MED Species Research Articles

Bemisia tabaci MEAM1 still remains the dominant species in open field crops in Brazil.

Among Bemisia tabaci species, the invasive MEAM1 and MED species are key agricultural pests for many crops. In Brazil, most part of B. tabaci population outbreaks were associated with MEAM1, which, since 1990s quickly spread across the entire country. Later in 2014, the MED was identified in Brazil, initially more restricted to greenhouses, but suddenly reaching new areas in the South and Southeast open regions. Thus, our objective was to investigate the geographical distribution of MEAM1 and MED on open field crops in Brazil. MEAM1 is still the predominant species on open field crops such as soybean, cotton, and tomato. The sequencing of a cytochrome c oxidase subunit I (COI) gene fragment revealed a single haplotype of MEAM1, suggesting the establishment of a single MEAM1 strain in the country. The haplotypes found for MEAM1 and MED are genetically related to the globally dispersed strains, Jap1 and Mch1, respectively. Continuous monitoring of B. tabaci species is crucial because landscape alterations, climatic changes, and pest management methods may shift the B. tabaci species distribution and dominance in Brazilian crop areas.

Evidence of the association between the Q2 mitochondrial group of Bemisia tabaci MED species (Hemiptera: Aleyrodidae) and low competitive displacement capability.

The whitefly, Bemisia tabaci (Gennadius), is one of the most serious agricultural pests worldwide. Bemisia tabaci is a cryptic species complex of more than 40 species among which the invasive MEAM1 and MED species are the most widespread and economically important. Both MEAM1 and MED present intraspecific genetic variability and some haplotypes are reported to be more invasive than others. MED can be further deconstructed into different genetic groups, including MED-Q1 and MED-Q2. However, distinct biological phenotypes discerning the different MED mitochondrial haplotypes are yet to be characterized. Competitive displacement and life-history trials were carried out between MED-Q2 and MEAM1 populations collected in Florida, USA. In addition, a phylogenetic analysis was carried out including populations from previous whitefly competitive displacement studies for identification and comparison of the MED mitochondrial groups. In contrast to other studies with MED-Q1, the MED-Q2 population from Florida is less likely to displace MEAM1 on pepper. In addition, both pepper and watermelon were a more favorable host to MEAM1 compared to MED-Q2 according to the life history trials.

Can Biological Traits Serve as Predictors for Fishes' Introductions, Establishment, and Interactions? The Mediterranean Sea as a Case Study.

The Mediterranean Sea (MED) is prone to species' introductions, induced by human activities and/or climate change. Recent studies focus on the biological traits that result in such introductions, yet on a single-area-type approach. Here, we used, analyzed, and compared biological traits derived from FishBase for MED, non-indigenous (NIS) and neonative (NEO) in the Mediterranean, and adjacent Atlantic (ATL) and Red Sea (RS) species. A quantitative trait-based analysis was performed using random forest to determine the importance of traits in the successful establishment in the Mediterranean. MED fishes were mainly demersal, slow growing and small-medium sized, preferring intermediate temperatures. Conversely, ATL were mainly deep-dwelling species, preferring low temperatures. RS and NIS were predominantly reef-associated, thermophilus, and stenothermic. NEO species were stenothermic with preference to intermediate-high temperatures. Omnivores with preference to animals was the most common trophic group among regions. MED species exhibited higher phylogenetic uniqueness (PD50) compared to RS and NIS, indicating that they have long ancestral branches and few descendants. Preferred temperature, habitat type preference and maximum reported length (Lmax) and infinite length (Linf) were the most important predictors in the establishment process. Overall, the results presented here could serve as a baseline for future research, especially by using more refined and/or additional biological trail estimates.

Population variation of Bemisia tabaci MED and MEAM1 species in an agricultural landscape: the case of Çukurova plain

Population variation of Bemisia tabaci MED and MEAM1 species in an agricultural landscape: the case of Çukurova plain

The Costs and Benefits of Two Secondary Symbionts in a Whitefly Host Shape Their Differential Prevalence in the Field.

