Analysis of sex pheromone production and field trapping of the Asian corn borer(Ostrinia furnacalis Guenée)in Xinjiang,China

Identifying the sex pheromone systems of local pest populations facilitates their management,especially for moth species that show significant geographic variation in sex pheromone communication.We investigated the pheromone production and behavioral responses of the Asian corn borer(Ostrinia furnacalis Guenée;ACB)in Xinjiang,China.The ACB produces three compounds:(Z)-12-tetradecenyl acetate(Z12-14:Ac)and(E)-12-tetradecenyl acetate(E12-14:Ac)which are two sex pheromone compounds,and n-tetradecyl acetate(14:Ac)which has variable roles in mediating behavioral responses.The ratios of these three compounds produced in female gland are geographically distinct among different populations.Quantitative analysis of pheromone production showed that the proportions of Z12-14:Ac in the E/Z isomers(i.e.,Z and E12-14:Ac)and the proportions of 14:Ac in the ternary blend respectively averaged 60.46%(SD=5.26)and 25.00%(SD=7.37),with their probabilities normally or near-normally distributed.Trapping experiments in a cornfield indicated that deploying the E/Z isomers and the three compounds in rubber septa close to their gland ratios yielded the most captured males,while other ratios that deviated from the gland ratios showed reduced field captures.The ternary blend was significantly more attractive to males than the E/Z isomers in the field,indicating a functional role of 14:Ac as the third pheromone component used by the local population.Additionally,the dose-response test demonstrated that the application of the three compounds at dosages between 200 and 350μg attracted significantly more males compared to other dosages.Therefore,the characterization of this local ACB pheromone system provides additional information about its geographic variation and serves as a basis for optimizing the pheromone-mediated control of this pest in Xinjiang.

Determination and evaluation on field control efficacy of Trichogramma dendrolimi against Ostrinia furnacalis

The results of evaluation on field control efficacy of Trichogramma dendrolimi against Ostrinia furnacalis showed that the correction rates of Ostrinia furnacalis egg mass parasitism were 71.75% and 73.57%,the average control effect were 65.85% and 70.24%,the restoration yield loss rates were 6.78% and 7.97%,input-output ratio at 1:27.8 and 1:33.5 in Longjiang county of Heilongjiang province in 2009 and 2010,respectively.The technology is a integration of advanced,practical,environmental safety,effective biocontrol measures,embodies the "public plant protection,green plant protection" fully,has significant economic,social and ecological benefits.

Expression profiles and functional prediction of ionotropic receptors in Asian corn borer, Ostrinia furnacalis(Lepidoptera:Crambidae)

Genes involved in chemosensation are essential for odorant-mediated insect behaviors. Odorant receptors(ORs) bind and respond to pheromones and plant volatiles, regulating insect behaviors such as mating and host-plant selection, while ionotropic receptors(IRs), which are present at lower levels in insects than ORs, influence ion channels, especially in agricultural pests. Asian corn borer, Ostrinia furnacalis, is the main pest of maize that causes huge economic losses in Asia. Twenty-one Ofur IRs have been identified, but none has been characterized. In this study, tissue-specific expression profiling, phylogenetic analysis, and electroantennography(EAG) analysis were applied to characterize the evolution, expression, and the potential function of Ofur IRs. It was found that 20 Ofur IRs were highly expressed in the antennae, except for Ofur IR75p3, whereas 10 and nine Ofur IRs were highly expressed in the proboscis and genitalia, respectively, indicating that these Ofur IRs were functionally associated with feeding and oviposition. EAG results showed that seven acids elicited responses in the antennae of O. furnacalis and that 2-oxopentanoic acid displayed a significant femalebiased response. Combined with the phylogenetic analysis, 10 Ofur IRs in clade 4 were roughly predicted to be candidate receptors for 2-oxopentanoic acid and other tested acids. These results provide basic information about Ofur IRs and may help advance the knolwedge on the olfactory system of O. furnacalis.

