Common Cutworm Research Articles

Plant growth-promoting rhizobacteria modulate induced corn defense against Spodoptera litura (Lepidoptera: Noctuidae).

Common cutworm, Spodoptera litura is an important pest of corn causing significant crop yield loss. Synthetic insecticides have mostly been used to combat this pest, raising human and environmental health concerns. Plant growth-promoting rhizobacteria (PGPR) could compensate for or augment the harmful effects of agrochemicals. Herein, we aimed to assess whether PGPR-induced defenses in corn plants impact the host-plant selection behavior of S. litura. Headspace volatile organic compounds were analyzed using gas chromatography-mass spectrometry. Larvae fed inoculated corn exhibited lower weights and relative growth rate than noninoculated plants. Under choice experiments, PGPR-treated plants significantly reduced percentage leaf damage area and oviposition rate compared to untreated plants. Volatile organic compound ratio emission varied significantly between control and PGPR treatments, which, in part, explains feeding and oviposition deterrence in PGPR-treated plants. The results demonstrate that PGPR inoculation can enhance corn resistance to S. litura, making it a promising candidate for crop protection strategies.

Migration Activity of Spodoptera litura (Lepidoptera: Noctuidae) between China and the South-Southeast Asian Region.

The common cutworm, Spodoptera litura (F.), feeds on a wide variety of food and cash crops and is one of the most widespread and destructive agricultural pests worldwide. Migration is the biological basis of its regional population outbreaks but the seasonal movement of this pest between east and south Asia regions remains unknown. In this study, searchlight traps were used to monitor the seasonal migration of S. litura from 2019 to 2023 in Ruili City (Yunnan, China), located along the insect migratory route between China and the south Asia region. The results showed that migratory activity could occur throughout the year, with the main periods found in spring (April-May) and autumn (October-December). The ovarian development and mating status of the trapped females indicated that most individuals were in the middle or late stages of migration and that Ruili City was located in the transit area of the long-distance migration of the pest. In the migration trajectory simulation, populations of S. litura moved from northeast India, Bangladesh, and northern Myanmar to southwestern China along the southern margin of the Himalayas in spring and returned to the south Asia region in autumn. Our findings clarify the seasonal migration patterns of S. litura in China and South Asia and facilitate the development of regional cross-border monitoring and management systems for this pest.

Identification and biocontrol potential of entomopathogenic nematodes, Steinernema siamkayai occurring in western Thailand against the common cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) under laboratory and screenhouse conditions

AbstractThe common cutworm, Spodoptera litura, is a serious insect pest of many vegetables and crops worldwide. Entomopathogenic nematodes (EPN) have been utilized as biological control agents for controlling various insect pests, including the larvae of S. litura. Many indigenous EPN have been recognized to be more effective in specific field applications. Among the 160 soil samples collected in undisturbed areas of western Thailand, three samples tested positive for EPN. Three indigenous EPN were identified as Steinernema siamkayai namely, EPNKU63, EPNKU70 and EPNKU85, based on ITS and D2/D3 expansion region analysis of the 28s rRNA genes. Additionally, genetic analysis of the symbiotic bacteria using recA rRNA sequences confirmed their identity as Xenorhabdus stockiae namely, PEPNKU63, PEPNKU70 and PEPNKU85. To evaluate their initial biocontrol potential against the 6th instar larvae of Galleria mellonella, virulence assays were conducted. The application of 100 infective juveniles (IJs)/insects resulted in the mortality of 80–100% of G. mellonella larvae after 72 h. When symbiotic bacteria were applied at 1 × 106 cells/insect, they exhibited 63–93% mortality against G. mellonella larvae after 120 h. In further laboratory tests, three S. siamkayai isolates achieved 100% mortality of 3rd instar Spodoptera litura larvae within 72 h, with LC50 values ranging from 29 to 30 IJs/insect. In screenhouse experiments, it was revealed that all S. siamkayai isolates displayed substantial virulence, ranging from 62% to 74%, against 3rd instar S. litura larvae within 72 h. This study demonstrates the biocontrol potential of S. siamkayai in controlling S. litura larvae.

