Kyung Saeng Boo

Olfactory reactions of the twelve-spotted lady beetle, Coleomegilla maculata and the green lacewing, Chrysoperla carnea to semiochemicals released from their prey and host plant : Electroantennogram and behavioral responses

Electroantennograms (EAGs) were recorded from two predatory insect species, the twelve-spotted lady beetle, Coleomegilla maculata and the green lacewing, Chrysoperla carnea in response to semiochemicals emitted from one of their prey species, the pea aphid Acyrthosiphon pisum and their host plant. EAG responses were also recorded from C. maculata in response to extracts from individuals of the opposite sex and to extracts from an herbaceous plant, catnip Nepeta cataria. Extracts of catnip and two sex pheromone components of aphids, (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol, elicited significant EAG responses from the antennae of both predatory species. Of 10 corn volatile compounds tested, C. carnea adults responded most strongly to 2-phenylethanol and (E)-β-farnesene. A significant difference in EAG response to extracts of corn leaf collections was observed between male and female C. carnea. In C. maculata, significant EAG responses were elicited by most of the tested corn volatile compounds, except α-pinene and (E)-2-hexenal. The highest EAG responses were observed in response to (E)-β-farnesene, α-terpineol, 2-phenylethanol, and β-caryophyllene. Sexual differences in EAG responses of C. maculata were only found in response to 1-octen-3-ol. Male antennae of C. maculata produced significant EAG responses to extracts from conspecific females, but not to males, which indicates that some chemicals from females could be involved in sexual communication. A significant EAG response also was recorded in response to the extracts of fluids produced during “reflex bleeding.” Male and female antennae of both species exhibited similar dose–response curves to most of the selected compounds, although female C. maculata antennae exhibited higher thresholds in response to several compounds including α-terpineol, (Z)-3-hexenol, and (4aS,7S,7aR)-nepetalactone. Field tests showed that 2-phenylethanol was highly attractive to both sexes of the two investigated species. Only C. maculata was attracted to traps baited with α-terpineol.

Response of The Lacewing Chrysopa cognata to Pheromones of its Aphid Prey

The lacewing Chrysopa cognata, one of the principal predators of aphids in Korea, was tested for responses to the aphid sex pheromone components (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol and the aphid alarm pheromone (E)-β-farnesene. Electroantennogram responses were obtained to the sex pheromone components but not to (E)-β-farnesene. The sex pheromone components were attractive in a Y-tube olfactometer assay and in field trials with water traps, but no attraction was observed to (E)-β-farnesene.

Female sex pheromone of oriental tobacco budworm,Helicoverpa assulta (Guenee) (Lepidoptera: Noctuidae): Identification and field testing

Analysis of ovipositor washings from virgin femaleHelicoverpa assulta (Guenée) (Lepidoptere: Noctuidae) from Korea by gas chromatography (GC) linked to electroantennography and GC linked to mass spectrometry resulted in the identification of nine compounds, hexadecanal, (Z)-9-hexadecenal, (Z)-11-hexadecenal, hexadecyl acetate, (Z)-9-hexadecenyl acetate, (Z)-11-hexadecenyl acetate, hexadecan-l-ol, (Z)-9-hexadecen-l-ol, and (Z)-11-hexadecen-1-ol. However, ovipositor washings from females from Thailand contained mainly the 16-carbon aldehydes with very small amounts of (Z)-9-hexadecenyl acetate. Field tests conducted in Korea, China, and Thailand indicated that a binary blend of (Z)-9-hexadecenal and (Z)-11-hexadecenal was sufficient for attraction, although the most attractive ratio of compounds varied with location. In Korea a 20∶1 blend of compounds was the most attractive, while in Thailand a 7.5∶1 blend was most attractive. In China both blends of hexadecenal isomers were equally attractive. Addition of the hexadecenyl acetates to the 20∶1 blend of hexadecenals in the ratio of 1∶3.3 increased the trap catch of maleH. assulta compared to lures containing the aldehydes alone in Korea but reduced trap catch in China. Addition of the hexadecenyl acetates to the 7.5∶1 blend of hexadecenals had no significant effect on trap catch in Thailand or China compared to the aldehydes alone. The addition of the 16-carbon alcohols to the aldehydes had a significantly inhibitory effect in all three countries, suggesting they are not pheromone components. Taken together these results indicate thatH. assulta is polymorphic with at least two populations responding to different sex pheromones.

