Single Whitefly Research Articles

A multiplex RT-qPCR assay for simultaneous detection of cucurbit viruses from individual whitefly and plant samples.

Whiteflies (Bemisia tabaci) are a significant pest of cucurbits and vectors many viruses leading to substantial economic losses. Modern diagnostic tools offer the potential for early detection of viruses in the whiteflies before crop production. One such tool is the multiplex reverse transcriptase quantitative PCR (RT-qPCR) probe-based technique, which can detect multiple targets in a single reaction and simultaneously quantify the levels of each target, with a detection limit of 100 copies per target. In this study, a multiplex RT-qPCR-based detection system capable of identifying one DNA virus and three RNA viruses in whiteflies: cucurbit leaf crumple virus (CuLCrV), cucurbit chlorotic yellows virus (CCYV), cucurbit yellow stunting disorder virus (CYSDV), and squash vein yellowing virus (SqVYV) was developed. To ensure the reliability of the assay, an internal gene control as the fifth target to monitor false-negative results was incorporated. This newly developed molecular diagnostic tool possesses several advantages. It can detect up to five desired targets from a single whitefly RNA sample, even at concentrations as low as 1 ng/µl. To evaluate its sensitivity, we conducted experiments using serially diluted cloned plasmids and in vitro transcribed RNA transcripts of the target viruses. We also assessed the specificity of the assay by including aphid-transmitted viruses and other viruses known to infect cucurbits. The diagnostic method successfully detected all five targets simultaneously and allowed for the quantification of up to 100 copies using a mixture of healthy? RNA and in vitro transcribed RNA. Our aim with this study was to develop a highly specific and sensitive one-step multiplex RT-qPCR system for the simultaneous detection of viruses transmitted by whiteflies in cucurbits. This system offers significant advantages for early detection, enabling prompt control measures to mitigate the further spread of viral infections and reduce yield losses. Additionally, we demonstrated the ability to simultaneously detect mixed viruses (CCYV, CYSDV, CuLCrV, and SqVYV) in individual whiteflies and quantify the number of viral copies carried by each whitefly. The multiplex RT-qPCR assay outperforms currently available techniques for detecting many samples at a given time and can be effectively utilized for early monitoring of plant viruses in individual whiteflies and symptomless plants.

Low-cost water boiling method successfully employed to extract DNA from a single whitefly to detect yellow mosaic disease-causing viruses in PCR

A cost-effective DNA extraction approach was developed and applied to PCR-based identification of yellow mosaic disease (YMD) causing viruses in individual whiteflies. Whiteflies were collected from urdbean and eggplant, representing host and non-host plants of target viruses, respectively. DNA from whiteflies was successfully extracted using the nuclease-free water boiling method and optimised template concentration for PCR assays. An average nucleic acid content of 3.844 ± 0.14 ng/µl was extracted from individual whiteflies in 50 µl nuclease-free water. PCR assays revealed Mungbean yellow mosaic India virus (MYMIV) presence in 90% of the whiteflies collected from urdbean. Conversely, YMD-causing viruses were not present in whiteflies collected from eggplant or in the eggplant plants themselves. The use of this low-cost approach for detecting YMD-causing viruses in whiteflies is very effective for the surveillance and monitoring of viruses. Early detection facilitates the deployment of appropriate management strategies, reducing both crop losses and the potential for outbreaks.

Enhanced transmission efficiency of begomoviruses by a single whitefly (Bemisia tabaci) using a microcage technique

Enhanced transmission efficiency of begomoviruses by a single whitefly (Bemisia tabaci) using a microcage technique

Use of UV-LED light to enhance establishment of Nesidiocoris tenuis for control of Bemisia tabaci infesting greenhouse tomato