Perfect cooperative pest control via nano-pesticide and natural predator: High predation selectivity and negligible toxicity toward predatory stinkbug

The improper use of synthetic pesticides has caused adverse effects on global ecosystems and human health. As a part of sustainable pest management strategy, natural predators, along with nano-pesticides, have made significant contributions to ecological agriculture. The cooperative application of both approaches may overcome their limitations, substantially reducing pesticide application while controlling insect pests efficiently. Herein, the current study introduced a cationic star polymer (SPc) to prepare two types of nano-pesticides, which were co-applied with predatory stinkbugs Picromerus lewisi to achieve perfect cooperative pest control. The SPc exhibited nearly no toxicity against predatory stinkbugs at the working concentration, but it led to the death of predatory stinkbugs at extremely high concentration with the lethal concentration 50 (LC50) value of 13.57 mg/mL through oral feeding method. RNA-seq analysis revealed that the oral feeding of SPc could induce obvious stress responses, leading to stronger phagocytosis, exocytosis, and energy synthesis to ultimately result in the death of predatory stinkbugs. Then, the broflanilide and chlorobenzuron were employed to prepare the self-assembled nano-pesticides via hydrogen bond and Van der Waals force, and the complexation with SPc broke the self-aggregated structures of pesticides and reduced their particle sizes down to nanoscale. The bioactivities of prepared nano-pesticides were significantly improved toward common cutworm Spodoptera litura with the corrected mortality increase by approximately 30%. Importantly, predatory stinkbugs exhibited a strong predation selectivity for alive common cutworms to reduce the exposure risk of nano-pesticides, and the nano-pesticides showed negligible toxicity against predators. Thus, the nano-pesticides and predatory stinkbugs could be applied simultaneously for efficient and sustainable pest management. The current study provides an excellent precedent for perfect cooperative pest control via nano-pesticide and natural predator.

Armyworm population dynamics and damage assessment in rice agroecosystems at Jampuijala, Tripura, India

Rice cultivation faces persistent challenges from various insect pests, including invasive species. The emergence of four armyworm species (rice swarming caterpillar, Spodoptera mauritia (Boisduval), common cutworm, Spodoptera litura (F.); rice ear-cutting caterpillar/paddy armyworm, Mythimna separata (Walker); and fall armyworm, Spodoptera frugiperda (J.E. Smith), along with other herbivores, poses significant threats to Asian rice ecosystems, causing considerable economic losses. This study investigates the occurrence and distribution of these armyworm species in rice agro-ecosystems across three Village Councils (VCs). Only S. mauritia larvae were observed, appearing in nursery fields approximately16-27 days after sowing and displaying sudden mass attacks primarily targeting seedlings at the 1-5 leaf stages. Damage manifestations included cutting leaf tips, creating shot holes on leaf blades, and occasionally severing seedlings at the base. The Ranjit variety in Kalaibari VC and the Gomati variety in Killa Verma VC showed the highest infestation rates (18.0%) and larval populations (1.7 larvae/m2). These findings offer valuable insights for stakeholders involved in rice cultivation across Asian rice-producing nations. Keywords: Oryza sativa, Spodoptera mauritia, Spodoptera frugiperda, Spodoptera litura, Mythimna separata.

Construction of a nontoxic nano-pesticide and its co-application with natural predators for perfect cooperative pest management: an innovative strategy for pesticide reduction

The current study develops a nano-pesticide that is nontoxic toward the predatory stinkbug but with enhanced bioactivity toward the common cutworm, which proposes to co-apply the nano-pesticide with predator as an innovative pest control technique.

Genomic blueprints of soybean (Glycine max) pathogen resistance: revealing the key genes for sustainable agriculture.

