Beet Armyworm Spodoptera Exigua Research Articles

Identification and genomic sequence analysis of a new Spodoptera exigua multiple nucleopolyhedrovirus, SeMNPV-QD, isolated from Qingdao, China.

A new beet armyworm (Spodoptera exigua) multiple nucleopolyhedrovirus SeMNPV-QD was isolated from dead larvae in the field in Qingdao, Shandong, China. The virus has a polyhedron size of 1.39 ± 0.28 μm, and typical virions contain one to seven nucleocapsids per envelope. SeMNPV-QD only infects the larvae of S. exigua; it does not infect larvae of S. litura, Agrotis ipsilon, A. segetum, Bombyx mori, Hyphantria cunea, or Stilpnotia salicis, and thus, has higher host specificity. SeMNPV-QD has a circular double-stranded DNA genome of 128,525 bp with a GC content of 37.41% and 127 putative open reading frames (ORF), each of which encodes more than 50 amino acids. These were identified and annotated in the SeMNPV-QD genome, accounting for 87.53% of the whole genome. Phylogenetic analysis of 38 core genes of the baculovirus confirmed that SeMNPV-QD is a Group II Alphabaculovirus and is most closely related to SeMNPV American isolate (SeMNPV-US1), S. litura nucleopolyhedrovirus II (SpliNPV-II), S. frugiperda multiple nucleopolyhedrovirus (SfMNPV), A. segetum nucleopolyhedrovirus (AgseNPV), A. segetum nucleopolyhedrovirus B (AgseNPV-B) and A. ipsilon multiple nucleopolyhedrovirus (AgipNPV). The pairwise distance of the nucleotide sequences of lef-8, lef-9, polh and concatenated lef-8/lef-9/polh fragments between SeMNPV-QD and several sister viruses mentioned above were all above 0.05 substitutions/site. SeMNPV-QD has 123 ORFs similar to those of SeMNPV-US1, and the genomic similarity was 45.8%. Compared to SeMNPV-US1, SeMNPV-QD has four additional ORFs such as two baculovirus repeat ORF (bro) genes, bro-1, bro-2, orf39 and orf95, but lacks 17 ORFs that have no effect on viral transcription and replication. The above results indicate that SeMNPV-QD is a new species of S. exigua multiple nucleopolyhedrovirus.

Contrasting consequences of plant domestication for the chemical defenses of leaves and seeds in lima bean plants

Plant domestication is assumed to result in reduced levels of defensive compounds in crops, because this makes the plants more suitable for consumption by humans and livestock. We argue that this should mainly be reflected in the concentrations of defense compounds in the plant parts that are used for consumption and not necessarily for other parts of crop plants. We tested this hypothesis for domesticated lima bean (Phaseolus lunatus), by comparing its chemical defenses against a leaf herbivore, the beet armyworm (Spodoptera exigua), and a seed predator, the beetle Zabrotes subfasciatus. For seeds and leaves we determined the concentrations of cyanogenic glycosides (CNGs) in cultivated varieties and wild populations and evaluated the preference and performance of the herbivores when exposed to leaves and seeds from wild and cultivated plants. Concentrations of CNGs were significantly different between wild and cultivated plants. In the leaves the concentration of CNGs in the cultivated varieties were more than double that of the wild leaves. In contrast, seeds from cultivated plants had up to 20 times lower CNG concentration compared to seeds from the wild populations. Insect preference and performance do not parallel the chemical data. Larvae of S. exigua preferred wild leaves but had higher survival on cultivated leaves. The beetles, however, strongly preferred seeds from cultivated plants and females developed more quickly on these seeds. We conclude that domestication of P. lunatus has altered the concentration of CNGs in both the seeds and the leaves in opposite directions. This results in differential effects on the herbivores that attack these two plant structures. The contrasting effect of domestication on different plant tissues can be explained by the fact that bean plants have been specifically selected for human consumption of the seeds. Tissue-specific effects of plant domestication on plant defenses can be expected for other crops as well.

