Litura Larvae Research Articles

A larval expressed chemosensory protein involved in recognition of anthocyanins in Spodoptera litura (Lepidoptera: Noctuidae).

Anthocyanins are secondary metabolites which act as diverse functions during plant growth. Insects can discriminate host plants by their sensitive gustatory systems. It is hypothetical that chemosensory proteins (CSPs) play a crucial role in regulating this behavioral process. However, the underlying molecular mechanisms remain obscure. In the present study, we characterized a CSP SlitCSP8 from the Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). Quantitative real-time-polymerase chain reaction analysis demonstrated that SlitCSP8 was mainly expressed in the head of the 7th S. litura larvae, especially labrum. Further, recombinant SlitCSP8 was obtained using bacterial expression system. Fluorescence competitive binding assays demonstrated that the purified SlitCSP8 exhibited a strong binding affinity to anthocyanins, a natural compound derived from the host plant. Silencing SlitCSP8 through RNAi significantly reduced the sensitivity of S. litura larvae to anthocyanins-treated leaf disks, the development from larva to pupae was not affected. These data provide insight into the molecular basis that CSP8 can detect anthocyanins in host plants by chemosensory system of insects. It can be further used in designing novel optimal food attractant targeting to the CSPs for pest control.

Effect of Chlorantraniliprole on Life History Traits and Relative Fitness of Laboratory-Selected Resistant and Susceptible Populations of Spodoptera litura (Lepidoptera: Noctuidae).

Insecticides are widely used to control pests and improve agricultural yield. The use of indiscriminate amounts and persistent pesticides has not only resulted in insect pest resistance challenges but has also harmed non-target organisms and contaminated the environment. We assessed the cost-effectiveness of Spodoptera litura (Fabricius) resistance to chlorantraniliprole (CTPR) as part of insect resistance control programs. S. litura larvae were collected from the fields and treated with chlorantraniliprole for 15 generations. Compared to the unselected population (Unsel-Lab), the chlorantraniliprole-selected population (CTPR-Sel) of S. litura exhibited a resistance level of 98.23 times. The findings demonstrated that the chlorantraniliprole-resistant genotype had lower egg-to-adult survivability, longer egg-to-adult developing times, and lower fecundity than the chlorantraniliprole-susceptible genotype. Compared to the Unsel-Lab population, the CTPR-Sel population of S. litura had a poorer relative fitness (0.44) at LC30 and shorter male/female longevity. Demographic parameters, including net reproductive rate (R0) and intrinsic (rm) and finite rate of increase (λ), were lower in the CTPR-Sel strain than in Unsel-Lab S. litura. These findings demonstrate that chlorantraniliprole resistance in S. litura has fitness costs at the individual and population levels, implying that removing the selecting agent from the environment might result in less resistance and opportunities for susceptibility restoration. As a result, the current work could help to determine effective management strategies to prevent chlorantraniliprole resistance in S. litura.

Phytochemical screening and toxicity assessment of compounds isolated from the leaves of Mangifera indica L. for the control of Spodoptera litura (Lepidoptera; Noctuidae)

This study aimed to analyze the phytochemical composition and antioxidative capabilities of mango leaves (Mangifera indica L., Nam Dok Mai), indigenous to Sa Kaeo Province, Thailand. Various solvents with differing polarities, including n-hexane, DCM, ethyl acetate, and MeOH, were utilized for leaf extraction. The findings revealed the existence of eight groups of phytochemical compounds: alkaloids, flavonoids, coumarins, saponins, tannins, terpenoids, steroids, and cardiac glycosides. The MeOH crude extract exhibited the highest concentration of total phenolic compounds at 409.88 ±0.02 mg GAE/g. Furthermore, the MeOH crude extract demonstrated the strongest antioxidant activity, with an IC50 value of 0.52 ±0.02 μg/ml, as determined by the DPPH method. High-performance liquid chromatography (HPLC) was employed to identify gallic acid and mangiferin in the MeOH crude extract. Laboratory tests were conducted using the topical application method to evaluate the toxicity of the M. indica leaf crude extract on 2nd instar Spodoptera litura larvae. The MeOH crude extract exhibited high efficacy, with an LD50 value of 10.58 µg per larvae within 24 hours. Gallic acid and mangiferin were identified as the primary active ingredients, with LCD50 values of 1.19 µg per larvae and 1.90 µg per larvae, respectively, within 24 hours. Additionally, the impact on detoxification enzymes (24 hours post-treatment) was assessed in surviving 2nd instar S. litura larvae using the topical application method. The MeOH extract treatment resulted in 1.31-fold inhibition of carboxylesterase (CE), 1.31-fold inhibition of glutathione-S-transferase (GST), and 1.32-fold inhibition of acetylcholinesterase (AChE).

