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The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is a notorious agricultural pest and the effective vector of many plant viruses worldwide. Cucurbit chlorotic yellows virus (CCYV), exclusively transmitted by B. tabaci in a semipersistent manner, is a serious causal agent in cucurbit crops in many countries. Plant viruses can manipulate the behaviors of insect vectors to promote the spread of themselves, but underlying mechanisms are remaining unclear.In this study, our observations indicated that B. tabaci, when carrying CCYV, oriented more actively to the host plant cucumber. Transcriptome analysis and quantitative polymerase chain reaction with reverse transcription analysis showed that the odorant-binding protein 5 (OBP5) was upregulated with viral acquisition. Sequence and phylogenetic analysis showed that BtabOBP5 was highly homologous with nine OBPs from other hemipteran insects. In addition, OBP5-silenced whiteflies significantly altered their orientation behavior towards cucumber plants and towards some typical volatile organic compounds released from cucumbers.This study described a novel mechanism by which the olfactory system of vector insects could be regulated by a semipersistent plant virus, thereby affecting insect olfactory behavior and relationship with host plants. These results provided a basis for developing potential olfaction-based pest management strategies in the future. © 2022 The Authors. Pest Management Science published by John WileySons Ltd on behalf of Society of Chemical Industry.

The tobacco whitefly, Bemisia tabaci, is a fast-evolving complex species consisting of more than 35 cryptic species (biotypes). Among these species, the Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) are the most widely distributed and often cooccurrent. Field investigations showed that MED has eventually replaced MEAM1in most areas in China, but MEAM1still exists alone or together with MED in some areas. There are several hypotheses for species replacement in B. tabaci, but underlying mechanisms need further investigation. In this study, we focused to compare their adaptability and competitiveness of the two species under insecticide-free conditions by using electrical penetration graph (EPG). Feeding behaviors of the two species were recorded on each other’s pre-infested cotton or cucumber plants to mimic their interactions. Fourteen EPG variables indicated that two B. tabaci species performed remarkably differently on both pre-infested cotton and cucumber plants. Specifically, MEAM1 adults exhibited a shorter pathway for probing and a longer phloem sap ingestion than MED on either healthy or pre-infested plants. Both species had more efficient on its own pre-infested plants than on plants pre-infested by the other B. tabaci species. However, MEAM1 showed an advantage on pre-infested plants than MED under the same conditions. Our results clearly indicated that MEAM1 had stronger adaptability and competitiveness than MED on either cotton or cucumber plants without insecticide stresses.

The genus-level relationships within the subfamily Amphinemurinae have been controversial, although attempts have been made based on morphology and limited molecular data. With the establishment of two new genera, the phylogenetic relationships within Amphinemurinae should be re-examined. In this study, the complete mitochondrial genome (mitogenome) of Malenka flexura of the genus Malenka was firstly sequenced and analyzed. The phylogeny of Amphinemurinae was also reconstructed using 13 proteincoding genes (PCGs) from previously published stoneflies. This mitogenome was 15,744 bp long and encoded the typical 37 genes, as well as a putative control region. The gene arrangement of M. flexura mitogenome is identical with the putative ancestral mitogenome in Drosophila yakuba. Most PCGs used standard ATN as start codons and TAA/TAG as termination codons. All tRNA genes exhibited the typical cloverleaf secondary structure, except for tRNASer(AGN), whose dihydrouridine (DHU) arm was lacking. Some structural elements in the control region were founded, such as tandem repeat regions, stemloop structures, polyN stretch and microsatellite structure, etc. Phylogenetic analyses of sequenced Amphinemurinae mitogenomes unsupported the sister relationship of Amphinemura and Malenka. Finally, the phylogenetic analyses inferred a relationship within Amphinemurinae: Amphinemura + (Malenka + (Protonemura + (Indonemoura + (Sphaeronemoura + Mesonemoura)))).

Insect electrical penetration graph (EPG) instrument is a powerful tool to study the feeding behavior of piercing-sucking insect and insect transmission virus mechanism. However, the classification of EPG waveforms has been carried out manually. It is urgent to identify EPG waveforms automatically to improve the analysis efficiency. Machine learning methods are widely used in classifying human bioelectrical signals, but rarely in EPG signals. In this study, the kernel extreme learning machine (ELM) was applied to the classification of EPG waveforms. Morlet wavelet function was used as the kernel function of the ELM, and the number of neurons was selected adaptively by incremental algorithm to solve the classification problem of EPG waveforms quickly and accurately. In the experiment, the 6-dimensional feature vector was used to enter the wavelet kernel extreme learning machine (WKELM) which was composed of low frequency wavelet energy in the 2nd and 3rd layers, fractal box dimension, Hurst exponent and spectral centroid in the first two layers of HHT. The average classification accuracy was 94.47%, which was 3.04% higher than the previous study. The experimental results showed that the proposed classification method of EPG waveforms based on WKELM has high identification performance, which laid a theoretical foundation for the research and development of EPG waveforms automatic identification and analysis system.