Soybean (Glycine max ) is an important oilseed, protein and biodiesel crop. It faces significant threats from bacterial, fungal and viral pathogens, which cause economic losses and jeopardises global food security. In this article, we explore the relationship between soybeans and these pathogens, focusing on the molecular responses that are crucial for soybeans defence mechanisms. Molecular responses involve small RNAs and specific genes, including resistance (R) genes that are pivotal in triggering immune responses. Functional genomics, which makes use of cutting-edge technologies, such as CRISPR Cas9 gene editing, allows us to identify genes that provide insights into the defence mechanisms of soybeans with the focus on using genomics to understand the mechanisms involved in host pathogen interactions and ultimately improve the resilience of soybeans. Genes like GmKR3 and GmVQ58 have demonstrated resistance against soybean mosaic virus and common cutworm, respectively. Genetic studies have identified quantitative trait loci (QTLs) including those linked with soybean cyst nematode, root-knot nematode and Phytophthora root and stem rot resistance. Additionally, resistance against Asian soybean rust and soybean cyst nematode involves specific genes and their variations in terms of different copy numbers. To address the challenges posed by evolving pathogens and meet the demands of a growing population, accelerated soybean breeding efforts leveraging functional genomics are imperative. Targeted breeding strategies based on a deeper understanding of soybean gene function and regulation will enhance disease resistance, ensuring sustainable agriculture and global food security. Collaborative research and continued technological advancements are crucial for securing a resilient and productive agricultural future.

Inhibition of oenocytoid lysis of the common cutworm Spodoptera litura (Lepidoptera: Noctuidae) by carbon dioxide gas

Inhibition of oenocytoid lysis of the common cutworm Spodoptera litura (Lepidoptera: Noctuidae) by carbon dioxide gas

The Identification of a Quantative Trait Loci-Allele System of Antixenosis against the Common Cutworm (Spodoptera litura Fabricius) at the Seedling Stage in the Chinese Soybean Landrace Population.

Common cutworm (CCW) is an omnivorous insect causing severe yield losses in soybean crops. The seedling-stage mini-tray identification system with the damaged leaf percentage (DLP) as an indicator was used to evaluate antixenosis against CCW in the Chinese soybean landrace population (CSLRP) under three environments. Using the innovative restricted two-stage multi-locus genome-wide association study procedure (RTM-GWAS), 86 DLP QTLs with 243 alleles (2-11/QTL) were identified, including 66 main-effect loci with 203 alleles and 57 QTL-environment interaction loci with 172 alleles. Among the main-effect loci, 12 large-contribution loci (R2 ≥ 1%) explained 25.45% of the phenotypic variation (PV), and 54 small-contribution loci (R2 < 1%) explained 16.55% of the PV. This indicates that the CSLRP can be characterized with a DLP QTL-allele system complex that has not been found before, except for a few individual QTLs without alleles involved. From the DLP QTL-allele matrix, the recombination potentials expressed in the 25th percentile of the DLP of all possible crosses were predicted to be reduced by 41.5% as the maximum improvement and 14.2% as the maximum transgression, indicating great breeding potential in the antixenosis of the CSLRP. From the QTLs, 62 candidate genes were annotated, which were involved in eight biological function categories as a gene network of the DLP. Changing from susceptible to moderate plus resistant varieties in the CSLRP, 26 QTLs had 32 alleles involved, in which 19 genes were annotated from 25 QTL-alleles, including eight increased negative alleles on seven loci and 11 decreased positive alleles on 11 loci, showing the major genetic constitution changes for the antixenosis enhancement at the seedling stage in the CSLRP.

INDUCTION OF TOMATO POLYPHENOL OXIDASES IN RESPONSE TO COMMON CUTWORM (Spodoptera litura) AND JACK BEARDSLEY MEALYBUG (Pseudococcus jackbeardsleyi) INFESTATIONS

Our objectives were to evaluate the induction of polyphenol oxidases (PPOs) and expression patterns of PPO A, B, D, E, and F genes upon infestations by common cutworm (Spodoptera litura) and Jack Beardsley mealybug (Pseudococcus jackbeardsleyi). After common cutworm infestation at leaf node 4, PPO activities increased 10.2-fold locally, leading to systemic increase in PPO activities at upper leaf nodes 1-2 (3.0-fold) and lower leaf node 6 (1.7-fold). While infestation at leaf node 6 locally induced PPO activities 14.5-fold, and systemically induced PPO activities 3.0-fold at leaf node 4. By contrast, no significant induction of PPO was observed at any leaf nodes when either leaf node 4 or 6 was infested by mealybug. When common cutworm fed on PPO B::GUS fusion tomatoes, induced PPO B expression was observed locally particularly in mature leaves at veins, petioles, and abscission zones. However, PPO D::GUS fusion tomatoes showed locally induced expression especially in older leaves at veins and petioles. Systemically induced expression was also observed. Mealybug feeding also locally induced PPO B and PPO D expression in vascular tissues but at lower levels.