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a major pest of greenhouse tomato and Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is an effective predator of this whitefly. Previously, we found that 385 nm LED lighting improved the predatory performance of N. tenuis on B. tabaci under laboratory conditions, ostensibly via mutual attraction of bugs and whiteflies to this wavelength, and improved aggregation of both insects around the light sources. Here we verified that LED lighting at 385 nm enhances the establishment of N. tenuis releases on tomato plants infested with B. tabaci under greenhouse conditions. In the first trial, conducted May-July, both whiteflies and predators were released three times; whitefly densities were not affected by LED lighting when predators were absent, but ended the experiment at lower densities when N. tenuis releases were combined with LED lighting than when they were not. In a second trial, conducted September-November under cooler conditions, a single whitefly release established an infestation and was followed by a single release of N. tenuis in two treatments, with and without LED. The LED lighting treatment maintained lower whitefly densities over a two month period in the crop, and higher densities of predators, than the predators-only treatment. Therefore, possible applications of short wavelength LED lighting to enhance N. tenuis augmentation programs in greenhouse settings appear worthy of further evaluation.

Whiteflies at the Intersection of Polyphagy and Insecticide Resistance

Abstract The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is one of the most damaging, polyphagous insect pests of agricultural cropping systems around the world. Insecticide control is one of the main tactics used to mitigate damage and crop injury caused by the species. Similarly, plant chemical defenses are primary natural mechanisms that reduce attacks from whiteflies. Like all Sternorrhyncha insects, whiteflies have piercing/sucking mouthparts and feed on phloem sap from vascular plants through a stylet. Therefore, if this insect can overcome the physical barriers of the plant and pierce the vascular bundle, the main remaining barriers to nutrition uptake and utilization are phytochemicals that might exhibit some degree of toxicity toward the insect. Bemisia tabaci has been reported to feed on over 1,000 plant species representing an enormous range of phytochemicals to which whiteflies are potentially exposed. Recently, whiteflies were shown to have acquired a gene from plants to detoxify the plant’s phenolic glycosides that are usually toxic. Additionally, host plants have been shown to alter the response of a single whitefly population to insecticides. Herein, we review possible interactions between the highly polyphagous B. tabaci, the potential phytochemicals associated with its extensive plant host range, and the main chemical insecticides used to control this pest. This review aims to provide a conceptual framework for studying possible biological interactions between the insect, host plant, and insecticidal toxins used to control this pest at the mechanistic and population selection levels.

A reproducible and sensitive method for generating high-quality transcriptomes from single whitefly salivary glands and other low-input tissues.

Transcriptomic studies are an important tool for understanding the molecular pathways underlying host plant use by agricultural pests, including vectors of damaging plant pathogens. Thus far, bulk RNA-Seq has been the main approach for non-model insects. This method relies on pooling large numbers of whole organisms or hundreds of individually dissected organs. The latter approach is logistically challenging, may introduce artifacts of handling and storage, and is not compatible with biological replication. Here, we tested an approach to generate transcriptomes of individual salivary glands and other low-input body tissues from whiteflies (Bemisia tabaci MEAM1), which are major vectors of plant viruses. By comparing our outputs to published bulk RNA-Seq datasets for whole whitefly bodies and pools of salivary glands, we demonstrate that this approach recovers similar numbers of transcripts relative to bulk RNA-Seq in a tissue-specific manner, and for some metrics, exceeds performance of bulk tissue RNA-Seq. Libraries generated from individual salivary glands also yielded additional novel transcripts not identified in pooled salivary gland datasets, and had hundreds of enriched transcripts when compared with whole head tissues. Overall, our study demonstrates that it is feasible to produce high quality, replicated transcriptomes of whitefly salivary glands and other low-input tissues. We anticipate that our approach will expand hypothesis-driven research on salivary glands of whiteflies and other Hemiptera, thus enabling novel control strategies to disrupt feeding and virus transmission.

A multiplex RT-PCR assay combined with co-extraction of DNA and RNA for simultaneous detection of TYLCV and ToCV in whitefly

Tomato yellow leaf curl virus (TYLCV) and tomato chlorosis virus (ToCV) were transmitted by the sweet potato whitefly Bemisia tabaci (Gennadius) and cause serious yield losses on tomato around the world. To understand the actual situation of co-infection of TYLCV and ToCV of individual whiteflies, we developed multiplex RT-PCR combined with co-extraction of DNA and RNA from a single whitefly. First, a nucleic acid extraction method previously reported was modified and adopted to obtain the RNA-DNA mixture including TYLCV and ToCV in a simple form without manual homogenization. Second, primers were newly designed in actin gene of B. tabaci for the confirmation of extraction and PCR success, and multiplex RT-PCR method was developed using specific primer sets for TYLCV, ToCV and B. tabaci. This method enables the detection of TYLCV and ToCV from a single insect and efficient use of field samples obtained using sticky traps. The method will be useful to monitor infection status of TYLCV and ToCV in the field while reducing labor and cost.