Increased insecticide resistance among insect vectors and arboviruses results in significant economic losses to agricultural production and poses a continuous threat to human health. To date, many studies have been conducted on how virus-infected host plants indirectly and plant virus directly change the physiological characteristics of insect vectors. However, the relationship between the insecticide resistance of the insect vector and the virulence of the viral pathogen has not received sufficient attention. Here, we investigated the effect of Cucurbit chlorotic yellows virus (CCYV), a plant virus transmitted by whitefly (Bemisia tabaci) in a semi-persistent manner, on the tolerance of B. tabaci to the neonicotinoid imidacloprid. We found CCYV enhanced the tolerance of B. tabaci to imidacloprid. The CYP6CM1 gene was significantly up-regulated in viruliferous susceptible B. tabaci compared with non-viruliferous B. tabaci after an acquisition access period of 10 d, including its upstream regulators. Silencing the CYP6CM1 gene by RNA interference reduced the ability of B. tabaci to acquire CCYV compared with the control. Additionally, imidacloprid-resistant B. tabaci outperformed sensitive adults in terms of virus transmission ability. These results suggest that CCYV enhances the ability of imidacloprid-sensitive B. tabaci to resist adverse external factors (insecticides). In turn, B. tabaci resistance affects virus transmission. Thus, to a certain extent, the plant virus and insect vector establish a mutually beneficial relationship that facilitates virus transmission.

Background Plant metabolites play vital roles in regulating the behavior of herbivore insects. Virus infection can universally alter plant metabolites to manipulate the orientation and feeding behaviors of insect vector, to favor the transmission of virus. Thus, determining the differentially accumulated metabolites of plant upon virus infection could provide insights into understanding how the triple interactions among plant, virus and insect vector happens. Our previous studies have found that vector whitefly Bemisia tabaci (Gennadius, Hemiptera: Aleyrodidae) showed different orientation behavior and performance on CCYV-infected and healthy cucumber plants. Cucurbit chlorotic yellows virus (CCYV) is exclusively transmitted by B. tabaci in a semi-persistent mode. In this study, we take the CCYV, B. tabaci and cucumber as a research system to explore the functions of phyto-metabolites in the triple interactions. Results A total of 612 metabolites changed upon CCYV infection were monitored. Metabolites mainly enriched in flavonoids, lipids, nucleotides and their derivatives. At 7 days post CCYV inoculation (dpi), the contents of lipids, terpenoids and flavonoids remarkably decreased, while amino acids, nucleotides and their derivatives notably up-accumulated. At 15 dpi, the accumulation of flavonoids were still significantly reduced upon CCYV infection, while lipids, amino acids, nucleotides and derivatives were remarkably enhanced. Most of significantly increased metabolites were lipids (lysophosphatidylethanolamine, LPE; lysophosphatidylcholine, LPC and their isomers). Also, the number of significantly changed metabolites increased with the infection period. However, only a few organic acids and phenolic acids showed difference between CCYV-infected and healthy cucumber plants. Conclusions CCYV infection repressed the defensive flavonoids, terpeneoids metabolism but triggered the lipids, amino acids and nucleotides metabolism with the inoculation period. This result suggests that CCYV-infection makes cucumber plants more susceptible for whiteflies attack and CCYV infection. The reduction of defensive comounds and the increase of amino acids may be partially responsible for enhancing feeding preference of whiteflies to CCYV-infected hosts. CCYV may hijacked lipid metabolism for virus replication and assembly.

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.

Cucurbit chlorotic yellows virus (CCYV) has caused serious damage to melon crops in many countries in recent years. It is exclusively transmitted by the notorious pest Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in a semi-persistent manner. Previous studies have shown that both persistently and non-persistently transmitted viruses can manipulate orientation and performance of vector insects through changing host phenotype to facilitate virus spread. However, as a semi-persistently transmitted virus, how CCYV affect vector B. tabaci in locating host plants by altering physiological traits of host plants is still unknown. In this study, we investigated B. tabaci visual and olfactory preference between healthy and CCYV-infected host plant Cucumis sativus. Volatile profiles of healthy and CCYV-infected C. sativus plants were analyzed by using gas chromatography-mass spectrometry (GC-MS). Initially, it was found that vector insects preferred to settle down CCYV-infected Cucumis sativus seedlings in free choice. The concentrations of total volatiles and terpenes in cucumber plants were notably decreased after CCYV infection, and especially, the concentrations of α-pinene, β-ocimene, α-farnesene, and nonanal, responsible for olfactory attraction of B. tabaci, dramatically reduced in CCYV-infected plants. Subsequently, we investigated the visual preference of B. tabaci to CCYV-infected and healthy host, and found that B. tabaci adults showed significant preference to CCYV-infected host. CCYV induced yellowing symptoms in host leaves may explain the visual preference of B. tabaci adults to infected hosts. This study indicated that visual cues could play a vital role in vector insects locating virus-infected host plants.