The ryanodine receptor mutation I4728M confers moderate-level resistance to diamide insecticides in Spodoptera litura.

The common cutworm, Spodoptera litura (Fabricius), is one of the most widespread and destructive polyphagous pests in tropical and subtropical Asia. S. litura has evolved resistance to different insecticides, including diamide insecticides. Here, we identified a ryanodine receptor (RyR) mutation (I4728M) associated with target site resistance to diamides in a field-collected population of S. litura. The contribution of this mutation to diamide resistance was investigated through establishing a near-isogenic resistant strain of S. litura. The ND21 population of S. litura, collected from Ningde, Fujian province of China in 2021, exhibited 130.6-fold resistance to chlorantraniliprole compared to the susceptible NJ-S strain. S. litura RyR mutation I4728M, corresponding to Plutella xylostella RyR I4790M, was identified in the ND21 population. SlRyR I4728M mutation of ND21 was introgressed into a susceptible background strain (NJ-S) with marker-assisted backcrossing. The introgressed strain named ND21-R, which was homozygous for the mutant 4728M allele, shared about 94% of the genetic background with the NJ-S strain. ND21-R strain showed moderate levels of resistance to two anthranilic diamides (19.1-fold to chlorantraniliprole, 19.7-fold to cyantraniliprole) and the phthalic diamide flubendiamide (23.4-fold). Genetic analysis showed that chlorantraniliprole resistance was autosomal, incompletely recessive and tightly linked with SlRyR I4728M mutation in the introgressed ND21-R strain of S. litura. Identification of the I4728M mutation and its contribution to diamide resistance in S. litura will help develop allelic discrimination assays for resistance monitoring and guide resistance management practices for diamides in S. litura. © 2023 Society of Chemical Industry.

Varied selectivity of caterpillar-specific Metarhizium rileyi and generalist entomopathogenic fungi against last instar larvae and pupae of common cutworm, Spodoptera litura (Lepidoptera: Noctuidae)

Varied selectivity of caterpillar-specific Metarhizium rileyi and generalist entomopathogenic fungi against last instar larvae and pupae of common cutworm, Spodoptera litura (Lepidoptera: Noctuidae)

GmERF54, an ERF Transcription Factor, Negatively Regulates the Resistance of Soybean to the Common Cutworm (Spodoptera litura Fabricius)

Soybean is attacked by various herbivorous insect pest species during the whole course of its life cycle in the field. It is important for soybean production to improve insect resistance by identifying and utilizing soybean endogenous insect-resistant genes. The ethylene-responsive transcription factor (ERF) plays a significant role in plant biotic and abiotic stresses; however, few studies focus on its role in insect resistance in soybean. Here, based on our previous common cutworm (CCW)-induced soybean transcriptome data, a soybean ERF gene GmERF54 was cloned, which responded to CCW feeding. Transcriptional analysis revealed that GmERF54 was ubiquitous in all soybean tissues and was expressed differently in insect-resistant and insect-susceptible soybean cultivars. RNA interference of GmERF54 increased the resistance to CCW, while the overexpression of GmERF54 decreased the resistance to CCW in transgenic soybean hairy roots compared with their controls. GmERF54 was localized to the nucleus, had transcriptional activation activity, and interacted with AP2/ERF GmPLT2. Several putative hormone response elements were predicted in the promoter sequence of GmERF54. Four putative elements were only found in the GmERF54 promoter sequence of insect-resistant cultivar Wanxianbaidongdou (WX), but not in the insect-susceptible cultivar Nannong 99-10 (99-10). GmERF54 promoter sequences of WX and 99-10 were cloned into the pCAMBIA1381z vector containing the β-glucuronidase (GUS) gene to generate GmERF54WX:GUS and GmERF5499-10:GUS recombinant vectors, respectively. GUS staining of soybean hairy roots containing GmERF54WX:GUS and GmERF5499-10:GUS showed that GmERF54 was induced by CCW attack and both MeJA (methyl jasmonate) and IAA (indole-3-acetic acid) treatments. Alleles in insect-resistant and insect-sensitive cultivars responded to these inductions differently. Overall, our results reveal that GmERF54 may be involved in the regulation of soybean resistance to CCW.