Susceptibility of Ostrinia furnacalis to Bacillus thuringiensis and Bt Corn Under Long-Term Laboratory Selection

The susceptibility of the Asian corn borer, Ostrinia furnacalis to Bacillus thuringiensis (Bt) formulation and Bt corn was evaluated using insect bioassays for 6 years. Four strains of O. furnacalis were developed by laboratory selection from the laboratory strain reared on a non-agar semi-artificial diet. The RR-1 strain was exposed to a commercial formulation of B. thuringiensis subsp. kurstaki (Btk) incorporated into the artificial diet,the RR-2 strain was exposed to Bt corn (MON810) tissue incorporated into the diet, and the SS-1 and SS-2 strains were reared on the standard diet with or without non-Bt corn tissues material. Decreasing susceptibility of O. furnacalis to Bt and to Bt corn were found in each selected strain although the ED50 and larval weight fluctuated from generation to generation. The resistance of Bt-exposed strain (RR-1) to Btk increased 48-fold by generation 39; the Bt corn-exposed strain (RR-2) increased its resistance 37-fold to Btk by generation 24. No larvae of SS-1 survived when they were exposed to the leaves of Bt corn, Bt11 and MON810. However, 2-54% of the RR-1 (generation 46) and RR-2 (generation 20) larvae survived a 3 day-exposure to the leaves of Bt11 and MON810. The survival of both selected strains on Bt corn silk increased by 10-69%, and the larval weights after many generations selection were increased by 15-22% compared with the unselected susceptible strain. The young larvae were much more susceptible to Bt than older larvae. The highest mortality occurred when the larvae were exposed to Bt at the neonate stage. All of the results suggested that ACB could not only develop resistance to Bt preparation but also to Bt corn. Bt had significant effects on the growth and development of Asian corn borer than on the larval mortality. In order to maintain the long-term effectiveness of Bt pesticide and Bt corn, the resistance management should pay much attention to the larvae that may have opportunities to grow and developed on non-Bt corn or alternate hosts before they attack the Bt corn plants and the survival of larvae after Bt application.

Control Effect of Sex Pherom one Lure against the Asian Corn Borer( Ostrinia furnacalis) in Field

We studied the trapping effects on Ostrinia furnacalis from the aspects of different hanging heights and different color traps. The results suggested that the hanging height of 1.5 - 2.0 m received a better trapping effect, but trap color had little impact on trapping effect. The sex pheromone traps at different densities were placed in corn field. The results showed that sex pheromone lure could trap adult O. furnacalis, and it was feasible to apply sex pheromone in short term fore- cast. Meanwhile, it reduced the number of larvae and eggs, thereby reducing the damage of O. furnacalis. The lure number of 10 per hm2 was more appropriate, which could result in increasing yield of 8.61% compared with control

Volatiles induced by the larvae of the Asian corn borer （Ostrinia furnacalis） in maize plants affect behavior of conspecific larvae and female adults

Effects of maize （Zea mays L.） volatiles induced by larvae of the Asian corn borer, Ostriniafurnacalis （Guenee）, on the orientation behaviors of Asian corn borer larvae and oviposition of the females were investigated. Nineteen volatile chemicals, with terpenes being the major components, were identified from maize plants attacked by third instar Asian corn borer larvae. Coupled gas chromatographic-electroantennographic detection （GC-EAD） analyses revealed some electroantennographic differences between female and male Asian corn borer antennae in response to larvae-induced maize volatiles; female responded to （E）-2-hexenal, nonanal, （Z）-3-hexen-l-ol and three unknown compounds while the male only responded to （E）-2-hexenal, nonanal and one unknown compound. In laboratory orientation bioassays, Asian corn borer neonate larvae were attracted to extracts collected from Asian corn borer-damaged plants as well as to synthetic farnesene, but were repelled by （Z）-3-hexen- 1 -ol. In laboratory oviposition bioassays, gravid females laid fewer eggs on plants damaged by larvae than on mechanically damaged plants or undamaged plants. Adult Asian corn borer females deposited fewer eggs on wax paper treated with （E）-2-hexenal or （Z）-3-hexen-l-ol than on wax paper treated with hexane （control）. The results suggest that Asian corn borer can affect the behaviors of conspecific larvae and adults by changing host plant volatiles.

A dsRNA-degrading nuclease(dsRNase2)limits RNAi efficiency in the Asian corn borer(Ostrinia furnacalis)

