Female Whiteflies Research Articles

Orco mediates olfactory behavior and oviposition in the whitefly Bemisia tabaci

Chemical signals play a central role in mediating insect feeding and reproductive behavior, and serve as the primary drivers of the insect-plant interactions. The detection of chemical signals, particularly host plant volatiles, relies heavily on the insect's complex olfactory system. The Bemisia tabaci cryptic species complex is a group of globally important whitefly pests of agricultural and ornamental crops that have a wide range of host plants, but the molecular mechanism of their host plant recognition is not yet clear. In this study, the odorant coreceptor gene of the Whitefly MEAM1 cryptic species (BtOrco) was cloned. The coding sequence of BtOrco was 1413 bp in length, with seven transmembrane structural domains, and it was expressed primarily in the heads of both male and female adult whiteflies, rather than in other tissues. Knockdown of BtOrco using transgenic plant-mediated RNAi technology significantly inhibited the foraging behavior of whiteflies. This inhibition was manifested as a reduced percentage of whiteflies responding to the host plant and a prolonged foraging period. Moreover, there was a substantial suppression of egg-laying activity among adult female whiteflies. These results indicate that BtOrco has the potential to be used as a target for the design of novel active compounds for the development of environmentally friendly whitefly control strategies.

Neuropeptide hormone bursicon mediates female reproduction in the whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae).

Bursicon, a neuropeptide hormone comprising two subunits-bursicon (burs) and partner of burs (pburs), belongs to the cystine-knot protein family. Bursicon heterodimers and homodimers bind to the lucine-rich G-protein coupled receptor (LGR) encoded by rickets to regulate multiple physiological processes in arthropods. Notably, these processes encompass the regulation of female reproduction, a recent revelation in Tribolium castaneum. In this study we investigated the role of burs/pburs/rickets in mediating female vitellogenesis and reproduction in a hemipteran insect, the whitefly, Bemisia tabaci. Our investigation unveiled a synchronized expression of burs, pburs and rickets, with their transcripts persisting detectable in the days following eclosion. RNAi-mediated knockdown of burs, pburs or rickets significantly suppressed the transcript levels of vitellogenin (Vg) and Vg receptor in the female whiteflies. These effects also impaired ovarian maturation and female fecundity, as evidenced by a reduction in the number of eggs laid per female, a decrease in egg size and a decline in egg hatching rate. Furthermore, knockdown of burs, pburs or rickets led to diminished juvenile hormone (JH) titers and reduced transcript level of Kruppel homolog-1. However, this impact did not extend to genes in the insulin pathway or target of rapamycin pathway, deviating from the results observed in T. castaneum. Taken together, we conclude that burs/pburs/rickets regulates the vitellogenesis and reproduction in the whiteflies by coordinating with the JH signaling pathway.

Rickettsia Infection Benefits Its Whitefly Hosts by Manipulating Their Nutrition and Defense.

Endosymbionts play an essential role in the biology, physiology and immunity of insects. Many insects, including the whitefly Bemisia tabaci, are infected with the facultative endosymbiont Rickettsia. However, the mutualism between Rickettsia and its whitefly host remains unclear. This study investigated the biological and physiological benefits of Rickettsia infection to B. tabaci. Results revealed that infection of Rickettsia increased the fertility, the survival rate from nymph to adult and the number of female whiteflies. In addition, this facilitation caused a significant reduction in nymphal developmental duration but did not affect percentage rate of egg hatching. Rickettsia infected B. tabaci had significantly higher glycogen, soluble sugar and trehalose contents than Rickettsia negative B. tabaci individuals. Rickettsia also improved the immunity of its whitefly hosts. Rickettsia infested B. tabaci had lower mortality rates and higher semi-lethal concentrations (LC50) when exposed to the fungus Akanthomyces attenuatus and the insecticides imidacloprid and spirotetramat. The percentage of parasitism by Encarsia formosa was also reduced by Rickettsia infection. Overall, Rickettsia infection benefits B. tabaci by improving the nutritional composition of its host, and also protects B. tabaci by enhancing its resistance towards insecticides (imidacloprid and spirotetramat), entomopathogenic fungi (A. attenuatus) and its main parasitoid (E. formosa); all of which could significantly impact on current management strategies.

