Tabaci Genetic Groups Research Articles

A new record of Asia II 5 genetic group of Bemisia tabaci (Gennadius) in the major potato growing areas of India and its relationship with tomato leaf curl New Delhi virus infecting potato.

The whitefly, Bemisia tabaci (Gennadius), is responsible for significant yield losses in many crops, including potato, by sucking the phloem sap and transmitting a number of plant viruses. B. tabaci is a complex of cryptic species which is commonly designated as genetic groups. The B. tabaci genetic groups differ biologically with respect to host plant preference, insecticidal resistance, reproduction capacity, and ability to transmit begomoviruses. Therefore, understanding genetic variation among populations is important for establishing crop-specific distribution profile and management. We sequenced the mitochondrial cytochrome oxidase I (mtCOI) gene of B. tabaci collected from major potato growing areas of India. BLAST analysis of the 24 mtCOI sequences with reference Gene Bank sequences revealed four B. tabaci genetic groups prevailing in this region. mtCOI analysis exhibited the presence of Asia II 1, Asia II 5, Asia 1, and MEAM1 B. tabaci genetic groups. Our study highlighted that a new genetic group Asia II 5 has been detected in Indo-Gangetic Plains. Further virus-vector relationship study of ToLCNDV with Asia II 5 B. tabaci revealed that females are efficient vector of this virus as compared to males. This behavior of females might be due to their ability to acquire more virus titer than males. This study will help in better understanding of whitefly genetic group mediated virus diseases.

Genetic Diversity of Mitochondrial DNA of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Associated with Cassava and the Occurrence of Cassava Mosaic Disease in Zambia.

Simple SummaryBemisia tabaci is an important vector that transmits cassava brown streak viruses and cassava mosaic begomoviruses that cause cassava brown streak and cassava mosaic diseases, respectively. In 2013 and 2015 we carried out a study to determine the genetic variability within the Bemisia tabaci complex associated with cassava in Zambia. This investigation made use of mitochondrial cytochrome oxidase I gene sequences of samples collected from selected provinces of Zambia. We found three population subgroups (SGs): SSA1-SG1, SSA1-SG2 and SSA1-SG3 within the sub-Saharan Africa 1 (SSA1) genetic group. Whitefly abundance and the incidence of cassava mosaic disease were both greatest in Western Province, in which the SSA1-SG1 subgroup predominated. Establishing which genetic groups and populations of the B. tabaci species complex are associated with cassava mosaic disease and their distribution in the country is key to guiding the strategic deployment of resources to monitor disease spread and ensure food security for millions of cassava-dependent households.Bemisia tabaci is an important vector of cassava brown streak viruses and cassava mosaic begomoviruses, the causal agents of cassava brown streak disease and cassava mosaic disease (CMD), respectively. A study was carried out to determine the genetic variability of B. tabaci associated with cassava and the occurrence of CMD in Zambia in 2013 and 2015. Phylogenetic analysis showed the presence of only the sub-Saharan Africa 1 (SSA1) genetic group in Zambia. The SSA1 population had three population subgroups (SGs): SSA1-SG1, SSA1-SG2 and SSA1-SG3. All three SSA1 population subgroups occurred in Western Province. However, only SSA1-SG3 occurred in Eastern Province, while only SSA1-SG1 occurred in North Western and Luapula Provinces. Adult B. tabaci were most abundant in Western Province in 2013 (11.1/plant) and 2015 (10.8/plant), and least abundant (0.2/plant) in Northern Province in both 2013 and 2015. CMD was prevalent in all seven provinces surveyed, with the highest incidence recorded in Lusaka Province in both 2013 (78%) and 2015 (83.6%), and the lowest in Northern Province in both 2013 (26.6%) and 2015 (29.3%). Although SSA1-SG1 occurred at greater abundances than the other subgroups, there was no direct association demonstrated between whitefly subgroup and incidence of CMD. Establishing which B. tabaci genetic groups and populations are associated with CMD and their distribution in the country is a key factor in guiding the development of CMD control strategies for cassava-dependent households.