Evaluating, Screening and Selecting Yardlong Bean [Vigna unguiculata subsp. sesquipedalis (L.) Verdc.] for Resistance to Common Cutworm (Spodoptera litura Fabricius)

The yardlong bean [Vigna unguiculata subsp. sesquipedalis (L.) Verdc.] is an important vegetable crop, but it is prone to pest infestation. Therefore, breeding insect-resistant varieties is essential to reduce pesticide applications and to increase bean quality and yield. In the present study, 64 yardlong bean varieties were screened for their resistance to the common cutworm (Spodoptera litura Fabricius). In the greenhouse, leaves, pods, and seeds of yardlong beans were harmed by naturally occurring common cutworms. Seventeen insect-resistant and four insect-susceptible yardlong bean varieties were identified based on the weight of the nine-day-old larvae and 72 h weight increases of 4th instar larvae through feeding newly hatched and 4th instar larvae, respectively. Subsequent verification feeding experiments with newly hatched larvae showed that Zhuzaidou and Pingtangjiangdou’s insect resistance are the weakest and Jiangdou No.5, j-1, Zhijiangtezao No. 30, and Changcaidou have the strongest insect resistance. In 21 yardlong bean varieties, starch content and larval weight showed negative correlation and there was positive correlation between crude protein and larval weight, but almost neither of them reached significant levels. Through organ antibiotic and antixenotic experiments, it was concluded that common cutworms preferred feeding on yardlong bean leaves, and the weight increase of common cutworms feeding on leaves was higher than that of pods and seeds. These insect-resistant yardlong bean varieties warrant further investigation in basic antibiosis mechanism research in yardlong beans and can serve as germplasm resources for breeding programs engaged in reducing pesticide usage.

Inducible chemical defenses in wild mungbean confer resistance to Spodoptera litura and possibly at the expense of drought tolerance

Mungbean ( Vigna radiata ) is susceptible to many insect pests, but genotypes resistant to the common cutworm ( Spodoptera litura ) have yet to be identified. We screened for natural variants among wild mungbean populations and identified resistant (R1) and susceptible (S1) accessions. RNA-Seq data from R1 leaves exposed to larval feeding for 0, 2, 6 and 24 h suggested the involvement of CaMK, MAPK and jasmonic acid (JA) signaling, which diverts resources from primary metabolism to the biosynthesis of defense-related proteins and secondary metabolites. We compared the temporal expression of candidate genes in R1 and S1 plants exposed to larval feeding and observed the stronger induction of CAMK, MAPK, JA signaling, terpene and flavonoid biosynthesis genes in R1 plants. Accordingly, higher levels of JA accumulated in R1 leaves after larval feeding for 24 h, and metabolic profiling revealed elevated levels of tryptophan and tyrosine in R1 plants, possibly triggering the accumulation of glucosylated kaempferols and the emission of the volatile (E)-β-ocimene. Drought stress experiments showed that the inducible chemical defense system in accession R1 may come at the expense of drought tolerance. This potential trade-off between abiotic and biotic stress tolerance may reflect the lower levels of endogenous proline in R1 plants. • The wild mungbean accession CQ3114 (R1) have greater resistance against S. litura . • The resistant R1 plants have a robust jasmonate-induced chemical defenses. • The roles of β-ocimene in indirect defense/defense activation warrant more studies. • A trade-off between pest resistance and drought tolerance in wild mungbeans.

Soybean CALCIUM-DEPENDENT PROTEIN KINASE17 Positively Regulates Plant Resistance to Common Cutworm (Spodoptera litura Fabricius).

