Analysis of the genetic diversity of Bemisia tabaci populations in Shanxi province, China

Five different primer combinations were used for the analysis of 152 B biotype Bemisia tabaci (Gennadius) individuals and five Trialeurodes vaporairiorum individuals collected from 19 counties and seven host plants in Shanxi province in China, respectively. The main objective of the present study was to use AFLP markers to determine the genetic diversity of B. tabaci populations collected from Shanxi Province. The use of these primer combinations allowed the identification of 127 polymorphic bands (52.26%) from 60 to 500 bp. The average number of polymorphic bands per primer was 25.4 while the range for the five primers was 20–32. The average degree of heterozygosity was 0.251, while the range for the five primers was 0.204–0.289. The results suggested definite genetic diversity among different B. tabaci populations. Cluster analysis showed that B. tabaci populations were firstly scattered to three genetic groups according to the regions, then every genetic group was scattered to several subgroups according to the host plants, which revealed the genetic variability of B biotype B. tabaci populations has been not only among different regions, but also among different host plants in Shanxi Province.     

中国马铃薯晚疫病菌AFLP遗传多样性分析

The genetic diversity of the populations of Phytophthora infestans from some major potato production regions in China were detected by amplified restriction fragment polymorphism (AFLP) analysis. Among 200 combinations of primer pair screened, 12 combinations could generate consistent polymorphic bands using six tested isolates. The twelve combinations were used to amplify the genomic DNA of 50 isolates collected in China from 1997 to 2002. A total of 922 AFLP bands were obtained, and 530 of them,covering 57.5%, showed polymorphism. Cluster analysis using the unweighted pair-group method with arithmetic averages (UPGMA) separated 50 isolates into five AFLP groups which were correlated to groups defined by geographical origin, however, they were not correlated to groups defined by mating type, or response to metalaxyl and virulence. Parameters of genetic diversity calculated by POPGENE software indicated that the genetic diversity level of Phytophtora infestans population in China was not high.     

Invasive mechanism and management strategy of Bemisia tabaci (Gennadius) biotype B: Progress report of 973 Program on invasive alien species in China

Bemisia tabaci (Gennadius) biotype B, called a “superbug”, is one of the most harmful biotypes of this species complex worldwide. In this report, the invasive mechanism and management of B. tabaci bio-type B, based on our 5-year studies, are presented. Six B. tabaci biotypes, B, Q, ZHJ1, ZHJ2, ZHJ3 and FJ1, have been identified in China. Biotype B dominates the other biotypes in many regions of the country. Genetic diversity in biotype B might be induced by host plant, geographical conditions, and/or insecticidal application. The activities of CarE (carboxylesterase) and GSTs (glutathione-S-transferase) in biotype B reared on cucumber and squash were greater than on other host plants, which might have increased its resistance to insecticides. The higher activities of detoxification enzymes in biotype B might be induced by the secondary metabolites in host plants. Higher adaptive ability of biotype B adults to adverse conditions might be linked to the expression of heat shock protein genes. The in-digenous B. tabaci biotypes were displaced by the biotype B within 225 d. The asymmetric mating in-teractions and mutualism between biotype B and begomoviruses via its host plants speed up wide-spread invasion and displacement of other biotypes. B. tabaci biotype B displaced Trialeurodes vapo-rariorum (Westwood) after 4－7 generations under glasshouse conditions. Greater adaptive ability of the biotype B to adverse conditions and its rapid population increase might be the reasons of its suc-cessful displacement of T. vaporariorum. Greater ability of the biotype B to switch to different host plants may enrich its host plants, which might enable it to better compete with T. vaporariorum. Native predatory natural enemies possess greater ability to suppress B. tabaci under field conditions. The kairomones in the 3rd and 4th instars of biotype B may provide an important stimulus in host searching and location by its parasitoids. The present results provide useful information in explaining the mechanisms of genetic diversity, evolution and molecular eco-adaptation of biotype B. Furthermore, it provides a base for sustainable management of B. tabaci using biological and ecological measures.     