Effect of okra plant resistance on transmission rate of okra enation leaf curl virus by its vector whitefly, Bemisia tabaci

The present study aimed to investigate the effect of age of the okra plants that showed varying whitefly resistance responses on the transmission rate of okra enation leaf curl virus (OELCV) by its vector whitefly Bemisia tabaci. The OELCV infected whitefly adults were collected from whitefly colonies and were challenged on the test okra accessions (Upl mona 2, Co 1, Arka anamika and AE 64) of differential ages which were individually caged (7, 10 and 15 d after germination) with glass chimney and the number of such whiteflies used were at the rate of 2, 4, 6, 8, 10, 12, 14 and 20 adults per plant. Observations were made on the virus symptom expression 30 d after challenge. The efficiency of transmission was determined. The efficiency of transmission of OELCV was the highest (maximum T and P*, 0.80, 1.00 and 0.08, 0.10) when 7 d old seedlings were inoculated (Arka anamika and AE 64 respectively) and transmission had decreased as the age of seedlings increased. The estimated transmission rate for single whitefly (P*) increased with an increase in the number of whiteflies used per plant. Okra plant resistance to B. tabaci significantly changed the transmission rates of OELCV on okra. Understanding the resistance mechanisms of the okra accessions and interactions between plant viruses and their insect host can pave the way for novel approaches to protect plants from virus infection.

Understanding the interactions among the crop plants, a virus, insect vector whiteflies and their endosymbionts

Interactions among the four biotic agents - the host plants, a virus, insect vector whiteflies and their bacterial endosymbionts was investigated in this study. The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is an important crop pest that is infected by several endosymbiotic bacteria that can play varying roles on their hosts. Both whiteflies and endosymbionts are affected by the host plants they feed on, which in turn affect the fourth agent – the viruses, which are transmitted by the whiteflies. We investigated these interactions on five different host plants – eggplant, tomato, beans, okra and cotton - using a single whitefly species Asia 1 infected with three different bacteria Portiera, Wolbachia and Arsenophonus. B. tabaci Asia 1 transmits the Tomato leaf curl Bangalore virus (ToLCBV) effectively, which was the virus used in the study. We found host plants having a significant impact on whitefly growth and development. Eggplant was most favourable, while okra and tomato were least preferred. The endosymbiont Wolbachia was significantly affected by feeding of B. tabaci on different host plants while Portiera and Arsenophonus were unaffected. When whiteflies fed on ToLCBV-infected tomato plants, the concentration of Arsenophonus increased significantly while other endosymbionts remain unchanged. Understanding these interactions will help in managing both whiteflies and viral diseases.

Virus Vector Relationship of Yellow Mosaic Virus and Whitefly, Bemisia tabaci (Gennadius) in Soybean

Background: Whitefly is one of the most destructive sucking pest in the tropical and subtropical regions of the world and causing significant crop losses directly by sucking sap from the plants and indirectly through the transmission of viral diseases specifically caused by the genus Begomovirus. The Begomovirus species viz., Mungbean yellow mosaic India virus (MYMIV) and Mungbean yellow mosaic virus (MYMV) are causing yellow mosaic virus disease in soybean, which is transmitted by whiteflies. The disease accounts to 30-70 per cent yield loss and increases up to 80 - 100 per cent during severe incidence. Hence, there is a need for development of integrated pest management strategies against disease and whiteflies, for this the knowledge on virus-vector relationship is required. But, the studies on biological relationship of yellow mosaic virus disease and whitefly in soybean are scarce. At this juncture, considering the importance of disease in soybean, the present investigation was carried out to know the virus -vector relationship of the YMV and whitefly in soybean.Methods: The experiment on virus-vector relationship of yellow mosaic virus and whitefly in soybean was conducted at Department of Entomology, College of Agriculture, G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand during 2016-17. The data on number of whiteflies per plant, acquisition and inoculation access feeding period and pre and post starvation period required for effective transmission of virus was recorded.Result: A single viruliferous whitefly was able to transmit virus and ten viruliferous whiteflies per plant were required for cent per cent transmission of virus. The minimum acquisition access and inoculation access feeding periods required for virus transmission was 0.25h (15 min) each; while the 100 per cent virus transmission was recorded with acquisition and inoculation period of 12h, each. The per cent transmission was increased with the increase of acquisition and inoculation periods. The rate of transmission was positively correlated with pre-acquisition starvation period and negatively correlated with post- acquisition starvation period.

