The hits with a length of less than amino acids were ignored. In the neighbor-joining tree of IRs Fig. Among the nine IRs in C. Alignment analysis revealed that the similarity of IR25a was higher than Unfortunately, we cannot obtain the sequences belong to iGluRs.
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Figures Abstract Suitability of plant tissues as food for insects varies from plant to plant. In lepidopteran insects, fitness is largely dependent on the host-finding ability of the females. Existing studies have suggested that polyphagous lepidopterans preferentially select certain host plant species for oviposition.
However, the mechanisms for host recognition and selection have not been fully elucidated. For the polyphagous yellow peach moth Conogethes punctiferalis, we explored the effect of chestnut cultivar on the performance and fitness and addressed the mechanisms of plant-volatile-mediated host recognition.
By carrying out laboratory experiments and field investigation on four chestnut Castanea mollissima cultivars Huaihuang, Huaijiu, Yanhong, and Shisheng , we found that C.
Plant volatiles played important roles in host recognition by C. Nonanal and a mixture containing nonanal, that mimicked the emission of C. The outcome demonstrates the effects of chestnut cultivars on the performance of C. The observed olfactory plasticity in the plant-volatile-mediated host recognition may be important for the forming of the relationship between yellow peach moth and chestnuts since it allows the polyphagous herbivores to adjust to variation in volatile emission from their host plants.
This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: All relevant data are within the paper and its Supporting Information files.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Introduction Phytophagous insects are generally associated with a particular plant or a constellation of plant species. Insect species that feed on a wide range of plant species belonging to different plant families are called generalists or polyphagous.
Even though polyphagous insects can be adaptive to a range of plant species, their fitness differs among various host plants [ 1 ]. In lepidopteran insects, many polyphagous species have higher fitness on certain host plants than on others [ 2 ].
However, the fitness of lepidopteran insects is largely dependent on the host-finding abilities of the adult females because the hatching larvae i. Adult female lepidopterans have been shown to preferentially select certain host plant species for oviposition [ 3 , 4 ]. A prevailing hypothesis on oviposition preference is that a female will choose those hosts on which caterpillars perform best [ 5 — 9 ].
This preference-performance hypothesis has been clearly supported by a meta-analysis [ 10 ]. However, the strength of the relationship between female preference and offspring performance varies among insect groups with different dietary breadth. The preference-performance relationship was stronger in oligophagous insects than in polyphagous or monophagous insects [ 10 ].
Even though there was a tremendous body of literature investigating the preference-performance relationship, the effect of dietary breadth on the relationship is still a promising avenue for future research [ 10 ]. Especially, the underlying mechanisms of host recognition and selection remain elusive.
For most insect herbivores, olfactory cues are usually used to orientate toward a specific host plant within a plant patch [ 11 ]. The most important infochemicals used by herbivores are plant volatiles [ 2 , 11 — 18 ]. Previous studies on the use of plant volatiles by lepidopteran insects have indicated the existence of preference among potential host plants [ 19 , 20 ].
In some species, the preference of females for some host plants is determined by the concentrations of particular chemical compounds, whereas in other species the preference response is dependent on the relative proportions of ubiquitous plant volatiles [ 21 — 24 ]. Unfortunately, the mechanisms for host recognition and selection, as well as the linkage between the oviposition preference of females and the fitness of their offspring, have not been fully elucidated.
It is therefore necessary to address how plant volatiles affect host recognition by lepidopteran insects and consequently affect offspring performance. Although C. A behavioral preference of C. One of the potential mechanisms underlying cultivar selection of C. However, the ecological implications of volatile-mediated host recognition and selection by C. We hypothesized that 1 the suitability of different chestnut cultivars for C.
In the present study, experiments were carried out 1 to investigate the field infestation rates of four chestnut cultivars, Huaihuang, Huaijiu, Yanhong, and Shisheng, by C. The major objectives of the study were to address the roles of chestnut volatiles in host recognition by C. All experiments carried out in the orchard had been approved by the station, and the field studies did not involve endangered or protected species.
The insects used in this study were originated from field collection of caterpillars in cornfields of the Agricultural Experiment Station of Beijing University of Agriculture on October 9th, The field-captured C. Therefore, no specific permits were required for the described insect collection and experimentation. Plants Four chestnut Castanea mollissima Blume cultivars, Huaihuang, Huaijiu, Yanhong, and Shisheng, that were widely grown in local area of Beijing, China, were grown in a 6.
Plants used for volatile trapping were 29 years old. The different cultivars were planted in different units of the same orchard, and the space between trees was 2 m while the space between rows was 4 m. Insects A laboratory colony of C. Chemicals n-Hexane Shanghai, China. Toshima, Tokyo, Japan.
Other chemicals used in the experiments were all purchased from Sinopharm Chemical Reagent Beijing Co. Beijing, China. Investigation of field infestation rate Infestation of chestnuts by C. Briefly, five trees of each cultivar were randomly selected, and sampling of chestnut fruits on each tree was conducted at three height levels, i. Five spots at each height level were selected, and three fruits at each spot were collected. The collected fruits were visually examined and then cut open to confirm the infestation status.
Forty-five fruits were sampled from each tree, and totally fruits were collected for each cultivar. Oviposition selection test To test the oviposition selection of C. Ten 3-day-old naive no exposure experience to natural or synthetic sources of chestnut-related volatiles females and 10 3-day-old males were kept in the cage.
