Middle East-Asia Minor 1 Research Articles

Characterization and analysis of myosin gene family in the whitefly (<i>Bemisia tabaci</i>)

<abstract> <p>Myosin is an actin-based motor protein that widely exists in muscle tissue and non-muscle tissue, and myosin of a diverse subfamily has obvious differences in structure and cell function. Many eukaryotes and even some unicellular organisms possess a variety of myosins. They have been well characterized in human, fungi and other organisms. However, the myosin gene family in <italic>Bemisia tabaci</italic> MEAM1 (Middle East-Asia Minor1 species) is poorly studied. In the study, we identified 15 myosin genes in <italic>B. tabaci</italic> MEAM1 based on a genome database. Myosin genes can be divided into ten classes, including subfamilies I, II, III, V, VI, VII, IX, XV, XVIII, XX in <italic>B. tabaci</italic> MEAM1. The amounts of myosin in Class I are the largest of the isoforms. Expression profiling of myosins by quantitative real-time PCR revealed that their expression differed among developmental stages and different tissues of <italic>B. tabaci</italic> MEAM1. The diversely may be related to the development characteristics of <italic>B. tabaci</italic> MEAM1. The <italic>BtaMyo-IIIb-like X1</italic> was highly expressed in nymphs 4 instar which may be related to the development process before metamorphosis. Our outcome contributes to the basis for further research on myosin gene function in <italic>B. tabaci</italic> MEAM1 and homologous myosins in other biology.</p> </abstract>

Ecological niche complexity of invasive and native cryptic species of the Bemisia tabaci species complex in China

Bemisia tabaci is an important pest affecting agricultural and horticultural crops worldwide and comprises a complex of cryptic species. In China, the introduction of the two invasive cryptic species, Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED), has considerably affected the ecological niche of the native cryptic species. Based on occurrence records obtained through field surveys and high-resolution environmental data, using maximum entropy modelling, we established ecological niche models to predict the distribution of invasive and native cryptic species of B. tabaci in China and identified the differences in ecological niches. The results showed that the distribution range and niche breadth of the invasive cryptic species exceed that of the native cryptic species in the order of MED > MEAM1 > China1 > Asia1. There are different degrees of niche overlap and range overlap between cryptic species. Moreover, the important environmental variables affecting their distribution were different, as well as their response and adaptation to most environmental variables. Our results suggest that the B. tabaci species complex occupies a complex ecological niche in China. The findings improve our understanding of the ecological characteristics of B. tabaci species complex, which will be useful in the development of prevention and control strategies for this pest in China.

Nuances of Whitefly Vector-Crinivirus Interactions Revealed in the Foregut Retention and Transmission of Lettuce Chlorosis Virus by Two Bemisia tabaci Cryptic Species.

Lettuce infectious yellows virus is the first crinivirus for which the retention of purified virions ingested into the whitefly (Bemisia tabaci New World (NW)) vector’s foregut, has been demonstrated to be a requisite for successful virus transmission. This key finding supports the hypothesis that the determinant of foregut retention and transmission is present on the virion itself. However, whether this is also true for other criniviruses has not been established. Here, we provide evidence that lettuce chlorosis virus (LCV) acquired from plants is retained in the foreguts of both the B. tabaci NW and Middle East–Asia Minor 1 (MEAM1) vector species and transmitted upon inoculation feeding. An association between foregut retention and transmission by NW vectors is also observed following the acquisition and inoculation feeding of LCV virions purified using a standard procedure involving 2% or 4% (v/v) Triton™ X-100 (TX-100). However, while virions purified with 2% or 4% TX-100 are also retained in the foreguts of MEAM1 vectors, transmission is observed with the 4% TX-100-purified virions or when more vectors are used for acquisition and inoculation feeding. These results suggest that an intrinsic difference exists between NW and MEAM1 vectors in their interactions with, and transmission of, LCV virions.