Insects commonly harbor maternally inherited intracellular symbionts in nature, and the microbial partners often exert influence on host reproduction and fitness to promote their prevalence. Here, we investigated composition of symbionts and their biological effects in the invasive Bemisia tabaci MED species of a whitefly complex. Our field surveys revealed that populations of the MED whitefly, in addition to the primary symbiont Portiera, mainly contain two secondary symbionts Hamiltonella, which is nearly fixed in the host populations, and Cardinium with infection frequencies ranging from 0 to 86%. We isolated and established Cardinium-positive and Cardinium-free whitefly lines with a similar nuclear genetic background from a field population, and compared performance of the two whitefly lines. The infection of Cardinium incurred significant fitness costs on the MED whitefly, including reduction of fecundity and egg viability as well as delay in development. We then selectively removed Hamiltonella from the Cardinium-free whitefly line and compared performance of two whitefly lines, one harboring both Portiera and Hamiltonella and the other harboring only Portiera. While depletion of Hamiltonella had little or only marginal effects on the fecundity, developmental rate, and offspring survival, the Hamiltonella-free whitefly line produced very few female offspring, often reducing the progeny female ratio from about 50% to less than 1%. Our findings indicate that the varying costs and benefits of the association between these two symbionts and the MED whitefly may play an important role in shaping their differential prevalence in the field.

Identification and functional characterization of a novel acetyl-CoA carboxylase mutation associated with ketoenol resistance in Bemisia tabaci

Insecticides of the tetronic/tetramic acid family (cyclic ketoenols) are widely used to control sucking pests such as whiteflies, aphids and mites. They act as inhibitors of acetyl-CoA carboxylase (ACC), a key enzyme for lipid biosynthesis across taxa. While it is well documented that plant ACCs targeted by herbicides have developed resistance associated with mutations at the carboxyltransferase (CT) domain, resistance to ketoenols in invertebrate pests has been previously associated either with metabolic resistance or with non-validated candidate mutations in different ACC domains. A recent study revealed high levels of spiromesifen and spirotetramat resistance in Spanish field populations of the whitefly Bemisia tabaci that was not thought to be associated with metabolic resistance. We confirm the presence of high resistance levels (up to >640-fold) against ketoenol insecticides in both Spanish and Australian B. tabaci strains of the MED and MEAM1 species, respectively. RNAseq analysis revealed the presence of an ACC variant bearing a mutation that results in an amino acid substitution, A2083V, in a highly conserved region of the CT domain. F1 progeny resulting from reciprocal crosses between susceptible and resistant lines are almost fully resistant, suggesting an autosomal dominant mode of inheritance. In order to functionally investigate the contribution of this mutation and other candidate mutations previously reported in resistance phenotypes, we used CRISPR/Cas9 to generate genome modified Drosophila lines. Toxicity bioassays using multiple transgenic fly lines confirmed that A2083V causes high levels of resistance to commercial ketoenols. We therefore developed a pyrosequencing-based diagnostic assay to map the spread of the resistance alleles in field-collected samples from Spain. Our screening confirmed the presence of target-site resistance in numerous field-populations collected in Sevilla, Murcia and Almeria. This emphasizes the importance of implementing appropriate resistance management strategies to prevent or slow the spread of resistance through global whitefly populations.

Dominance of Bemisia tabaci MEAM1 species over MED (Hemiptera: Aleyrodidae) in greenhouse vegetables in Mersin, Turkey

In this study, using PCR-RFLP molecular identification methods, the species composition was determined in populations of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) which were collected from greenhouses located in the Akdeniz, Aydincik, Bozyazi, Erdemli, Gulnar, Silifke, and Tarsus districts of Mersin Province. For this purpose, adult whiteflies were collected from the greenhouses during the spring and autumn growing seasons of 2016 and 2017. In order to determine the species status in the off-season, samples were also collected from field crops around greenhouses during summer 2016. In all, 219, 195, and 129 females were analyzed from samples collected in spring, autumn, and off-seasons, respectively. According to the results of analysis, the species status of B. tabaci did not vary depending on location and season. Overall, MEAM1 and MED (with subgroups Q1 and Q2) species were found. The abundance rates of MEAM1 species were found to be very high in all locations, with values of 97.7% and 99.5% during spring and autumn, respectively. Similar to the greenhouse-collected populations, the MEAM1 species whiteflies collected from open field crops during the off-season were found to have a higher abundance rate (99.2%). The highest abundance rate for MED species (12.8%) was determined in Erdemli district during spring. The results of this study indicate that B. tabaci belonging to the MEAM1 is the most dominant species in greenhouses and open fields (off-season) of Mersin, Turkey, in both spring and autumn, and these results are also discussed aiming at contributing to B. tabaci management in greenhouses.