Kinetics of-Amylase activity in Asia-I and Asia II-1 Genetic groups of Whitefly, Bemisia Tabaci (Hemiptera: Aleyrodidae)

Whitefly, Bemisia tabaci (Gennadius.) has drawn global attention in recent past with its wide distribution across the world as it causes severe damage to crops directly by sucking the plant sap and indirectly as vector of several viral diseases. This pest is considered as a species complex and Asia represents the largest diversity with the distribution of about 16 out of 35 genetic groups recorded so far. Investigations were carried out on kinetics of a key digestive enzyme, a-amylase in adults of isogenic female lines of B. tabaci genetic groups Asia I and Asia II-1. Asia I has shown the higher specific activity of 0.267±0.007 μmol/ml/mg compared to that of 0.209±0.009 μmol/ml/mg in Asia II-1. However, kinetics of a-amylases revealed the high affinity of this enzyme in Asia II-1 with the least Km value of 0.03372±0.001 compared to that of 0.0353 ±0.002 in Asia I genetic group. Highest enzyme activities were recorded at 35° C in both the genetic groups of B. tabaci. Kinetics study of metabolically important digestive enzymes would improve our understanding on the metabolic capabilities of B. tabaci species complex.

Estimation of sugars and volatiles in the Honeydew of Bemisia tabaci genetic groups Meam-I and Asia-I

Bemisia tabaci (Gennadius) is a species complex, affecting wide varieties of crops globally, mainly a dreaded vector of Gemini viruses. It also causes extensive damage as a pest through direct feeding on the phloem sap and impacting crop yield by excreting copious amounts of honeydew. Sugars of honeydew serve as an excellent source for predators and parasitoids in pursuing their prey. In addition, the volatiles emitted by microbes in the honeydew are reported to attract the natural enemies of sucking pests. In the present study, an attempt was made to estimate sugars and identify volatiles in the honeydew of B. tabaci genetic groups viz; MEAM-I and Asia-I. HPLC analysis revealed that ribose sugar was highest in both phloem sap and honeydews followed by glucose, sucrose, and fructose. GC-MS result revealed volatiles, n-nonane, n-decane, 2-methyldecane, o-cymene benzene, n-undecane, propyl disulfide, n-dodecane, disulfide, bis (1-methylpropyl) are common in B. tabaci genetic groups.

Prevalence of a New Genetic Group, MEAM-K, of the WhiteflyBemisia tabaci(Hemiptera: Aleyrodidae) in Karnataka, India, as Evident frommtCOISequences

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is an economically important agricultural pest globally that costs growers billions of dollars to control. Given the pest status of B. tabaci and its propensity for invasiveness, a detailed work to resolve the prevalence of B. tabaci genetic groups is warranted. Hence, we analyzed mitochondrial cytochrome oxidase I sequences from 71 samples of B. tabaci to determine the prevalence of genetic groups on various host plants in India. Results revealed the prevalence of the 4 previously existing genetic groups, namely Asia-I, Asia-II-7, Asia-II-8, and Middle East Asia Minor-1 (MEAM-1), and of a new group called Middle East Asia Minor-K, which is genetically close (92.6%) to MEAM-1.

Abundance, diversity and geographic distribution of cassava mosaic disease pandemic‐associated Bemisia tabaci in Tanzania

AbstractBemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), one of the most economically important agricultural pests worldwide, is the vector of cassava mosaic geminiviruses that cause cassava mosaic disease (CMD). In East and Central Africa, a severe CMD pandemic that spread from Uganda in the late 1980s still continues to devastate cassava crops. To assess the association of distinct B. tabaci genetic groups with the CMD pandemic, mitochondrial cytochrome oxidase I gene sequences were analysed from whiteflies collected during surveys conducted from 2010 to 2013 in Tanzania. Four genetic groups – Sub‐Saharan Africa 1 (SSA1), Mediterranean, Indian Ocean and East Africa 1, and a group of unknown whitefly species were identified. SSA1 comprised four subgroups: SSA1‐SG1, SSA1‐SG2, SSA1‐SG1/2 and SSA1‐SG3. SSA1‐SG1 was confined to the pandemic‐affected north‐western parts of Tanzania whilst SSA1‐SG2 and SSA1‐SG3 were found in the central and eastern parts not yet affected by the pandemic. The CMD pandemic front was estimated to lie in Geita Region, north‐western Tanzania, and to be spreading south‐east at a rate of ca 26 km/year. The pandemic‐associated B. tabaci SSA1‐SG1 predominated up to 180 km ahead of the CMD front indicating that changes in whitefly population characteristics precede changes in disease characteristics.