Species‐specific COI primers for rapid identification of Bemisia tabaci Mediterranean (MED) species

AbstractBemisia tabaci (Gennadius) is a rapidly evolving species complex, and is small in size and difficult to identify quickly and accurately. For the accurate identification and effective prevention of this species, the specific PCR method based on the mitochondrial DNA cytochrome oxidase subunit I (mt DNA COI) gene was used in the present study to evaluate rapid molecular detection technological applications for Mediterranean (MED) species. The MED was targeted and whitefly species from different regions were used as references. Fragments of the mt DNA COI gene of the MED and other closely related species were amplified with universal primers. Species‐specific mitochondrial DNA cytochrome oxidase subunit I (SS‐COI) primers BQLF/BQLR and BQJF/BQJR were designed from variable sites of MED and other whitefly species partial COI gene sequences. Subsequently, the lengths of target fragments were amplified by two pairs of SS‐COI primers. Meanwhile, the accuracy, specificity and sensitivity of SS‐COI primers were determined using various life stages of the MED and other related species collected from different locations. The primer pairs BQLF/BQLR and BQJF/BQJR generated 334 bp and 483 bp amplified fragment length respectively. Accuracy test results showed that primers can detect the MED single‐head adults and also accurately detect single‐egg and first instar, second instar and third instar nymphs, MED pupae, etc. Specific detection results demonstrated that the primers were able to amplify the MED but not the following species/populations: Middle East‐Asia Minor 1 (MEAM1), Asia I, Asia II 1, Asia II 6 and Asia II 7, Aleurocanthus spiniferus (Quaintanca), A. camelliae, Siphoninus phillyreae, Aleuroclava rhododendri, A. thysanospermi, Aleurolobus taonabae, Dialeurodes citri and Trialeurodes vaporariorum (Westwood) in different areas. Sensitivity detection results showed that primers can detect the minimum threshold of 2,160 pg/μl and 1.38 pg/μl, respectively (equivalent to 1/1280 and 1/2000000 adult). This technique solves the problem that MED cannot be identified based on morphology. This method simultaneously adopted SS‐COI PCR technological applications that improved detection accuracy and saved detection time.

Pymetrozine-resistant whitefly Bemisia tabaci (Gennadius) populations in China remain susceptible to afidopyropen

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the most destructive pests in the world because of its serious damage to various crops and rapid development of insecticide resistance. Afidopyropen is a novel pyropene insecticide with high insecticidal activity against sucking insects and has been registered to control whitefly in China since 2019. In this study, 33 field populations of B. tabaci were collected across China between August 2019 and October 2020 and their cryptic species compositions were investigated. The toxicity of afidopyropen to B. tabaci were measured at different times, which was further compared to the toxicity of pymetrozine. The results showed that only Mediterranean (MED) and Middle East-Asia Minor 1 (MEAM1) species were detected in the field populations. The LC50 values of afidopyropen were significantly higher in the first five days, and subsequently became stable at a lower level after day five. The LC50 value of afidopyropen to field whitefly populations ranged from 1.15 to 4.52 mg/L, and the variation in susceptibility was 1.9-fold. The LC50 value of the mixed susceptible population was 2.31 mg/L, which was established as the whitefly susceptible baseline to afidopyropen in China. The resistance to pymetrozine in field populations ranged from 1.8- to 116.6-fold, but no cross-resistance between afidopyropen and pymetrozine was observed. Taken together, afidopyropen exhibited a great insecticidal potency against 33 field populations of B. tabaci in China and it did not show cross-resistance with pymetrozine, suggesting it could be considered as an effective insecticide in the insecticide resistance management (IRM) of B. tabaci.

Updated status of whiteflies (Hemiptera: Aleyrodidae) in Jordan with emphasis on the Bemisia tabaci species complex

Whiteflies are economically important plant pests that cause damage to crops worldwide. This study aimed to update the status of whiteflies in Jordan by combining the classical morphological identification and the DNA markers using the mitochondrial cytochrome oxidase I (mtCOI) gene. Over the course of three consecutive years, 111 whiteflies were collected from different geographical regions and different plant hosts in Jordan. The results showed that, in addition to Bemisia tabaci, another nine different whitefly species were identified, including two species that were recorded for the first time in Jordan: Africaleurodes coffeacola, and Tetraleurodes neemani. A special focus has been given to economically important plant pests like the B. tabaci species complex. Three different diagnostic techniques were used to identify B. tabaci putative species based on mtCOI gene. All the collected samples of B. tabaci species complex were identified as Middle East–Asia Minor 1 (MEAM1) putative species.