Encounter With a Selfish Virus Sabotages Its Vector to Orient Toward Requisite Host Plant: A Case Study With Chili Leaf Curl Virus-Whitefly

Interactions of a virus with its vector and host plant have challenged entomologists, pathologists and biologists alike. Phytophagous insects depend on specific host volatile cues to locate suitable host plants for feeding and oviposition. Several studies have revealed that plant viruses modify their insect vector’s orientation toward specific host plants to facilitate their spread and survival. The ecological and molecular basis of this vector behavior modification remains largely unknown and was therefore explored in this study. Interestingly, host volatile preference for non-viruliferous female whiteflies [Bemisia tabaci (Genn.)] was found to be preferentially oriented toward infected chili plant [with chili leaf curl (ChLCV)] volatiles, while viruliferous whiteflies preferred healthy chili plant (Capsicum annum L.) volatiles in olfactometer. The electrophysiological studies involving electroantennogram (EAG) assays exhibited similar trend in EAG response amplitudes. Gas Chromatography linked electroantennodetection (GC EAD) revealed specific plant volatile cues responsible for altered host orientation behavior of the vector. Transcriptome profiling of the viruliferous and non-viruliferous whiteflies and Realtime qPCR validation showed differential expression of certain odorant binding proteins (OBPs) in viruliferous whiteflies. Our results suggest that there is a plant virus mediated altered chemoecological behavior in the vector with respect to orientation toward its host plant. Based on the findings we speculate that the virus mediates such change in the vector for a continued transmission success to the host.

Transmission attributes of Asian I Silverleaf whitefly (Bemisia tabaci) modulating the spread of Chili leaf curl virus disease in Chili (Capsicum spp.)

A dose-response relationship was documented throughout two-year greenhouse trial on chili in 2019 and 2020 wherein varying acquisition and inoculation times affected Chili leaf curl virus (ChLCV) transmission significantly. Transmissions of ChLCV to the highest levels were statistically equal between 42 and 48 hours acquisition and inoculation. ChLCV transmission by female whiteflies is far superior to that by males. Acquisition and inoculation lasting more than 12 hours inflicted only 50% ChLCV transmission. In ChLCV transmission, a short acquisition with extended inoculation outperformed a long acquisition with short inoculation, emphasizing inoculation over acquisition. Infectivity of ChLCV in B. tabaci peaked at 2–3 days and got nil at 11 days. Studied B. tabacci was identified as Asian I Silverleaf whitefly by bioinformatics (100% identity on cytochrome oxidase I). Overall, the study will help chili growers learn more about the biology of Asian I Silverleaf whiteflies, and how to better manage them.

Differential expression of gut protein genes and population density of Arsenophonus contributes to sex-biased transmission of Bemisia tabaci vectored Cotton leaf curl virus.

Whitefly, Bemisia tabaci (Gennadius) is an important pest of cotton causing direct damage as sap feeder and vector of Cotton leaf curl virus (CLCuV). Previous few studies suggest that female whiteflies are more efficient vector of begomovirusthan males, however the sex-biased transmission efficiency is still not clearly understood. Present studies with B. tabaci AsiaII-1 haplotype showed higher virus transmission efficiency of females compared to males. This variable begomovirus transmission efficiency has been related to previously identifiedkey factors associated with B. tabaci. The higher density of endosymbiont Arsenophonus and variable expression of some midgut proteins genes i.e. Cyclophilin, Knottin, Hsp40, Hsp70 may be possibly imparting higher vector competency to the females compared to males. The present studies suggest low abundance of Arsenophonus spp. as well as lower expressionof Cyclophilin genein males as compared to females. This is further supplemented by overexpression of Knottin, Hsp40, and Hsp70 genes in males compared to females and thus collectively all these factors might be playing a key role in low virus transmission efficiency of males. The relative density of Arsenophonus spp. and expression of midgut proteins genes in male and female whitefly first time enriches our understanding about sex-biased transmission efficiency of begomovirus.

