Academic literature on the topic 'Oviposition Induced Plant Volatile'

After 24-hour Hadena bicruris floral interaction on Silene latifolia (Caryophyllaceae) with or without oviposition, we examined temporal volatile emission patterns for 3 days from plants with moth interaction and from neighboring plants only exposed to plant volatiles. Several lilac aldehydes and veratrole were progressively reduced after moth exposure without oviposition (by 30 to 40% after 24 hours and by 60 to 90% after 72 hours), but β -myrcene and β -pinene emissions increased by 200 to 300% only when exposure involved oviposition. Exposing S. latifolia to H. bicruris floral interaction without oviposition yielded no change in volatile organic compound (VOC) emission of neighboring S. latifolia; with oviposition, neighboring plants had 80 to126% increases in emission rates for β -myrcene and β -pinene. Progressive reduction of S. latifolia VOC emission rates might help plants to avoid nursery pollinator oviposition. In contrast, with H. bicruris oviposition on S. latifolia flowers some VOCs (common herbivore induced plant volatiles i. e. HIPVs) were induced. Whether oviposition occurred on S. latifolia strongly influenced neighboring plant VOC emission.

Several phases of herbivorous insect attack including feeding and oviposition are known to induce plant defenses. Plants emit volatiles induced by herbivores to recruit insect parasitoids as an indirect defense strategy. So far, volatiles induced by herbivore walking and their putative role in the foraging behavior of egg parasitoids have not been investigated. In this paper we studied the response of the egg parasitoid Trissolcus basalis toward volatiles emitted by Vicia faba plants as consequence of the walking activity of the host Nezara viridula. Olfactometer bioassays were carried out to evaluate wasp responses to plants in which the abaxial or the adaxial surfaces were subjected to walking or/and oviposition. Results showed that host female walking on the abaxial but not on the adaxial surface caused a repellence effect in T. basalis 24 h after plant treatment. The emission of active volatiles also occurred when the leaf was turned upside-down, indicating a specificity of stress localization. This specificity was supported by the results, which showed that oviposition combined with feeding elicit the induction of plant volatiles, attracting the parasitoid, when the attack occurred on the abaxial surface. Analyses of plant volatile blends showed significant differences between the treatments.

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n-heptanal, α-pinene, and (Z)-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding (R)-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

The diamondback moth (DBM) is a destructive pest of crucifer crops. In this study, DBM larvae shown to herbivore induced plant volatiles (HIPVs) that were attractive to adult females exposed in a Y-tube olfactometer. Our results showed that olfactory responses of adult females to HIPVs induced by third instar larvae feeding on Barbarea vulgaris were significantly higher (20.40 ± 1.78; mean moths (%) ± SD) than those induced by first instar larvae (14.80 ± 1.86; mean moths (%) ± SD). Meanwhile, a significant concentration of Sulphur-containing isothiocyanate, 3-methylsulfinylpropyl isothiocyanate, and 4-methylsulfinyl-3-butenyl isothiocyanate were detected in HIPVs released by third instar larvae compared to those released by first instar larvae while feeding on B. vulgaris. When the DBM females were exposed to synthetic chemicals, singly and in blend form, a similar response was observed as to natural HIPVs. Our study demonstrated that the relationship between isothiocyanates acting as plant defense compounds, host plant cues emission and regulation of the DBM adult female behavior due to key volatile triggered by the DBM larvae feeding on B. vulgaris.

Plant volatile organic compounds (VOCs) mediate many interactions, and the function of common VOCs is especially likely to depend on ecological context. We used a genetic mapping population of wild tobacco, Nicotiana attenuata, originating from a cross of 2 natural accessions from Arizona and Utah, separated by the Grand Canyon, to dissect genetic variation controlling VOCs. Herbivory-induced leaf terpenoid emissions varied substantially, while green leaf volatile emissions were similar. In a field experiment, only emissions of linalool, a common VOC, correlated significantly with predation of the herbivore Manduca sexta by native predators. Using quantitative trait locus mapping and genome mining, we identified an (S)-(+)-linalool synthase (NaLIS). Genome resequencing, gene cloning, and activity assays revealed that the presence/absence of a 766-bp sequence in NaLIS underlies the variation of linalool emissions in 26 natural accessions. We manipulated linalool emissions and composition by ectopically expressing linalool synthases for both enantiomers, (S)-(+)- and (R)-(−)-linalool, reported to oppositely affect M. sexta oviposition, in the Arizona and Utah accessions. We used these lines to test ovipositing moths in increasingly complex environments. The enantiomers had opposite effects on oviposition preference, but the magnitude of the effect depended strongly both on plant genetic background, and complexity of the bioassay environment. Our study reveals that the emission of linalool, a common VOC, differs by orders-of-magnitude among geographically interspersed conspecific plants due to allelic variation in a linalool synthase, and that the response of a specialist herbivore to linalool depends on enantiomer, plant genotype, and environmental complexity.