It is known that plant viruses, to facilitate their transmission, can change the phenotypes and defense pathways of the host plants and the performance of their vectors. Cucurbit chlorotic yellows virus (CCYV), a newly reported virus occurring on cucurbit plants and many other plant species, is transmitted specifically by Middle East-Minor Asia 1 (B biotype) and Mediterranean (Q biotype) cryptic species of whitefly, Bemisia tabaci (Gennadius), in a semipersistent manner. This study evaluated the direct and indirect effects of CCYV on B. tabaci biology to better understand the plant-virus-vector interaction. By using CCYV-B. tabaci-cucumber as the model, we investigated whether or how a semipersistent plant virus impacts the biology of its whitefly vectors. CCYV mRNA were detectable in nymphs from 1st to 4th instars and adults of B. tabaci with different titers. Female nymph duration and female adult longevity greatly extended on CCYV-infected plants, but male nymph duration and male adult longevity were not significantly influenced. In addition, on CCYV-infected plants, the body length and oviposition of adult B. tabaci increased, 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 0.506:1 in whitefly populations on CCYV-infected plants, while the ratio remained about 0.979:1 on healthy plants. These results indicated that CCYV can significantly impact the biological characteristics of its vector B. tabaci through the host plants. It is speculated that CCYV and B. tabaci have established a typical mutualist relationship mediated by host plants.

Background: It is known that plant viruses, to facilitate their transmission, can change the phenotypes and defense pathways of the host plants and thereby the performance of their vectors. Cucurbit chlorotic yellows virus (CCYV), a newly reported virus occurring on cucurbit plants and many other plant species, is transmitted specifically by B and Q biotypes of tobacco whitefly, Bemisia tabaci (Gennadius), in a semipersistent manner. This study evaluated the direct and indirect effects of CCYV on B. tabaci performance to better understand the plant-virus-vector interaction in terms of its impacts on the biological characteristics of its vector.Methods: In this study, by using CCYV-B. tabaci-cucumber as the model, we investigated whether or how a semipersistent plant virus impacts the biology of its whitefly vectors directly and/or indirectly. Virion titer, body size, life table parameters, survival rate of nymphs and adults, reproduction capacity of both adult sexes as well as sex ratio were compared between whiteflies on CCYV-infected plants and ones on healthy plants. Results: CCYV virions were detectable in nymphs from 1st to 4th instar and adults of B. tabaci with different titers. Female nymph duration and female adult longevity greatly extended on CCYV-infected plants, but male nymph duration and male adult longevity were not significantly influenced. In addition, on CCYV-infected plants, the body length and oviposition of adult B. tabaci increased, but the egg hatching rate and survival rate of different stages of the whiteflies were not affected. Most interestingly, the sex ratio (female:male) significantly increased up to 66.40% in whitefly populations on CCYV-infected plants, while the female ratio remained about 50.53% on healthy plants. Conclusions: These results indicated that CCYV can significantly impact the biological characteristics of its vector B. tabaci through the host plants. It is speculated that CCYV and B. tabaci have established a typical mutualist relationship mediated by host plants.

Background: Although the ability of silicon to induce plant resistance against some insect is known, it is still unknown that the effect of the different concentrations of silicon on activates the secondary defense system in wheat, and then influence the life cycle table of wheat aphids. In this experiment, different levels of silicon (Si) fertilizer was applied to change the secondary defense system of wheat, to study the impact on the life table parameters of aphid (Sitobion avenae F.) (Hemiptera: Aphididae), and to explore the mechanism of Si application in enhancing wheat resistance to aphids. Wheat seedlings were cultured in a hydroponic experiment with the seven different levels of Si (0, 0.3, 1, 2, 3, 4, 5 and 9 mmol/L). Results: Our findings indicated that the application of Si can suppress the net reproductive rate (R0), intrinsic rate of increase (rm), mean generation time (T), finite rate of increase (λ), and prolong the population doubling time (t) of aphid. Besides, aphid infection elicited immune responses in wheat, which was enhanced by Si: Between the treatments, a foliar application of Si improved the activity of four defense enzymes (PAL, PPO, CAT, LOX), and increased the content of signal transduction substances (JA, SA) and secondary metabolites (tannin, alkaloids, lignin, total phenolics and flavonoids). Moreover, the results of the correlation analysis showed that the concentration of Si in wheat was positively associated with the activities of defense enzymes and the concentrations of secondary metabolites and signal transduction substances. There was a significant positive correlation between the activities of four defense enzymes and the concentrations of secondary metabolites and signal transduction substances in wheat. Furthermore, the activities of defense enzymes, the concentrations of secondary metabolites and signal transduction substances and Si in wheat were negatively associated with the R0, T, rm, ƛ and positively related to the t of the life table parameters from the aphid. Conclusions: In conclusion, the current result suggested that the application of Si can increase the signal transduction pathway of wheat and regulate the secondary metabolism by influencing the concentration of Si in wheat. As a result, the application of Si affected the life table parameters of aphids and enhanced the resistance of wheat. Also that 3 mmol/L Si application was more beneficial to enhance the resistance of wheat than higher or lower concentrations. The application of Si in wheat might provide an important basis for pest management control.