Impacts of Cucurbit Chlorotic Yellows Virus (CCYV) on Biological Characteristics of Its Vector Bemisia tabaci (Hemiptera: Aleyrodidae) MED Species.

Plant viruses can change the phenotypes and defense pathways of the host plants and the performance of their vectors to facilitate their transmission. Cucurbit chlorotic yellows virus (CCYV) (Crinivirus), a newly reported virus occurring on cucurbit plants and many other plant species, is transmitted specifically by Bemisia tabaci MEAM1 (B biotype) and MED (Q biotype) cryptic species in a semipersistent manner. This study evaluated the impacts of CCYV on B. tabaci to better understand the plant-virus-vector interactions. By using CCYV-B. tabaci MED-cucumber as the model, we investigated whether or how a semipersistent plant virus impacts the biology of its whitefly vector. CCYV mRNAs were detectable in nymphs from first to fourth instars and adults of B. tabaci with different titers. Nymph instar durations and adult longevity of female whiteflies greatly extended on CCYV-infected plants, but nymph instar durations and adult longevity of male whiteflies were not significantly influenced. In addition, the body length and oviposition increased in adults feeding on CCYV-infected plants, but the hatching rates of eggs and survival rates of different stages were not affected. Most interestingly, the sex ratio (male:female) significantly reduced to 0.5:1 in whitefly populations on CCYV-infected plants, while the ratio remained about 1:1 on healthy plants. These results indicated that CCYV can significantly impact the biological characteristics of its vector B. tabaci. It is speculated that CCYV and B. tabaci have established a typical mutualist relationship mediated by host plants.

Mesta yellow vein mosaic virus: application of loop-mediated isothermal amplification method to study efficiency of acquisition, retention and transmission by Bemisia tabaci (Hemiptera: Aleyrodidae) in Kenaf

Whitefly is an important pest and vector of many plant begomoviruses. Investigations were carried out to understand the acquisition, retention, transmission, and gender basis transmission efficiency of Mesta yellow vein mosaic virus (MeYVMV) by whitefly. The minimum acquisition access feeding period (AAFP) was 0.10 h which resulted in 11.1% infected plants. Based on LAMP assay and yellowing symptoms, 100% virus acquisition was achieved by whitefly with an exposure of 18 to 48 h. Virus was transmitted in tested plants up to 88.8% after 1 to 10 days retention time of viruliferous whiteflies, whereas no symptoms were observed after 35 days. Fifteen minutes of exposure to viruliferous whiteflies on healthy plants resulted in 11.1% transmission. Cent percent transmission of virus was achieved in plants with 12 h exposure period. Highest virus transmission efficiency of 55.60% was observed in female whitefly compared to 33.3% in single male whitefly. Present study shall help to understand the interaction of insect-plant–virus relationship, epidemiological knowledge, and formulation of management strategies against virus and its vector.

Correlation between Epidermis Thickness, Leaf Trichome Length and Density with the Whitefly Bemisia tabaci Population on Five Local Soybean Cultivars

Soybeans compsumsion in Indonesia is about 2.7 million ton, while the national production is only about 0.7 million ton per year. There are some problems in the soybean production in Indonesia, including pests and diseases. Whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is one of the important pests in soybeans causes a significant loss of yields. Developing soybean cultivars resistant to whitefly is one of method to reduce the production loss. This study aimed to determine the relationship between the physical characteristics of lower surface leaves and B. tabaci population on five local soybean cultivars. The experiments were conducted in the IPB greenhouse by Completely Randomized Design (RCD) using five soybean cultivars (Anjasmoro, Dena-1, Detam-3, Devon-1, and Wilis) with 3 replicates. Three plants of each cultivar were planted in a polybag, put under a cage, and after one week then infested with 5 female whiteflies. The parameters observed in this study were leaf epidermal thickness; density and length of trichome on lower leaf surface; and the number of egg, nymph, and adult of the whitefly. Observations were carried out every week, from 1−7 weeks after the plant was infested with the whitefly. The population of whitefly was affected by trichome density and length, as well as by the epidermal thickness of the lower leaf surface. The infestation of B. tabaci was higher in the soybean cultivars with denser and longer leaf trichomes, and thinner epidermal of the lower leaf surface. This result of this research suggests that it is necessary to include the characteristics of leaf trichome and epidermal thickness in the breeding program to produce soybean cultivars that are superior in productivity and resistant to whitefly.