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.

A temperature-driven model for potato yellow vein virus transmission efficacy by Trialeurodes vaporariorum (Hemiptera: Aleyrodidae)

Management of viral plant diseases can be improved by using models to predict disease spread. Potato yellow vein virus (PYVV) of the genus Crinivirus (Closteroviridae) is transmitted in a semi-persistent manner by the greenhouse whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). Although several approaches exist for modeling insect population growth, modeling vector-born virus spread remains difficult because fundamental knowledge on the relationship between virus transmission and temperature is lacking for most vector transmitted viruses. To address this challenge, we initially developed a temperature-dependent phenology model for the whitefly vector using the Insect Life Cycle Modeling (ILCYM) software. In the present study, the effect of temperature on the efficiency of virus transmission by the whitefly was determined through controlled laboratory experiments at 8 constant temperatures in the range from 10 to 25 °C. The vector capacity to transmit the virus was highest at 15 °C (about 70 % probability of infection) but decreased radically as temperature deviated from this optimum temperature to <10 % at temperatures of 10 and 20 °C, respectively. The temperature-dependent probability of virus transmission by a single adult whitefly could be described by a nonlinear function, which was validated by transmission frequencies observed at fluctuating temperatures. This function combined with life table parameters calculated from previously established temperature-dependent phenology model for the vector provided a full temperature-responsive model for predicting PYVV spread potential and transmission probabilities. For spatial risk predictions, we devised two virus transmission risk indexes and tested their performance in correctly predicting virus presence/absence with field survey data. The best performing risk index was used to generate risk maps, which reflected well the current (real) occurrence of the virus but also predicted areas at high risk, where the virus has not previously been reported. One of them in western Panama was targeted for surveillance and resulted in identification of the virus in the country, where it was not previously known to occur. Simulated risk maps for the year 2050 revealed that climate change may significantly affect, the risk of distribution, generally reducing in tropical areas of the world, but increasing in the temperate regions.

Transmission and host range of Horsegram yellow mosaic virus (HgYMV) causing common bean (Phaseolus vulgaris L.) yellowing disease in Sri Lanka

The common bean (Phaseolus vulgaris L.) yellowing disease (BYD) is caused by the Horsegram yellow mosaic virus (HgYMV), which is a begomovirus transmitted by whiteflies (Bemisia tabaci Genn.). It is a serious threat to the common bean cultivation in Sri Lanka. Despite the fact that the disease has been affecting bean production for a long time, its etiology and virus vector relationships are not understood well. Therefore, the present work was carried out to identify major aspects of the etiology of the virus. Initially a survey was conducted to determine the prevalence of the virus in representative bean growing locations in Sri Lanka, followed by a host range study using 54 plant species. Characteristics of virus-vector relationships were determined by conducting a series of virus transmission tests under glass-house conditions. The survey results revealed the incidence of BYD at some time or the other in most of the sampled localities, which are scattered around all four major districts where the common bean is grown. Through the host range study, it was demonstrated that Ageratum sp., Glycine max Merrill., Macrotyloma uniflorum (Lam.) Verdc., and Phaseolus lunatus L. are susceptible to HgYMV, indicating a narrow host range. In addition to the symptomatology, the successful entry of the virus following inoculation was confirmed through PCR using degenerate primers. Relative transmission efficiency was found to be 96.7 %, which corresponds to 0.24 of the estimated probability of transmission through a single whitefly (p*). The virus could be transmitted through probing by a single viruliferous whitefly with an incidence of 36.7 % (p* = 0.37). The minimum acquisition access period and inoculation access period were 20 min in each case and the respective disease incidence values were 30.0 % (p* = 0.04) and 36.7 % (p* = 0.05). The whiteflies could retain the virus in an active state for up to 9 days.

