Ostrinia Species Research Articles

Comparative susceptibility of Ostrinia furnacalis, Ostrinia nubilalis and Diatraea saccharalis (Lepidoptera: Crambidae) to Bacillus thuringiensis Cry1 toxins

Transgenic corn hybrids that express toxins from Bacillus thuringiensis (Bt) are highly effective against the European corn borer, Ostrinia nubilalis (Hübner), and the closely related Asian corn borer, Ostrinia furnacalis (Guenée). Since the registration of Bt corn hybrids in the U.S. in 1996, there has been a great deal of information generated on O. nubilalis. However, relatively little information exists for O. furnacalis. To help determine whether the information generated for O. nubilalis can be leveraged for decisions regarding the use of transgenic Bt corn against O. furnacalis, experiments were designed to determine whether the pattern of sensitivity to various Bt Cry1 toxins is similar between the two species. Test insects included laboratory-reared O. furnacalis originating from Malaysia, a Bt-susceptible laboratory colony of O. nubilalis maintained at the University of Nebraska-Lincoln (UNL) and an out-group consisting of the sugarcane borer, Diatraea saccharalis (F.), from Louisiana which represents a different genus from the same family. O. furnacalis and O. nubilalis exhibited a similar pattern of susceptibility to all the Cry1 toxins and were highly susceptible to the range of Bt toxins tested including Cry1Aa, Cry1Ab, Cry1Ac and Cry1F. Both of the Ostrinia species were more tolerant to Cry1Ba compared with D. saccharalis, although sensitivity of O. furnacalis was intermediate and did not differ significantly from that of O. nubilalis and D. saccharalis. D. saccharalis was also susceptible to the range of toxins tested but unlike the two Ostrinia species, was more tolerant to Cry1F and more susceptible to Cry1Ba. These results indicate that both of the Ostrinia corn borer species are similar in sensitivity to the Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba and Cry1F toxins, thus suggesting shared toxin receptors and mechanisms of toxicity for the two species.

Comparison of ultrastructure among sibling species of Ostrinia (Lepidoptera: Crambidae) from China

AbstractScanning electron microscopy on the ultrastructure of scales on the forewings and labial palpi suggests species-diagnostic differences among six sibling species of the genus Ostrinia Hübner. Among four species with small mid-tibiae, O. furnacalis (Guenée) and O. nubilalis (Hübner) show similar ultrastructure of the distal forewing scales, which is distinctly different from that of O. orientalis Mutuura and Munroe and O. dorsivittata (Moore). The diameter of windows between longitudinal ridges and cross ribs of forewing scales in O. dorsivittata is the largest among examined species, and clearly different from that in the other three small mid-tibiae species. Scales of the labial palpi of O. orientalis have indistinct vestigial windows; windows of O. nubilalis are more numerous and larger than in the other three small mid-tibiae species. Among two species with massive mid-tibiae, window diameter of forewing scales is larger in O. zealis (Guenée) than in O. scapulalis (Walker). Moreover, the number and diameter of windows in scales of the labial palpi differs between these two species. In addition to other known morphological differences, these ultrastructural differences provide further evidence that closely related Ostrinia species are distinct.

Physiological adaptation of the Asian corn borer Ostrinia furnacalis to chemical defenses of its host plant, maize

A number of gramineous plants such as maize contain cyclic hydroxamic acids (cHx) that are toxic to many herbivores. Among the Ostrinia species found in Japan, the Asian corn borer Ostrinia furnacalis is the only one that utilizes maize, a gramineous plant. We used O. furnacalis and two congeners, Ostrinia scapulalis and Ostrinia latipennis, to obtain insights into the physiological adaptation of O. furnacalis to cHx. When an artificial diet containing a low concentration (0.3 mg/g diet) of cHx was fed to the larvae of O. furnacalis and O. scapulalis, larval growth and survival were significantly less affected in O. furnacalis than O. scapulalis. An artificial diet containing a high level (0.7 mg/g diet) of cHx was found to severely retard the growth of both species, albeit to different degrees. In an assay in vitro, homogenate of the digestive tract of O. furnacalis larvae degraded cHx more rapidly than that of O. scapulalis or O. latipennis. The degradation was found to be enzymatic and dependent on a cofactor, UDP-glucose, suggesting that UDP-glucosyltransferase or other UDP-glucose-dependent enzymes were involved. This enzymatic adaptation probably has enabled O. furnacalis to utilize plants containing cHx.