Frankliniella occidentalis is a destructive pest of horticultural plants, while Orius similis is a natural enemy of thrips. It has been demonstrated that exogenous calcium could induce plant defenses against herbivore attack. We examined whether CaCl2 supplementation altered the volatile emissions of kidney bean plants, which influence the oviposition preference of F. occidentalis. We also assessed the influence of volatile cues on O. similis. Using Y-tube olfactometer tests, we found that exogenous CaCl2 treatment inhibited the selectivity of F. occidentalis but attracted O. similis. In addition, CaCl2 treatment reduced the oviposition preference of F. occidentalis. Gas chromatography–mass spectrometry analyses revealed that CaCl2 treatment altered the number and relative abundance of the volatile compounds in kidney bean plants and that (E)-2-hexen-1-ol, 1-octen-3-ol, β-lonone, and (E,E)-2,4-hexadienal might be potential olfactory cues. Furthermore, the results of the six-arm olfactometer test indicated that 1-octen-3-ol (10−2 μL/μL), β-lonone (10−2 μL/μL), and (E,E)-2,4-hexadienal (10−3 μL/μL) repelled F. occidentalis but attracted O. similis. Overall, our results suggested that exogenous CaCl2 treatment induced defense responses in kidney bean plants, suggesting that CaCl2 supplementation may be a promising strategy to enhance the biological control of F. occidentalis.

Plants are known to increase the emission of volatile organic compounds upon the damage of phytophagous insects. However, very little is known about the composition and temporal dynamics of volatiles released by wild plants of the genus Crotalaria (Fabaceae) attacked with the specialist lepidopteran caterpillar Utetheisa ornatrix (Linnaeus) (Erebidae). In this work, the herbivore-induced plant volatiles (HIPV) emitted by Crotalaria nitens Kunth plants were isolated with solid phase micro-extraction and the conventional purge and trap technique, and their identification was carried out by GC/MS. The poly-dimethylsiloxane/divinylbenzene fiber showed higher affinity for the extraction of apolar compounds (e.g., trans-β-caryophyllene) compared to the Porapak™-Q adsorbent from the purge & trap method that extracted more polar compounds (e.g., trans-nerolidol and indole). The compounds emitted by C. nitens were mainly green leaf volatile substances, terpenoids, aromatics, and aldoximes (isobutyraldoxime and 2-methylbutyraldoxime), whose maximum emission was six hours after the attack. The attack by caterpillars significantly increased the volatile compounds emission in the C. nitens leaves compared to those subjected to mechanical damage. This result indicated that the U. ornatrix caterpillar is responsible for generating a specific response in C. nitens plants. It was demonstrated that HIPVs repelled conspecific moths from attacked plants and favored oviposition in those without damage. The results showed the importance of volatiles in plant–insect interactions, as well as the choice of appropriate extraction and analytical methods for their study.

The aim of this study was to validate a workflow that allows structural identification of plant volatiles that induce a behavioral response in insects. Due to the complexity of plant volatile emissions and the low levels at which these bioactive components tend to occur, gas chromatography-electroantennography (GC-EAD) was applied as the prime differentiator technique, i.e., to indicate particular peaks of interest in the chromatogram. In a next step, the analysis was repeated under identical conditions using GC-Orbitrap mass spectrometry (MS). Combining electron impact (EI) ionization and chemical ionization (CI) with the superior spectral resolution and mass accuracy of the technique enabled straightforward identification of these unknowns, with high confidence in a minute amount of time. Moreover, because of the intrinsic sensitivity of the technique, components that occur at trace amounts but may induce disproportional large behavioral responses are evenly well-identified. We were able to positively identify β-caryophyllene as a bioactive compound in female carob moths. Behavioral attraction was negatively correlated with the amount of β-caryophyllene in host fruits. In an oviposition experiment on filter paper, β-caryophyllene was stimulated in the range of 40–100 ng, while concentrations above 200 ng inhibited oviposition.