The first transcriptomes from field-collected individual whiteflies ( Bemisia tabaci, Hemiptera: Aleyrodidae):a case study of the endosymbiont composition.

Background:Bemisia tabaci species ( B. tabaci), or whiteflies, are the world's most devastating insect pests. They cause billions of dollars (US) of damage each year, and are leaving farmers in the developing world food insecure. Currently, all publically available transcriptome data for B. tabaci are generated from pooled samples, which can lead to high heterozygosity and skewed representation of the genetic diversity. The ability to extract enough RNA from a single whitefly has remained elusive due to their small size and technological limitations. Methods: In this study, we optimised a single whitefly RNA extraction procedure, and sequenced the transcriptome of four individual adult Sub-Saharan Africa 1 (SSA1) B. tabaci. Transcriptome sequencing resulted in 39-42 million raw reads. De novo assembly of trimmed reads yielded between 65,000-162,000 Contigs across B. tabaci transcriptomes. Results: Bayesian phylogenetic analysis of mitochondrion cytochrome I oxidase (mtCOI) grouped the four whiteflies within the SSA1 clade. BLASTn searches on the four transcriptomes identified five endosymbionts; the primary endosymbiont Portieraaleyrodidarum and four secondary endosymbionts: Arsenophonus, Wolbachia, Rickettsia, and Cardinium spp. that were predominant across all four SSA1 B. tabaci samples with prevalence levels of between 54.1 to 75%. Amino acid alignments of the NusG gene of P. aleyrodidarum for the SSA1 B. tabaci transcriptomes of samples WF2 and WF2b revealed an eleven amino acid residue deletion that was absent in samples WF1 and WF2a. Comparison of the protein structure of the NusG protein from P. aleyrodidarum in SSA1 with known NusG structures showed the deletion resulted in a shorter D loop. Conclusions: The use of field-collected specimens means time and money will be saved in future studies using single whitefly transcriptomes in monitoring vector and viral interactions. Our method is applicable to any small organism where RNA quantity has limited transcriptome studies.

The first transcriptomes from field-collected individual whiteflies ( Bemisia tabaci, Hemiptera: Aleyrodidae).

Background: Bemisia tabaci species ( B. tabaci), or whiteflies, are the world's most devastating insect pests. They cause billions of dollars (US) of damage each year, and are leaving farmers in the developing world food insecure. Currently, all publically available transcriptome data for B. tabaci are generated from pooled samples, which can lead to high heterozygosity and skewed representation of the genetic diversity. The ability to extract enough RNA from a single whitefly has remained elusive due to their small size and technological limitations. Methods: In this study, we optimised a single whitefly RNA extraction procedure, and sequenced the transcriptome of four individual adult Sub-Saharan Africa 1 (SSA1) B. tabaci. Transcriptome sequencing resulted in 39-42 million raw reads. De novo assembly of trimmed reads yielded between 65,000-162,000 Contigs across B. tabaci transcriptomes. Results: Bayesian phylogenetic analysis of mitochondrion cytochrome I oxidase (mtCOI) grouped the four whiteflies within the SSA1 clade. BLASTn searches on the four transcriptomes identified five endosymbionts; the primary endosymbiont Portiera aleyrodidarum and four secondary endosymbionts: Arsenophonus, Wolbachia, Rickettsia, and Cardinium spp. that were predominant across all four SSA1 B. tabaci samples with prevalence levels of between 54.1 to 75%. Amino acid alignments of the NusG gene of P. aleyrodidarum for the SSA1 B. tabaci transcriptomes of samples WF2 and WF2b revealed an eleven amino acid residue deletion that was absent in samples WF1 and WF2a. Comparison of the protein structure of the NusG protein from P. aleyrodidarum in SSA1 with known NusG structures showed the deletion resulted in a shorter D loop. Conclusions: The use of field-collected specimens means time and money will be saved in future studies using single whitefly transcriptomes in monitoring vector and viral interactions. Our method is applicable to any small organism where RNA quantity has limited transcriptome studies.