Intricate intracellular kinase network regulates the Spodoptera lituta-derived elicitor response signaling in Arabidopsis.

Plants defend themselves against herbivores by recognizing herbivore-derived elicitors and activating intracellular signaling. In Arabidopsis, the receptor-like kinase HAK1 recognizes the poly-saccharide elicitor (FrA) from Spodoptera litura larvae, leading to the expression of defense-related genes such as PDF1.2. During this process, the cytoplasmic kinase CRK2 phosphorylates PBL27, triggers the ERF13 expression via ethylene signaling and subsequently leads to PDF1.2 expression. Herein, we investigated four cytoplasmic kinases from the same receptor-like cytoplasmic kinase (RLCK) VII family as PBL27 that interacts with CRK2. Among them, PBL11, like PBL27, is phosphorylated by CRK2 and induces PDF1.2 expression but does not affect ERF13 expression. The weight gain of S. litura larvae on PBL11-deficient mutant plants was only slightly higher than that of wild-type plants, suggesting that PBL11 may function as a minor RLCK that supports the defense response.

The impact of lethal and sub-lethal exposure of emamectin benzoate on populations of Spodoptera litura (Lepidoptera: Noctuidae) under laboratory conditions

Emamectin benzoate is an avermectin bio-insecticide commonly used for managing several insect pests including Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), a major polyphagous pest of many cultivated crops. The current study was conducted to evaluate the effects of emamectin benzoate on the fitness of S. litura populations exhibiting differential susceptibility to insecticide. The selection process and all the bioassays were carried out using 6-day-old 2nd instar larvae of S. litura. A field-collected population of S. litura was divided into two groups: one selected with emamectin benzoate for eight generations (EB-Sel) and the other kept unexposed (Unsel-Lab) to insecticide in the laboratory. An increase in resistance ratio from 1.71-fold in the F1 generation to 22.54-fold in the F8 generation of the EB-Sel population was observed compared to the Unsel-Lab (F8) population. The EB-Sel and Unsel-Lab populations were treated with their respective lethal and sub-lethal concentrations which resulted in an extended development period, decreased larval survival, and adult emergence along with increased morphological abnormalities in adults. Significant reductions were observed in both male and female longevity, fecundity, egg hatching, net reproductive rate (R0), intrinsic rate of increase (rm), and finite rate of increase (λ) in EB-Sel and Unsel-Lab populations. Higher concentrations of the insecticide also reduced the relative fitness (Rf) of S. litura larvae, with maximum effect at LC50 of the EB-Sel population where the Rf value was 0.32 compared to the Unsel-Lab population. Both populations have been affected by emamectin benzoate exposure, however, the impact was more pronounced in the EB-Sel population indicating fitness costs. Our results suggested the fitness cost linked to emamectin benzoate resistance in S. litura which might favor managing insecticide resistance by reducing the frequency of resistant alleles by removing selection pressure. Consequently, our research provides significant insights to devise better pest management strategies for S. litura.

Screening of newly isolated indigenous entomopathogenic nematodes against Spodoptera litura Fabricius (Lepidoptera: Noctuidae)

Aim: Insecticides have traditionally been used to control S. litura, although bio-pesticides as alternative control measures are also in demand due to soil residual issues and other environmental dangers. Another safe technique for controlling this important pest is entomopathogenic nematodes (EPNs). Methodology: This study evaluated the infectivity of ten native recently isolated entomopathogenic nematodes against S. litura by assessing their penetration and multiplication in S. litura. The efficiency of the promising EPNs against second, third and fourth instars S. litura larvae was further examined. Results: Among the tested EPNs, Steinernema sp. (IARI-EPN RP 03), Heterorhabditis sp. (IARI-EPN RP 06), and Oscheius sp. (IARI-EPN RP 07) were intensely harmful to S. litura, producing 100 percent mortality in 72 hrs, followed by Steinernema sp. (IARI-EPN RP 09), which caused 92 percent mortality, and Oscheius sp. (IARI-EPN RP 10) was the least pathogenic recording 58 percent mortality. Heterorhabditis sp. (IARI-EPN RP 06) showed the maximum penetration, followed by Oscheius sp. (IARI-EPN RP 07) and Oscheius sp. (IARI-EPN RP 08), with Oscheius sp. (IARI-EPN RP 04) showed the least penetration. The second instar larvae of S. litura were highly vulnerable to EPNs, followed by third and fourth instar larvae. According to the findings, Steinernema sp. (IARI-EPN RP 03) and Heterorhabditis sp. (IARI-EPN RP 06) were most virulent against S. litura. Interpretation: As a result, both EPNs have the potential to act as biological control agents for S. litura. Furthermore, the fifth instar S. litura larva were more suited for multiplication, indicating that this insect is suitable for EPN production. Field testing of these promising EPNs will reveal their efficacy in managing S. litura in a sustainable manner. Key words: Bio-pesticides, Entomopathogenic nematodes, Heterorhabditis, Insects, Oscheius, Steinernema