Soybean is frequently attacked by herbivorous pests throughout the growth period. Exploring anti-insect genes to improve insect resistance in soybean is an important soybean breeding goal. Here, we cloned and characterized the gene for a quantitative trait locus (QTL) related to insect resistance, Glyma.06g189600, which encodes CALCIUM-DEPENDENT PROTEIN KINASE17 (GmCDPK17) in soybean. The pairwise sequence alignment analysis revealed that the presumed protein of GmCDPK17 shares 52.06% similarity with that of GmCDPK38, a known negative regulatory gene of insect resistance in soybean. Ectopic expression of GmCDPK17 and GmCDPK38 restored the phenotypes of the Arabidopsis insect-susceptible mutant cpk10 and insect-resistant mutant cpk28, respectively. Moreover, transgenic hairy roots of the soybean cultivar Jack were generated by Agrobacterium-mediated transformation. Overexpression of GmCDPK17 increased soybean hairy root resistance to common cutworm (CCW), while RNA interference of the gene decreased soybean hairy root resistance to CCW. Sequencing data from the cultivated and wild soybeans were used to analyze the genetic diversity of GmCDPK17. This gene was subjected to domestication selection. Six and seven haplotypes (Haps) were identified in cultivated and wild soybeans, respectively. The resistance Hap1 is not widely used in cultivated soybeans and is mainly distributed at low latitudes. Accessions with resistance haplotypes of the GmCDPK17 and GmCDPK38 genes showed high resistance to CCW. Altogether, we revealed a novel positive regulatory insect resistance gene, GmCDPK17, which may further improve insect resistance in soybean.

Beneficial effects of cadmium on plant defense of an invasive plant

Soil contamination by heavy metals is widespread as an inevitable consequence of every-increasing industrial and mining activities. In contaminated habitats, many sensitive plant species may extinct, and a few species, specifically the invasive plants with higher metal tolerance, can survive or colonize in such empty niche. The accumulation of heavy metals in plant tissues is one of the defense strategies against pathogens and herbivores. However, little is known regarding whether increased metal content is beneficial to the defense of invasive plants when competing with native plants. In this study, we explored the foliar chemistry of invasive alligator weed, Alternanthera philoxeroides , and its native congener sessile joyweed, A. sessilis , in response to cadmium (Cd) stress, and further examined how Cd amendment affected the performance and host selection of common cutworm Spodoptera litura (generalist), and alligator weed flea beetle Agasicles hygrophila (specialist). We found that the overall defense ability of invasive A. philoxeroides was higher than its native congener, but the defense mechanisms against specialist and generalist herbivores differed under Cd stress. Agasicles hygrophila was susceptible to high Cd stress, and the Cd amendment caused the beetle to shift hosts from A. philoxeroides to A. sessilis . For S. litura , organic rather than inorganic elemental defenses reduced its fitness on invasive plant, and the larvae prefer native plant against invasive plant in most scenarios. Native plant will be more vulnerable to herbivores when competing with invasive plant, especially in metal-polluted habitats. Our study provides a richer view of invasive mechanism in natural systems and appeals for paying more attention to soil contamination in assessing the potential ecological risk of plant invasion. • The overall defense of invasive A. philoxeroides is higher than native A. sessilis . • The specialist was susceptible to elemental defense. • Heavy metal promotes a host shift of specialist from invasive to native plant. • The generalist was susceptible to the organic defense. • Heavy metal promotes the plant invasion via apparent competition.

The genotoxic, cytotoxic and growth regulatory effects of plant secondary metabolite β-caryophyllene on polyphagous pest Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