Exploring botanical biopesticide is one of the eco-friendly approaches for pest control in current crop protection. L-arabinose, a plant-specific and less absorptive pentose, is known for its selective inhibitory effect on the sucrose digestion in mammals. In this study, we investigated the effects of L-arabinose on the feeding preference, the peripheral gustatory perception, the larval development, as well as the activity of intestinal sucrase of an insect pest species, the cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), in an attempt to explore the antifeedant activities of this pentose. The results showed that L-arabinose deterred the feeding preferences of H. armigera caterpillars for its two host plants and two phagostimulants, the tobacco, the pepper, the sucrose and the fructose. Gustatory receptor neurons (GRNs) sensitive to L-arabinose were not found in the peripheral maxillary sensilla of H. armigera caterpillars, but the sensitivities of GRNs sensitive to sucrose, fructose and tobacco saps were suppressed by the additions of L-arabinose. Exposure of H. armigera caterpillars to dietary L-arabinose resulted in a prolonged larval developmental duration, a suppressed activity of intestinal sucrase and a reduced glucose level in midgut. In vitro, L-arabinose inhibited activities of the intestinal sucrase of H. armigera caterpillars in an uncompetitive manner. Taken together, these findings demonstrate that L-arabinose is a behavioral, gustatory and physiological inhibitor to caterpillars of the extremely generalist pest species H. armigera, suggesting the great potential of L-arabinose to be an effective antifeedant.

Object: To investigate the VOCs from living Prunus persica flowers of different branches and their correlation with floral insects. Special, dominant and 20 VOCs were analysed from living Prunus persica flowers captured by closely and circularly headspace way in adsorbent tubes and ATD-GC/MS on 29 April in Wanbailin Ecological Garden, China. VOCs from high altitude tree are more than low altitude in sunny site, and floral volatile constituents from upslope branches are less than downslope of the same tree on high altitude. Special floral VOCs were alpha-dimethyl-benzenemethanol, isopropyl palmitate, ethylbenzene, p-xylene, acetophenone, 3-ethyl-2-methyl-Heptane on sunny slope, and propylene glycol, decanal, hexadecane on shady slope. Dominant VOCs founded during 8 temporal quanta were toluene, hexane, 2-ethyl-1-hexanol, dodecane, pentadecane. Floral VOCs’ number from sunny slope was significantly negative correlated with flower-visiting insect community richness, abundance, diversity on sunny or shady slope, which from shady slope was significantly positive correlated with flower-visiting insect community parameters on both slopes tried dividing insects visiting floral branches from Prunus persica in sunny site with n/2 + 1 or n/2 - 1, and shady site with n/2 before sampled volatiles day. On sampled volatiles day, 2-ethyl-1-hexanol from sunny slope was significantly positive correlated with flower-visiting insect community parameters on shady slope (P < 0.001). After sampled day, hexanal, toluene, dodecane were significantly negative correlated with SUSR, SUSA, SUSD, and positive with SHSR, SHSD, while tetradecane, pentadecane were positive related to SUSR, SUSA, SUSD with n/2 - 1 dividing insects visiting floral branches, but reversely with n/2 + 1 dividing insects visiting floral branches. We concluded that special and dominant volatiles applied to lure flower-visiting insects to promote pollination, and odd floral branches should be kept for every tree when pruning the Prunus persica on sunny slope, and even floral branches kept on shady slope.

Background Plant viruses can affect vector’s behaviors in order to enhance viral transmission. Cucurbit chlorotic yellows virus (CCYV) (genus Crinivirus) is an emergent RNA plant virus and is transmitted specifically by biotypes B and Q of tobacco whitefly, Bemisia tabaci (Gennadius), in a semipersistent manner. Methods We used the electrical penetration graph (EPG) to investigate the effect of CCYV on the feeding behaviors of B. tabaci biotypes B and Q. Results CCYV could affect, both directly and indirectly, the feeding behaviors of B. tabaci to various degrees, depending on biotypes and sexes of the insect. CCYV showed stronger direct effects on biotype Q than on biotype B in terms of increased non-phloem probing and phloem salivation. CCYV increased non-phloem probing and phloem salivation more on females than on males of biotype Q, and increased phloem salivation more on females than on males of biotype B. CCYV had stronger indirect effects, via virus-infested plants, on biotype B than on biotype Q by enhancing phloem sap ingestion and feeding bouts. CCYV increased non-phloem probing and feeding bouts more on males than on females of biotype B, and decreased phloem sap ingestion more on males than on females on biotype Q indirectly. Conclusions The results clearly indicated that CCYV affects the feeding behaviors of B. tabaci, which may lead to increased ability of the B. tabaci for CCYV transmission.

Taihangia rupestris Yu et Li is an ancient species endemic to the Taihang Mountains, where it originated and evolved. Six chloroplast DNA (cpDNA) (trnTUGU-trnLUAA 5′exon, trnLUAA 5′exon-3′exon, trnLUAA 3′exon-trnFGAA, trnHGUG-trnKUUU, psbC-trnS and rps12-rpl20) and five mitochondrial DNA regions (rrn5/rrn18-2, nad1/2-3, nad4/3-4, nad7/1-2 and nad7/2-3) were employed to investigate the nucleotide diversity and subspecies differentiation. The results showed that T. rupestris had high nucleotide diversity at the species level, and T. rupestris var. ciliate possessed higher levels of haplotype and nucleotide diversity than did T. rupestris var. rupestris. Cytoplasmic DNA revealed a phylogenetic pattern of individuals that was in disagreement with the patterns obtained from nuclear DNA. These results primarily reflect the past habitat fragmentation of the species and different modes of inheritance and spread of these genomes. Together, our results advance our understanding of plant speciation in this region.