Isolation and identification of the cDNA encoding the pheromone biosynthesis activating neuropeptide and additional neuropeptides in the oriental tobacco budworm, Helicoverpa assulta (Lepidoptera: Noctuidae)

The present study is concerned with cloning and characterizing Has-PBAN cDNA which is 756 nucleotides long, isolated from the brain and suboesophageal ganglion complex (Br-Sg) of Helicoverpa assulta adults. The 194-amino acid sequence deduced from this cDNA possessed the proteolytic endocleavage sites to generate multiple peptides. From the processing of the prepro-hormone, it can be predicted that the cDNA has a PBAN domain with 33 amino acids and four additional peptide domains: 24 amino acid-, 7 amino acid-, 18 amino acid- and 8 amino acid-long sequences, with FXPR (or K) L (X = G, T or S) amidated at their C-termini. The amino acid sequence of all five predicted peptides, including the PBAN, are identical to that of Helicoverpa zea (Raina, A.K., Jaffe, H., Kempe, T.G., Keim, P., Blacher, R.W., Fales, H.M., Riley, C.T., Klun, J.A., Ridgway, R.L., Hayes, D.K., 1989. Identification of a neuropeptide hormone that regulates sex pheromone production in female moths. Science 244, 796-798 and Ma, P.W.K., Knipple, D.C., Roelofs, W.L., 1994. Structural organization of the Helicoverpa zea gene encoding the precursor protein for pheromone biosynthesis-activating neuropeptide and other neuropeptides. Proc. Natl. Acad. Sci., U.S.A. 91, 506-510). A single mRNA species corresponding to the size of Has-PBAN cDNA was detected from the Br-Sg of 1-3-day old female and male adults, and their expression was also at a similar level. Pheromone production was induced upon injection of female or male Br-Sg extracts or synthetic PBAN into the haemocoel of decapitated 1-3-day old female adults during the photophase when they are not supposed to produce pheromone. From these results, H. assulta adult females seem to use their own PBAN for regulating sex pheromone biosynthesis. Functions of the four other peptides ending with FXPR (or K) L in the Has-PBAN cDNA and of the male PBAN remain to be elucidated.

Variation in Sex Pheromone Composition of a Few Selected Lepidopteran Species

Abstract Composition of insect sex pheromone is not always constant for any particular species. It may be different depending on the geographical area in the distribution of a species, as can be seen in the case of the European corn borer moth, Ostrinia nubilalis (Pyralidae). During the course of examining sex pheromone compositions of several lepidopteran species damaging agricultural and horticultural crops in South Korea, some subtle or apparent differences were noticed in sex pheromone compositions of Korean population belonging to those same species distributed in her neighboring countries. The oriental tobacco budworm moth, Helicoverpa assulta (Noctuidae), in Korea prefers the blend of 100 : 5 between (Z)-9-hexadecenal and (Z)-11-hexadecenal, while Thailand population responds best to 100 : 13 and Chinese population to wider blends from 100 : 2 to 100 : 20. Among lepidopteran insect pests on apples and apple tree leaves, the oriental fruit moth, Grapholita molesta (Tortricidae), showed almost no difference from one region to another. Korean population responded best to the blend of 100 : 5, with other populations to 100 : 6∼100 : 9 between (Z)-8-dodecen-1-ol acetate and (E)-8-dodecen-1-ol acetate. On the other hand, the peach fruit moth, Carposina sasakii (C. niponensis) (Carposinidae), males were attracted best to a single component, (Z)-7-eicosen-11-one in the case of Korean population, in contrast to Japanese population which was shown to be preferentially attracted to the mixture of the (Z)-7-eicosen-11-one and (Z)-7-nonadecen-11-one at the ratio of 100 : 5. The yellow peach moth, Dichocrocis punctiferalis (Pyralidae), seems to consist of two different populations in the northeastern Asia region, with one group responding to the blend of 100 : 8∼100 : 11 between (E)-10-hexadecenal and (Z)-10-hexadecenal and the other to that of 100 : 43. The first group was found in Japan and China and the second in Korea and also China. Korean population of the apple leaf miner, Phyllonorycter ringoniella (Gracillariidae), was best attracted to the blend of 100 : 150 between (Z)-10-tetradecen-1-ol acetate and (E, Z)-4,10-tetradecen-1-ol acetate, while Japanese and Chinese populations to the blends of 100 : 10∼30 and 100 : 43∼67, respectively. Furthermore, Korean Adoxophyes (Tortricidae) seemed to be a totally different species from Japanese Adoxophyes sp., or Adoxophyes orana fasciata, when viewed in terms of their pheromone composition.

Kairomones Used by Trichogramma chilonis to Find Helicoverpa assulta Eggs

Chemically mediated interactions between an egg parasitoid, Trichogramma chilonis, and its host insect, Helicoverpa assulta, were studied in laboratory experiments. T. chilonis was attracted to the sex pheromone of H. assulta, and, among four components of its sex pheromone, (Z)-11-hexadecenyl acetate seemed to be most attractive. T. chilonis was also highly attracted to (E)-12-tetradecenyl acetate, a component of the sex pheromone of Ostrinia furnacalis, another host. H. assulta eggs were more parasitized by T. chilonis when the eggs were treated with male moth scale extract (MSE) of H. assulta. Parasitism was also affected by the age of the parasitoid, time of day, and MSE concentration. Silica gel chromatography and subsequent argentation chromatography for MSE fractionation indicated the activity was associated with the fraction of saturated hydrocarbons. A linear olfactometer experiment revealed that H. assulta eggs also contain a short-range attractant(s).