Analysis of genetic diversity in the endangered Hucho taimen from China

Hucho taimen are listed as endangered in China. The population size has declined recently, prompting an increase in the level of listing from grade three in 2002 to grade five in 2006. We analyzed the genetic diversity of wild populations using 17 microsatellite markers to establish a scientific basis for conservation of this species. We collected tissue samples from four populations in the Heilongjiang River basin: Huma River (HM), Hutou (HT), Haiqing (HQ), and Zhuaji (ZJ). A total of 21 loci were amplified, 18 of which were polymorphic. The number of alleles per locus ranged from 2 to 9 (mean: 4.1905). There were 13 highly polymorphic loci and 5 moderately polymorphic loci. Analysis of five genetic diversity parameters (Na, Ne, Ho, He, and PIC) suggested moderate levels of diversity within the populations. The populations were ranked HT > HQ > ZJ > HM, but the differences in diversity were not statistically significant (P > 0.05). A comparison of variation among all four populations suggested Hardy–Weinberg disequilibrium at 20% of the loci. Genetic differentiation (Fst) was 0.0644 and the gene flow among populations was estimated at 3.36 individuals per generation. The majority of diversity (93.88%) occurred among individuals within a population. In contrast, relatively little (6.12%) of the genetic diversity was distributed between the populations. An analysis of genetic differentiation and genetic distance between pairs of populations revealed that both parameters were higher in comparisons of the HM population to the HT, HQ, and ZJ populations than among the three latter populations. This suggests that the HM population has a distinct genetic structure. We hypothesize that habitat degradation and excessive fishing, not low genetic diversity, has caused the decline in H. taimen populations. However, this species should be protected from further declines in genetic diversity.     

Analysis of genetic diversity in the endangered Hucho taimen from China

Hucho taimen are listed as endangered in China. The population size has declined recently, prompting an increase in the level of listing from grade three in 2002 to grade five in 2006. We analyzed the genetic diversity of wild populations using 17 microsatellite markers to establish a scientific basis for conservation of this species. We collected tissue samples from four populations in the Heilongjiang River basin: Huma River (HM), Hutou (HT), Haiqing (HQ), and Zhuaji (ZJ). A total of 21 loci were amplified, 18 of which were polymorphic. The number of alleles per locus ranged from 2 to 9 (mean: 4.1905). There were 13 highly polymorphic loci and 5 moderately polymorphic loci. Analysis of five genetic diversity parameters (Na, Ne, Ho, He, and PIC) suggested moderate levels of diversity within the populations. The populations were ranked HT > HQ > ZJ > HM, but the differences in diversity were not statistically significant (P > 0.05). A comparison of variation among all four populations suggested Hardy–Weinberg disequilibrium at 20% of the loci. Genetic differentiation (Fst) was 0.0644 and the gene flow among populations was estimated at 3.36 individuals per generation. The majority of diversity (93.88%) occurred among individuals within a population. In contrast, relatively little (6.12%) of the genetic diversity was distributed between the populations. An analysis of genetic differentiation and genetic distance between pairs of populations revealed that both parameters were higher in comparisons of the HM population to the HT, HQ, and ZJ populations than among the three latter populations. This suggests that the HM population has a distinct genetic structure. We hypothesize that habitat degradation and excessive fishing, not low genetic diversity, has caused the decline in H. taimen populations. However, this species should be protected from further declines in genetic diversity.     

Low genetic diversity and high genetic differentiation in the critically endangered Omphalogramma souliei （Primulaceae）： implications for its conservation

Omphalogramma souliei Franch. is an endangered perennial herb only distributed in alpine areas of SW China. ISSR markers were applied to determine the genetic variation and genetic structure of 60 individuals of three populations of O. souliei in NW Yunnan, China. The genetic diversity at the species level is low with P=42.5% （percentage of polymorphic bands） and Hsp=0.1762 （total genetic diversity）. However, a high level of genetic differentiation among populations was detected based on different measures （Nei＇s genetic diversity analysis： Gst=0.6038; AMOVA analysis： Fst=0.6797）. Low level of genetic diversity within populations and significant genetic differentiation among populations might be due to the mixed mating system in which xenogamy predominated and autogamy played an assistant role in O. souliei. The genetic drift due to small population size and limited current gene flow also resulted in significant genetic differentiation. The assessment of genetic variation and differentiation of the endangered species provides important information for conservation on a genetic basis. Conservation strategies for this rare endemic species are proposed.     

Genetic diversity analysis by RAPD in Cathaya argyrophylla Chun et Kuang

Genetic diversity level of Cathaya argyrophylla was confirmed by random amplified polymorphic DNA (RAPD) markers. Seventy five samples (individuals), collected from Hunan and Sichuan provinces of China were used in the study. 21 10-mer oligonucleotide primers detected 106 sites, and 34 (32% ) of them were polymor-phic. The level of genetic variation in C. argyrophylla was lower than those of other conifers, and was considered to be associated with the complexity of habitats. The percentages of polymorphic sites (PPS) in the Hunan and Sichuan pop-ulations were 18% and 25% respectively. 7.99% of genetic variation existed between the two populations; this value was higher than the mean value (6.8%) among populations in conifers displayed by allozyme. Some subpopulations of C. argyrophylla were greatly differentiated because of site mutation and genetic drift. The highest value of genetic dif-ference between subpopulations amounted to 16. 23% . In addition, a concept of diversity coefficient(DC), a value us     