Broadly and narrowly tuned odorant receptors are involved in female sex pheromone reception in Ostrinia moths

Mate-finding communication in many moths is mediated by sex pheromones produced by females. Since the differentiation of sex pheromones is often associated with speciation, it is intriguing to elucidate how the changes in sex pheromones are tracked by the pheromone recognition system of the males. Moths of the genus Ostrinia, which show distinct differentiation in female sex pheromones, are good models to study this. The present study was initiated with the aim of identifying ORs from Ostrinia scapulalis that respond to its own pheromone components, ( E)-11- and ( Z)-11-tetradecenyl acetates. We isolated six OR gene candidates ( OscaOR3–8) from O. scapulalis. The same set of genes homologous to OscaOR3–8 were conserved in all (eight) Ostrinia species examined in addition to the previously reported OscaOR1 (tuned to ( E)-11-tetradecenol) and the Or83b homologue OscaOR2. OscaOR3 not only responded to ( E)-11- and ( Z)-11-tetradecenyl acetates, but also to the pheromone components of the congeners, ( Z)-9-, ( E)-12-, and ( Z)-12-tetradecenyl acetates. OscaOR4 responded with a relatively high specificity to ( E)-11-tetradecenyl acetate. While OscaOR5 responded only marginally to a few pheromone components, OscaOR6–8 did not respond to any of the compounds tested. A few conserved ORs, including a unique one with very broad responsiveness, appear to be involved in the sex pheromone reception in O. scapulalis. The findings of the present study are discussed with reference to knowledge on electrophysiological response profiles of olfactory receptor neurons in Ostrinia moths.

A male-specific odorant receptor conserved through the evolution of sex pheromones in Ostrinia moth species

In many moths, mate-finding communication is mediated by the female sex pheromones. Since differentiation of sex pheromones is often associated with speciation, it is intriguing to know how the changes in female sex pheromone have been tracked by the pheromone recognition system of the males. A male-specific odorant receptor was found to have been conserved through the evolution of sex pheromone communication systems in the genus Ostrinia (Lepidoptera: Crambidae). In an effort to characterize pheromone receptors of O. scapulalis, which uses a mixture of (E)-11- and (Z)-11-tetradecenyl acetates as a sex pheromone, we cloned a gene (OscaOR1) encoding a male-specific odorant receptor. In addition, we cloned a gene of the Or83b family (OscaOR2). Functional assays using Xenopus oocytes co-expressing OscaOR1 and OscaOR2 have shown that OscaOR1 is, unexpectedly, a receptor of (E)-11-tetradecenol (E11-14:OH), a single pheromone component of a congener O. latipennis. Subsequent studies on O. latipennis showed that this species indeed has a gene orthologous to OscaOR1 (OlatOR1), a functional assay of which confirmed it to be a gene encoding the receptor of E11-14:OH. Furthermore, investigations of six other Ostrinia species have revealed that all of them have a gene orthologous to OscaOR1, although none of these species, except O. ovalipennis, a species most closely related to O. latipennis, uses E11-14:OH as the pheromone component. The present findings suggest that the male-specific receptor of E11-14:OH was acquired before the divergence of the genus Ostrinia, and functionally retained through the evolution of this genus.