Phytochemical variation mediates the susceptibility of insect herbivores to entomoviruses

AbstractIt has been reported that the susceptibility of insect herbivores to entomoviruses is affected by phytochemicals ingested during the acquisition of viral inoculum on the foliage of host plants. However, the relationship between this susceptibility and phytochemicals is poorly understood. To test this hypothesis of plant‐mediated effects on this susceptibility, we measured the effects of foliage from three plants, soybeans (Glycine max), collards (Brassica oleracea) and water convolvuluses (Ipomoea aquatica), on the susceptibility of larval beet armyworm (Spodoptera exigua) to nucleopolyhedrovirus (NPV), and analysed six foliar chemicals (total phenolics, peroxidase [POD], catalase [CAT], superoxide dismutase [SOD], endochitinase and exochitinase) in the three plants, respectively. The results of exponential modelling indicated that the LD50s (median lethal dose) of NPV to larvae increased with the increase in both phenolics and POD but declined with the increase in four other foliar chemicals, while the opposite trend was found between median lethal time (LT50) of NPV and the six foliar chemicals. This study reveals that phenolics and POD decrease host susceptibility to the entomoviruses and that CAT, SOD, endochitinase and exochitinase increase this susceptibility.

Parasitism of Two Spodoptera spp. by Microplitis prodeniae (Hymenoptera: Braconidae).

Early instar larvae of the tobacco cutworm Spodoptera litura (Lepidoptera: Noctuidae) and the beet armyworm Spodoptera exigua (Lepidoptera: Noctuidae) are recognized hosts of the parasitic wasp Microplitis prodeniae Rao and Kurian (Hymenoptera: Braconidae), although M. prodeniae has previously been regarded as monophagous. In this study, we found the immature period and longevity of M. prodeniae developing in S. exigua was similar to that in S. litura. It was shown that the development time of M. prodeniae in S. exigua was 15.1 ± 0.3 d, not significantly different from 15.0 ± 0.2 d in S. litura. The parasitism rate of M. prodeniae attacking S. exigua was significantly lower than on S. litura (65.48 ± 2.29 and 43.83 ± 2.20%, respectively), whilst the female ratio of the wasp's offspring was not significantly different when developing on the two species. M. prodeniae females prefer to oviposit on the second- and third-instar host larvae of S. exigua, rather than other instars. The effects of development of M. prodeniae on two important lepidopterous pests are discussed.

Increased RNAi Efficacy in Spodoptera exigua via the Formulation of dsRNA With Guanylated Polymers.

Lepidoptera comprise some of the most devastating herbivorous pest insects worldwide. One of the most promising novel pest control strategies is exploiting the RNA interference (RNAi) mechanism to target essential genes for knockdown and incite toxic effects in the target species without harming other organisms in the ecosystem. However, many insects are refractory to oral RNAi, often due to rapid degradation of ingested dsRNA in their digestive system. This is the case for many lepidopteran insects, including the beet armyworm Spodoptera exigua, which is characterized by a very alkaline gut environment (pH > 9.0) and a strong intestinal nucleolytic activity. In this research, guanidine-containing polymers were developed to protect dsRNA against nucleolytic degradation, specifically in high pH environments. First, their ability to protect dsRNA against nucleolytic degradation in gut juice of the beet armyworm S. exigua was investigated ex vivo. Polymers with high guanidine content provided a strong protection against nucleolytic degradation at pH 11, protecting the dsRNA for up to 30 h. Next, cellular uptake of the dsRNA and the polyplexes in lepidopteran CF203 midgut cells was investigated by confocal microscopy, showing that the polymer also enhanced cellular uptake of the dsRNA. Finally, in vivo feeding RNAi bioassays demonstrated that using these guanidine-containing polymer nanoparticles led to an increased RNAi efficiency in S. exigua. Targeting the essential gene chitin synthase B, we observed that the mortality increased to 53% in the polymer-protected dsRNA treatment compared to only 16% with the naked dsRNA and found that polymer-protected dsRNA completely halted the development of the caterpillars. These results show that using guanylated polymers as a formulation strategy can prevent degradation of dsRNA in the alkaline and strongly nucleolytic gut of lepidopteran insects. Furthermore, the polymer also enhances cellular uptake in lepidopteran midgut cells. This new delivery strategy could be of great use in further fundamental research in lepidopterans, using RNAi as a research tool, and could lead to future applications for RNAi-based pest control of lepidopteran insects.