Seed treatments with the neonicotinoid insecticides imidacloprid and thiamethoxam were evaluated to determine whether the chemicals at effective concentrations for aphid control would influence the germination and early growth of oilseed rape, Brassica napus. Treatment with imidacloprid or thiamethoxam did not affect the cumulative germination rate, but significantly inhibited establishment potential by suppressing root system development in the cotyledon stage. However, these alterations in seedling development in the thiamethoxam-treated seeds appeared not to be detrimental as leaves developed; in contrast, for the seedlings with imidacloprid as seed treatment agent, a significantly decreased shoot/root ratio was still evident at the late two-leaf stage. After two leaves developed, chlorophyll content per leaf in the thiamethoxam treatment was significantly higher than that of the control, while chlorophyll content per leaf in the imidacloprid treatment remained close to that in the control. Most other parameters, i.e., height, leaf area, weight of stem, leaf or root, and other growth indexes, between the treatments and the control showed no significant difference. Additionally, it was found that storage time of the treated seeds had a significant effect on cumulative germination rate. Treatment 30 d before planting significantly reduced germination relative to that of the control. All of the plants treated with neonicotinoids were shown to have significant anti-aphid characteristics that persisted until the end of the trial.

The sweetpotato whitefly Bemisia tabaci is a highly destructive agricultural and ornamental crop pest. It damages host plants through both phloem feeding and vectoring plant pathogens. Introductions of B. tabaci are difficult to quarantine and eradicate because of its high reproductive rates, broad host plant range, and insecticide resistance. A total of 791 Gb of raw DNA sequence from whole genome shotgun sequencing, and 13 BAC pooling libraries were generated by Illumina sequencing using different combinations of mate-pair and pair-end libraries. Assembly gave a final genome with a scaffold N50 of 437 kb, and a total length of 658 Mb. Annotation of repetitive elements and coding regions resulted in 265.0 Mb TEs (40.3%) and 20 786 protein-coding genes with putative gene family expansions, respectively. Phylogenetic analysis based on orthologs across 14 arthropod taxa suggested that MED/Q is clustered into a hemipteran clade containing A. pisum and is a sister lineage to a clade containing both R. prolixus and N. lugens. Genome completeness, as estimated using the CEGMA and Benchmarking Universal Single-Copy Orthologs pipelines, reached 96% and 79%. These MED/Q genomic resources lay a foundation for future ‘pan-genomic’ comparisons of invasive vs. noninvasive, invasive vs. invasive, and native vs. exotic Bemisia, which, in return, will open up new avenues of investigation into whitefly biology, evolution, and management.

BACKGROUND Cytochrome P450 monooxygenases have been proven to be associated with high resistance in Bemisia tabaci B biotype (Middle East–Asia Minor 1 genetic group) and Q biotype (Mediterranean genetic group) to the neonicotinoid class of insecticides. In this study, the RNA interference (RNAi) effects on P450 CYP6CM1 gene expression, mortality and pesticide-detoxifying ability between B. tabaci B and Q biotypes were compared in an attempt to provide a basis for potential RNAi application in management of this pest. RESULTS Double-stranded RNAs (dsRNAs) of P450 CYP6CM1 genes corresponding to the B and Q biotypes were synthesised using specific primers and introduced into the insect body of B. tabaci adults through membrane feeding. The results showed that dsRNAs significantly silenced the target genes in B. tabaci with dsRNA concentration or treatment time, and silencing was more effective in B biotype than in Q biotype. Feeding dsRNAs led to high mortality in both biotypes, with higher mortality in B biotype (up to 85.88%) than in Q biotype (up to 56.40%). In addition, ability to detoxify imidacloprid and nicotine was inhibited in dsRNA-treated adults of both biotypes, more efficiently in B biotype than in Q biotype. CONCLUSION RNA interference of the P450 CYP6CM1 gene reduced gene expression, increased mortality, and inhibited the ability to detoxify a pesticide or a plant secondary metabolite in both biotypes of B. tabaci, with better efficacy in B biotype than in Q biotype. © 2014 Society of Chemical Industry

Morphology and morphometry of six biotypes (B, Q, Cv, ZHJ-1, ZHJ-2 and ZHJ-3) of Bemisia tabaci (Gennadius) from China on cotton plants were studied by using microscopes. Nymphal body sizes and characters were measured and observed, especially on the 4th instar (pupal case), including the vasiform orifice, operculum, lingula, length and thickness of anterior and posterior wax margins, width of thoracic tracheal combs. Adult characters of both sexes were investigated including the body size, compound eyes, antennal segments, vasiform orifice, hind tarsi and genitals. The results indicated that differences of some morphological characters or morphometrics were significant among the six biotypes of B. tabaci in China: (1) Pupal sizes of the exotic biotypes (B and Q) were significantly larger than the indigenous biotypes with the following order as B>Q>ZHJ-1>Cv>ZHJ-3>ZHJ-2; (2) for both male and female adults, sizes of all characters investigated in the invading biotypes (B and Q), especially B, were much larger than those of the indigenous ones.