Sex pheromone of Ostrinia sp. newly found on the leopard plant Farfugium japonicum

AbstractRecently, larvae of Ostrinia were found feeding on the leopard plant Farfugium japonicum (Asteraceae), previously unrecorded as a host plant of this genus. The adult moths that developed from these borers were morphologically similar to, but distinct from, Ostrinia zaguliaevi, a monophagous species specialized for feeding on another Asteraceae plant, the butterbur Petasites japonicus. Although the taxonomical status of the moth feeding on F. japonicum is to be determined, distinct morphological differences in the adults strongly suggest this to be a new species (hereafter referred to as O. sp.). To gain an insight into the reproductive isolation between O. sp. and other members of the genus Ostrinia, the female sex pheromone and the males’ response to it were investigated using samples collected from F. japonicum. (Z)‐9‐tetradecenyl acetate (Z9‐14:OAc), (Z)‐11‐tetradecenyl acetate (Z11‐14:OAc), (E)‐11‐tetradecenyl acetate (E11‐14:OAc), tetradecyl acetate, and (Z)‐11‐hexadecenyl acetate were identified as candidates for sex pheromone components by analyses using gas chromatographs coupled to a mass spectrometer (GC‐MS) and electroantennographic detector (GC‐EAD). A series of bioassays of male responses in a wind‐tunnel and a field cage indicated that the former three compounds are essential for attracting males, and the latter two have no synergistic effect on the attraction. We therefore concluded that Z9‐14:OAc, Z11‐14:OAc and E11‐14:OAc are the sex pheromone components of O. sp. Although the same three compounds are used as the sex pheromone components of O. zaguliaevi and another congener, Ostrinia zealis, the blend proportions differed greatly among the three (Z9‐14:OAc/Z11‐14:OAc/E11‐14:OAc = 18/76/6 in O. sp., 45/50/5 in O. zaguliaevi and 70/6/24 in O. zealis). Differences in sex pheromones could contribute to the reproductive isolation between O. sp. and the other two Ostrinia species if males of each species exhibit a narrow window of response to their own blend ratio.

Differences in oviposition behaviour of two sympatric sibling species of the genus Ostrinia

Changes in host preferences are thought to be a major source of genetic divergence between phytophagous insect taxa. In western Europe, two sympatric taxa, O. nubilalis (the European corn borer) and O. scapulalis, feed mainly on maize and hop or mugwort, respectively. These two species may have diverged without geographic isolation after a host shift of ancestral populations onto maize or another cultivated species (e.g. sorghum). A previous study using inbred laboratory strains revealed that the two species differ in their oviposition choices in maize-mugwort tests. We sampled four natural populations in France (two of each taxon) and tested their oviposition behaviour toward four of their main host plant species: maize, sorghum, mugwort and hop. O. nubilalis females showed a very high preference for laying their eggmasses on maize, whereas O. scapulalis females displayed a more balanced range of preferences. O. nubilalis females were attracted slightly to sorghum, suggesting that this plant is an accidental, rather than a regular and ancestral host plant of O. nubilalis. One important result arising from this study is the significant proportion of eggs laid by both Ostrinia species on hop. This may explain why some stands of hop are sometimes not only infested by O. scapulalis but also by O. nubilalis larvae, a situation preventing assortative mating based on microallopatry. Hence, further studies must be conducted to see whether the host preference in the genus Ostrinia might be linked to assortative mating by a mechanism that is not mediated by the host plant.

Reconsidering the taxomony of several Ostrinia species in the light of reproductive isolation: a tale for Ernst Mayr

We reconsider the taxonomy of a group of closely related Ostrinia spp., illustrating how useful Mayr's biological spe- cies concept remains for studying speciation patterns and processes. We review and re-analyse recent data on Ostrinia scapulalis , Ostrinia nubilalis , Ostrinia narynensis and Ostrinia orientalis , along with those obtained over > 45 years in the former Soviet Union. The ten species of the 'trilobed uncus' group in the Ostrinia genus are clas- sified into subgroups according to male mid-tibia morphology. However, none of the characters that further discrim- inate between them (female sex pheromones, male genitalia and calling time) varies together with male mid-tibia morphology, and neither do molecular markers. Moreover, male mid-tibia morphology appears to depend on only two diallelic loci and seems to be unrelated to reproductive isolation between Ostrinia taxa. By contrast, reproductive iso- lation is strongly related to host-plant type. In accordance with Mayr's species concept, we thus propose a revision of the trilobed uncus Ostrinia spp. based primarily on host-plant type. We propose that O. narynensis Mutuura & Munroe, 1970 ( syn. nov. ) and O. orientalis Mutuura & Munroe, 1970 ( syn. nov. ) be synonymized with O. scapulalis (Walker, 1859). We further demonstrate that O. nubilalis auctt. pro parte feeding on mugwort, hop, and several other dicotyledons (previously called the ' O. nubilalis mugwort-race' in France) also belongs to O. scapulalis . Consequently, we propose that only O. nubilalis specimens feeding on maize (the former French ' O. nubilalis maize- race') belong to O. nubilalis (Hubner, 1796). The implications of this revision are discussed. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 49-72. ADDITIONAL KEYWORDS: biological species concept - host-races - Ostrinia furnacalis - Ostrinia narynensis - Ostrinia nubilalis - Ostrinia orientalis - Ostrinia scapulalis - speciation - taxonomy.