Monitoring and biochemical characterization of beta-cypermethrin resistance in Spodoptera exigua (Lepidoptera: Noctuidae) in Sichuan Province, China

The beet armyworm Spodoptera exigua, a major pest affecting numerous cultivated crops in China, has developed a serious resistance to many traditional chemical insecticides. The resistance levels of the field-collected populations from different districts in Sichuan Province, China, to nine insecticides were detected with a diet-incorporation bioassay. Compared to the Lab-ZN strain, five (in 2014) and three (in 2016) field populations displayed either high or extremely high levels of resistance to beta-cypermethrin. All the field populations collected in 2014 were susceptible to emamectin benzoate, hexaflumuron, methoxyfenozide, chlorantraniliprole, cyantraniliprole and indoxacarb but exhibited low or moderate levels of resistance to abamectin. The resistances of field populations collected in 2016 were significantly higher than two years earlier, especial for chlorantraniliprole and cyantraniliprole with RRs rising from 173.4- to 582.6-fold and 175.3- to 287.6-fold, respectively, even though the field populations had retained moderate or low levels of resistance to chlorpyrifos and hexaflumuron. The synergism experiment revealed that the resistance of the LS16 population to beta-cypermethrin may be mainly related to cytochrome P450 monooxygenases (P450s), which was responsible for the highest increase ratio of 37.97-fold, for piperonyl butoxide, rather than either carboxylesterase (CarE) or glutathione S-transferase (GST). The cytochrome P450 ethoxycoumarin O-deethylase activity of the LS16 population was also the strongest among the treatments (P < 0.05). Non-denaturing polyacrylamide gel electrophoresis (native PAGE) indicated that enhanced E11, E13 and E15-E16 bands in the LS16 population likely contribute to the development of resistance to beta-cypermethrin.

Resistance to new insecticides and their synergism in Spodoptera exigua (Lepidoptera: Noctuidae) from Pakistan

The beet armyworm Spodoptera exigua (Hübner) is an important pest of field and vegetable crops in Pakistan. Due to persistent use of insecticides, it developed high levels of resistance to organophosphates and pyrethroids in the mid 2000s and farmers then switched to new chemistries. In the present study, its resistance to new chemistries such as indoxacarb, spinosad, chlorfenapyr, methoxyfenozide and avermectins was monitored from 1998 to 2017 using a leaf-dip bioassay. There was generally a very low to low resistance to these insecticides during the first 11 years of their introduction (1998-2008). Resistance to methoxyfenozide remained very low throughout the 20 years of monitoring. A moderate resistance was recorded to indoxacarb (2011-2015), spinosad (2009-2012), chlorfenapyr (2011-2017), abamectin (2016-2017) and emamectin benzoate (2010-2013). A high resistance was found to indoxacarb during 2016–2017, spinosad during 2013–2017 and emamectin benzoate during 2014–2017. A rotation of diverse chemistries, having novel modes of action, along with other integrated pest management tactics, is recommended for the management of insecticide resistance in S. exigua.

Vitellogenin and vitellogenin receptor gene expression profiles in Spodoptera exigua are related to host plant suitability.