In the process of host location and selection several cues associated with host’s play a major role. Volatile compounds emitted by plants as a consequence of herbivore activities are often attractive to insect natural enemies including the Hymenopteran egg parasitoids, Trichogramma species. We studied the plant - parasitoid interactions where the plant surface chemicals act as infochemicals that attract or arrest the parasitoids for egg parasitization and strategically help in preventing the pest infestation. The leaf surface chemicals of R. communis, damaged due to the feeding of the host, Achaea janata (L) (castor semilooper) (Lepidoptera: Noctuiidae), and a non – host, Serpentine leaf miner Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) were evaluated for their influence on host location, host acceptance and ovipositional behavior against the egg parasitoid, T. chilonis in laboratory bioassays. The A. janata damaged leaf emissions had synomonal effects on the parasitoid and induced orientation and oviposition, whereas, the surface chemicals from the plant infested with non-host L. trifolii ceased to produce any such effects. The maximum egg parasitization was observed in A. janata infested castor leaf extracts compared to the leaf miner infested or normal healthy castor leaf extracts. The results are interesting in the context of tritrophic interactions between the pest, parasite and the host plant and are useful in biological control of insect pests.

Host searching behavior of females of the endoparasitoid Toxoneuron nigriceps Vierick (Hymenoptera: Braconidae) was observed in the field for three tobacco herbivores, Heliothis virescens (F.), Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), and Manduca sexta L. (Lepidoptera: Sphingidae). The only developmentally suitable host for the parasitoid was H. virescens. Hovering, searching, and oviposition (for plants with herbivores) by T. nigriceps were observed for a combination of two plant types, plants with only herbivore-induced plant volatiles or damaged plants with herbivores, and three insect species. The six treatments were as follows: (1) plants with only H. virescens-induced plant volatiles, (2) plants with only H. zea-induced plant volatiles, (3) plants with only M. sexta-induced plant volatiles, (4) plants damaged by H. virescens, (5) plants damaged by H. zea, and (6) plants damaged by M. sexta. Parasitoid females readily hovered around and searched on plants of both types. However, females spent more time foraging for H. virescens than for the nonhosts, H. zea and M. sexta. For plants with only herbivore-induced plant volatiles, T. nigriceps females spent more time searching on H. virescens plants than on H. zea and M. sexta plants. For damaged plants, parasitoid females visited more H. virescens plants than M. sexta plants and spent more time searching for H. virescens larvae than for M. sexta and H. zea larvae. Even though T. nigriceps females laid eggs in M. sexta and H. zea larvae, oviposition was higher for H. virescens than for the nonhosts. In conclusion, T. nigriceps females utilized more of their energy searching for and parasitizing H. virescens over the nonhosts on tobacco.