Outbreaks of Bemisia tabaci Mediterranean species in vegetable crops in São Paulo and Paraná States, Brazil.

The whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is one of the most important agricultural pests and virus vectors worldwide. Bemisia tabaci is considered a complex of cryptic species with at least 44 species. Among them, the species Middle East-Asia Minor 1 (MEAM1, formerly B biotype) and Mediterranean (MED, formerly Q biotype) are the most important, and they have attained global status. In Brazil, MEAM1 was first reported in the 1990s and is currently the predominant species in the country, meanwhile, MED was recently reported in the South and Southeast regions and was found to be mainly associated with ornamental plants. Currently, an increasing problem in the management of whitefly infestations in greenhouses associated with bell pepper was observed in São Paulo State, Brazil. The whiteflies were collected and identified based on a microsatellite locus (primer pair BEM23F and BEM23R) and the mitochondrial cytochrome oxidase I gene followed by restriction fragment length polymorphism analysis and sequencing. We observed that MED was the predominant species collected on bell pepper, but it was also found on tomato, cucumber, eggplant, and weeds grown in greenhouses. In open field, we found MED on tomatoes, bell peppers, and eggplants. In addition, MED was identified in Goiás State in association with ornamental plants. The begomovirus Tomato severe rugose virus and the crinivirus Tomato chlorosis virus was detected on bell pepper and tomato, respectively. Only MED specimens were found associated with the virus-infected plants. Moreover, we also investigated the endosymbionts present in the MED whiteflies. The collected populations of B. tabaci MED harbored a diversity of secondary endosymbionts, with Hamiltonella (H) found predominantly in 89 specimens of the 129 tested. These results represent a new concern for Brazilian agriculture, especially for the management of the newly introduced whitefly MED species, which must be implemented to limit the spreading and establishment of this pest in different crops in this country.

Abundance of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) and its parasitoids on vegetables and cassava plants in Burkina Faso (West Africa).

The whitefly Bemisia tabaci is a pest of many agricultural and ornamental crops worldwide and particularly in Africa. It is a complex of cryptic species, which is extremely polyphagous with hundreds of host plants identified around the world. Previous surveys in western Africa indicated the presence of two biotypes of the invasive MED species (MED‐Q1 and MED‐Q3) living in sympatry with the African species SSA and ASL. This situation constitutes one of the rare cases of local coexistence of various genetic entities within the B. tabaci complex. In order to study the dynamics of the distribution and abundance of genetic entities within this community and to identify potential factors that could contribute to coexistence, we sampled B. tabaci populations in Burkina Faso in 2015 and 2016 on various plants, and also their parasitoids. All four genetic entities were still recorded, indicating no exclusion of local species by the MED species. While B. tabaci individuals were found on 55 plant species belonging to eighteen (18) families showing the high polyphagy of this pest, some species/biotypes exhibited higher specificity. Two parasitoid species (Eretmocerus mundus and Encarsia vandrieschei) were also recorded with E. mundus being predominant in most localities and on most plants. Our data indicated that whitefly abundance, diversity, and rate of parasitism varied according to areas, plants, and years, but that parasitism rate was globally highly correlated with whitefly abundance suggesting density dependence. Our results also suggest dynamic variation in the local diversity of B. tabaci species/biotypes from 1 year to the other, specifically with MED‐Q1 and ASL species. This work provides relevant information on the nature of plant–B. tabaci‐parasitoid interactions in West Africa and identifies that coexistence might be stabilized by niche differentiation for some genetic entities. However, MED‐Q1 and ASL show extensive niche overlap, which could ultimately lead to competitive exclusion.

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

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

Genome-wide analyses of the Bemisia tabaci species complex reveal contrasting patterns of admixture and complex demographic histories.