The beet armyworm Spodoptera exigua, a worldwide phytophagous pest, causes considerable economic agricultural losses. Understanding the relationship between its fecundity and the host plant is a basic and important component of early forecasting of beet armyworm outbreaks. However, little is known about the molecular mechanism by which distinct hosts affect S. exigua fecundity. In this study, key life-history parameters of S. exigua reared on distinct hosts were investigated; the host plants could be ranked as lettuce > shallot > tomato > celery in their order of suitability. Full-length S. exigua vitellogenin receptor (SeVgR) cDNA was cloned, and sex-, stage- and tissue-specific expression characteristics were assessed. Spodoptera exigua vitellogenin (SeVg) and SeVgR expression levels were markedly modulated by host nutrients (P < 0.05). SeVg and SeVgR expression levels were significantly higher in S. exigua reared on lettuce, the most preferred and most nutritive host, than in those reared on tomato and celery. Interestingly, significant linear regression correlations were found between SeVg and SeVgR expression levels and key S. exigua life-history parameters, especially life span, pupa weight, and female fecundity (P < 0.01). Host plant type and suitability could affect the expression pattern of SeVg and SeVgR, which influenced S. exigua fecundity. Vg and VgR have the potential to be used as molecular markers of S. exigua fecundity and for forecasting outbreaks of S. exigua on different hosts. © 2017 Society of Chemical Industry.

Experimental temperature elevation promotes the cooperative ability of two natural enemies in the control of insect herbivores

One of the major drivers of global change is temperature elevation, which plays an important role in ecological interactions among species. However, it is still not known whether experimental temperature elevation promotes or inhibits the coexistence of multiple natural enemies of insect herbivores. We hypothesize that increased temperatures will favor synergisms among natural enemies. We examined the effects of temperature increases on an insect herbivore, beet armyworm (Spodoptera exigua) and its two most important natural enemy groups — parasitic wasps (Microplitis pallidipes) and entomoviruses (nucleopolyhedrovirus, NPV). Specifically, we examined the discriminatory response of parasitoids to NPV-infected and non-infected herbivores in the face of rising temperatures. Over a range of increasing temperature (19, 23, 27, 31 and 35°C) and two virus dosages (5.33×107 and 5.33×105OB·mL−1) at five different time periods (24, 48, 72, 84 and 96h after treatment), both searching time and attacking time of parasitoids, to both NPV-infected and non-infected caterpillars, decreased with increasing temperatures. Consequently, the number of hosts attacked and the parasitism rates achieved by parasitoids increased. The percentage of first attacks by parasitoids that occurred in NPV-infected herbivores decreased with increasing temperature, with an increasing proportion of first attacks by parasitoids occurring, consequently, in uninfected caterpillars. Our study reveals that increased temperatures will make natural enemies more synergistic in the control of insect herbivores, and suggests that global warming might promote the coexistence of multiple natural enemies.

New Antifeedant Grayanane Diterpenoids from the Flowers of Pieris formosa.

Three new grayanane diterpenoids, pierisoids C‒E (1–3), as well as 10 known ones (4–13), were evaluated from the flowers of Pieris formosa, which is used as an insecticide in rural areas of China. Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analyses. Significant antifeedant activity of 1, 3 and 10 against the beet armyworm (Spodoptera exigua) was found, indicating that these diterpenoids might also be involved in the plant defense against insect herbivores.

Knockout of a P-glycoprotein gene increases susceptibility to abamectin and emamectin benzoate in Spodoptera exigua.

P-glycoprotein [P-gp or the ATP-binding cassette transporter B1 (ABCB1)] is an important participant in multidrug resistance of cancer cells, yet the precise function of this arthropod transporter is unknown. The aim of this study was to determine the importance of P-gp for susceptibility to insecticides in the beet armyworm (Spodoptera exigua) using clustered regularly interspaced short palindromic repeats/CRISPR-associated 9 (CRISPR/Cas9) gene-editing technology. We cloned an open reading frame (ORF) encoding the S.exigua P-gp protein (SeP-gp) predicted to display structural characteristics common to P-gp and other insect ABCB1 transporters. A knockout line with a frame shift deletion of four nucleotides in the SeP-gp ORF was established using the CRISPR/Cas9 gene-editing system to test its potential role in determining susceptibility to chemical insecticides or insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). Results from comparative bioassays demonstrate that knockout of SeP-gp significantly increases susceptibility of S.exigua by around threefold to abamectin and emamectin benzoate (EB), but not to spinosad, chlorfenapyr, beta-cypermethrin, carbosulfan indoxacarb, chlorpyrifos, phoxim, diafenthiuron, chlorfluazuron, chlorantraniliprole or two Bt toxins (Cry1Ca and Cry1Fa). Our data support an important role for SeP-gp in susceptibility of S.exigua to abamectin and EB and imply that overexpression of SeP-gp may contribute to abamectin and EB resistance in S.exigua.