Experiments were conducted to assess whether a concept termed 'attract and reward' (A&R) could enhance conservation biological control (CBC). In A&R, a synthetically-produced herbivore induced plant volatile (HIPV) ('attract') is combined with a floral resource ('reward'). It is anticipated that the two will work synergistically attracting natural enemies into the crop ('attract') and maintaining them within the crop ('reward'). The study system consists of brassica, the most commonly occurring brassica herbivores, their natural enemies and higher order natural enemies. The HIPV deployed is methyl salicylate (MeSA) and the floral resource is buckwheat Fagopyrum esculentum. The aim of the first two field experiments, in 2007 and 2008, was to evaluate the effects of MeSA and MeSA combined with buckwheat (A&R) on the abundance of arthropods from three trophic levels. In 2007, a field experiment was conducted using MeSA alone. The mean abundance of the leafmining fly Scaptomyza flava (trophic level 2), the diamondback moth (trophic level 2)(DBM) parasitoid Diadegma semiclausum (trophic level 2) and the hoverfly Melangyna novaezealandiae (trophic level 3) was increased in MeSA-treatments by up to 300% and for the brown lacewing parasitoid Anacharis zealandica a maximum mean increase of 600% was recorded. Significantly more females of the D. semiclausum and M. novaezealandiae were attracted to MeSA than males. When A&R was deployed in 2008, were arthropods from the third and fourth trophic levels affected. For none of the species was there a synergistic effect between 'attract' and 'reward' on their abundance. The brown lacewing Micromus tasmaniae (trophic level 3), two parasitoids of DBM and one of cabbage white butterfly Pieris rapae (trophic level 2) increased significantly in treatments with buckwheat. The hoverfly Melanostoma fasciatum (trophic level 3) was significantly more abundant in treatments with MeSA, but significantly less abundant in treatments with buckwheat. The effect of MeSA on the fourth trophic level parasitoid Anacharis zealandica (trophic level 4) was inconsistent between years. Here it significantly decreased its abundance, while treatments with buckwheat increased it. Significantly fewer male than female D. semiclausum were attracted to MeSA only treatments. These experiments show that MeSA and buckwheat can have unwanted effects on arthropod abundance which may disrupt CBC. To assess the effect of A&R on CBC a further field experiment evaluating herbivore densities, predation, parasitism and hyper-parasitism rates was conducted. The only effect was significantly higher aphid parasitism in treatments with MeSA. Based on the results from the field experiments it remained unclear whether it was MeSA or a blend of volatiles produced by MeSA-induced host plants that were attractive to the arthropods. An olfactory experiment was conducted to evaluate if the aphid parasitoid Aphidius colemani can be attracted to two different concentrations of MeSA diluted in Synertrol oil. Significantly more parasitoids were attracted to 2.0% MeSA than to air while the parasitoid did not respond to the 0.5% concentration. These results indicate that A&R has potential as a CBC technique, as long as any unwanted side effects can be managed. Although there were no synergistic effects between 'attract' and 'reward' on the abundance of individual natural enemies, combining MeSA and buckwheat could still be beneficial because the two techniques increase the abundance of different natural enemies.