The efficiency of RNA interference(RNAi)varies substantially among different insect species.Rapid degradation of double-stranded RNA(dsRNA)by dsRNA-degrading nucleases(dsRNases)has been implicated to cause low RNAi efficiency in several insect species.In this study,we identified four dsRNase genes(OfdsRNaseL Ofd-sRNase2,OfdsRNase3 and OfdsRNase4)from the Asian corn borer(Ostrinia furnacalis)transcriptome database.Bioinformatic analyses showed that each deduced protein sequence contained endonuclease NS domains and signal peptides.Gene expression analysis revealed that OfdsRNase2 was exclusively expressed in the midgut of larvae.RNAi efficiency was investigated in 2-d-old fifth-instar larvae(high expression of dsRNase2)and 2-d-old pupae(low expression of dsRNase2)by feeding or injecting dsRNA targeting a marker gene that encodes the lethal giant larvae protein(OfLgl).Our results showed that OfLgl only partially silenced the expression of OfLgl in pupae,but not in larvae,suggesting that OfdsRNase2 could contribute to lower RNAi efficiency in larval stages.This hypothesis was supported by our RNAi-of-RNAi experiment using a tissue culture technique where the silencing efficiency against the reporter gene,OfHexl,was significantly improved after knockdown of OfdsRNase2.When double luciferase assays were performed to evaluate the role of the four dsRNases in vitro,only OfdsRNase2 expressed in S2 cells significantly affected RNAi efficiency by degrading dsRNA.Taken together,our results suggested that the degradation of dsRNA by OfdsRNase2 in the midgut contributed to low RNAi efficiency in O.furnacalis larvae.

PLA_(2) mediates the innate immune response in Asian corn borer, Ostrinia furnacalis

The eicosanoid signaling pathway mediates insect immune reactions to a wide range of stimuli. This pathway begins with the biosynthesis of arachidonic acid (AA) from the hydrolysis of phospholipids catalyzed by phospholipase A_(2) (PLA_(2)). We report here that the PLA_(2) inhibitor, dexamethasone (DEX), impaired the innate immune response including nodulation, encapsulation, and melanization in Ostrinia furnacalis larvae, while AA partially reversed these effects of DEX. We cloned a full-length complementary DNA encoding a PLA_(2), designated as OfsPLA_(2), from O. furnacalis. The open reading frame of OfsPLA_(2) encodes a 195-amino acid residue protein with a 22-residue signal peptide. Sequence alignment analyses indicated that O. furnacalis PLA_(2) might be a Group III secretory PLA_(2). The highest transcript levels of OfsPLA_(2) were detected in the fat body, and its transcript levels increased dramatically after infection with Escherichia coli, Micrococcus luteus, or Beauveria bassiana. Recombinant OfsPLA_(2) significantly induced prophenoloxidase (PPO) activation in larval hemolymph in the presence of Ca^(2+) and encapsulation of agarose beads. Injection of recombinant OfsPLA_(2) into larvae resulted in increased transcript levels of attacin, defencin, and moricin-3 genes. Our results demonstrate the involvement of the eicosanoid signaling pathway in the innate immune response of O. furnacalis larvae and provide new information about the roles of O. furnacalis secretory PLA_(2) in activating PPO and antimicrobial peptide production.

Molecular characterization of glutaredoxin 2 from Ostrinia furnacalis

Glutaredoxins(GRXs)play very important roles in maintaining intracellular redox homeostasis.In the present study,the full-length cDNA sequence encoding GRX2,named OfurGRX2(GenBank accession no.GU393246),was obtained from Ostrinia furnacalis,using reverse transcription polymerase chain reaction and rapid amplification of cDNA ends.Sequence analysis revealed that the open reading frame of OfurGRX2 consists of 351 nucleotides encoding 116 amino acid residues with a predicted molecular weight of 12.6 kDa.Homolog research revealed that OfurGRX2 shares a common active site,CPYC/CPFC,with other insect counterparts.Expression profiles revealed that OfurGRX2 is a ubiquitous gene expressed in insect heads,fat bodies,epidermises,mid guts and muscles.The OfurGRX2 transcript peaked in 36-h larvae of 4th instars,and then suddenly declined in the molting stage.Hormone treatment experiments revealed that 20-hydroxyecodyson(20e)significantly induces the expression of the OfurGRX2 transcript,whereas juvenile hormone(JH)counteracts 20e effects.Adverse stress factors(including starvation,ultraviolet light,mechanical injury,Escherichia coli exposure,and high and low temperatures)dramatically induced OfurGRXGRX2 transcript expression,which confirmed for the first time that GRX2 play important roles in insecta during exposure to adverse environments.