Effects of Dietary Zinc Chloride and Zinc Sulfate on Life History Performance and Hemolymph Metabolism of Spodoptera litura (Lepidoptera: Noctuidae).

Zinc is an essential micronutrient crucial in various biological processes of an organism. However, the effects of zinc vary depending on its chemical form. Therefore, the aim of this study was to conduct a comparative analysis of the life history performances and hemolymph metabolism of Spodoptera litura exposed to different concentrations of dietary zinc chloride (ZnCl2) and zinc sulfate (ZnSO4), utilizing two-sex life tables and untargeted metabolomics. The preadult survival rate of S. litura significantly decreased, while the preadult developmental period of S. litura was prolonged as the dietary ZnCl2 concentration increased. However, the fecundity of S. litura at 50 mg/kg dietary ZnCl2 was significantly increased. The intrinsic rate of increase (r) and the finite rate of increase (λ) in S. litura in the control group (CK, no exogenous ZnCl2 or ZnSO4 added) and with 50 mg/kg dietary ZnCl2 were significantly higher than those at 100 mg/kg, 200 mg/kg, and 300 mg/kg. Dietary ZnSO4 exerts a devastating effect on the survival of S. litura. Even at the lowest concentration of 50 mg/kg dietary ZnSO4, only 1% of S. litura could complete the entire life cycle. Furthermore, as the dietary ZnSO4 concentration increased, the developmental stage achievable by the S. litura larvae declined. High-throughput untargeted metabolomics demonstrated that both 100 mg/kg dietary ZnCl2 and ZnSO4 decreased the hemolymph vitamins levels and increased the vitamin C content, thereby helping S. litura larvae to counteract the stress induced by ZnCl2 and ZnSO4. Simultaneously, dietary ZnCl2 obstructed the chitin synthesis pathway in the hemolymph of S. litura, thus extending the developmental period of S. litura larvae. These results indicate that low concentrations of Zn2+ positively impact populations of S. litura, but the effectiveness and toxicity of Zn depend on its chemical form and concentration.

Effect of Insecticides on Generative Potential of Entomopathogenic Nematode, Steinernema abbasi PN-1 in Spodoptera litura Fabricius

This study aimed to evaluate the effects of different insecticides at varying concentrations on the progeny production of the entomopathogenic nematode Steinernema abbasi PN-1 in Spodoptera litura larvae, with a focus on determining the insecticides' compatibility with biological control agents. S. litura larvae were treated with a mixture of S. abbasi PN-1 and insecticides (fipronil, emamectin benzoate, cyantraniliprole, indoxacarb, and chlorantraniliprole) at three different concentrations (lower, medium, and higher). Progeny production of S. abbasi PN-1 was assessed and compared across treatments, with control groups consisting of larvae treated with S. abbasi PN-1 alone. The study found that progeny production was significantly influenced by the type and concentration of insecticides. Fipronil exhibited the least negative impact on progeny production across all concentrations, followed by emamectin benzoate, cyantraniliprole, indoxacarb, and chlorantraniliprole, with the latter showing the most significant inhibitory effects. Higher concentrations of insecticides resulted in a greater reduction in progeny production, indicating a dose-dependent relationship. The results suggest that certain insecticides, particularly at higher concentrations, can negatively affect the progeny production of S. abbasi PN-1, potentially compromising the effectiveness of EPNs in integrated pest management (IPM) programs. The study highlights the importance of selecting compatible insecticides and their appropriate concentrations to enhance the success of biological control strategies involving EPNs.