Multiple Gene Markers to Understand Genetic Diversity in theBemisia tabaci(Hemiptera: Aleyrodidae) Species Complex

Abstract The analysis of sequence variation in the mitochondrial and ribosomal regions has been shown to provide an efficient method for the identification of species in a wide range of animal taxa. In order to assess its effectiveness in the discrimination of genetic groups of Bemisia tabaci (Gennadius) species complex, populations from ten cotton cultivars were analyzed. MtCOI, and ITS1 sequences were evaluated to find out the genetic diversity through phylogenetic methods, viz., maximum likelihood and network neighbor-net analysis. Analysis of mtCOI-1 or barcoding region did not reveal significant variation. On the contrary, the mtCOI-II region revealed the presence of three B. tabaci genetic groups or subgroups corresponded with the global data. However, the ITS1 region could not discriminate these groups of the species complex. Our results indicate that more than the barcoding and ITS1 regions, mtCOI-II region or 3′ end of the gene will be more appropriate for the identification of variations among t...

Diversity and localization of bacterial symbionts in three whitefly species (Hemiptera: Aleyrodidae) from the east coast of the Adriatic Sea

Several whitefly species (Hemiptera: Aleyrodidae) are cosmopolitan phloem-feeders that cause serious damage in numerous agricultural crops. All whitefly species harbor a primary bacterial symbiont and a diverse array of secondary symbionts which may influence several aspects of the insect's biology. We surveyed infections by secondary symbionts in Bemisia tabaci (Gennadius), Trialeurodes vaporariorum (Westwood) and Siphoninus phillyreae (Haliday) from areas in the east cost of the Adriatic Sea. Both the Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) B. tabaci genetic groups were detected in Montenegro, whereas only the MED was confirmed in Croatia. Trialeurodes vaporariorum and S. phillyreae were found in all areas surveyed. MEAM1 and MED exhibited similarity to previously reported infections, while populations of T. vaporariorum from Montenegro harbored Rickettsia, Wolbachia and Cardinium in addition to previously reported Hamiltonella and Arsenopnohus. Siphoninus phillyreae harbored Hamiltonella, Wolbachia, Cardinium and Arsenophonus, with the latter appearing in two alleles. Multiple infections of all symbionts were common in the three insect species tested, with some reaching near fixation. Florescent in situ hybridization showed new localization patterns for Hamiltonella in S. phillyreae, and the morphology of the bacteriosome differed from that observed in other whitefly species. Our results show new infections with bacterial symbionts in the whitefly species studied. Infections with the same symbionts in reproductively isolated whitefly species confirm complex relationships between whiteflies and bacterial symbionts, and suggest possible horizontal transfer of some of these bacteria.

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.

Bemisia tabaci Phylogenetic Groups in India and the Relative Transmission Efficacy of Tomato leaf curl Bangalore virus by an Indigenous and an Exotic Population

Bemisia tabaci adults from various host-plant species were collected from 31 regions across India. 266 B. tabaci samples were first screened by RAPD-PCR to examine molecular variability and to select individuals with different fingerprints. Host-plant and region of collection were then used to select 25 individuals for PCR amplification and sequencing of their partial mitochondrial cytochrome oxidase subunit one (mtCOI) genes. Pairwise comparisons with mtCOI consensus sequences showed that the majority of these samples had <3.5% sequence divergence from groups currently termed Asia I, Asia II-5, Asia II-7, and Asia II-8. The biotype-B B. tabaci from India clustered into the Middle East-Asia Minor 1 group. A new group of B. tabaci from Coimbatore, collected from pumpkin, was related most closely to the Asia I group (6.2% sequence divergence from the consensus Asia I sequence). To increase our understanding of the epidemiology of tomato leaf curl disease (ToLCD) and the key B. tabaci genetic groups involved in virus spread, the indigenous Asia I and the exotic biotype-B population from South India were used to carry out transmission experiments using Tomato leaf curl Bangalore virus (ToLCBV). The acquisition access periods (AAP), inoculation access periods (IAP), latent periods (LP), and ToLCBV transmission efficiencies of the two populations were compared and the biotype-B had the more efficient transmission characteristics. These results are discussed in relation to recent changes in the epidemiology of tomato leaf curl disease in South India.