Dietary exposure of insects to a feeding deterrent substance for hours to days can induce habituation and concomitant desensitization of the response of peripheral gustatory neurons to such a substance. In the present study, larvae of the herbivore Helicoverpa armigera were fed on diets containing either a high, medium or low concentration of sucrose, a major feeding stimulant. The responsiveness of the sucrose-best neuron in the lateral sensilla styloconica on the galea was quantified. Results showed the response of the sucrose-best neuron exposed to high-sucrose diets decreased gradually over successive generations, resulting in complete desensitization in the 5th and subsequent generations. However, the sensitivity was completely restored in the ninth generation after neonate larvae were exposed to low-sucrose diet. These findings demonstrate phenotypic plasticity and exclude inadvertent artificial selection for low sensitivity to sucrose. No significant changes were found in the sensitivity of caterpillars which experienced low- or medium-sucrose diets over the same generations. Such desensitization versus re-sensitization did not generalise to the phagosimulant myo-inositol-sensitive neuron or the feeding deterrent-sensitive neuron. Our results demonstrate that under conditions of high sucrose availability trans-generational desensitization of a neuron sensitive to this feeding stimulant becomes more pronounced whereas re-sensitization occurs within one generation.

It is known that plant viruses can change the performance of their vectors. However, there have been no reports on whether or how a semipersistent plant virus manipulates the feeding behaviors of its whitefly vectors. Cucurbit chlorotic yellows virus (CCYV) (genus Crinivirus, family Closteroviridae) is an emergent plant virus in many Asian countries and is transmitted specifically by B and Q biotypes of tobacco whitefly, Bemisia tabaci (Gennadius), in a semipersistent manner. In the present study, we used electrical penetration graph (EPG) technique to investigate the effect of CCYV on the feeding behaviors of B. tabaci. The results showed that CCYV altered feeding behaviors of both biotypes and sexes of B. tabaci with different degrees. CCYV had stronger effects on feeding behaviors of Q biotype than those of B biotype, by increasing duration of phloem salivation and sap ingestion, and could differentially manipulate feeding behaviors of males and females in both biotype whiteflies, with more phloem ingestion in Q biotype males and more non-phloem probing in B biotype males than their respective females. With regard to feeding behaviors related to virus transmission, these results indicated that, when carrying CCYV, B. tabaci Q biotype plays more roles than B biotype, and males make greater contribution than females.

Cucurbit chlorotic yellows virus (CCYV) (genus Crinivirus, family Closteroviridae) is an emerging plant virus, and is now spreading and causing severe economic losses to cucurbit crops in many Asian countries. CCYV is believed to be transmitted specifically by the sweetpotato whitefly, Bemisia tabaci, in a semipersistent manner. In the present study, we provide direct evidence for the semipersistent transmission of CCYV by Mediterranean (MED) cryptic species of B. tabaci complex. We investigated CCYV transmission characteristics, and immunofluorescently labeled and localized the virus retention site within the vector by laser confocal microscopy. Whiteflies required ≥1 h of acquisition access period (AAP) to successfully acquire CCYV, and the proportion of RT-PCR positive whitefly individuals reached to 100% at 48 h of AAP. CCYV virons could be retained within vectors as long as 12 d, but the proportion of RT-PCR positive whiteflies dropped to 55% by 3 d. Groups of thirty whiteflies given a 24 h of inoculation access period (IAP) to inoculate CCYV on cucumber plants showed a transmission efficiency rate of 72.73%. The retention site of CCYV virons was located in the foregut of virion-fed vectors. These results definitely indicated the semipersistent transmission mode of CCYV by B. tabaci MED.

Cucurbit chlorotic yellows virus (CCYV), a recently identified bipartite crinivirus, causes economic losses in cucurbit plants. CCYV is naturally transmitted only by whitefly Bemisia tabaci. Here we constructed full-length cDNA clones of CCYV (RNA1 and RNA2) fused to the T7 RNA polymerase promoter and the cauliflower mosaic virus 35S promoter. CCYV replicated and accumulated efficiently in Cucumis sativus protoplasts transfected with in vitro transcripts. Without RNA2, RNA1 replicated efficiently in C. sativus protoplasts. Agroinoculation with the infectious cDNA clones of CCYV resulted in systemic infection in the host plants of C. sativus and Nicotiana benthamiana. Virus derived from the infectious clones could be transmitted between cucumber plants by vector whiteflies. This system will greatly enhance the reverse genetic studies of CCYV gene functions.

In China, Bemisia tabaci Q (commonly known as biotype Q) has rapidly displaced B (commonly known as biotype B) in the past 6 years. The mechanisms underlying such phenomenon have been studied extensively in recent years; however, we have not come to a definitive conclusion yet. In the present study, the differences in host suitability between B and Q whitefly adults to five host plants (cabbage, cotton, cucumber, poinsettia, and tomato) were evaluated based on their respective feeding behaviors using a direct-current electrical penetration graph (DC-EPG) system. Pair-wise comparisons of B. tabaci B and Q feeding on each of the five host plants clearly indicate that Q feeds better than B on tomato, cotton and poinsettia, while B feeds better than Q on cabbage and cucumber. The EPG parameters related to both phloem and non-phloem phases confirm that cabbage and cucumber are best suited to B, while tomato, cotton, and poinsettia are best suited to Q. Our present results support the contention that host suitability and adult feeding behavior contribute to the competitive displacement of biotype B by biotype Q. The discrepancy between field (previous studies) and laboratory results (this study), however, suggests that 1) whitefly displacement is apparently contributed by multiple factors; and 2) factor(s) other than the host plant suitability may play a vital role in dictating the whitefly biotypes in the field.