Differential susceptibility of whitefly-associated bacteria to antibiotic as revealed by metagenomics analysis

BackgroundRecent reports have suggested that different symbionts of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) have differential susceptibility to antibiotic treatment. Changes in the community structure of B. tabaci-associated bacterial microbiota (BABM) following antibiotic treatment, however, remain poorly understood, although increasing numbers of B. tabaci-associated bacteria have been reported in recent years. Methodology and resultsThe BABM of male or female B. tabaci Q (also known as B. tabaci MED species) were analyzed after being fed on artificial diet containing the antibiotic rifampicin and compared with untreated controls. The bacterial 16S rDNA gene amplicon metagenomic sequencing method was used in the analyses. The results showed that the BABM in male and female adults have different characteristics, and that the community structure of the BABM changes drastically following antibiotic treatment. Further analysis of the endosymbionts in B. tabaci showed that the relative abundance of the primary endosymbiont, Portiera, increased in females but was unchanged in male whiteflies, while that of the secondary endosymbiont, Hamiltonella, significantly decreased in both male and female whiteflies. The secondary endosymbionts, Cardinium and Rickettsia, were apparently not affected in either male or female whiteflies. ConclusionsThe community structure of BABM can be drastically altered following treatment with the antibiotic, rifampicin. This may be due to different antibiotic susceptibilities among the bacterial species. These results provide valuable insights into the innate differences in the BABM of male and female whiteflies, as well as structural changes that occur in the BABM in response to exposure to an antibiotic.

Effectiveness of aromatic plant species for repelling and preventing oviposition of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae)

AbstractThis study assesses the effectiveness of essential oils for repelling whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), and deterring oviposition. We evaluated essential oils from four plants: Curcuma longa (Zingiberaceae), Litsea cubeba (Lauraceae), Piper nigrum (Piperaceae) and Zanthoxylum bungeanum (Rutaceae), under laboratory and glasshouse conditions. In the laboratory, ethanol‐extracted essential oils were applied uniformly on both sides of a tomato leaf in the treatment groups, and the same volume of liquid but without essential oil was used for the control. Results showed that essential oils from L. cubeba, P. nigrum, C. longa and Z. bungeanum provided some repellency of whiteflies and reduced oviposition. Oils from L. cubeba repelled adult females (69.14% and 62.49% repellency at 24 and 48 hr, respectively), and oils from C. longa deterred oviposition (68.46% and 65.94% at 24 and 48 hr exposures, respectively). In the glasshouse, potted tomato plants with eight leaves were sprayed with treatments and control material. Five‐day‐old adult female whiteflies were released in a cage between both pots. Essential oils from L. cubeba repelled females 54.77 at 24 hr and P. nigrum 44.37% at 48 hr whereas oils from P. nigrum reduced oviposition by 43.35 at 24 hr and Z. bungeanum 21.08% at 48 hr, under glasshouse conditions. Essential oils show potential to be used to reduce feeding and oviposition, and thus being important components of integrated pest management programs. However, future research is needed to investigate individual compounds of these oils against whitefly, and to enhance their effectiveness.

Volatile-Mediated Attraction of Greenhouse Whitefly Trialeurodes vaporariorum to Tomato and Eggplant.