The first transcriptomes from field-collected individual whiteflies ( Bemisia tabaci, Hemiptera: Aleyrodidae): a case study of the endosymbiont composition

Background: Bemisia tabaci species ( B. tabaci), or whiteflies, are the world’s most devastating insect pests. They cause billions of dollars (US) of damage each year, and are leaving farmers in the developing world food insecure. Currently, all publically available transcriptome data for B. tabaci are generated from pooled samples, which can lead to high heterozygosity and skewed representation of the genetic diversity. The ability to extract enough RNA from a single whitefly has remained elusive due to their small size and technological limitations. Methods: In this study, we optimised a single whitefly RNA extraction procedure, and sequenced the transcriptome of four individual adult Sub-Saharan Africa 1 (SSA1) B. tabaci. Transcriptome sequencing resulted in 39-42 million raw reads. De novo assembly of trimmed reads yielded between 65,000-162,000 Contigs across B. tabaci transcriptomes. Results: Bayesian phylogenetic analysis of mitochondrion cytochrome I oxidase (mtCOI) grouped the four whiteflies within the SSA1 clade. BLASTn searches on the four transcriptomes identified five endosymbionts; the primary endosymbiont Portiera aleyrodidarum and four secondary endosymbionts: Arsenophonus, Wolbachia, Rickettsia, and Cardinium spp. that were predominant across all four SSA1 B. tabaci samples with prevalence levels of between 54.1 to 75%. Amino acid alignments of the NusG gene of P. aleyrodidarum for the SSA1 B. tabaci transcriptomes of samples WF2 and WF2b revealed an eleven amino acid residue deletion that was absent in samples WF1 and WF2a. Comparison of the protein structure of the NusG protein from P. aleyrodidarum in SSA1 with known NusG structures showed the deletion resulted in a shorter D loop. Conclusions: The use of field-collected specimens means time and money will be saved in future studies using single whitefly transcriptomes in monitoring vector and viral interactions. Our method is applicable to any small organism where RNA quantity has limited transcriptome studies.

The first transcriptomes from field-collected individual whiteflies (Bemisia tabaci, Hemiptera: Aleyrodidae)

Background: Bemisia tabaci species (B. tabaci), or whiteflies, are the world’s most devastating insect pests. They cause billions of dollars (US) of damage each year, and are leaving farmers in the developing world food insecure. Currently, all publically available transcriptome data for B. tabaci are generated from pooled samples, which can lead to high heterozygosity and skewed representation of the genetic diversity. The ability to extract enough RNA from a single whitefly has remained elusive due to their small size and technological limitations. Methods: In this study, we optimised the single whitefly RNA extraction procedure, and sequenced the transcriptome of four individual adult Sub-Saharan Africa (SSA1) B. tabaci. Transcriptome sequencing resulted in 39-42 million raw reads. De novo assembly of trimmed reads yielded between 65,000-162,000 transcripts across B. tabaci transcriptomes. Results: Bayesian phylogenetic analysis of mitochondrion cytochrome I oxidase (mtCOI) grouped the four whiteflies within the SSA1 clade. BLASTn searches on the four transcriptomes identified five endosymbionts; the primary endosymbiont Portiera aleyrodidarum and four secondary endosymbionts: Arsenophonus, Wolbachia, Rickettsia, and Cardinium spp. that were predominant across all four SSA1 B. tabaci samples with prevalence levels between 54.1-75%. Amino acid alignments of the NusG gene of P. aleyrodidarum for the SSA1 B. tabaci transcriptomes of samples WF2 and WF2b revealed an eleven amino acid residue deletion that was absent in samples WF1 and WF2a. Comparison of the protein structure of the NusG protein from P. aleyrodidarum in SSA1 with known NusG structures showed the deletion resulted in a shorter D loop. Conclusions: The use of field-collected specimens means time and money will be saved in future studies using single whitefly transcriptomes in monitoring vector and viral interactions. Our method is applicable to any small organism where RNA quantity has limited transcriptome studies.

Survey, symptomatology, transmission, host range and characterization of begomovirus associated with yellow mosaic disease of ridge gourd in southern India.