Bemisia tabaci (Gennadius) B biotype, a destructive pest causing heavy damage to crop production, has become an important economic pest of agriculture worldwide. Here, the proteome change of Arabidopsis thaliana leaves infested by B. tabaci was studied with two-dimensional electrophoresis and mass spectrometry. Twenty proteins showed a significant change in expression after B. tabaci infestation, including ten up-regulated and ten down-regulated. Using the Gene Ontology annotation, all except one were classified into one of four major groups based on their molecular function and biological process. Six of the proteins were involved in protein folding and regulation (HSP90.7, HSP90.3, HSP90.2, ERD1, FKB70, and ROC1), five in redox regulation (PRX2B, GPX6, MDAR3, MDARP, and Y4967), five in primary metabolism (TBA6, SPP2, PDX11, RR5, and RuBisCO activase (RCA)), and three in secondary metabolism (PR5, MYRO, and NMT2). All proteins belonging to the same group shared the same direction of change; the only exception was RCA. The proteins involved in protein folding and regulation were down-regulated indicating the inhibition of a plant defense response. Those involved in redox regulation were up-regulated, which may lead to an increase in tolerance as a result of a reduction in oxidation. Proteins involved in primary metabolism (except RCA) were inhibited while those involved in secondary metabolism were induced suggesting reallocation of resources with the host plant. These proteins will form the basis for future studies aimed at further understanding the mechanism underlying the host-adaptation capacity of B. tabaci.

In 2004 and 2005, we investigated the distribution of the Glanville fritillary butterfly (Melitaea cinxia) and its host plant in the Tianshan Mountains of China, in order to clarify its habitat utilization. Female butterflies were almost captured on dry meadows on slopes, where plenty of host plant (Veronica spicata) is distributed. Although there are host plants on meadows at higher altitude (>2,050 m), no butterfly was found there. Among the meadows with host plants, a patch of dry meadow (newly-found meadow) was considered as a natal site because of the high density and freshness of butterflies. Unlike females, male butterflies were almost captured in valleys, where there are no host plants and fewer nectar plants. It might be related to specific mating system of M. cinxia in the study site, or specific environmental factors. Thus valleys are important habitat for males. Although the status of M. cinxia is yet unknown in China, we give some suggestions for conservation based on this study. First, dry meadows with host plants are the essential component for persistence of M. cinxia, among which the specific sites with more favourable conditions, such as natal site, are most important. Second, as a site with adult resource requirement, valleys should be included as part of the habitat of the butterfly. Finally, meadows at higher altitude are not utilized at present but they are potential habitats which need to be maintained for any shifts in altitudinal range in response to global warming in the future. Hence, the trade-off of present cost and future benefit should be taken into account when formulating a conservation strategy for M. cinxia in the Tianshan Mountains of China.

Effects of maize (Zea mays L.) volatiles induced by larvae of the Asian corn borer, Ostrinia furnacalis (Guene), on the orientation behaviors of Asian corn borer larvaee and oviposition of the females were investigated. Nineteen volatile chemicals, with terpenes being the major components, were identified from maize plants attacked by third instar Asian corn borer larvae. Coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses revealed some electroantennographic differences between female and male Asian corn borer antennae in response to larvae-induced maize volatiles; female responded to (E)-2-hexenal, nonanal, (Z)-3-hexen-1-ol and three unknown compounds while the male only responded to (E)-2-hexenal, nonanal and one unknown compound. In laboratory orientation bioassays, Asian corn borer neonate larvae were attracted to extracts collected from Asian corn borer-damaged plants as well as to synthetic farnesene, but were repelled by (Z)-3-hexen-1-ol. In laboratory oviposition bioassays, gravid females laid fewer eggs on plants damaged by larvae than on mechanically damaged plants or undamaged plants. Adult Asian corn borer females deposited fewer eggs on wax paper treated with (E)-2-hexenal or (Z)-3-hexen-1-ol than on wax paper treated with hexane (control). The results suggest that Asian corn borer can affect the behaviors of conspecific larvae and adults by changing host plant volatiles.

Stylet penetration behaviors of cotton aphids Aphis gossypii Glover on a transgenic cotton line “GK-12” expressing Bt toxic protein of Cry1A (Bt cotton) and a non-Bt conventional cotton line “Simian-3” (CK cotton) were recorded with the direct current electrical penetration graph (DC-EPG) technique. Cotton aphids reared on Bt cotton (abbreviated as Bt-aphids) and its parental non-Bt control line (CK-aphids) for more than 20 generations each, were used for recordings on two cotton lines. Among 47 selected parameters reflecting the activities of aphid stylets within plant tissues, there were eight parameters of CK-aphids showing significant differences between the performances of CK-aphids on Bt cotton and CK cotton, while for Bt-aphids, all the parameters were statistically equal between the performances on the two cotton lines. All parameters with significant differences indicated that CK-aphids could penetrate into Bt cotton more easily, but the phloem saps of Bt cotton were not as good as those of regular cotton for CK-aphids. Based on the present results, we concluded that there were some factors in Bt cotton affecting penetration behaviors of CK-aphids, but it just took several generations for CK-aphids to completely adapt Bt cotton, and Bt-aphids could feed on two cotton lines without difficulty.