Doppler weather radar detects emigratory flights of noctuids during a major pest outbreak

An outbreak of beet armyworm (Spodoptera exigua (Hübner)), cabbage looper, (Trichoplusia ni (Hübner)), and other noctuid pests devastated cotton production in the Lower Rio Grande Valley, TX, in 1995. Major infestations occurred later in the year several hundred kilometers away in other cotton production areas in Texas and Oklahoma, but information is lacking to connect regional infestations by these migratory pests. The objective of this study was to evaluate the capability of WSR-88D Doppler weather radar in locating and monitoring pest emigration from severely infested areas. Maximum radar reflectivity identified possible source areas in the vicinity of major infestations in cotton by beet armyworms and cabbage loopers that had been reported in Willacy County, TX. Areas of maximum clear-air radar reflectivity 13.5–16.5dBZ) appeared approximately 0.5h after sunset and displaced downwind toward susceptible cotton production regions in the Winter Garden and Southern Rolling Plains of west-central TX. Our results suggest that WSR-88D weather radar data may be useful in the development of crop pest advisories that estimate the timing, intensity, and displacement of insect migration flights, especially with recent enhancements in timely public access to WSR-88D radar data and radar data processing and analysis software.

Purification and properties of the chymotrypsin inhibitor from wild emmer wheat (Triticum dicoccoides) of Israel and its toxic effect on beet armyworm, Spodoptera exigua

A novel chymotrypsin inhibitor, which detected in the seed of wild emmer wheat (Triticum dicoccoides), was purified by ion-exchange chromatography, affinity chromatography and Ultracentrifugation. On the basis of its specificity, this inhibitor was named WeCI (wild emmer chymotrypsin inhibitor). SDS-PAGE analysis displayed that the purified WeCI is a single chain polypeptide with a molecular weight of approximately 13kDa. The inhibition constants (Ki) for amylase and bovine pancreatic chymotrypsin were 1.12×10−9M and 2.41×10−9M, respectively. Automated sequencing and mass spectrometry analyses revealed that WeCI is a neutral monomeric protein consisting of 119 residues. In vitro, WeCI strongly suppressed bovine pancreatic chymotrypsin as well as chymotrypsin-like activities separated from the midgut of the beet armyworm Spodoptera exigua. No inhibitory activities were found against bovine pancreatic trypsin, bacterial subtilisin, or porcine pancreatic elastase. The primary structure of WeCI was markedly similar (46–95%) to those of several proteins belonging to the wheat crop chymotrypsin/α-amylase inhibitor superfamily and displayed the typical sequence motif of the α-amylase inhibitor–seed storage protein group. WeCI significantly inhibited the growth and development of Spodoptera exigua, dependent on inhibitor concentration. WeCI significantly increased the mortality rate of Spodoptera exigua and caused a significant decrease in its fertility.

Rapid defense responses in maize leaves induced by Spodoptera exigua caterpillar feeding

Insects such as the beet armyworm (Spodoptera exigua) cause extensive damage to maize (Zea mays). Maize plants respond by triggering defense signaling, changes in gene expression, and biosynthesis of specialized metabolites. Leaves of maize inbred line B73, which has an available genome sequence, were infested with S. exigua for 1 to 24 h, followed by comparisons of the transcript and metabolite profiles with those of uninfested controls. The most extensive gene expression responses occurred rapidly, within 4-6 h after caterpillar infestation. However, both gene expression and metabolite profiles were altered within 1 h and continued to change during the entire 24 h experiment. The defensive functions of three caterpillar-induced genes were examined using available Dissociation transposon insertions in maize inbred line W22. Whereas mutations in the benzoxazinoid biosynthesis pathway (Bx1 and Bx2) significantly improved caterpillar growth, the knockout of a 13-lipoxygenase (Lox8) involved in jasmonic acid biosynthesis did not. Interestingly, 9-lipoxygenases, which lead to the production of maize death acids, were more strongly induced by caterpillar feeding than 13-lipoxygenases, suggesting an as yet unknown function in maize defense against herbivory. Together, these results provide a comprehensive view of the dynamic transcriptomic and metabolomic responses of maize leaves to caterpillar feeding.