Evidence of diversity and recombination in Arsenophonus symbionts of the Bemisia tabaci species complex

BackgroundMaternally inherited bacterial symbionts infecting arthropods have major implications on host ecology and evolution. Among them, the genus Arsenophonus is particularly characterized by a large host spectrum and a wide range of symbiotic relationships (from mutualism to parasitism), making it a good model to study the evolution of host-symbiont associations. However, few data are available on the diversity and distribution of Arsenophonus within host lineages. Here, we propose a survey on Arsenophonus diversity in whitefly species (Hemiptera), in particular the Bemisia tabaci species complex. This polyphagous insect pest is composed of genetic groups that differ in many ecological aspects. They harbor specific bacterial communities, among them several lineages of Arsenophonus, enabling a study of the evolutionary history of these bacteria at a fine host taxonomic level, in association to host geographical range and ecology.ResultsAmong 152 individuals, our analysis identified 19 allelic profiles and 6 phylogenetic groups, demonstrating this bacterium's high diversity. These groups, based on Arsenophonus phylogeny, correlated with B. tabaci genetic groups with two exceptions reflecting horizontal transfers. None of three genes analyzed provided evidence of intragenic recombination, but intergenic recombination events were detected. A mutation inducing a STOP codon on one gene in a strain infecting one B. tabaci genetic group was also found. Phylogenetic analyses of the three concatenated loci revealed the existence of two clades of Arsenophonus. One, composed of strains found in other Hemiptera, could be the ancestral clade in whiteflies. The other, which regroups strains found in Hymenoptera and Diptera, may have been acquired more recently by whiteflies through lateral transfers.ConclusionsThis analysis of the genus Arsenophonus revealed a diversity within the B. tabaci species complex which resembles that reported on the larger scale of insect taxonomy. We also provide evidence for recombination events within the Arsenophonus genome and horizontal transmission of strains among insect taxa. This work provides further insight into the evolution of the Arsenophonus genome, the infection dynamics of this bacterium and its influence on its insect host's ecology.

Prevalence of Wolbachia Supergroups A and B in Bemisia tabaci (Hemiptera: Aleyrodidae) and Some of Its Natural Enemies

Wolbachia, a bacterial symbiont, is maternally transmitted in arthropods and nematodes. We report a systematic survey of Wolbachia taxonomy in the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), and in some of its natural enemies. For the first time, Wolbachia infections in B. tabaci are correlated with various whitefly genetic groups, host plants, and natural enemies as well as with geographical regions. Polymerase chain reaction using 16S rDNA and fisZ genes revealed two Wolbachia supergroups, A and B, exist as single or double infections in B. tabaci as well as in some of its aphelinid parasitoids and predatory beetles. Approximately 89% of B. tabaci sampled were infected by Wolbachia, among which 34% were infected by A, 51% were infected by B, and 5% were infected by both A and B supergroups. These infection frequencies differed among B. tabaci genetic groups and locations. The invasive B. tabaci genetic group from the Middle East Asia Minor 1 (also referred as B biotype) and Mediterranean (also referred as Q biotype) was more likely to harbor A than B, whereas native genetic groups in AsiaI and AsiaII were more likely to harbor B than A. Although 60% of aphelinid parasitoids and 72% of coccinellid beetles also were infected by Wolbachia, they were more likely to host B than A. Furthermore, for the first time we report Wolbachia in B biotype from specimens collected outside of China. Construction of a phylogenetic tree clearly indicated that the Wolbachia sequences from different genetic groups of B. tabaci were not only similar to each other but also to sequences from beetles and parasitoids, which may provide evidence of coevolution and horizontal transmission of Wolbachia populations.