Insecticidal activities of three recombinant venom proteins of the predatory stink bug, Arma custos.

Widespread resistance of insect pests to insecticides and transgenic crops in the field is a significant challenge for sustainable agriculture, and calls for the development of novel alternative strategies to control insect pests. One potential resource for the discovery of novel insecticidal molecules is natural toxins, particularly those derived from the venoms of insect predators. In this study, we identified three insecticidal proteinaceous toxins from the venom glands (VGs) of the predatory stink bug, Arma custos (Hemiptera: Asopinae). Transcriptomic analysis of A. custos VGs revealed 151 potentially secreted VG-rich venom proteins. Three VG-rich venom proteins (designated AcVP1 ~ 3) were produced by overexpression in Escherichia coli. Injection of the recombinant proteins into tobacco cutworm (Spodoptera litura) larvae showed that all of the three recombinant proteins caused paralysis, liquefaction and death. Injection of recombinant proteins into rice brown planthopper (Nilaparvata lugens) nymphs showed higher insecticidal activities, among which a trypsin (AcVP2) caused 100% mortality postinjection at 1.27 pmol mg-1 body weight. A natural toolkit for the discovery of insecticidal toxins from predatory insects has been revealed by the present study. © 2024 Society of Chemical Industry.

Expressional respones of hsp70 genes against abiotic and entomopathgenic stresses in four different noctuid larval species (Lepidoptera: Noctidae)

Heat shock proteins (Hsps) are stress response proteins. In a previous study, host larval Hsp70s were identified as the structural proteins of virions of Heliothis virescens ascovirus 3h (HvAV-3h), an insect virus that mainly infects noctuid larvae. To investigate the response of hsp70s of healthy Mythimna separata, Spodoptera exigua, Spodoptera frugiperda, and Spodoptera litura larvae to various abiotic or entomopathogenic stresses, quantitative PCR was used to detect larval hsp70s expression patterns. Results showed distinct expression patterns of hsp70s in response to different abiotic stresses. Notably, Mshsp70 expression pattern resembled Slhsp70 under most treatments. In healthy larvae, no tissue tropism was observed concerning the relative expression of Mshsp70, Sfhsp70, and Slhsp70. After infection with HvAV-3h, the expression of hsp70s in all dissected tissues of all tested larval species increased. Significant differences were found in the fat bodies of M. separata, S. exigua, and S. litura as well as in the hemolymph of S. exigua and S. litura. Subsequent silencing of Slhsp70, resulted in a significant decrease in DNA replication levels of HvAV-3h in S. litura larvae at 24 and 72 h post RNA interference, indicating that Slhsp70 is necessary for DNA replication in HvAV-3h. These data can provide references for the studying on the stress response of noctuid larvae to different environmental factors.

Biopesticide effect on crops for the bioactive components extracted from Tagetes erecta and Tagetes patula

Botanicals from Marigold, Chrysanthemum, Basil, Rosemary and other medicinal plants have been analysed as potential replacements of chemical pesticides as they are effective and non-hazardous to the environment. The bioactive components thiophene is present in large amount in Tagetes sp. which have a wide range of biocidal properties. In this study the crude extracts of different parts of Tagetes erecta and Tagetes patula were obtained by Soxhlet extraction method. The leaf extracts were subjected to GC–MS to identify their components and to confirm the presence of thiophenes. Two major disastrous crop pests namely, Spodoptera litura and Corcyra cephalonica belongs to Order Lepidoptera, Family Noctuidae and Pyralidae were used for the experimental study. The effect of bioactive extract was tested by direct and indirect methods for their larvicidal effect. The S. litura larvae was allowed to feed on castor leaves coated with spraying different concentrations of methanolic sample extracts as indirect method. In the direct spraying method, the S. litura and C. cephalonica larvae were sprayed with low and high concentrations of crude sample extracts of both T. patula and T. erecta. Significant decrease in larval activity and survival rate within 24 h to 48 h were recorded for both the methods. The trials were performed using variousvolumes from 10 to 1000 µl to check larvicidal activity. The roots and stem extracts of T. erecta for 25 µl kill 100% larvae within 24 h whereas 50 µl of T. patula flowers, roots and stem extract effectively kill only 50% of the larvae in 48 h. A mini nursery evaluation were conducted by direct spraying method on larvae growing on jowar saplings, which displayed 100% mortality of larvae within 24 h for 25 µl of T. erecta leaf and flower extracts and T. patula flower extract. From these trials, it can be inferred that the extracts of T. patula and T. erecta provided effective outcomes as larvicides of S. litura and C. cephalonica.