Elevated carbon dioxide reduces emission of herbivore-induced volatiles in Zea mays.

Terpene volatiles produced by sweet corn (Zea mays) upon infestation with pests such as beet armyworm (Spodoptera exigua) function as part of an indirect defence mechanism by attracting parasitoid wasps; yet little is known about the impact of climate change on this form of plant defence. To investigate how a central component of climate change affects indirect defence, we measured herbivore-induced volatile emissions in plants grown under elevated carbon dioxide (CO2 ). We found that S.exigua infested or elicitor-treated Z.mays grown at elevated CO2 had decreased emission of its major sesquiterpene, (E)-β-caryophyllene and two homoterpenes, (3E)-4,8-dimethyl-1,3,7-nonatriene and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene. In contrast, inside the leaves, elicitor-induced (E)-β-caryophyllene hyper-accumulated at elevated CO2 , while levels of homoterpenes were unaffected. Furthermore, gene expression analysis revealed that the induction of terpene synthase genes following treatment was lower in plants grown at elevated CO2 . Our data indicate that elevated CO2 leads both to a repression of volatile synthesis at the transcriptional level and to limitation of volatile release through effects of CO2 on stomatal conductance. These findings suggest that elevated CO2 may alter the ability of Z.mays to utilize volatile terpenes to mediate indirect defenses.

Novel amino acid ester-chlorantraniliprole conjugates: design, synthesis, phloem accumulation and bioactivity.

Conjugating amino acid and glucose fragments with existing pesticide structures has been shown to be an effective way to introduce phloem mobility into non-phloem mobile species. However, the resulting derivatives always suffer from lower bioactivity compared with their parent compound. To solve this problem, we designed and synthesised a series of ester-capped amino-acid-conjugated chlorantraniliproles. The systemic test showed that all conjugates exhibited excellent phloem mobility and xylem mobility in a Ricinus communis model. In particular, compounds 7b, 8b and 8c were able to accumulate in phloem tissues in the form of their hydrolysis products, and the concentrations in phloem sap can reach 3 times the concentration in the incubation medium. Although their insecticidal activity (LC50 ) against the beet armyworm (Spodoptera exigua) in vitro was weaker than that of chlorantraniliprole, compounds 7b, 8b and 8c showed similar insecticidal activity in vivo against beet armyworm compared with the parent compound. This work provides a potential strategy to obtain pesticide derivatives that possess both improved uptake and improved mobility in crops while retaining the in vivo insecticidal effect of the parent compound. © 2017 Society of Chemical Industry.

Aminopeptidase N1 is involved in Bacillus thuringiensis Cry1Ac toxicity in the beet armyworm, Spodoptera exigua

Understanding how insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) interact with their hosts is crucial to fully explain the molecular bases of Bt specificity and insecticidal activity. Previous studies support ATP binding cassette transporters (ABCC2/3) and one cadherin-like protein are Cry1Ac functional receptors in the beet armyworm (Spodoptera exigua). In this study, a combined one-dimensional gel electrophoresis and immunoblotting approach identified aminopeptidase N (APNs) as putative Cry1Ac binding proteins in the midgut brush border membrane of S. exigua larvae. Functional analyses by gene silencing of six different S. exigua APN genes (SeAPN1, SeAPN2, SeAPN3, SeAPN4, SeAPN5 and SeAPN6) showed that only suppression of SeAPN1 resulted in decreased larval susceptibility to Cry1Ac toxin. These results support that SeAPN1 plays important functional role in Cry1Ac toxicity in S. exigua.