Diversity and infectivity of the RNA virome among different cryptic species of an agriculturally important insect vector: whitefly Bemisia tabaci

A large number of insect-specific viruses (ISVs) have recently been discovered, mostly from hematophagous insect vectors because of their medical importance, but little attention has been paid to important plant virus vectors such as the whitefly Bemisia tabaci, which exists as a complex of cryptic species. Public SRA datasets of B. tabaci and newly generated transcriptomes of three Chinese populations are here comprehensively investigated to characterize the whitefly viromes of different cryptic species. Twenty novel ISVs were confidently identified, mostly associated with a particular cryptic species while different cryptic species harbored one or more core ISVs. Microinjection experiments showed that some ISVs might cross-infect between the two invasive whitefly cryptic species, Middle East Asia Minor 1 (MEAM1) and Mediterranean (MED), but others appeared to have a more restricted host range, reflecting the possibility of distinct long-term coevolution of these ISVs and whitefly hosts. Moreover, analysis of the profiles of virus-derived small-interfering RNAs indicated that some of the ISVs can successfully replicate in whitefly and the antiviral RNAi pathway of B. tabaci is actively involved in response to ISV infections. Our study provides a comprehensive analysis of the RNA virome, the distinct relationships and cross-cryptic species infectivity of ISVs in an agriculturally important insect vector.

Detection of Bemisia tabaci Mediterranean cryptic species on soybean in São Paulo and Paraná States (Brazil) and interaction of cowpea mild mottle virus with whiteflies

AbstractSince the detection of Bemisia tabaci Middle East‐Asia Minor 1 (MEAM1) species in Brazil in the early 1990s, this whitefly has been the predominant species and the main viral vector in the country. In this work, whiteflies were collected from commercial soybean fields near and far from greenhouses where Mediterranean (MED) species had previously been detected infesting vegetable crops. Results indicated that MEAM1 was the predominant whitefly species in soybean in most sampling sites, while MED was found colonizing soybean plants in open field conditions alone and/or with MEAM1 in several places. Among the tested insects, MED species was mostly detected harbouring the facultative endosymbiont Hamiltonella. We also detected cowpea mild mottle virus (CPMMV) infecting soybean plants. Transmission assays demonstrated that MED species was more efficient transmitting CPMMV from beans to beans and from soybean to soybean plants than MEAM1, while MEAM1 was more efficient in transmitting the virus from soybean to bean than MED. Performance assays indicated that adult emergence of both species on CPMMV‐infected soybean plants was higher when compared with the emergence on healthy plants. Moreover, nonviruliferous MED and MEAM1 adults preferred to settle more often on healthy plants, while viruliferous adults settled more often on CPMMV‐infected soybean plants. As MED has already been found in soybean open fields in São Paulo and Paraná States, Brazil, and it is a good vector of CPMMV, we anticipate problems related to whitefly management and to increase in the incidence of the virus in soybean.

Evidence of Spread of Bemisia tabaci (Hemiptera: Aleyrodidae) Mediated by Internal Transportation of Ornamental Plants in Brazil.

Two Bemisia tabaci (Gennadius) species, Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED), are major pests that are dispersed throughout the world. While MEAM1 was introduced in Brazil in the 1990s, MED was reported recently with limited spread. Here, a survey was performed to examine whether MED whiteflies are widely present in the Federal District region, in central Brazil. Whiteflies were collected in various locations in the Federal District and surroundings between 2018 and 2020, including garden centers and small- and large-scale farms. The species were identified using RFLPand sequencing of the mitochondrial cytochrome c oxidase I subunit gene region. Out of 108 whitefly batches, 63.89% were composed exclusively by MEAM1, followed by 16.67% presenting only MED, and another 7.40% containing unidentified whitefly species (NI). Plant varieties serving as hosts for more than one whitefly species were observed in 12.04% of the samples, either by MEAM1/MED, MEAM1/NI, or MED/NI. This study highlights the still limited presence of MED in the Federal District and surroundings, predominantly in garden centers and in the green belt of Brasília, closer to urban areas. In contrast, only MEAM1 was identified in large-scale cultivated areas.

Natural Infection Rate of Known Tomato chlorosis virus-Susceptible Hosts and the Influence of the Host Plant on the Virus Relationship With Bemisia tabaci MEAM1.