Encapsulation of Bacillus thuringiensis using sodium alginate and chitosan coacervates for insect-pest management

The study investigates the complex coacervation process of sodium alginate (SA) and chitosan (CS), aiming to optimize the yield of coacervates formed from these marine polysaccharides. Structural interactions between SA and CS were analyzed across varying chitosan concentrations (0.01 mg to 20 mg/mL) using turbidimetric analysis. The optimal chitosan concentration for maximum coacervate formation was determined to be 10 mg/mL. Under these conditions, Bacillus thuringiensis var. kurstaki (Bt) strain Bt-127 was successfully microencapsulated, achieving an entrapment rate of 56 %. Boric acid was selected as the cross-linking agent due to its compatibility with Bt and the SA-CS coacervates. Microscopic analysis confirmed the formation of coacervates/microcapsules and effective entrapment of Bt within them, with an entrapment efficiency of 98 %. Fourier transform infrared spectroscopy verified the chemical interactions between SA and CS within the coacervates. Bioassays against Spodoptera litura larvae using the leaf dip method demonstrated the efficacy of the encapsulated Bt formulation, showing an LC50 of 0.51 g/L. These findings highlight the potential of SA-CS coacervates for effective Bt microencapsulation and application in pest control.

Effectiveness of Bacillus thuringiensis (Bt) application in controlling mortality of Spodoptera litura on rice plants (Oryza sativa L.)

Rice (Oryza sativa L.) is the primary commodity for the Indonesian people because most of the Indonesian population depends on rice. The armyworm pests Spodoptera litura causes irregular holes in the leaves, thus disrupting the photosynthesis process and reducing rice production, so it is necessary to treat the pest. Bacillus thuringiensis is a pathogenic bacterium for insects, such as S. litura. This study aimed to look at the effectiveness of B. thuringiensis on the mortality of S. litura on a laboratory and field scale. The research was conducted in the Agrotechnology Laboratory, Faculty of Agriculture, Musamus University. The research design was a complete randomized design (RAL). The research study was conducted on five treatment doses of B. thuringiensis, which were 20 g/500 ml of water; 40g/500 ml of water; 60 g/500 ml of water; 80 g/500 ml of water; 100 g/500 ml of water. Each treatment was repeated five times. The results showed that, applying B. thuringiensis can significantly decrease the population and intensity of S. litura. The highest mortality rate in laboratory trials was observed at a dose of 100 grams/500 ml of water, with 50 dead individuals. In contrast, the lowest mortality rate was recorded at a dose of 20 gram of material/500ml of water, with only 12 death S. litura larvae. In field testing, the best dose was 50 gram/14 liters of water, and it caused the death of 50 S. litura larvae. Spraying B. thuringiensis on rice plants can reduce the population and intensity of S. litura.

Patogenisitas Jamur Entomopatogen Metarhizium Anisopliae Metch. Terhadap Larva Spodoptera Litura F. Pada Tanaman Kubis (Brassicae Oleracea L.) Di Laboratorium

This study aims to analyze the pathogenicity of the entomopathogenic fungus M. anisopliae in infecting S. litura. The research was conducted over a period of 3 months, from February to May 2024. It took place at the Kalasey Biological Agents Laboratory, Balai Perlindungan dan Pengujian Mutu Tanaman Pangan dan Hortikultura (BPPMTPH) in North Sulawesi Province. The study employed a Completely Randomized Design (CRD) with 4 treatments, each replicated 4 times. The number of samples per replication was 20 larvae, resulting in a total of 80 larvae per treatment. Data were analyzed using probit analysis and ANOVA followed by Least Significance Different (LSD) test at a 5% significance level. The results indicated that the pathogenicity of the entomopathogenic fungus M. anisopliae could infect S. litura larvae as early as one day after application. The concentration of 108 conidia/ml was highly effective, achieving 100% mortality within 6 days of application. The fastest LT50 value was observed at the concentration of 108 conidia/ml, which required only 2.8 days, while the LC50 value was found at a concentration of 107.6 conidia/ml.

Gut Microbial Diversity Reveals Differences in Pathogenicity between Metarhizium rileyi and Beauveria bassiana during the Early Stage of Infection in Spodoptera litura Larvae.