Gossypium hirsutum, le coton Upland, représente plus de 95% de la fibre de coton produite annuellement dans le monde et est cultivé dans environ 40 pays. La protection des champs de coton contre l’attaque des arthropodes herbivores nécessite des quantités importantes d’insecticides de synthèse, environ 18% de la consommation mondiale en 2000, bien que cela ait beaucoup diminué grâce au coton Bt et aux programmes d’éradication de certains ravageurs. Les composés organiques volatils (COV) naturellement émis par les plantes cultivées peuvent réduire les attaques d'insectes, les COV ayant une influence sur le comportement des arthropodes herbivores et des arthropodes auxiliaires. La recherche scientifique sur les COV des plantes a beaucoup augmenté depuis deux ou trois décennies. La stimulation des émissions de COV dans les champs de coton est désormais recommandée par les entomologistes du Cirad en tant que composante de la stratégie de protection. L’écimage (topping en anglais), c'est-à-dire couper la tête des cotonniers au cours de la floraison, stimule l'émission de COV de défense, une protection écologique qui limite les risques pour la santé dus aux insecticides synthétiques, pour les agriculteurs et les personnes des environs. L'objectif de la thèse était d'améliorer nos connaissances sur les bases génétiques des émissions de COV après l’écimage. La combinaison de plusieurs disciplines telles que la bio-informatique, l'écologie chimique et la génétique moléculaire nous a permis de: 1) analyser les séquences génomiques des gènes des voies de biosynthèse des COVs terpènes et terpénoïdes et des facteurs de transcription (TF) liés à la réponse au stress, à l'aide des bases de données publiées sur les génomes de trois espèces de coton, G. raimondii, G. arboreum (cotons diploïdes) et G. hirsutum (coton tétraploïde), 2) étudier les émissions de COV par les feuilles de coton des plants de G. hirsutum en réponse à l’écimage, en capturant ces molécules en serre et en caractérisant leurs profils cinétiques par chromatographie en phase gazeuse-spectrométrie de masse (GC-MS), incluant des mesures quantitatives, et 3) étudier les modifications de l'expression ARN des plants de coton G. hirsutum après l’écimage, pour 44 gènes impliqués dans la biosynthèse des COV, et également par une comparaison du transcriptome complet au moyen d'une analyse RNA-seq. Les résultats des trois domaines scientifiques, bio-informatique, analyse chimique et expression des gènes, ont pu être liés dans notre thèse de recherche: par ex., deux des gènes initialement identifiés par la bio-informatique, correspondant à deux enzymes, TPS50 (EC: 4.2.3.106 - (E ) bêta-ocimène synthase) et TPS16 (EC: 4.2.3.111 - alpha-terpinéol synthase), ont montré une augmentation de leur expression après l’écimage, et l'analyse GC-MS montre une modification correspondante des profils d'émission de COV. Ces mêmes composés avaient déjà été caractérisés dans d'autres plantes en réponse aux dégâts d’arthropodes. Ce travail de thèse constitue une première exploration des bases génétiques des émissions défensives de COV par les cotonniers cultivés G. hirsutum. La variabilité des comportements d’expression génique observés entre les trois génotypes étudiés de coton Upland africain G. hirsutum, permet de supposer qu’une diversité génétique est présente pour les émissions défensives de COV, ce qui pourrait permettre d’améliorer et d’adapter ces mécanismes de défense naturels et leur réponse à l’écimage, dans la perspective d'une protection naturelle plus efficace des champs de coton
Gossypium hirsutum, the Upland cotton, represents more than 95% of the cotton fiber annually produced worldwide and is grown in about 40 countries. The protection of cotton fields against the attack of herbivorous arthropods needs important quantities of synthetic insecticides, around 18% of the world consumption for the year 2000, although this decreased very much thanks to Bt cotton and eradication programs for some pests. Volatile organic compounds (VOCs) naturally emitted by crop plants can reduce insect attacks through the influence of VOCs on the behaviors of herbivorous arthropods and auxiliary arthropods. Scientific research about plant VOCs has been increasing much since two or three decades. The stimulation of VOCs emissions by cultivated cotton plants is now recommended by entomologists of CIRAD as a component of the cotton fields protection strategy. “Topping", that is, cutting the head of the cotton plants during the useful floriferous period, stimulates the emission of defense VOCs. It is an environmentally friendly method and it limits health hazards due to the use of synthetic insecticides for the farmers and the surrounding human populations. The objective of the thesis was to improve our knowledge about the genetic bases of VOCs emissions after topping. The combination of several disciplines such as bioinformatics, chemical ecology and molecular genetics allowed us to: 1) analyze the genomic sequences of VOCs genes of the terpene and terpenoid biosynthesis pathways and transcription factors (TF) related to stress response, using the published genome databases of three cotton species, G. raimondii, G. arboreum (both diploid cottons) and G. hirsutum (tetraploid cotton), 2) study the VOCs emissions by cotton leaves of G. hirsutum plants in response to topping, by capturing these molecules in greenhouse and then characterizing their kinetic profiles by means of gas-chromatography mass-spectrometry (GC-MS), with quantitative measurements, and, 3) study the modifications of the RNA expression of G. hirsutum cotton plants after topping, for genes involved in VOCs biosynthesis through quantitative PCR measurements on 44 targeted genes and also by means of a whole-transcriptome comparison through an RNA-seq analysis. The results from the three different fields, bioinformatics, chemical analysis and gene expression, could be interrelated in our research thesis: e.g., two of the genes initially identified by bioinformatics, corresponding to two enzymes, TPS50 (EC: 4.2.3.106 - (E) -beta-ocimene synthase) and TPS16 (EC: 4.2.3.111 - alpha-terpineol synthase), were shown to increase their expression after topping, while the GC-MS analysis showed an modification of the corresponding VOCs in emission profiles. These compounds have been already characterized in other organisms in response to wounds produced by herbivorous insects. This thesis work is a first exploration of the genetic bases of defensive VOCs emission by G. hirsutum cultivated cottons. The variability of genic expression behaviors observed amongst the three genotypes of African Upland cotton G. hirsutum that were studied permits to hypothesize that a genetic diversity is present for defensive VOCs emissions, that could permit to improve and adapt by breeding these natural defense mechanisms and the response to topping, in perspective of a more efficient natural protection of cotton fields