Once considered a single species, the whitefly, Bemisia tabaci, is a complex of numerous morphologically indistinguishable species. Within the last three decades, two of its members (MED and MEAM1) have become some of the world's most damaging agricultural pests invading countries across Europe, Africa, Asia and the Americas and affecting a vast range of agriculturally important food and fiber crops through both feeding-related damage and the transmission of numerous plant viruses. For some time now, researchers have relied on a single mitochondrial gene and/or a handful of nuclear markers to study this species complex. Here, we move beyond this by using 38,041 genome-wide Single Nucleotide Polymorphisms, and show that the two invasive members of the complex are closely related species with signatures of introgression with a third species (IO). Gene flow patterns were traced between contemporary invasive populations within MED and MEAM1 species and these were best explained by recent international trade. These findings have profound implications for delineating the B. tabaci species status and will impact quarantine measures and future management strategies of this global pest.

Standardized molecular diagnostic tool for the identification of cryptic species within the Bemisia tabaci complex.

The whitefly Bemisia tabaci complex harbours over 40 cryptic species that have been placed in 11 phylogenetically distinct clades based on the molecular characterization of partial mitochondrial DNA COI (mtCOI) gene region. Four cryptic species are currently within the invasive clade, i.e. MED, MEAM1, MEAM2 and IO. Correct identification of these species is a critical step towards implementing reliable measures for plant biosecurity and border protection; however, no standardized B. tabaci-specific primers are currently available which has caused inconsistencies in the species identification processes. We report three sets of polymerase chain reaction (PCR) primers developed to amplify the mtCOI region which can be used for genotyping MED, MEAM1 and IO species, and tested these primers on 91 MED, 35 MEAM1 and five IO individuals. PCR and sequencing of amplicons identified a total of 21, six and one haplotypes in MED, MEAM1 and IO respectively, of which six haplotypes were new to the B. tabaci database. These primer pairs enabled standardization and robust molecular species identification via mtCOI screening of the targeted invasive cryptic species and will improve quarantine decisions. Use of this diagnostic tool could be extended to other species within the complex. © 2017 Society of Chemical Industry.

Molecular cloning, characterization and mRNA expression of a ryanodine receptor gene from whitefly, Bemisia tabaci MED

The Bemisia tabaci (Gennadius) cryptic species complex comprises very destructive insect pests for agricultural crops worldwide. In China, the B. tabaci MED species (also known as biotype ‘Q’), has supplanted the MEAM1 species (biotype ‘B’) which is threatening agricultural production around the country. The new anthranilic diamide insecticide, cyantraniliprole, provides one novel step for the management of B. tabaci and the development of resistance to other insecticides. Ryanodine receptors of insect are the main target sites of the diamide insecticides. In this study, the full-length cDNA of a ryanodine receptor gene (BtRyR) was cloned and characterized from B. tabaci MED. The cDNAs of BtRyR contain a 15,369-bp open reading frame with encoding 5122 amino acids (GenBank ID: KY244091). BtRyR shares 76–83% identity with other insect RyR isoforms and 42–45% identity with vertebrate RyR isoforms. Spatial and temporal expression of BtRyR mRNA was at the highest relative level in pseudopupae and head, and at the lowest expression level in egg and abdomen. The expression levels of whole body BtRyR mRNA were increased remarkably after insecticide-treatments of adults with cyantraniliprole at 0.01 to 1mg/l. This structural and expression data on BtRyR provides the basis for further understanding the selective action of cyantraniliprole.

Lethal and sublethal effects of cyantraniliprole, a new anthranilic diamide insecticide, on Bemisia tabaci (Hemiptera: Aleyrodidae) MED