Beauveria bassiana and Metarhizium rileyi are extensively utilized to investigate fungal pathogenic mechanisms and to develop biological control agents. Notwithstanding, notable distinctions exist in their pathogenicity against the same host insect. This study aimed to elucidate the pathogenic differences between M. rileyi and B. bassiana by examining the impact of various ratios of B. bassiana strain AJS91881 and M. rileyi strain SXBN200920 on fifth instar larvae of Spodoptera litura, focusing on early infection stages and intestinal microbial community structure. The lethal time 50 (LT50) for B. bassiana was significantly lower than that for M. rileyi, indicating greater efficacy. Survival analyses in mixed groups (ratios of 1:9, 1:1, and 9:1 M. rileyi to B. bassiana) consistently demonstrated higher virulence of B. bassiana. Intestinal microbial diversity analysis revealed a significant increase in Achromobacter and Pseudomonas in larvae infected with M. rileyi, whereas Weissella was notably higher in those infected with B. bassiana. Additionally, significant shifts in microbial genera abundances were observed across all mixed infection groups. KEGG pathway enrichment analysis indicated that M. rileyi and B. bassiana employ distinct pathogenic strategies during early infection stages. In vitro tests confirmed the superior growth and stress resistance of B. bassiana compared to M. rileyi, but the antifungal ability of M. rileyi was better than that of B. bassiana. In conclusion, our findings provide preliminary insights into the differential pathogenic behaviors of M. rileyi and B. bassiana during the early infection stages in S. litura larvae, enhancing our understanding of their mechanisms and informing biological pest control strategies in agriculture and forestry.

Antifeedant Activity of Crude Extracts and Fractions Isolated from Cymodocea serrulate (R.Br.) Leaf against Tobacco Caterpillar Spodoptera litura (Fab.) Lepidoptera: Noctuidae

Different organic solvent extracts of Cymodocea serrulata leaves exhibited antifeedant activity against Spodoptera litura larvae. Maximum antifeedant activity (88.95%) was observed in ethyl acetate extract at a 5 percent concentration. Five fractions were isolated from ethyl acetate extract by column chromatography and tested individually at four different concentrations, viz., 125, 250, 500, and 1000 ppm, for antifeedant activity. Among the five fractions, fraction I showed promising antifeedant activity (91.12%) at a 1000 ppm concentration. Deformities in larvae, pupae, and adults were also recorded. The preliminary phytochemical analysis showed the presence of alkaloids, terpenoids, flavonoids, tannins, phenolic compounds, glycosides, and steroids.

Gustatory Receptor 206 Participates in the Foraging Behavior of Larvae of Polyphagous Pest Spodoptera litura.

Insect gustatory receptors (GRs) aid in the precise identification of deterrent or stimulant compounds associated with food, mating, and egg-laying. Thus, they are promising targets for developing efficient insecticides. Here, 61 GRs in the chemosensory organs of Spodoptera litura larvae and adults were identified. Among them, SlitGR206 exhibited larval labium (LL)-specific expression characteristics. To explore the role of SlitGR206, a bacterial expression system was established to produce high-quality double-stranded RNA (dsRNA) and suppress SlitGR206 expression in LL. Subsequent behavioral assessments revealed that SlitGR206 silencing influenced larval feeding preferences and absorption. Moreover, it was found to reduce the ability of larvae to forage the five crucial host odorants. These findings demonstrate that SlitGR206 likely plays an indirect regulatory role in host recognition, consequently affecting foraging behavior. This provides a crucial foundation for the analysis of functional diversity among insect GRs and the precise development of nucleic acid pesticides in the future.

Systemic defense induced by fatty acid compounds from marine macroalgae, Chaetomorpha antennina in tomato (Solanum lycopersicum) plants alters the susceptibility of the polyphagous agricultural pest, Spodoptera litura Fab