Molecular detection and identification of Rickettsia endosymbiont in different biotypes of Bemisia tabaci

Although Rickettsia are the causative agents of several human and animal diseases, they are also found as endosymbionts of many invertebrates. Such symbionts maintain intimate relationships with their hosts and share common features, including intracellular localisation, maternal inheritance, and ability to influence a wide range of host traits. Others, such as Wolbachia, a genus related to Rickettsia, are known to manipulate arthropod reproduction. These abilities to manipulate the host’s reproduction in their favour allow these bacteria to reach high prevalences, even fixation, within the host population, even though some of these symbionts may also harm the host, e.g., via a lessened life span [1]. Some members of R. bellii group are known to be vertically transmitted with induction of reproductive distortions in several insect species [2]. Conversely, hostspecific pathogenic Rickettsia of the spotted fever and typhus groups are easily transmitted between their ticks and lice vectors to the vertebrate host with unknown effect on host vectors. This suggests evolutionary transition between different life styles, including transmission modes, beneficial or deleterious effects, manipulation of host reproduction, acquisition of new host species, evolution and emergence of vertebrate pathogenecity. To date, the way the different characteristics of Rickettsia have evolved remains unknown but this requires the analysis of different host-bacteria associations. In the framework of a study on the symbiotic bacterial community associated with the major worldwide insect pest Bemisia tabaci, we characterised Rickettsia and other bacterial endosymbionts in different whitefly populations. B. tabaci is a species complex consisting of several genetic groups, among which are the closely related invasive B and Q biotypes. These biotypes are morphologically identical but differ in some important economic traits, such as insecticide resistance, and they are mostly recognised on mitochondrial CO1 gene sequences [3]. The Q biotype is divided into three genetic subgroups named Q1, Q2 and Q3 (or AfricaSL). All individuals harbour an obligatory symbiont and up to six different facultative bacteria, among which is a recently described Rickettsia spp. [4]. Here we establish the phylogenetic position of Rickettsia infecting B. tabaci and analyse correlation between bacterial distribution and variability with B. tabaci genetic groups to analyse the evolutionary history of the association.

Global relationships of Bemisia tabaci (Hemiptera: Aleyrodidae) revealed using Bayesian analysis of mitochondrial COI DNA sequences

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a species complex that is one of the most devastating agricultural pests worldwide and affects a broad range of food, fiber and ornamental crops. Unfortunately, using parsimony and neighbor joining methods, global phylogenetic relationships of the major races/biotypes of B. tabaci remain unresolved. Aside from the limitations of these methods, phylogenetic analyses have been limited to only small subsets of the global collection of B. tabaci, and thus limited taxon sampling has confounded the analyses. To improve our understanding of global B. tabaci phylogenetic relationships, a Bayesian phylogenetic technique was utilized to elucidate the relationships among all COI DNA sequence data available in GenBank for B. tabaci worldwide (366 specimens). As a result, the first well-resolved phylogeny for the B. tabaci species complex was produced showing 12 major well-resolved (0.70 posterior probability or above) genetic groups: B. tabaci (Mediterranean/Asia Minor/Africa), B. tabaci (Mediterranean), B. tabaci (Indian Ocean), B. tabaci (sub-Saharan Africa silverleafing), B. tabaci (Asia I), B. tabaci (Australia), B. tabaci (China), B. tabaci (Asia II), B. tabaci (Italy), B. tabaci (New World), B. tabaci (sub-Saharan Africa non-silverleafing) and B. tabaci (Uganda sweet potato). Further analysis of this phylogeny shows a close relationship of the New World B. tabaci with Asian biotypes, and characteristics of the major sub-Saharan Africa non-silverleafing clade strongly supports an African origin of B. tabaci due to its position at the base of the global phylogeny, and the diversity of well-resolved sub-clades within this group. Bayesian re-analyses of B. tabaci ITS, COI, and a combined dataset from a previous study resulted in seven major well-resolved races with high posterior probabilities, also showing the utility of the Bayesian method. Relationships of the 12 major B. tabaci genetic groups are discussed herein.