Tomato chlorosis virus (ToCV; genus Crinivirus, family Closteroviridae) was identified in tomato crops in São Paulo State, Brazil, in 2006. Management strategies to control external sources of inoculum are necessary, because chemical control of the whitefly vector Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) has not efficiently prevented virus infections and no commercial tomato varieties or hybrids are resistant to this crinivirus. We first evaluated the natural infection rate of some known wild and cultivated ToCV-susceptible hosts and their attractiveness for B. tabaci MEAM1 oviposition. Physalis angulata was the most susceptible to natural infection in all six exposures in 2018 and 2019. No plants of Capsicum annuum 'Dahra' or Chenopodium album became infected. Solanum melongena 'Napoli' had only two infected plants of 60 exposed. Capsicum annuum and Chenopodium album were the least preferred, and Nicotiana tabacum and S. melongena were the most preferred for whitefly oviposition. In addition, from 2016 to 2019, we surveyed different tomato crops and the surrounding vegetation to identify ToCV in weeds and cultivated plants in the region of Sumaré, São Paulo State. Only S. americanum, vila vila (S. sisymbriifolium), and Chenopodium album were found naturally infected, with incidences of 18, 20, and 1.4%, respectively. Finally, we estimated the ToCV titer (U.S. and Brazilian isolates ToCV-FL and ToCV-SP, respectively) by quantitative reverse transcription PCR in different ToCV-susceptible host plants and evaluated the relationship between virus acquisition and transmission by B. tabaci MEAM1. The results clearly showed significant differences in ToCV concentrations in the tissues of ToCV-susceptible host plants, which appeared to be influenced by the virus isolate. The concentration of the virus in plant tissues, in turn, directly influenced the ToCV-B. tabaci MEAM1 relationship and subsequent transmission to tomato plants. To minimize or prevent damage from tomato yellowing disease through management of external sources of ToCV, it is necessary to correctly identify potentially important ToCV-susceptible hosts in the vicinity of new plantings.

CAP Analysis of the Distribution of the Introduced Bemisia tabaci (Hemiptera: Aleyrodidae) Species Complex in Xinjiang, China and the Southerly Expansion of the Mediterranean Species

Bemisia tabaci (Gennadius) cryptic complex has invaded Xinjiang, China, since 1998. The distribution of Mediterranean (MED) and Middle East-Asia Minor 1 (MEAM1) B. tabaci substrains has been gradually identified due to the development of molecular technology. In this study, the distribution of MED and MEAM1 in Xinjiang was determined by cleaved amplified polymorphic sequence (CAPs). Results showed that MED dominated in northern Xinjiang (84%), whereas MEAM1 was dominant in southern Xinjiang (72%). Five pairs of simple sequence repeat (SSR) primers were used to analyze the genetic diversity of B. tabaci among 36 geographic populations. The genetic diversity of MED and MEAM1was low and varied little among populations in Xinjiang (0.09 ± 0.14 and 0.09 ± 0.13, respectively). Based on ∆K statistic, 13 populations of MEAM1 could be classified into two subgroups at K = 2, whereas the 23 populations of MED could be classified into four subgroups at K = 4. However, Mantel t-test demonstrated no correlation between geographical and genetic distances among B. tabaci complex (R = 0.42, P = 1.00). Neighbor-joining and principal coordinate analysis showed that geographical isolation and interspecific differences were the main causes of the genetic variation. Gene flow predicted that MEAM1 was most likely introduced from Urumqi to the southern Xinjiang. Meanwhile, a large proportion of MED in Kashi region came from Changji and Yining. To block ongoing dispersal, strict detection and flower quarantine regulations need to be enforced.

Bemisia tabaci on Vegetables in the Southern United States: Incidence, Impact, and Management.

Simple SummaryThe sweetpotato whitefly, Bemisia tabaci, was initially discovered in the United States in 1894 but was not considered an economic insect pest on various agricultural crops across the southern and western states. After the introduction of B. tabaci Middle East-Asia Minor 1 (MEAM1) into the United States around 1985, the insect rapidly spread throughout the Southern United States to Texas, Arizona, and California. Extreme field outbreaks occurred on vegetable and other crops in those areas. The sweetpotato whitefly is now regarded as one of the most destructive insect pests in vegetable production systems in the Southern United States. The direct and indirect plant damage caused by B. tabaci has led to substantial economic losses in vegetable crops. Bemisia tabaci outbreaks on vegetables in Georgia resulted in significant economic losses of 132.3 and 161.2 million US dollars (USD) in 2016 and 2017, respectively. Therefore, integrated pest management (IPM) tactics are warranted, including cultural control by manipulation of production practices, resistant vegetable varieties, biological control using various natural enemies, and the judicious use of insecticides.Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is among the most economically important insect pests of various vegetable crops in the Southern United States. This insect is considered a complex of at least 40 morphologically indistinguishable cryptic species. Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) was initially introduced in the United States around 1985 and has since rapidly spread across the Southern United States to Texas, Arizona, and California, where extreme field outbreaks have occurred on vegetable and other crops. This pest creates extensive plant damage through direct feeding on vegetables, secreting honeydew, causing plant physiological disorders, and vectoring plant viruses. The direct and indirect plant damage in vegetable crops has resulted in enormous economic losses in the Southern United States, especially in Florida, Georgia, and Texas. Effective management of B. tabaci on vegetables relies mainly on the utilization of chemical insecticides, particularly neonicotinoids. However, B. tabaci has developed considerable resistance to most insecticides. Therefore, alternative integrated pest management (IPM) strategies are required, such as cultural control by manipulation of production practices, resistant vegetable varieties, and biological control using a suite of natural enemies for the management of the pest.