The biocontrol fungus Trichoderma virens is an avirulent symbiont with the ability to control plant disease by the production of antibiotic compounds, induction of plant resistance to pathogens, and mycoparasitism of other fungi. In this document, the analysis of a putative terpene biosynthesis gene cluster (vir cluster) in T. virens is described. The vir cluster contains genes coding for four putative cytochrome P450s, an oxidoreductase, MFS transporter, and a terpene cyclase. To determine the function of this cluster in secondary metabolism biosynthesis, a strain of T. virens with a deletion of the putative cyclase, vir4, was constructed. Deletion mutants were deficient in the synthesis of sesquiterpene volatiles and complementation of vir4 restored this loss in transformants, albeit at a lower level of production. An analysis of phenotypic characteristics between mutant and wild-type strains did not identify any differences when the strain interacted with other fungi, bacteria, or Arabidopsis seedlings. Paralogs of the gene encoding the elicitor SM1 were examined as genetic sources for potential elicitors to induce systemic resistance in plants. A search of the T. virens genome revealed the presence of three paralogs of sm1. One paralog, sm3, was found to be expressed when grown in association with plant roots and in still-culture. The Pichia pastoris protein expression system was used to generate sufficient quantities of SM3 to allow characterization of its function. The purified protein from the yeast system (picSM3) was shown to be glycosylated and to increase expression of a plant defense gene in maize seedlings. Mutant strains in which sm3 was either deleted or over-expressed were constructed to further explore the potential of sm3 as an elicitor of ISR. The differential production of SM1 and SM3 by these strains suggested that SM1 and SM3 may be co-regulated and native SM3 may be glycosylated. To further understand the role of a putative glycosylation site as a mechanism to prevent dimerization and subsequent elicitor activity, a point mutation was created in a sm1 deletion strain. Analysis of the behavior of the protein demonstrates that the putative glycosylation site is not involved in protein aggregation and deletion of this site does not prevent the protein from testing positive for glycosylation. We propose that SM1is not glycosylated but instead may interact with an oligosaccharide or other small molecule. However, the mechanism of dimerization in SM1 remains unknown.

碩士
國立中興大學
昆蟲學系所
97
Plant can increase the accumulation of endogenous jamonic acid (JA) after wounding by herbivore insect. The elevated JA can induce plants’ anti-insect defensive proteins to affect herbivore performance and can also change the components of herbivore-induced plant volatiles to affect preference of female adults. During past three decades, various studies on plant induced defense found that application of exogenous JA can induce similar defensive responses with insect-wounding. Studies of the difference between induced defensive responses on different plant species pre-treated with insect-wounding (I), exogenous MeJA, (M) both treatments (MI) are lacking. Aims of this investigation are to compare induced response of polyphenol oxidase (PPO) and trypsin inhibitor (TI) activities on tomato, sweet pepper, water spinach and Chinese radish that pre-treated with different five treatments and to compare effects of different induced responses on the larva growth performance and adult oviposition preference of Spodoptera litura. Results indicate that induction of insect-wounding on tomato, sweet pepper and radish increase PPO activity 1.5 to 1.8-folds higher than that of control treatment and on water spinach can enhance TI activity up 1.2-folds. Induction of exogenous MeJA on tomato, sweet pepper and water spinach increase PPO activity 1.2 to 1.4-folds higher than that of control and TI activity increase on four different plants pre-treated MeJA significantly. However, induction of MI treatment on tomato and water spinach can enhance PPO activity up 1.2 to 1.4-folds higher than that of control and there is significant increasing of TI activity on four plant species with MI treatment. In addition, feeding on tomato with I, M and MI, sweet pepper with M and MI, and radish with M treatments, third instars larvae grew slower significantly. And there is no significant difference on oviposition preference between inductions of five treatments on different four plants. Base on the results, we conclude that the application of MeJA can induce various defensive responses on four different plant species. However, there are different induced defensive responses between insect-wounding and exogenous MeJA treatments on four plants. The combination treatment of insect-wounding and exogenous MeJA did not cause synergistic effects of defensive responses on these four plant species.