The Bemisia tabaci (Gennadius) cryptic species complex comprises important insect pests that cause devastating damage to agricultural crops worldwide. In China, the B. tabaci MED species, formerly known as biotype ‘Q’, has surpassed the MEAM1 species, formerly known as biotype ‘B’, which is threatening agricultural production all over the country as an increasing number of resistance cases have been reported. This situation highlights the need for alternative pest control measures. In this study, the lethal effects of six neonicotinoid and two anthranilic diamide insecticides including the novel compound cyantraniliprole on B. tabaci MED were examined. The sublethal effects of cyantraniliprole on the physiology and behavior of B. tabaci MED were also assessed. Among eight insecticides tested, cyantraniliprole was the most toxic to B. tabaci MED with a LC50 of 2.05 mg/L. The sublethal effects of cyantraniliprole to adult B. tabaci MED were observed at LC10 (0.22 mg/L) and LC25 (0.63 mg/L) concentrations. At these concentrations, cyantraniliprole prolonged the developmental duration and decreased the survival rate of nymph stages, pseudopupae and adults. The oviposition duration and fecundity of females were also reduced significantly. The hatching rate of eggs laid by females exposed to LC10 and LC25 concentrations was also reduced. Altogether, these results demonstrate that cyantraniliprole could be an alternative insecticide for efficient control of B. tabaci MED populations in China.

Evaluation of tomato entries with different combinations of resistance genes to tomato yellow leaf curl disease in Tunisia

AbstractTomato yellow leaf curl virus (TYLCV) is one of the most widespread begomoviruses transmitted by the whitefly Bemisia tabaci that cause tomato yellow leaf curl virus diseases (TYLCDs). TYLCD losses can be especially severe in open‐field tomato (Solanum lycopersicum L.) crops. TYLCV is particularly well known and widespread in the Mediterranean (Med) countries where TYLCD control is mostly based on insecticidal control of B. tabaci populations. Unfortunately, Tunisian B. tabaci populations include Middle East‐Asia Minor I and the Med species that have developed resistance to many classes of insecticides. Therefore, TYLCD‐resistant cultivars are essential for sustainable disease management. Six TYLCD resistance genes (Ty) have been introgressed from wild species into cultivated tomato and are available for breeding. Information on the Ty genes or gene combinations is useful for breeding resistant cultivars. To this end, 14 tomato lines carrying different Ty gene combinations and two susceptible tomato entries were evaluated for TYLCD incidence and severity in two field trials during late season in Tunisia. Entries with Ty‐1/Ty‐3 + Ty‐2 offered the highest levels of resistance in Tunisia.

Lethal and sublethal effects of a novel cis-nitromethylene neonicotinoid insecticide, cycloxaprid, on Bemisia tabaci

The tobacco whitefly, Bemisia tabaci (Gennadius), is an important pest because of its potential to threaten agricultural crops worldwide. Currently, this pest is controlled by the application of chemical insecticides. In our pursuit to identify better insecticides for an effective control of this insect pest, we investigated the lethal effects of five neonicotinoid insecticides including four commercial neonicotinoids and a novel neonicotinoid (cycloxaprid) on B. tabaci MED and MEAM1 cryptic species. In addition, we assessed the sublethal effects of cycloxaprid on B. tabaci MED. Lethal effects of the insecticides were determined using the leaf-dip bioassay, and the results showed that among the tested insecticides cycloxaprid was more toxic to B. tabaci MED and MEAM1 than others, with LC50 values of 0.70 mg/L and 0.59 mg/L, respectively. Cycloxaprid at LC25 (0.16 mg/L) induced sublethal effects in adult MED by prolonging the developmental periods and decreasing the survival rates of all larval instars, pseudopupal and adult stages. Moreover, it significantly shortened the oviposition period of females and decreased their fecundity. Hatching rate of eggs laid by females exposed to LC25 was also markedly reduced. These results indicate that cycloxaprid is a novel alternate insecticide that may effectively control B. tabaci populations.

Only a minority of broad-range detoxification genes respond to a variety of phytotoxins in generalist Bemisia tabaci species.

Generalist insect can utilize two different modes for regulating their detoxification genes, the constitutive mode and the induced mode. Here, we used the Bemisia tabaci sibling species MEAM1 and MED, as a model system for studying constitutive and induced detoxification resistance and their associated tradeoffs. B. tabaci adults were allowed to feed through membranes for 24 h on diet containing only sucrose or sucrose with various phytotoxins. Quantitative real-time PCR analyses of 18 detoxification genes, indicated that relatively few transcripts were changed in both the MEAM1 and MED species, in response to the addition of phytotoxins to the diet. Induced transcription of detoxification genes only in the MED species, in response to the presence of indole-3-carbinol in the insect’s diet, was correlated with maintenance of reproductive performance in comparison to significant reduction in performance of the MEAM1 species. Three genes, COE2, CYP6-like 5 and BtGST2, responded to more than one compound and were highly transcribed in the insect gut. Furthermore, functional assays showed that the BtGST2 gene encodes a protein capable of interacting with both flavonoids and glucosinolates. In conclusion, several detoxification genes were identified that could potentially be involved in the adaptation of B. tabaci to its host plants.