For each combination test, one fruit of each cultivar was wrapped with a wet cheese cloth and randomly placed into an inner corner of the cage to allow oviposition of C. The test lasted for 4 days, and during the test the chestnut fruits and the cheesecloth were renewed every day.
The renewed fruits were randomly placed in any one of the four cage corners. Ten replicates with a total number of females were performed. Egg numbers on each sheet were counted separately, and the data were statistically treated on the basis of daily average number of eggs by 10 females.
Development and reproduction test Laboratory rearing experiments were carried out to determine the performance of C. In each chestnut a 2-mm hole was punched with a stainless awl, and then neonates of C. Five replicates with a total of 50 caterpillars were performed for each cultivar. When pupating, the survival of the caterpillars was checked, and newly molted pupae were picked up, counted, weighted and individually placed into a ml tube with a ventilated lid, and then transferred to the incubator to allow emergence of the moths.
An apple wrapped with wet cheesecloth was placed into the cage, and the female was allowed to lay eggs F1 on it. The cheesecloth was renewed every day until the death of the female moth. The hatched F1 caterpillars were collected and counted every day until no neonates were available anymore. Ten repetitions with a total number of 20 moths 10 males and 10 females, respectively were performed for each group of moths with experience on the same chestnut cultivar.
The developmental duration of eggs and caterpillars, as well as the survival rate of caterpillars and the fecundity of adult females number of F1 eggs per female , were determined using the methods described in our previous study [ 28 ]. Collection and identification of chestnut volatiles Chestnut volatiles were collected from August 18 to 28, , during which time the chestnut fruits were in the enlargement stage.
Meanwhile, in this period the C. Chestnut volatiles were collected for fruits of all four cultivars. Briefly, a chestnut twig ca. In the upper corners of the bag, two small holes were made; one was connected to a Teflon tube and the other was connected to a glass tube 6 mm diameter, 10 cm long containing 50 mg of Porapark Q adsorbent 80— mesh, Waters Corporation, Milford, MA, USA.
Volatiles were trapped by the Porapark Q adsorbent when they passed through the glass tube. Four setups were used in parallel for the collection of volatiles, and one setup made in the same way but containing no twig was used as a control blank. The collection was run for 4 h, and three replicates were performed for each cultivar. To investigate time-dependent emission of chestnut volatiles in response to C.
The caterpillars were starved for 12 h before being placed onto the fruits and normally bored into the fruits within 3 h after coming into contact with them. Starting the next day, volatiles emitted from the infested fruits were collected from to AM on days 1, 2 and 3 following the methods described above. Three replicates were performed. Characterization and quantification of chestnut volatiles were carried out using an Agilent gas chromatograph GC coupled to an Agilent Mass Spectrometer MS.
One microliter of sample was injected by splitless mode. Compounds were quantified by their total ion abundance relative to that of the internal standard. Behavioral assay A Y-tube olfactometer was used to test dual choice responses of C. The olfactometer consisted of two glass chambers 2. Test solutions used for the behavioral assay were made by serially dissolving each single compound or volatile mixture into laboratory-grade mineral oil to obtain the same concentration as in the natural Huaijiu blend Tables 2 and 3.
The preparation of the simulated blends followed the prescriptions presented in Table 1 , in which the combinations of compounds were based on the concentrations and proportions quantified in the natural blends Tables 2 and 3. Ltd, China. One moth was introduced into the entrance of the common arm of the Y-tube olfactometer using a glass vial, and its behavioral response was observed under a W red light lamp.
Conversely, no-choice was assigned if the test moth remained in the common arm for 3 min. A new pair of filter paper was used for each individual female tested, and the position of the lateral chambers along with the Y-tube olfactometer was systematically exchanged after testing 2 moths to avoid positional bias. Each individual moth was used only once, and the moths were allowed to acclimatize to the test conditions for 1 h before the start of the test.
At least 40 individual moths were used for each dual choice test, and both virgin and mated females 3 day old were tested.
Conogethes punctiferalis (Guenee, 1854)
Antennal-expressed receptors are important for insects to detect olfactory cues for host finding, mate attraction and oviposition site selection. However, few olfactory related genes were reported in YPM until now. In the present study, we sequenced and characterized the antennal transcriptomes of male and female YPM. In total, 15 putative odorant binding proteins OBPs , 46 putative odorant receptors ORs and 7 putative ionotropic receptors IRs were annotated and identified as olfactory-related genes of C. Further analysis of RT-qPCR revealed that all these olfactory genes are primarily or uniquely expressed in male and female antennae.
Antennal-expressed receptors are important for insects to detect olfactory cues for host finding, mate attraction and oviposition site selection. However, few olfactory related genes were reported in YPM until now. In the present study, we sequenced and characterized the antennal transcriptomes of male and female YPM. In total, 15 putative odorant binding proteins OBPs , 46 putative odorant receptors ORs and 7 putative ionotropic receptors IRs were annotated and identified as olfactory-related genes of C. Further analysis of RT-qPCR revealed that all these olfactory genes are primarily or uniquely expressed in male and female antennae. The predicted protein sequences were compared with homologs in other lepidopteran species and model insects, which showed high sequence homologies between C.
This moth is referred to as the cardamom shoot borer in the Himalayas and the yellow peach moth in Australia and elsewhere. It is thought to be the one that is attacking ginger in Sikkim. The eggs are laid on the leaves and the grubs burrow into emerging leaves and kill the shoots. The question asked was whether Tichogramma chilonis is likely to be effective against it.