Abstract The areas of concern regarding the future importance of climate change and variability on nematode damage and integrated management include: shifts in the distribution of nematodes, stimulation of additional generations, increased reproductive potential, development of more severe nematode-pathogen complexes, inability to monitor with remote sensing populations over multiple seasons, negative yield due to nematodes and reduced soil moisture levels, adapting integrated nematode management (INM) to highly volatile interannual fluctuations, loss of organic matter and soil antagonistic potential, lack of an effective in-season plant curative pesticide, enhancement of cumulative multi-species impact, and inactivation or loss of plant resistance to nematodes. This chapter reflects on some of the above points and how long-term climate change and increasing climate variability may impact nematodes, crop losses and potential modification of INM under climate change induced risk. It discusses climate change and climate variability in the context of INM, climate impacts on agricultural crops, critical climate change hotspots, climate influence on nematode biological processes, and the use of degree-days to monitor temperature effects on nematode development. The use of plant parasitic nematodes as research models and immediate priorities for improved near-term climate risk management within INM are also described.

The whitefly (Bemisia tabaci) is a serious agricultural pest that afflicts a wide variety of ornamental and vegetable crop species. To enable survival on a great diversity of host plants, whiteflies must have the ability to avoid or detoxify numerous different plant defensive chemicals. Such toxins include a group of insect-deterrent molecules called glucosinolates (GSs), which also provide the pungent taste of Brassica vegetables such as radish and cabbage. In our BARD grant, we used the whitefly B. tabaci and Arabidopsis (a Brassica plant model) defense mutants and transgenic lines, to gain comprehensive understanding both on plant defense pathways against whiteflies and whitefly defense strategies against plants. Our major focus was on GSs. We produced transgenic Arabidopsis plants accumulating high levels of GSs. At the first step, we examined how exposure to high levels of GSs affects decision making and performance of whiteflies when provided plants with normal levels or high levels of GSs. Our major conclusions can be divided into three: (I) exposure to plants accumulating high levels of GSs, negatively affected the performance of both whitefly adult females and immature; (II) whitefly adult females are likely to be capable of sensing different levels of GSs in their host plants and are able to choose, for oviposition, the host plant on which their offspring survive and develop better (preference-performance relationship); (III) the dual presence of plants with normal levels and high levels of GSs, confused whitefly adult females, and led to difficulties in making a choice between the different host plants. These findings have an applicative perspective. Whiteflies are known as a serious pest of Brassica cropping systems. If the differences found here on adjacent small plants translate to field situations, intercropping with closely-related Brassica cultivars could negatively influence whitefly population build-up. At the second step, we characterized the defensive mechanisms whiteflies use to detoxify GSs and other plant toxins. We identified five detoxification genes, which can be considered as putative "key" general induced detoxifiers because their expression-levels responded to several unrelated plant toxic compounds. This knowledge is currently used (using new funding) to develop a new technology that will allow the production of pestresistant crops capable of protecting themselves from whiteflies by silencing insect detoxification genes without which successful host utilization can not occur. Finally, we made an effort to identify defense genes that deter whitefly performance, by infesting with whiteflies, wild-type and defense mutated Arabidopsis plants. The infested plants were used to construct deep-sequencing expression libraries. The 30- 50 million sequence reads per library, provide an unbiased and quantitative assessment of gene expression and contain sequences from both Arabidopsis and whiteflies. Therefore, the libraries give us sequence data that can be mined for both the plant and insect gene expression responses. An intensive analysis of these datasets is underway. We also conducted electrical penetration graph (EPG) recordings of whiteflies feeding on Arabidopsis wild-type and defense mutant plants in order to determine the time-point and feeding behavior in which plant-defense genes are expressed. We are in the process of analyzing the recordings and calculating 125 feeding behavior parameters for each whitefly. From the analyses conducted so far we conclude that the Arabidopsis defense mutants do not affect adult feeding behavior in the same manner that they affect immatures development. Analysis of the immatures feeding behavior is not yet completed, but if it shows the same disconnect between feeding behavior data and developmental rate data, we would conclude that the differences in the defense mutants are due to a qualitative effect based on the chemical constituency of the phloem sap.