Aa33.33 ± 4.81 Aa36.11 ± 2.78 Aa
Note: Different letters in the table indicate significant differences between samples. Data in the same row followed by different lowercase letters differed significantly (p < 0.05); data in the same row followed by different capital letters differed significantly (p < 0.01, ANOVA).
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Zhang, W.; Li, H.; Zhang, C.; Hou, J.; Guo, X.; Dong, D.; Li, X. Impact of Maize Nutrient Composition on the Developmental Defects of Spodoptera frugiperda. Agronomy 2024, 14, 1690. https://doi.org/10.3390/agronomy14081690

AMA Style

Zhang W, Li H, Zhang C, Hou J, Guo X, Dong D, Li X. Impact of Maize Nutrient Composition on the Developmental Defects of Spodoptera frugiperda. Agronomy. 2024; 14(8):1690. https://doi.org/10.3390/agronomy14081690

Chicago/Turabian Style

Zhang, Wenjie, Haolin Li, Cuifang Zhang, Jiangan Hou, Xiaxia Guo, Dengfeng Dong, and Xuesheng Li. 2024. "Impact of Maize Nutrient Composition on the Developmental Defects of Spodoptera frugiperda" Agronomy 14, no. 8: 1690. https://doi.org/10.3390/agronomy14081690

APA Style

Zhang, W., Li, H., Zhang, C., Hou, J., Guo, X., Dong, D., & Li, X. (2024). Impact of Maize Nutrient Composition on the Developmental Defects of Spodoptera frugiperda. Agronomy, 14(8), 1690. https://doi.org/10.3390/agronomy14081690

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