Ridge gourd is an important vegetable crop and is affected by several biotic and abiotic factors. Among the different biotic factors, ridge gourd yellow mosaic disease (RgYMD) is new emerging threat for the production of ridge gourd. The incidence of the RgYMD varied from 30 to 100% in southern India with highest disease incidence of 100% observed in Belagavi district of Karnataka state. The infected plants showed chlorosis, mosaic, cupping of leaves, blistering, reduction in leaf size and stunted growth. The varieties/hybrids grown in the farmer's fields were found to be susceptible to the disease. Begomovirus was detected in 61 out 64 samples collected from different areas of southern India. Further, all the samples failed to give amplification for beta and alpha satellites. The transmission studies revealed that single whitefly (Bemisia tabaci) is enough to transmit the virus, however, 100% transmission was observed with 10 whiteflies. The minimum acquisition access period and inoculation access period for transmission of virus by whitefly was 15min. Among the 56 host plants belonging to diversified families tested for host range, sponge gourd, ash gourd, bottle gourd, pumpkin, cucumber, summer squash, cluster bean, tobacco and datura were shown to be susceptible. Seventy six varieties/hybrids evaluated for identifying the resistance source for RgYMD, all were found highly susceptible. Sequence analysis of DNA-A revealed that the causal virus shared highest nucleotide sequence identity (92.3%) with Tomato leaf curl New Delhi virus (ToLCNDV) infecting sponge gourd from northern India. Sequence and phylogenetic analysis of both DNA-A and DNA-B components showed that the begomovirus associated with RgYMD is found to be strain of ToLCNDV. This is first report of ToLCNDV association with RgYMD from southern India.

Performance of Bemisia tabaci Biotype B on Soybean Genotypes.

Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) has been recognized as an important pest of many agricultural systems including soybean [Glycine max (L.) Merrill] crops. As an alternative to chemical control, the use of resistant genotypes represents an important tool for integrated pest management (IPM). This study aimed to evaluate the biological development of Bemisia tabaci biotype B confined on 13 soybean genotypes under greenhouse conditions. Initially, the nymphal period, complete development period (egg-adult), and the viability of the silverleaf whitefly nymphs were evaluated in all genotypes. Then, four genotypes promising for resistance ('Jackson,' UX-2569-159, 'P98Y11,' and 'TMG132 RR') and a susceptible genotype (PI-227687) were selected for further assays, where two insect populations were compared: a first population from the initial rearing (cabbage plants) and another corresponding to insects previously reared out on the selected genotypes. In addition to the parameters evaluated in preliminary tests, we also determined the viability and incubation period of eggs. Moderate levels of resistance (antibiosis/antixenosis) to B. tabaci biotype B were found in three genotypes. 'P98Y11' and 'TMG132 RR' were less suitable for insect development, extending the development cycle, and UX-2569-159 caused high nymphal mortality. We did not observe a significant increase in the level of plant resistance by the use of previously stressed insects. This suggests that the evaluation of a single whitefly generation may be sufficient to make correct decisions on promising soybean genotypes.

Survey of Natural Enemies of Whiteflies (Hemiptera: Aleyrodidae) in Egypt with New Local and World Records

ABSTRACT Whiteflies (Hemiptera: Aleyrodidae) are some of the most problematic global pests of agricultural crops. Yet, natural enemies help control whiteflies. A field survey was conducted to identify and record the natural enemies associated with whiteflies in Egypt. Fifty-two natural enemies (29 species of parasitoids, 8 species of pathogens, and 15 species of predators) were found attacking or isolated from 14 whitefly species in Egypt. New world records are reported herein for two parasitoids [Encarsia lutea Masi and Eretmocerus mundus (Mercet)] on eight species of whiteflies, and for three predators [Chilocorus bipustulatus L., Chrysoperla carnea (Stephens), and Coccinella septempunctata L.] on a single whitefly species [Siphoninus phillyreae (Haliday)]. In addition, new local records of natural enemies on whiteflies are reported; this is the first local report of six predators and three entomopathogenic fungi of whiteflies in Egypt. This work helps in defining the natural enemies of whiteflies in an...