CHARACTERIZATION OF (1R,4S,4aR,7S,7aR)-DIHYDRONEPETALACTOL AS A SEMIOCHEMICAL FOR LACEWINGS, INCLUDING Chrysopa spp. AND Peyerimhoffina gracilis

The enantiomerically pure diastereoisomers (1R,4S,4aR,7S,7aR)- (1) and (1R,4R,4aR,7S,7aR)-dihydronepetalactol (2) were synthesized diastereoselectively from a renewable resource, (4aS,7S,7aR)-nepetalactone (3), isolated as the main constituent of the essential oil of the catmint plant Nepeta cataria. The stereochemistry of the compounds was determined by NMR spectroscopy and X-ray crystallography, and the compounds were identified, respectively, as neomatatabiol and isoneomatatabiol, natural products from Actinidia polygama, for which the lactol stereochemistry was previously incompletely defined. Compound 1 was found to catch significant numbers of three species of lacewing in the field: in Korea, Chrysopa cognata, and in the United Kingdom, Nineta vittata and most notably Peyerimhoffina gracilis. All species caught in significant numbers were found more frequently in traps releasing 1 than 2, while more C. cognata, C. formosa, and C. phyllochroma were found in traps releasing (1R,4aS,7S,7aR)-nepetalactol (4). The catch of P. gracilis with 1 is of particular interest as this lacewing has only recently been recorded in the United Kingdom. Where sexed, the lacewings of all species trapped were found to be male, implying a possible pheromonal role for these or structurally related compounds.

Isolation and characterization of a Bacillus thuringiensis ssp. kurstaki strain toxic to Spodoptera exigua and Culex pipiens.

A strain of Bacillus thuringiensis with dual toxicity was isolated from Korean soil samples and named K2. K2 was determined as ssp. kurstaki (H3a3b3c) by serological test and produced bipyramidal-shaped parasporal inclusions. The plasmid and protein profiles of B. thuringiensis K2 were different from those of the reference strain, ssp. kurstaki HD-1. To verify gene type of B. thuringiensis K2, PCR analysis with specific cry gene primers was performed. The result showed that B. thuringiensis K2 had cry1Aa, cry1Ab, cry1C, and cry1D type genes, whereas ssp. kurstaki HD-1 had cry1Aa, cry1Ab, cry1Ac, and cry2 type genes. In addition, B. thuringiensis K2 had high toxicity against Spodoptera exigua and Culex pipiens, whereas B. thuringiensis ssp. kurstaki HD-1 does not have high toxicity against these two insect species.

Molecular characterization of pheromone biosynthesis activating neuropeptide from the diamondback moth, Plutella xylostella (L.).

Pheromone biosynthesis activating neuropeptide (PBAN) produced in the subesophageal ganglion stimulates pheromone production in the pheromone gland. A cDNA isolated from female adult heads of the diamondback moth (Plutella xylostella (L.)) encodes 193 amino acids including PBAN, designated as Plx-PBAN, and four other neuropeptides (NPs): diapause hormone (DH) homologue, alpha-NP, beta-NP and gamma-NP. All of the peptides are amidated in their C-termini and shared a conserved motif, FXPR(or K)L structure, as reported from other PBAN cDNAs. Plx-PBAN consists of 30 amino acids, the shortest PBAN so far reported. Plx-PBAN exhibited below 50% homology, compared with other known PBANs. The Plx-DH homologue is structurally different from DH of Bombyx mori. The length of Plx-beta-NP (16 amino acids) was the shortest and showed relatively low similarity, whereas gamma-NP (10 amino acids in length) was the longest among examined gamma-NPs. When female adults were injected with synthetic Plx-PBAN, pheromone production showed a maximal increase 1h post-injection. RT-PCR screening revealed that Plx-PBAN cDNA was expressed in all examined body parts, with the highest expression level in the head of female adults. Analysis of RT-PCR products indicated the Plx-PBAN sequence was identical in all examined body parts of both sexes. Phylogenetic analysis revealed that the Plx-PBAN gene is distantly related to other PBANs, demonstrated by the relatively low similarity.

(Z)-9-tetradecenal: a potent inhibitor of pheromone-mediated communication in the oriental tobacco budworm moth, Helicoverpa assulta

The behavioural significance of (Z)-9-tetradecenal to male H. assulta was tested by comparing the number of moths attracted to lures containing a standard synthetic female sex pheromone with lures in which (Z)-9-tetradecenal was also added. The standard pheromone mixture used contained 1000 μg (Z)-9-hexadecenal, 50 μg (Z)-11-hexadecenal, 300 μg (Z)-9-hexadecenyl acetate and 15 μg (Z)-11-hexadecenyl acetate impregnated on rubber septa. Addition of (Z)-9-tetradecenal to the standard pheromone was shown to significantly reduce the caught of male H. assulta when added in amounts greater than 10 μg or 1% of the major pheromone component in both field and net-house experiments. The reduction in catch was found to be dependent on the quantity of (Z)-9-tetradecenal added to the standard pheromone. The implications of these results on conspecific and inter-specific pheromone-mediated communication in H. assulta and related sympatric heliothine species is discussed.