Here, we reconstructed the Hemiptera phylogeny based on the expanded mitochondrial protein-coding genes and the nuclear 18S rRNA gene, separately. The differential rates of change across lineages may associate with long-branch attraction (LBA) effect and result in conflicting estimates of phylogeny from different types of data. To reduce the potential effects of systematic biases on inferences of topology, various data coding schemes, site removal method, and different algorithms were utilized in phylogenetic reconstruction. We show that the outgroups Phthiraptera, Thysanoptera, and the ingroup Sternorrhyncha share similar base composition, and exhibit "long branches" relative to other hemipterans. Thus, the long-branch attraction between these groups is suspected to cause the failure of recovering Hemiptera under the homogeneous model. In contrast, a monophyletic Hemiptera is supported when heterogeneous model is utilized in the analysis. Although higher level phylogenetic relationships within Hemiptera remain to be answered, consensus between analyses is beginning to converge on a stable phylogeny.

Sequence divergence of mitochondrial COII was analyzed in 50 specimens belonging to five subspecies of Polyura eudamippus (Lepidoptera: Nymphalidae) collected from southern China. There were nine haplotypes in the 405 bp of partial COII sequence. Distribution of the five subspecies was primarily consistent with the spatial distribution of haplotypes. The K st statistic showed genetic differentiation among these subspecies, except between the pair of P. e. kuangtungensis and P. e. formosana, which were separated by the Taiwan Strait. This is consistent with the 10,000-year history of the Taiwan Strait, not long enough for detectable differentiation. The present distribution pattern of COII haplotypes of P. eudamippus should be shaped by the alteration of Pleistocene glaciations, and Yunnan might be the refugium of P. eudamippus in the ice age, judging from the abundant haplotypes remaining. There were two routes for P. eudamippus in the postglacial expansion, one northward to Sichuan, Chongqing, and Hubei and another eastward to the southeastern coast of mainland China and Taiwan Island. Because the haplotype of butterflies on Hainan Island (P. e. whiteheadi) was completely different from that of mainland China, it was estimated that butterflies on Hainan Island might be from the Indo-China Peninsula rather than from mainland China.

Field experiments and surveys were conducted in 2003 and 2004 to evaluate the efficacy of using the parasitoid Microplitis mediator (Haliday) to control populations of Helicoverpa armigera (Hubner) in cotton fields in Northwestern China’s Xinjiang Province. The population levels of the second generation of H. armigera in southern Xinjiang in 2003 and 2004 were ≈20–60% above the economic threshold of this pest. The longevity of field-released female and male parasitoids was 7.6 ± 0.4 and 3.9 ± 0.4 d, respectively. Field tests showed that the number of parasitized H. armigera increased with an increasing number of M. mediator cocoons released in the field. The release of 2,250 or 15,000 laboratory-reared M. mediator cocoons per hectare in cotton fields resulted in 38–61% parasitism of H. armigera in 2003 and 35–66% parasitism in 2004. The efficiency of the parasitoids varied considerably with different numbers of parasitoid cocoons and with the frequency and sites of release. However, the highest d...

Glassy-winged sharpshooter, Homalodisca coagulata (Say), is an efficient vector of Xylella fastidiosa (Xf), the causal bacterium of Pierce's disease, and leaf scorch in almond and oleander. Acquisition and inoculation of Xf occur sometime during the process of stylet penetration into the plant. That process is most rigorously studied via electrical penetration graph (EPG) monitoring of insect feeding. This study provides part of the crucial biological meanings that define the waveforms of each new insect species recorded by EPG. By synchronizing AC EPG waveforms with high-magnification video of H. coagulata stylet penetration in artifical diet, we correlated stylet activities with three previously described EPG pathway waveforms, A1, B1 and B2, as well as one ingestion waveform, C. Waveform A1 occured at the beginning of stylet penetration. This waveform was correlated with salivary sheath trunk formation, repetitive stylet movements involving retraction of both maxillary stylets and one mandibular stylet, extension of the stylet fascicle, and the fluttering-like movements of the maxillary stylet tips. Waveform B1 was ubitquious, interspersed throughout the other waveforms. B1 sub-type B1w was correlated with salivation followed by maxillary tip fluttering. This tip fluttering also occurred before and during B1 sub-type B1s, but was not directly correlated with either the occurrence or frequency of this waveform. Waveform B2 was correlated with sawing-like maxillary stylet movements, which usually occurred during salivary sheath branching. Waveform C was correlated with ingestion. Fluid outflow was also observed as a mechanism to clear the maxillary tips from debris during waveform C. This detailed understanding of stylet penetration behaviors of H. coagulata is an important step toward identifying the instant of bacterial inoculation which, in turn, will be applied to studies of disease epidemiology and development of host plant resistance.