Insecticidal activities and biochemical properties of Pinellia ternata extracts against the beet armyworm Spodoptera exigua

The beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae), is a key pest of various agricultural crops in many countries throughout the world. The pest requires extensive use of pesticides and field-evolved resistances to conventional insecticides in China and other countries. Pinellia ternata Breit is native to the eastern part of Asia and found mainly in China, which has been used in traditional Chinese medicines for >1000years, but few studies have focused on the insecticidal activity of the P. ternate. In order to find natural products that could be used to control the pest in an safe, efficient and ecofriendly manner, we first time analyzed the components of the anhydrous ethanolic extracts from the tubers of Pinellia ternate by using GC–MS method, and then investigated the insecticidal activities and biochemical mechanisms of the extracts against S. exigua. The result of GC–MS showed that 2-Methoxy-4-vinylphenol may be an insecticidal active component, and we also found the extracts had notable insecticidal activity and disturbed the regular metabolism of S. exigua mainly through altering the activities of detoxification enzymes, digestive enzymes and protective enzymes. These properties suggest that the anhydrous ethanolic extracts from P. ternate can serve as a potential, efficient and ecofriendly S. exigua-control biopesticide.

Ecological fitness of transgenic GAFP cotton and its effects on the field insect community.

The ecological fitness of transgenic cotton and its effects on the insect communities in cotton fields is one of the key aspects of the evaluation of the environmental safety of transgenic cotton. New transgenic GAFP (Gastrodia anti-fungal protein) cotton and its parental varieties were used in this study to explore their ecological fitness and their effects on insect community infield in Anyang, Henan Province in 2013 and 2014. The results showed that there was no significant difference in dry mass for transgenic cotton leaves compared to that of parental cotton. Specific leaf areas of transgenic cotton were lowered obviously at seedling stage, while enhanced significantly at budding, flowering and bolling stages relative to parental cotton. The plant height of transgenic cotton was lowered only at seedling stage, and no significant difference was showed between the two cultivars at budding, flowering and bolling stages. No significant differences were discovered on plant branch numbers, bud numbers and falling numbers between the transgenic cotton and control material in any of the four key stages during the cotton growth. However, the number of bolls per plant for transgenic cotton was lower than that of the control cotton at the bolling stage. In the 2nd, 3rd, and 4th generation of cotton bollworm (Helicoverpa armigera), the mortality rate of cotton bollworm and beet armyworm (Spodoptera exigua) of transgenic cotton had no significant difference with parental cotton. Compared to parental cotton, total individuals of insect community, pest sub-communities and enemy sub-communities in transgenic cotton field didn't show any significant difference. The above results showed that after the GAFP gene was imported into cotton, the cotton growth was enhanced significantly, while the whole yield component traits and the insect community in the field were not significantly changed. Our study on the competition of new transgenic cotton and survival of transgenic cotton insect communities in cotton field would provide the theoretical basis for the evaluation of new transgenic cotton and environmental safety, and accumulate scientific data for environmental safety evaluation of the transgenic cotton.

Expression of ribosome-inactivating proteins from apple in tobacco plants results in enhanced resistance to Spodoptera exigua

Some ribosome-inactivating proteins (RIPs) possess insecticidal activity. In this study we investigated the activity of type 1 and type 2 RIPs from apple (Malus domestica) against an economically important pest insect belonging to the order of Lepidoptera, the beet armyworm (Spodoptera exigua), with the use of tobacco plants overexpressing the apple RIPs.Insect bioassays using detached leaves from transgenic tobacco lines demonstrated that the ectopically expressed type 1 or type 2 RIPs from apple exerted a high entomotoxic activity. We scored up to 78% mortality during the larval stages of S. exigua. Moreover, a significant reduction in the larval weight was observed in the surviving larvae fed on the transgenic lines at different time points as compared to wild type plants. In addition, apple RIPs also retarded the development of the larvae. These results provide further support for RIPs having a potential role in plant defense. It can be envisaged that these RIPs could be used in genetically engineered crops to enhance resistance against agronomically important insect pests.