BackgroundSeaweeds contain a widespread range of fatty acids (FA), and several of them have potential bioactivity. FAs are dynamic members of all biota, as well as being acknowledged for their critical function in initiating phytohormone interactions and acting as important participants in many defense signalling pathways of the plant system. The current study looks at the defense-eliciting potentials of fatty acids from the green seaweed Chaetomorpha antennina (Bory) Kützing and their impact on the polyphagous insect pest Spodoptera litura (Fab).ResultsThe seaweed was detected with 19 fatty acids, with larger proportion of hexa and octadecanoic and linoleic acids. The algal fatty acid compounds (CFA) were successful in eliciting salicylic acid and phenolic compounds biosynthesis along with defense enzymes peroxidase (PO) and polyphenol oxidase (PPO). CFA enhanced the synthesis of defense enzymes, PO and PPO and phenols, post infestation with S. litura (> 50%) compared to control plants exposed to the pest. CFA was also effective in causing direct mortalities (96–98%) to the larvae (II-V instars). S. litura larvae exposed to elicited tomato plants displayed physiological incursions that extended larval-pupal duration to 26–28 days, preventing both morphogenetic transitions as well as affecting their morphology, that lead to the emergence of adults with malformed wings, legs. As a consequence, the fecundity was reduced by 60% affecting the reproductive performances of second-generation adults. The consumption rate (RCR) of larvae exposed to CFA was decreased by 84%, depicting feeding deterrence. These larvae were also observed with > 50% reduction in the levels of phosphatase enzyme secretion, bringing down larval growth rate from 0.58 to 0.34 mg/day. Histological analysis of exposed larvae displayed midgut cell disruption.ConclusionHence, the study finally confirms the elicitor potentials of fatty acid compounds from C. antennina, by inducing natural systemic defenses. This investigation unlocks novel forecasts besides delivering an unconventional method for crop protection to moderate or interchange the solicitation of chemical pesticides.Graphical

New prospective insecticidal agents based on thiazolo[4,5-b]quinoxaline derivatives against cotton leafworm Spodoptera litura (Fabricius): Design, synthesis, toxicological, morphology, histological, and biomedical studies

In this study, a new series of thiazolo[4,5-b]quinoxaline derivatives 3–8 were synthesized by treating 2,3-dichloroquinoxaline with thiosemicarbazone and thiourea derivatives under reflux conditions. The chemical structure of the newly designed derivatives was conducted using spectroscopic techniques. The insecticidal bioassay of the designed derivatives was evaluated against the 2nd and 4th larvae of S. litura after five days as toxicity agents via median lethal concentration (LC50) and the lethal time values (LT50). The results indicated that all the tested compounds had insecticidal effects against both instar larvae of S. litura with variable values. Among them, thiazolo[4,5-b]quinoxaline derivative 3 was the most toxic, with LC50 = 261.88 and 433.68 ppm against 2nd and 4th instar larvae, respectively. Moreover, the thiazolo[4,5-b]quinoxaline derivative 3 required the least time to kill the 50% population (LT50) of 2nd larvae were 20.88, 13.2, and 15.84 hs with 625, 1250, and 2500 ppm, respectively, while for the 4th larval instar were 2.75, 2.08, and 1.76 days with concentrations of 625, 1250, and 2500 ppm, respectively. Larvae's morphological and histological studies for the most active derivative 3 were investigated. According to SEM analysis, the exterior morphology of the cuticle and head capsule was affected. In addition, there were some histological alterations in the cuticle layers and the midgut tissues. Columnar cells began breaking down, and vacuolization occurred in the peritrophic membrane. Moreover, treating 4th S litura larvae hemolymph with compound 3 showed significant changes in biochemical analysis, such as total proteins, GPT, GOT, acetylcholinesterase (AChE), and alkaline phosphatase (AlP). Finally, the toxicity prediction of the most active derivative revealed non-corrosive, non-irritant to the eye, non-respiratory toxicity, non-sensitivity to the skin, non-hepatotoxic, and don't have toxicity on minnow toxicity and T. pyriformis indicating a good toxicity profile for human.

Characterization of Neuropeptides from Spodoptera litura and Functional Analysis of NPF in Diet Intake.

Neuropeptides are involved in many biological processes in insects. However, it is unclear what role neuropeptides play in Spodoptera litura adaptation to phytochemical flavone. In this study, 63 neuropeptide precursors from 48 gene families were identified in S. litura, including two neuropeptide F genes (NPFs). NPFs played a positive role in feeding regulation in S. litura because knockdown of NPFs decreased larval diet intake. S. litura larvae reduced flavone intake by downregulating NPFs. Conversely, the flavone intake was increased if the larvae were treated with NPF mature peptides. The NPF receptor (NPFR) was susceptible to the fluctuation of NPFs. NPFR mediated NPF signaling by interacting with NPFs to regulate the larval diet intake. In conclusion, this study suggested that NPF signaling regulated diet intake to promote S. litura adaptation to flavone, which contributed to understanding insect adaptation mechanisms to host plants and provide more potential pesticidal targets for pest control.