The behavior of the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), is known to be affected by plant volatile cues, but its attraction or repellent to specific volatile cues has not been deeply studied yet. Therefore, the aim of our study was to identify the most attractive plant among cultivars of tomato (Solanum lycopersicum) and eggplant (Solanum melongena) to evaluate the volatiles of plants to identify the chemical compound(s) that attract T. vaporariorum. We speculated that whitefly–host plant interaction primarily depends on plant volatile emissions and that once the plant is damaged, it might attract more whiteflies. Three intact (uninfested) tomato, four intact eggplant cultivars and whitefly infested plants of the most whitefly attractive tomato and eggplant cultivars were examined by behavioral assay experiments for attractiveness to T. vaporariorum and headspace volatile were determined by solid-phase microextraction (SPME) and gas chromatography-mass spectrometry. Whiteflies had the highest preference for the intact eggplant Kuai Yuan Qie (KYQ) among the eggplant and the tomato plant cultivars in bioassay experiments. Although both male and female whiteflies were significantly more attracted to infested KYQ plants than to intact plants, whitefly females did not select conspecific-infested YG plants. The volatile emissions among different plant cultivars in individual species and infested versus intact plants were significantly different. Among these volatiles, identified major green leaf volatiles [(Z)-3-hexen-1-ol] and terpenoids [α-pinene, (E)-β-caryophyllene, α-humulene, azulene] showed a constitutive relationship with the most whitefly preference plants. Our findings provide new insights into the chemical compounds that attract or repel whiteflies.

Biology of citrus whitefly, Dialeurodes citri (Ashmead) on Citrus reticulate (Mandarin) var. Kinnow

Screen house studies on biology of citrus whitefly, Dialeurodes citri (Ashmead) (Hemiptera: Aleyrodidae), were conducted during 2014-15 in screen house of Department of Entomology College of Agriculture, CCS Haryana Agricultural University, Hisar on citrus mandarin (var. Kinnow). Results on biological studies of D. citri revealed that female on an average laid 151±42.99 eggs with an incubation period of 13.3±1.89 days. The mean duration of first, second and third instar nymphs were 13.1±1.77, 11.1±2.05 and 15.4±2.41 days, respectively. The pupal duration was 108.3±4.33 days. Adult Male lived for 16.5±1.96 days whereas adult female lived for 18.6±2.06 days. The male whitefly completed its life cycle in 178.8±6.73 days whereas the corresponding period for female whitefly was 180±7.02 days. This study established that biology of the insect is rather a stable trait because no significant variation was observed when compared with decade old reports despite the fact that agro-ecology including weather phenomenon have undergone significant change in the last decade.

Aphid-induced Defences in Chilli Affect Preferences of the Whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae).

The sweetpotato whitefly (WF), Bemisia tabaci, is a major pest that damages a wide range of vegetable crops in Malaysia. WF infestation is influenced by a variety of factors, including previous infestation of the host plant by other insect pests. This study investigated the effects of previous infestation of host chilli plants by the green peach aphid (Myzus persicae) on the olfactory behavioural response of B. tabaci, using free-choice bioassay with a Y-tube olfactometer. We analysed volatile organic compounds (VOCs) emitted by non-infested and M. persicae-infested chilli plants using solid-phase microextraction and gas chromatography–mass spectrometry. Our results showed that female WFs preferred non-infested to pre-infested plants. Collection and analysis of volatile compounds emitted by infested plants confirmed that there were significant increases in the production of monoterpenes (cymene; 1,8-cineole), sesquiterpenes (β–cadinene, α-copaene), and methyl salicylate (MeSA) compared to non-infested plants. Our results suggest that host plant infestation by aphids may induce production of secondary metabolites that deter B. tabaci from settling on its host plants. These results provide important information for understanding WF host selection and dispersal among crops, and also for manipulating WF behaviour to improve IPM in chilli.

Transcriptome analysis of host-associated differentiation in Bemisia tabaci (Hemiptera: Aleyrodidae).