More Rare Males in Ostrinia: Response of Asian Corn Borer Moths to the Sex Pheromone of the European Corn Borer

A previous flight tunnel study showed that 3-5% of European corn borer (ECB) moths, Ostrinia nubilalis (Z/E11-14:OAc), could fly upwind and make contact with sources releasing the sex pheromone of the related Asian corn borer (ACB), Ostrinia furnacalis (2:1 Z/E12-14:OAc). In this study, we show that rare males (3-4%) are also present in South Korean ACB that respond to the sex pheromone blends of the ECB UZ (97:3 Z/E11-14:OAc) and BE (1:99 Z/E11-14:OAc) pheromone races. We also show that the upwind flight response of a significant proportion of male ACB was antagonized by the addition of 1% Z9-14:OAc to the ACB blend, a compound that also antagonizes the upwind flight of ECB males. Male ACB flight behavior was not, however, affected by adding either of the ECB blends to the ACB blend, or by the addition of 50% 14:OAc, a compound identified from female pheromone glands of ACB and a number of other Ostrinia species. Additional flight tunnel tests with ACB to study the comparative aspects of ECB and ACB pheromone response specificity showed that male ACB exhibited maximal levels of upwind flight and source contact with doses of pheromone (30 and 100 microg on rubber septum sources) that also elicited maximal levels in the two ECB pheromone races. The maximal level of source contact for ACB (66%) was lower than observed with the UZ race of ECB to its pheromone blend (>95%), but comparable to those for the BE race of ECB (65-70%). Male ACB also flew upwind in high proportions to a broader range of ratios of Z/E12-14:OAc (80:20 to 20:80) than was previously observed for either of the ECB races.

The mitochondrial genome of the smaller tea tortrix Adoxophyes honmai (Lepidoptera: Tortricidae)

Almost complete mitochondrial genome from a representative of an insect order Lepidoptera, the smaller tea tortrix Adoxophyes honmai was determined. The 15,680 bp long A. honmai genome encodes 13 putative proteins, two ribosomal RNAs and 22 tRNAs. The nucleotide sequences of A. honmai mitochondrial DNA have been compared with those of five species from the Lepidoptera and insects in the other orders that are available in the databases. The orientation and gene order of A. honmai is almost same to that of other insects with a few minor exceptions in the order of tRNAs and distribution of non-coding regions. Nucleotide composition, amino acid composition and codon usage are in the range of values estimated from other insect mitogenomes. In AT rich region of A. honmai, tandem reiterations are observed with repeats of TAA. In a preliminary phylogenetic analysis based on the concatenated 7 protein coding genes, A. honmai, an apoditrysian tortricid moth joined basally within the monophyly of Lepidoptera, supporting its relationship with other more derived species including obtectomeran Ostrinia species.

Oviposition Deterrents in Larval Frass of Four Ostrinia Species Fed on an Artificial Diet

Behavioral bioassays have shown that volatile oviposition-deterring chemicals are present in the frass of Ostrinia zealis, O. furnacalis, O. scapulalis, and O. latipennis larvae fed on an artificial diet. These chemicals were extractable with acetone, and could be partitioned into a polar lipid fraction. This fraction mainly included palmitic, stearic, oleic, linoleic, and linolenic acids. No significant differences among the four Ostrinia species were found in the amount and composition of these free fatty acids. A mixture of the five authentic fatty acids of the composition found in the larval frass of O. zealis exhibited significant oviposition-deterring effects on all four species.