Field Evaluation of the Asian Corn Borer Control in Hybrid of Transgenic Maize Event MON 810

In this study, a transgenic Bt maize hybrid (event MON 810 from Monsanto Company) expressing Cry1Ab protein derived from Bacillus thuringiensis (Bt) and its negative isoline hybrid were evaluated for control of the Asian corn borer, Ostrinia furnacalis (Guenée) (Lepidoptera: Pyralidae), in a field trial. Maize plants were artificially infested with neonate larvae of Asian corn borer at the mid-whorl (first-generation), pre-tassel (first- and/or second-generation), and silk (second-generation) growth stages. The transgenic Bt maize hybrid sustained significantly less leaf feeding damage (rating 1.0±0.0) than its negative isoline control (rating 7.3±0.1). With the Bt maize, 1.36.8% of plants were damaged by corn borer tunneling with <0.5 cm tunneling per stalk under different levels of infestation, compared with 100% of plants damaged with 9.325.0 cm tunneling per stalk for the negative isoline control. On average, transgenic Bt maize hybrids had only 0.010.05 tunnels per stalk and no stems were broken. In contrast, the negative isoline control had 3.118.36 tunnels per stalk and 31.273.9% of stems broken. Yields were significantly higher in transgenic Bt maize than in the control. These results demonstrate that transgenic Bt maize can significantly minimize yield losses caused by the Asian corn borer through resistance to the first- and second-generation larvae.

Quantitative Trait Loci for Asian Corn Borer Resistance in Maize Population Mc37×Zi330

Asian corn borer, Ostrinia furnacalis （Guen6e）, is the most important pest of maize in China and Southeast Asia. The objective of this study was to understand the genetic basis for Asian corn borer resistance. The study included 162 F2：3 populations derived from Mc37 （resistant） × Zi330 （susceptible） and field data were collected in 2004 and 2005. A linkage map was constructed from 118 SSR markers. Combined quantitative trait loci （QTL） analysis combined across environments was performed by composite interval mapping method （CIM）. Four QTLs with additive effects were detected for resistance to Asian corn borer leaf feeding damage in chromosome bins 1.08, 2.04/05, 4.01, and 10.04. Three putative QTLs were detected for Asian corn borer stalk damage in chromosome bins 1.01, 2.05, and 9.01. Maize resistance to Asian corn borer and European corn borer, O. nubilalis （Hubner）, may share a common mechanism. Genes responsible for DIMBOA biosynthesis are in chromosome bin 4.01 and may increase the observed resistance to Asian corn borer leaf feeding.

Impact of Asarum Essential Oils on Physiological and Biochemical Indicators of Two Agricultural Pests

[Objective]The paper was to study the effects of asarum essential oils on physiological and biochemical indices of two agricultural pests. [Method]Asarum essential oils were extracted by different methods,and their effects on physiological and biochemical indices related to the structure of body wall（ chitin and phenoloxidase）,the physiological and biochemical indices acting on the nervous system（ Acetylcholinesterase）,and the physiological and biochemical indices acting on the digestive system（ protease,amylase and lipase） of Ostrinia furnacalis and Mythimna seperata were studied. [Result]Asarum essential oils had no effect no chitin content of body wall under the experimental concentration,and had no inhibitory effect but activated effect on polyphenol oxidase activity. Asarum essential oils could act on the nervous system of insect,and had strong inhibitory effect against acetylcholinesterase activity of O. furnacalis larvae,with inhibition rates of 24. 86%- 38. 79%. Asarum essential oils showed a significant activated effect on pepsin activity in midgut,but the activated amplitude became smaller with the prolongation of treatment time. Asarum essential oils showed a significant inhibitory effect on activities of amylase and lipase,indicating that it could play an insecticidal effect by inhibiting activity of amylase and lipase,and it could act on digestive system of insect. [Conclusion]The study laid the foundation for further development of asarum as botanical pesticide.

Prediction of effective RNA interference targets and pathway-related genes in lepidopteran insects by RNA sequencing analysis

When using RNA interference （RNAi） to study gene functions in Lepidoptera insects, we discovered that some genes could not be suppressed; instead, their expression levels could be up-regulated by double-stranded RNA （dsRNA）. To predict which genes could be easily silenced, we treated the Asian corn borer （Ostriniafilrnacalis） with dsGFP （green fluorescent protein） and dsMLP （muscle lim protein）. A transcriptome sequence analysis was conducted using the cDNAs 6 h after treatment with dsRNA. The results indicated that 160 genes were up-regulated and 44 genes were down-regulated by the two dsRNAs. Then, 50 co-up-regulated, 25 co-down-regulated and 43 unaffected genes were selected to determine their RNAi responses. All the 25 down-regulated genes were knocked down by their corresponding dsRNA. However, several of the up-regulated and unaffected genes were up-regulated when treated with their corresponding dsRNAs instead of being knocked down. The genes up-regulated by the dsGFP treatment may be involved in insect immune responses or the RNAi pathway. When the immune-related genes were excluded, only seven genes were induced by dsGFP, including ago-2 and dicer-2. These results not only provide a reference for efficient RNAi target predications, but also provide some potential RNAi pathway-related genes for further study.