Use of secondary metabolites as an alternative to organic pesticides is an eco-friendly and safe strategy in pest management. β-caryophyllene [(1R,4E,9S)-4,11,11-trimethyl-8-methylene bicyclo [7.2.0]undec-4-ene], a natural sesquiterpene is found as an essential oil in many plants like Syzygium aromaticum, Piper nigrum, Cannabis sativa. The present study aims at exploring the insecticidal, genotoxic and cytotoxic potential of β-caryophyllene against common cutworm Spodoptera litura (Fab.), a major polyphagous pest. S. litura larvae were fed on different concentrations (5, 25, 125, 625 and 3125 ppm) of β-caryophyllene. Results revealed delay in larval and pupal period with increase in concentration. Larval mortality increased and adult emergence declined significantly with increase in concentration. Higher concentrations of β-caryophyllene caused pupal and adult deformities. A negative impact of β-caryophyllene was also seen on the nutritional physiology of S. litura. Parameters such as relative growth rate, relative consumption rate, efficiency of conversion of ingested food, efficiency of conversion of digested food and approximate digestibility showed a significant reduction in a dose dependent manner. DNA damage assessed using comet assay revealed significant genotoxic effects at LC30 and LC50 concentrations. There was an increase in tail length, percent tail DNA, tail moment and olive tail moment. Phenol oxidase activity was suppressed at LC50 concentration with respect to control. Total hemocyte count also declined significantly at LC30 and LC50 concentrations as compared to control. β-caryophyllene induced genotoxic and cytotoxic damage affecting the growth and survival of S. litura larvae. Our findings suggest that β-caryophyllene has the potential to be used for the management of insect pests.

Functional characterization of CYP6AE subfamily P450s associated with pyrethroid detoxification in Spodoptera litura

The common cutworm, Spodoptera litura, has developed with varying degrees of resistance to most commonly used insecticides. Cytochrome P450 monooxygenases (P450s) with broad substrate specificities have been frequently reported to be involved in insecticide detoxification, but the underlying mechanisms remain obscure. Herein, seven CYP6AE subfamily P450s which possess six classical substrate recognition sites and several conserved catalytic motifs were identified from the genome of S. litura. Spatiotemporal expression profiles showed that these CYP6AE subfamily members were predominantly expressed in the larval midgut. Among them, CYP6AE43 and CYP6AE48 were significantly induced by three pyrethroids including β-cypermethrin, λ-cyhalothrin and fenvalerate. Knockdown of CYP6AE43 or CYP6AE48 by RNA interference dramatically increased the larval susceptibility to the pyrethroids. When silencing them simultaneously, the larval susceptibility to pyrethroids was higher than when silencing them individually, indicating a cooperative relationship between these two P450s in pyrethroid detoxification. Homology modeling and molecular docking analyses showed that these three pyrethroids could stably bind to CYP6AE43 and CYP6AE48, with the binding free energies from −37.58 to −84.24 kcal mol−1. These results indicate that induction of CYP6AE43 and CYP6AE48 contributes to pyrethroid detoxification and promotes the development of resistance to pyrethroids in S. litura.

Genome-Wide Association Studies Reveal Novel Loci for Herbivore Resistance in Wild Soybean (Glycine soja).

The production of soybean [Glycine max (L.) Merr.] is seriously threatened by various leaf-feeding insects, and wild soybean [Glycine soja Sieb. & Zucc.] has a greater resistance capacity and genetic diversity. In this study, a natural population consisting of 121 wild soybean accessions was used for detecting insect resistance genes. The larval weight (LW) of the common cutworm (CCW), the resistance level (RL) and the index of damaged leaf (IDL) were evaluated as resistance indicators to herbivores. An association synonymous SNP AX-94083016 located in the coding region of the respiratory burst oxidase gene GsRbohA1 was identified by genome-wide association study (GWAS) analyses. The overexpression of GsRbohA1 in soybean hairy roots enhanced resistance to CCW. One SNP in the promoter region cosegregated with AX-94083016 contributing to soybean resistance to CCW by altering GsRbohA1 gene expression and reactive oxygen species (ROS) accumulation. Two major haplotypes, GsRbohA1A and GsRbohA1G, were identified based on the SNP. The resistant haplotype GsRbohA1A predominates in wild soybeans, although it has been gradually lost in landraces and cultivars. The nucleotide diversity around GsRbohA1 is much lower in landraces and cultivars than in its ancestors. In conclusion, a new resistant haplotype, GsRbohA1A, was identified in wild soybean, which will be a valuable gene resource for soybean insect resistance breeding through introducing into improvement lines, and it offers a strategy for exploring resistance gene resources from its wild relatives.