Interactive effects of host plant and insecticide foliar application on oviposition and performance of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) cryptic species Mediterranean (MED) and Middle East-Asia minor 1 (MEAM1) in Brazil

The Bemisia tabaci (Gennadius) cryptic species complex is composed of important pest insects, with cryptic species Mediterranean (MED) and Middle East-Asia Minor 1 (MEAM1) having caused severe yield reduction on crops worldwide. The former was reported in Brazil in 2014, while the latter was first reported in the country in the 1990s. Although farmers have highly adopted insecticide application for B. tabaci management, its efficacy may vary among host plants and cryptic species. Cyantraniliprole is a new anthranilic diamide insecticide with a mode of action that activates the insect ryanodine receptor (RyR). In this context, the purpose of this study was to investigate the effects of cyantraniliprole spraying on the oviposition and performance of MEAM1 and MED cryptic species in tomato and sweet pepper plants. Cyantraniliprole caused high adult mortality for both cryptic species on sweet pepper (> 94%), while its efficacy was moderate for MEAM1 (~ 56%) and low for MED (~ 12%) on tomato. MED laid more eggs on sweet pepper and tomato treated with water and cyantraniliprole, respectively, than MEAM1. Additionally, cyantraniliprole reduced the hatchability of MED and MEAM1 on sweet pepper and tomato, respectively. Moreover, MED showed better performance than MEAM1 regardless of the treatment and host plant, except on tomato treated with water. Our results indicate that cyantraniliprole efficacy changes according to B. tabaci cryptic species and host plant. These findings will be important for redesigning cyantraniliprole doses for B. tabaci management in Brazil.

EPG-recorded Feeding Behaviors Reveal Adaptability and Competitiveness in Two Species of Bemisia tabaci (Hemiptera: Aleyrodidae)

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.

Laboratory virulence of entomopathogenic nematodes to the sweetpotato whitefly, Bemisia tabaci.

The sweetpotato whitefly, Bemisia tabaci Middle East-Asia Minor 1 (MEAM1), is a major insect pest on vegetable crops worldwide. Enormous economic losses result from direct and indirect plant damage caused by MEAM1. Biological control using entomopathogenic nematodes (EPN) may be an effective alternative strategy against MEAM1 because this pest has developed resistance to most insecticides. First, nine EPN species (Heterorhabditis bacteriophora, H. indica, H. georgiana, H. floridensis, Steinernema feltiae, S. carpocapsae, S. riobrave, S. glaseri, and S. rarum) were investigated for virulence to MEAM1 third instar nymphs on snap bean leaves under laboratory conditions. The mortality of MEAM1 nymphs was evaluated at 3 days post-inoculation (dpi). Compared to the water control, the application of the nine EPN species except S. glaseri resulted in significantly higher mortality of MEAM1 nymphs, such as H. bacteriophora (66.31%), H. floridensis (56.38%), S. carpocapsae (54.54%), and S. rarum (57.80%). Subsequently, the four virulent EPN species, H. bacteriophora, H. floridensis, S. carpocapsae, and S. rarum were evaluated further for virulence to MEAM1 nymphs on snap bean and tomato leaves. The mortality of MEAM1 nymphs was assessed at 3 dpi and 7 dpi. There were no significant differences in MEAM1 nymphal mortality between tomato and snap bean at either 3 dpi or 7 dpi. The mortality of MEAM1 nymphs caused by the application of H. floridensis (99.25%) was significantly higher than the other three EPN species and the water control at 7dpi. The results indicate that H. floridensis is a very promising biocontrol agent for B. tabaci management.