Host-associated differentiation is one of the driving forces behind the diversification of phytophagous insects. In this study, host induced transcriptomic differences were investigated in the sweetpotato whitefly Bemisia tabaci, an invasive agricultural pest worldwide. Comparative transcriptomic analyses using coding sequence (CDS), 5′ and 3′ untranslated regions (UTR) showed that sequence divergences between the original host plant, cabbage, and the derived hosts, including cotton, cucumber and tomato, were 0.11–0.14%, 0.19–0.26%, and 0.15–0.21%, respectively. In comparison to the derived hosts, 418 female and 303 male transcripts, respectively, were up-regulated in the original cabbage strain. Among them, 17 transcripts were consistently up-regulated in both female and male whiteflies originated from the cabbage host. Specifically, two ESTs annotated as Cathepsin B or Cathepsin B-like genes were significantly up-regulated in the original cabbage strain, representing a transcriptomic response to the dietary challenges imposed by the host shifting. Results from our transcriptome analysis, in conjunction with previous reports documenting the minor changes in their reproductive capacity, insecticide susceptibility, symbiotic composition and feeding behavior, suggest that the impact of host-associated differentiation in whiteflies is limited. Furthermore, it is unlikely the major factor contributing to their rapid range expansion/invasiveness.

Non-consumptive effects of the predatory beetle Delphastus catalinae (Coleoptera: Coccinellidae) on habitat use patterns of adult whitefly Bemisia argentifolii (Hemiptera: Aleyrodidae)

This study examined habitat use patterns by adult whiteflies, Bemisia argentifolii Bellows and Perring, in response to predators, Delphastus catalinae (Horn), at different spatial scales. When female whiteflies were confined to small arenas with leaf discs from which they could not escape, whiteflies significantly delayed settling on leaf discs when predators were present compared to when no predators were introduced. The presence of D. catalinae altered the vertical distribution of adult whiteflies (sex ratio = 1:1) on cucumber plants; adult whiteflies moved upward faster over time within the plant canopy when predators were present mainly on the lower leaves of the plants compared to whiteflies on plants without predators. Most D. catalinae remained in the lower parts of the plants during the experiment. Therefore, we inferred that female whiteflies more quickly moved to the upper plant strata to reduce the risk of predation of their progeny; this would induce subsequent movement of males seeking mates. Introduction of D. catalinae onto a cucumber plant with high whitefly density did not cause increased dispersal of adult whiteflies (sex ratio = 1:1) into neighboring uninfested plants. The results indicate that predator-avoidance behaviors by adult B. argentifolii differed at different spatial scales. The predator-avoidance behavior may have a negative impact at the within-plant scale by inducing more whiteflies to move into upper plant strata. However, the effect of predators on the among-plant dispersal of whiteflies was not significant.

Effect of Cotton leaf curl virus infected plants on the biology of the whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae): Vector–virus mutualism

Cotton leaf curl virus (CLCuV) (Geminiviridae : Begomovirus), the causative agent of leaf curl disease in cotton plants (Gossypium hirsutum), is exclusively transmitted by whitefly species Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). CLCuV transmission occurs in Sriganganagar (Rajasthan), an area endemic with cotton leaf curl disease. The relationships between plant viruses, their herbivore vectors and host plants can be beneficial, neutral, or antagonistic, depending on the species involved. To further understand these relationships, fecundity and life history parameters of an indigenous non- b (Asia II genetic group) biotype whitefly, B. tabaci, were compared on 10, 25, and 40 days post-inoculation (DPI), in CLCuV-infected and healthy cotton plants to determine the effect of virus on its vector. The development time of the immature stages of whiteflies was significantly reduced on CLCuV-infected plants. The development time of the immature stages did not change with severity of symptoms at 25 and 40 DPI (45- and 60-d-old plants). Cotton leaf curl virus infection increased percent egg viability of B. tabaci. Whiteflies deposited significantly fewer eggs on virus-infected plants than on healthy plants. Whiteflies had better egg viability on younger plants than older plants, whereas plant age did not affect the fecundity. Male and female whiteflies had shorter longevity on CLCuV-infected plants than on healthy plants.