Wolbachia infection and an all‐female trait in Ostrinia orientalis and Ostrinia zaguliaevi

AbstractSex ratio distortion toward females (SR trait), induced by a Wolbachia bacterium, has been reported in two species of the Ostrinia furnacalis group, viz., O. furnacalis, and O. scapulalis (Lepidoptera: Crambidae). In addition, an SR trait caused by abacterial, unidentified agent(s) is known in O. scapulalis. Here we examined the SR trait in four other species of the furnacalis group, viz., O. orientalis, O. zaguliaevi, and O. zealis from Japan, and O. nubilalis from central and eastern Europe. Wolbachia infection was detected in three O. orientalis females and in one O. zaguliaevi female, and the infection was always associated with the SR trait. In terms of wsp and ftsZ gene sequences, Wolbachia strains in O. orientalis and O. zaguliaevi were indistinguishable from each other, or from those in O. furnacalis and O. scapulalis. These findings suggest that Wolbachia strains in the four Ostrinia species are probably identical. In addition, one O. zealis female, which was negative in diagnostic PCRs for Wolbachia and general bacteria, produced an all‐female brood. This trait was very similar to the SR trait caused by abacterial agent(s) in O. scapulalis.

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Most studies of signal evolution have concentrated on auditory and visual signals. In some cases, studies have shown that receivers are able to respond to a wider range of signals than are commonly produced by conspecifics. A new study by Wendell Roelofs and colleagues demonstrates that a similar phenomenon can occur in chemical signaling between moths.Most insects rely on their sense of smell for sexual communication. Female moths emit a species-specific pheromone, either a single chemical or a blend of structurally related chemical compounds. The pheromone is produced by desaturase enzymes from unsaturated fatty acid precursors in an abdominal pheromone gland. Male antennae are finely tuned to the female pheromone. Males are able to identify their species-specific components and ratios and can follow small quantities of airborne pheromone to a calling female.Pheromones have been identified in five species of Ostrinia moths. Four use a blend of Z and E11-14 acetates, but the Asian corn borer, O. furnacalis, uses a blend of Z and E12-14 acetates. Roelofs et al. argue that both female production of and male response to the pheromone have changed in O. furnacalis, relative to the European corn borer, O. nubilalis.The authors found genes in both Ostrinia species for the Δ11 desaturase, which produces the O. nubilalis pheromone, and theΔ14 desaturase, which produces the O. furnacalis pheromone. While the Δ14 desaturase is non-functional in O. nubilalis, theΔ11 desaturase is non-functional in O. furnacalis. The biochemical pathways for pheromone production indicate that switching fromΔ11 desaturase to Δ14 desaturase produced the O. furnacalis blend rather than the O. nubilalis blend. If O. furnacalis arose from a species with a pheromone consisting of Z and E11-14 acetates, then evolution of the new pheromone blend is likely to have proceeded by duplication, mutation and a change in expression of desaturase genes.But what about the males? Female moth pheromone production and male response are not genetically linked, so without a male around who liked what he smelled, the female ancestors of O. furnacalis that produced the new pheromone blend would have quickly died out. In wind-tunnel experiments,Roelofs and his team found that a large proportion (4%) of male O. nubilalis were attracted to both their species-typical pheromone blend and that of O. furnacalis. This suggests that when the O. furnacalis pheromone blend appeared, males could have responded to the new female pheromone, allowing speciation to occur while preserving the sender—receiver coupling essential for chemical signaling.The research of Roelofs et al. presents one of the first examples of mechanisms by which evolution of a pheromone communication system and subsequent speciation may occur. This research raises practical issues for the practice of mating disruption, a pest control technique in which large amounts of insect pheromone are dispensed in agricultural environments, resulting in reduced larval damage to crops by disrupting adult sexual communication. Many pesticides have lost their effectiveness due to evolution of resistance in target insect species. Although resistance to mating disruption has never been observed, the findings of Roelofs et al. suggest mechanisms whereby it could occur.