Invasion Biology and Management of Sweetpotato Whitefly (Hemiptera: Aleyrodidae) in China

AbstractThe sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), is a broadly invasive pest of great economic significance to agricultural and horticultural systems in the world. Bemisia tabaci contains more than 44 cryptic species, among which B. tabaci Middle East Asia Minor 1 (MEAM1) and Mediterranean (MED) are the most invasive and destructive, and have spread to many countries. Research on B. tabaci cryptic species increased dramatically in China following the introduction of MEAM1 in the middle-late 1990s. Our report discussed significant advances over the past two decades to understand the invasive genetics of B. tabaci in China. We reviewed the main findings including changes in the cryptic species composition and invasion characteristics of B. tabaci, also summarizing the factors that affect the displacement of dominant cryptic species. Finally, the integrated management of B. tabaci in China was discussed. We hope that this review can stimulate interest in and deepen understanding of B. tabaci, which will lay a foundation for further research in this field.

Low Genetic Variability in Bemisia tabaci MEAM1 Populations within Farmscapes of Georgia, USA.

Simple SummarySweetpotato whitefly, Bemisia tabaci Gennadius, is a serious pest of many agricultural crops worldwide. Numerous studies have examined the genetic structure of whitefly populations separated by geographical barriers; however, very few have assessed the population structure of B. tabaci at a farmscape level. A farmscape in this study is defined as heterogenous habitat with crop and non-crop areas spanning approximately 8 square kilometers. To assess the roles of farmscapes as drivers of B. tabaci genetic variation, thirty-five populations of the sweetpotato whitefly were collected from crop and non-crop plant species from fifteen farmscapes. Using mitochondrial COI gene sequences (mtCOI) and six nuclear microsatellite markers, the genetic diversity and genetic differentiation among collected B. tabaci MEAM1 populations were examined. Haplotype analysis using mtCOI sequences revealed the presence of a single B. tabaci MEAM1 haplotype across farmscapes of Georgia. Results from microsatellite markers further showed no significant genetic structuring among populations that corresponded to plant species or farmscapes from which they were collected. Annual whitefly population explosions and subsequent dispersal might have facilitated the persistence of a single panmictic B. tabaci population over all sampled farmscapes in this region. Bemisia tabaci is a whitefly species complex comprising important phloem feeding insect pests and plant virus vectors of many agricultural crops. Middle East–Asia Minor 1 (MEAM1) and Mediterranean (MED) are the two most invasive members of the B. tabaci species complex worldwide. The diversity of agroecosystems invaded by B. tabaci could potentially influence their population structure, but this has not been assessed at a farmscape level. A farmscape in this study is defined as heterogenous habitat with crop and non-crop areas spanning ~8 square kilometers. In this study, mitochondrial COI gene (mtCOI) sequences and six microsatellite markers were used to examine the population structure of B. tabaci MEAM1 colonizing different plant species at a farmscape level in Georgia, United States. Thirty-five populations of adult whiteflies on row and vegetable crops and weeds across major agricultural regions of Georgia were collected from fifteen farmscapes. Based on morphological features and mtCOI sequences, five species/cryptic species of whiteflies (B. tabaci MEAM1, B. tabaci MED, Dialeurodes citri, Trialeurodes abutiloneus, T. vaporariorum) were found. Analysis of 102 mtCOI sequences revealed the presence of a single B. tabaci MEAM1 haplotype across farmscapes in Georgia. Population genetics analyses (AMOVA, PCA and STRUCTURE) of B. tabaci MEAM1 (microsatellite data) revealed only minimal genetic differences among collected populations within and among farmscapes. Overall, our results suggest that there is a high level of gene flow among B. tabaci MEAM1 populations among farmscapes in Georgia. Frequent whitefly population explosions driven by a single or a few major whitefly-suitable hosts planted on a wide spatial scale may be the key factor behind the persistence of a single panmictic population over Georgia’s farmscapes. These population structuring effects are useful for delineating the spatial scale at which whiteflies must be managed and predicting the speed at which alleles associated with insecticide resistance might spread.