Detoxification activity and energy cost is attenuated in whiteflies feeding on Tomato yellow leaf curl China virus‐infected tobacco plants

The begomovirus Tomato yellow leaf curl China virus (TYLCCNV) can benefit its vector, the whitefly Bemisia tabaci, through suppressing the defences of their shared host plants. However, the mechanisms of this vector-virus mutualism remain largely unknown on the insect side of the interaction. Here, we compared the transcriptional profiles of female adult whiteflies of B. tabaci Middle East-Asia Minor 1 feeding on TYLCCNV-free and TYLCCNV-infected tobacco plants using the next-generation sequencing technique and quantitative real-time PCR. Interestingly, the genes involved in the oxidative phosphorylation (OXPHOS) pathway and detoxification enzyme were down-regulated in whiteflies feeding on virus-infected plants. Decreased detoxification activity costs less energy, which may reduce OXPHOS activity. Moreover, the genes involved in redox activity were also down-regulated, which may indicate that the reduced OXPHOS activity decreased reactive oxygen species production. Reduced detoxification activity is likely to attenuate energy costs, thereby enhancing the performance of whiteflies on virus-infected plants. These results provide further insight into the mechanisms of the plant-mediated whitefly-virus mutualism. Moreover, our study suggests that investigating the transcriptional profiles on the insect side of the interaction can advance our understanding of the tripartite interactions.

Next Generation Transcriptome Sequencing and Quantitative Real-Time PCR Technologies for Characterisation of the Bemisia tabaci Asia 1 mtCOI Phylogenetic Clade

A programme of functional genomics research is underway at the University of Greenwich, UK, to develop and apply genomics technologies to characterise an economically-important but under-researched Bemisia tabaci (Hemiptera: Aleyrodidae), the Asia 1 mtCOI phylogenetic group. A comparison of this putative species from India with other important B. tabaci populations and insect species may provide targets for the development of more effective whitefly control strategies. As a first step, next-generation sequencing (NGS) has been used to survey the transcriptome of adult female whitefly, with high quality RNA preparations being used to generate cDNA libraries for NGS using the Roche 454 Titanium DNA sequencing platform. Contig assemblies constructed from the resultant sequences (301 094 reads) using the software program CLC Genomics Workbench generated 3 821 core contigs. Comparison of a selection of these contigs with related sequences from other B. tabaci genetic groups has revealed good alignment for some genes (e.g., HSP90) but misassemblies in other datasets (e.g., the vitellogenin gene family), highlighting the need for manual curation as well as collaborative international efforts to obtain accurate assemblies from the existing next generation sequence datasets. Nevertheless, data emerging from the NGS has facilitated the development of accurate and reliable methods for analysing gene expression based on quantitative real-time RT-PCR, illustrating the power of this approach to enable rapid expression analyses in an organism for which a complete genome sequence is currently lacking.

Behavioral Interactions betweenBemisia tabaci(Homoptera: Aleyrodidae) andTetranychus truncatus(Acarina: Tetranychidae)

Interspecific interactions between Bemisia tabaci (Gennadius) and the spidermite Tetranychus truncatus Ehara were evaluated by observation of behavioral responses over 30 min intervals on cowpea leaves. The response of adult female whiteflies was observed on 4 classes of leaf: (1) uninfested (2) previously fed upon by spidermite nymphs, (3) spidermite nymphs and webbing present, and (4) spidermite adults present. Likewise, adult female spidermite response was observed on (1) leaves uninfested with whiteflies, (2) leaves previously fed upon by whitefly nymphs, (3) leaves with whitefly nymphs present, and (4) leaves with whitefly adults present. Spidermites generally had a greater effect on whitefly behavior than vice versa. Whitefly feeding duration decreased while labial tapping duration and frequency increased on all 3 types of mite-infested leaves compared to uninfested leaves. Although whitefly oviposition duration and frequency did not change on leaves infested with spidermite nymphs, whitefly fecundity decreased compared to untreated leaves. Although whitefly effects on spidermite behavior were less marked, nevertheless, duration and frequency of cheliceral tapping by spidermites did increase in the presence of whiteflies, although duration or frequency of feeding did not. Thus, one would predict that spidermites would win out in competition with whiteflies on a common host plant. Behavioral observations of interactions between herbivores can provide valuable insight into competitive relationships which should, however, be verified by field studies.