First report of the Sub-Saharan Africa 2 species of the Bemisia tabaci complex in the Southern France

An extensive survey was conducted in the major crop producing regions of France, Spain, Greece, Tunisia and Morocco from 2003 to 2010, to determine the geographical distribution of the Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) complex in the Mediterranean basin. Based on diagnostic and highly discriminatory molecular markers (mitochondrial cytochrome oxidase I, COI, gene sequences and nuclear microsatellites) and multiple complementary genetic diagnostic approaches including population assignment and phylogenetic reconstruction, the two worldwide invasive members of the complex, Med and MEAM1 species, were shown to be present, with Med being the most prevalent. In addition, the sub-Saharan Africa 2 (SSA2) species was, for the first time, reported in Southern France in 2007 on soybean and nightshade either alone or in sympatry with B. tabaci populations of the middle-eastern Mediterranean group (i.e., Q2 Med). This first occurrence of SSA2 in France, although detected in a relatively small area illustrates the capacity of multiple members of the B. tabaci complex to invade new regions, and emphasizes the possible risk caused by the entry of a new species, such as the SSA2 species, in the Mediterranean area.

Salicylic acid is required for Mi-1-mediated resistance of tomato to whitefly Bemisia tabaci, but not for basal defense to this insect pest.

Plant defense to pests or pathogens involves global changes in gene expression mediated by multiple signaling pathways. A role for the salicylic acid (SA) signaling pathway in Mi-1-mediated resistance of tomato (Solanum lycopersicum) to aphids was previously identified and its implication in the resistance to root-knot nematodes is controversial, but the importance of SA in basal and Mi-1-mediated resistance of tomato to whitefly Bemisia tabaci had not been determined. SA levels were measured before and after B. tabaci infestation in susceptible and resistant Mi-1-containing tomatoes, and in plants with the NahG bacterial transgene. Tomato plants of the same genotypes were also screened with B. tabaci (MEAM1 and MED species, before known as B and Q biotypes, respectively). The SA content in all tomato genotypes transiently increased after infestation with B. tabaci albeit at variable levels. Whitefly fecundity or infestation rates on susceptible Moneymaker were not significantly affected by the expression of NahG gene, but the Mi-1-mediated resistance to B. tabaci was lost in VFN NahG plants. Results indicated that whiteflies induce both SA and jasmonic acid accumulation in tomato. However, SA has no role in basal defense of tomato against B. tabaci. In contrast, SA is an important component of the Mi-1-mediated resistance to B. tabaci in tomato.

A multiple PCR-LDR assay for identification of two invasive cryptic species of whiteflies Bemisia tabaci

The MEAM1 and MED species of the cryptic species complex Bemisia tabaci are important invasive pests that cause tremendous crop losses worldwide. A rapid and highly reliable molecular technique is necessary to identify these species because they are morphologically indistinguishable. Therefore, a multiple polymerase chain reaction coupled with a ligase detection reaction (PCR-LDR) that was based on polymorphisms in the mitochondrial cytochrome oxidase I (mtCOI) gene of B. tabaci was developed to distinguish the two cryptic species. An assessment of the method indicated that PCR-LDR provided high specificity and sensitivity in discriminating MEAM1 (SHB) and MED (SHQ) whiteflies. In field tests, PCR-LDR genotyping was performed in one 96-well plate to identify 93 individuals collected from 8 districts in the suburbs of Shanghai. Complete concordance was observed between PCR-LDR and sequencing methods. The method was used to confirm that MEAM1 and MED were found in two districts, but only the MED was found in the other six districts. PCR-LDR, which is a transplantable platform, provides an alternative method for species identification of B. tabaci at low cost.