Performance and preference of Bemisia tabaci on cucumbers: Understanding the recent outbreaks of Mediterranean cryptic species in Brazil

Currently, in Brazil, part of the cucumber production is cultivated in greenhouses, in rotation with bell pepper and tomato. However, this kind of cultivation seems to be contributing to heavy infestations of Bemisia tabaci Mediterranean cryptic species (MED) in cucumbers, which is indeed related to the recent detection of tomato chlorosis virus (ToCV) in this crop. Thus, the present study investigated the settling preference of B. tabaci Middle east Asia-Minor 1 (MEAM1) and MED cryptic species for cucumber, bell pepper, and tomato plants cultivated in the same area. In addition, the settling preference and biological performance of MEAM1 and MED on representative cucumber commercial cultivars were also compared. Cucumber was the most preferred host when compared with tomato and bell pepper for both whiteflies, which were also capable of establishing and ovipositioning in all cucumber cultivars tested. The Mediterranean species showed better adaptability than MEAM1 in almost all cucumber cultivars tested, by showing a better capacity of survival and resulting in a more significant number of adults. When evaluating cultivars, ‘Aodai’ stood out for presenting high MEAM1 nymph mortality, showing that it may be a good option to be implemented in areas with the absence of MED. In contrast, no cultivars were potentially satisfactory for use in the management of MED, reinforcing the need to develop specific management strategies directed for this cryptic whitefly species.

Spatial Distribution of Whitefly Species (Hemiptera: Aleyrodidae) and Identification of Secondary Bacterial Endosymbionts in Tomato Fields in Costa Rica.

In Costa Rica, tomato (Solanum lycopersicum Linnaeus) Linnaeus (Solanales: Solanaceae) is one of the crops most severely affected by the whiteflies (Hemiptera: Aleyrodidae) Trialeurodes vaporariorum (Westwood) and the Bemisia tabaci (Gennadius) species complex. The objective of this study was to monitor the spatial distribution and diversity of these species and to detect the presence of secondary bacterial endosymbionts in individuals collected in areas of intensive tomato production. In total, 628 whitefly individuals were identified to the species level using restriction analysis (PCR-RFLP) of a fragment of the mitochondrial cytochrome C oxidase I gene (mtCOI). Trialeurodes vaporariorum was the predominant species, followed by B. tabaci Mediterranean (MED). Bemisia tabaci New World (NW) and B. tabaci Middle East-Asia Minor 1 (MEAM1) were present in lower numbers. The mtCOI fragment was sequenced for 89 individuals and a single haplotype was found for each whitefly species. Using molecular markers, the 628 individuals were analyzed for the presence of four endosymbionts. Arsenophonus Gherna et al. (Enterobacterales: Morganellaceae) was most frequently associated with T. vaporariorum, whereas Wolbachia Hertig (Rickettsiales: Anaplasmataceae) and Rickettsia da Rocha-Lima (Rickettsiales: Rickettsiaceae) were associated with B. tabaci MED. This study confirmed that B. tabaci NW has not been completely displaced by the invasive species B. tabaci MED and B. tabaci MEAM1 present in the country. An association was found between whitefly species present in tomato and certain secondary endosymbionts, elevation was the most likely environmental factor to affect their frequency.

Transmission of the Bean-Associated Cytorhabdovirus by the Whitefly Bemisia tabaci MEAM1.

The knowledge of genomic data of new plant viruses is increasing exponentially; however, some aspects of their biology, such as vectors and host range, remain mostly unknown. This information is crucial for the understanding of virus–plant interactions, control strategies, and mechanisms to prevent outbreaks. Typically, rhabdoviruses infect monocot and dicot plants and are vectored in nature by hemipteran sap-sucking insects, including aphids, leafhoppers, and planthoppers. However, several strains of a potentially whitefly-transmitted virus, papaya cytorhabdovirus, were recently described: (i) bean-associated cytorhabdovirus (BaCV) in Brazil, (ii) papaya virus E (PpVE) in Ecuador, and (iii) citrus-associated rhabdovirus (CiaRV) in China. Here, we examine the potential of the Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) to transmit BaCV, its morphological and cytopathological characteristics, and assess the incidence of BaCV across bean producing areas in Brazil. Our results show that BaCV is efficiently transmitted, in experimental conditions, by B. tabaci MEAM1 to bean cultivars, and with lower efficiency to cowpea and soybean. Moreover, we detected BaCV RNA in viruliferous whiteflies but we were unable to visualize viral particles or viroplasm in the whitefly tissues. BaCV could not be singly isolated for pathogenicity tests, identification of the induced symptoms, and the transmission assay. BaCV was detected in five out of the seven states in Brazil included in our study, suggesting that it is widely distributed throughout bean producing areas in the country. This is the first report of a whitefly-transmitted rhabdovirus.