采用RAPD标记探讨瓣蕊唐松草(毛茛科唐松草属)的遗传多样性及其地理分布格局(英文)

Random amplified polymerphic DNA(RAPD)method was applied to assessg enetic variation and population structure of Thahctrum petalotdeum L(Ranunoulaceae),Two hundred and forty-six individuals from 11 populations of the species were investigated by RAPD profiles Twenty selected RAPD primers generated 125 bands．in which 120 were polymorphic Ther esults revealed a high level of genetic variation(ercentage of polymorphIc bands(PPB was 96％．Nei’s gene diversity(りwas 03502 and shannon’s information index(I) was 0．5199 at the species level) The differentiation among the populations was high(Gst=0．3511)in this species．Result of analyzing of molecularvariance(AMOVA)showedthat38．88％of genetic variance was found among the populations Positive correlation withr r=01945(P=00002)was found between genetic distance and geographic distance amongpo pulations Two populations distributed in the drainage basin of YanELz River affined genedcally and formed one clada and the rest nine populations formed the other clade in both unweighted pair-group method using arithmetic average(UPGMA)trees made by two different method different methods. It was yen/clear that these two populations were very special, andmust be closely related in history, despite the fact that they now share quite weak link to the restpopulations through gene communication.     

Loss of Genetic Diversity of Domesticated Panax notoginseng F H Chen as Evidenced by ITS Sequence and AFLP Polymorphism： A Comparative Study with P. stipuleanatus H T Tsai et K M Feng

In the present study, we evaluated the genetic diversity of Panax notoginseng F H Chen, a domesticated species, and P. stipuleanatus H T Tsai et K M Feng, an endangered wild species in southeastern Yunnan and adjacent areas in Vietnam, using sequences of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA and amplified fragment length polymorphism (AFLP) markers. Twenty-four accessions from three plantations of P. notoginseng and 51 samples from eight populations of P. stipuleanatus were assayed. A total of 694 bp of partial sequences of 18S, ITS 1, 5.8S, ITS2, and partial sequences of 26S were obtained. No sequence variation was detected within P. notoginseng and nine sites (1.30%) were variable in P. stipuleanatus. Two-thirds of the variable sites were found between Langqiao and other populations. In P. notoginseng, four pairs of AFLP primer combinations generated 312 bands, of which 240 (76.9%) were polymorphic and 60.15% of the polymorphisms were harbored within plantations. Approximately 41.0% and 66.9% of bands were polymorphic in population D7 and 5589, respectively. In P.stipuleanatus, the same four primer combinations produced 346 bands, of which 334 (96.5%) were polymorphic and approximately 62.14% of polymorphisms were maintained within populations. Considerable variations were observed. The percentage of polymorphic bands ranged from 50.2% to 84.9% and the average over populations was 70.9%. Cluster analysis did not show correlation of genetic differentiation with the distinctive leaf morphology of P. stipuleanatus (i.e. one form with bipinnatifid leaflets and the other with undivided leaflets). Because over 40% of genetic variations were maintained among populations and because of the very restricted distribution of P. stipuleanatus, all natural populations of this species should be conserved in situ. Considering that there are variations in P. notoginseng within and among plantations, we suggest establishing a genetic resource conservation garden or reintroducing P. notoginseng into its native habitats in southwestern China. Such reintroduction should be carefully executed after large-scale screening of genetic variation within the species.     

Simple Sequence Repeat Analysis of Genetic Diversity in Primary Core Collection of Peach （Prunus persica）

In this study, the genetic diversity of 51 cultivars in the primary core collection of peach （Prunus persica （L.） Batsch） was evaluated by using simple sequence repeats （SSRs）. The phylogenetic relationships and the evolutionary history among different cultivars were determined on the basis of SSR data. Twenty-two polymorphic SSR primer pairs were selected, and a total of 111 alleles were identified in the 51 cultivars, with an average of 5 alleles per locus. According to traditional Chinese classification of peach cultivars, the 51 cultivars in the peach primary core collection belong to six variety groups. The SSR analysis revealed that the levels of the genetic diversity within each variety group were ranked as Sweet peach 〉 Crisp peach 〉 Flat peach 〉 Nectarine 〉 Honey Peach 〉 Yellow fleshed peach. The genetic diversity among the Chinese cultivars was higher than that among the introduced cultivars. Cluster analysis by the unweighted pair group method with arithmetic averaging （UPGMA） placed the 51 cultivars into five linkage clusters. Cultivar members from the same variety group were distributed in different UPGMA clusters and some members from different variety groups were placed under the same cluster. Different variety groups could not be differentiated in accordance with SSR markers. The SSR analysis revealed rich genetic diversity in the peach primary core collection, representative of genetic resources of peach.     

Analysis of genetic diversity among different geographical populations and determination of biotypes of Bemisia tabaci in China

Abstract:  Analysis of the genetic diversity among 27 different geographical populations of Bemisia tabaci and determination of biotypes of B. tabaci in China based on amplified fragment-length polymorphism (AFLP) and the mitochondrial cytochrome oxidase I (mtDNA COI) gene sequences were conducted. In AFLP assay, the use of five primer combinations selected from 64 primer combinations allowed the identification of 229 polymorphic bands (97.03%) from 60 to 500 bp, suggesting abundant genetic diversity among different geographical populations of B. tabaci. To further identify biotypes of B. tabaci in China, the mtDNA COI gene sequences of nine representative populations from China, Israel and Spain were obtained. Molecular phylogenetic tree based on AFLP and mtDNA COI gene analyses revealed the presence, in China, of at least four different genetic groups of B. tabaci. B biotype, Q biotype and two non-B/Q biotype. B biotype was distributed nationwide. Q biotype was present only in the local region of China including the YunNan province and BeiJing city. This was also the first report about the invasion of Q biotype into China. Of the other two non-B/Q biotype groups, one was found in ShanDong and HeBei provinces, and another in ZheJiang province. The non-B/Q biotype ZheJiang population showed very high similarity with another Asian population India-IW ( AF110704 ) in mtDNA COI sequences and was possibly a Chinese indigenous population. The close monitoring of the Q biotype in locales of China where commercial plants were exported or imported, is now essential to avoid the further accidental distribution of the Q biotype.     

Genetic relatedness among Helicoverpa armigera (Hübner) occurring on different host plants as revealed by random amplified polymorphic DNA markers

The genetic relatedness among Helicoverpa armigera (Hübner) occurring on different host plants prevailing in South India was studied using PCR-RAPD. Genomic DNA was isolated individually from five larvae collected from each of 10 different host plants (except in okra). PCR-RAPD analysis was carried out using a set of 20 random primers which had produced repeatable banding patterns from a original set of 60 primers. A set of 155 amplicon levels were available for analysis, of which 154 were polymorphic. An average of 7.75 bands per primer was recorded. Similarity coefficients based on the frequency of band sharing among host strains varied from 0.25 in cotton and sunflower to 0.72 in groundnut. Clustering analysis on the basis of the PCR-RAPD-generating band sharing indicated that most of the individuals occurring on niger, safflower, green gram, abutilon and lagasca clustered together, indicating greater genetic similarity among themselves, than those occurring on other crops. Furthermore, the pattern of genetic variation in the individuals collected from niger, safflower, green gram, groundnut, abutilon and lagasca was seem to be largely host-dependent.     

Comparison of performance on different host plants between the B biotype and a non-B biotype of Bemisia tabaci from Zhejiang, China

The capacity of the B biotype of the whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), to invade has often been linked to its presumably wider host range than the non‐B indigenous biotypes. However, there are few experimental studies of the relative performance of the B biotype and non‐B biotypes on different host‐plant species. Here, we compared the performance of the B biotype and an indigenous non‐B biotype (China‐ZHJ‐1) of B. tabaci from Zhejiang, China on five commonly cultivated host plants, each from a different family: cotton, tobacco, cabbage, squash, and kidney bean. We also examined the effect of rearing host plants on the performance of the B biotype. Overall, the performance of the B biotype on the five species of plants was much better than that of the indigenous non‐B population. On tobacco, cabbage, and kidney bean, no individuals of ZHJ‐1 completed development to adulthood, whereas the B biotype developed successfully from egg to adult on all three plants. On squash, the B biotype survived better, developed to adulthood earlier and had a higher fecundity than ZHJ‐1. The two biotypes performed more equally on cotton, but even on this plant the B biotype female adults lived nearly twice as long as that of ZHJ‐1 and may have realized a higher life‐time fecundity. The B biotype also showed a substantial capacity to acclimatize to alternative host plants for improved survival and reproduction, on both highly suitable and marginally suitable host plants. We conclude that the host range of the B biotype of B. tabaci may be much wider than those of some indigenous biotypes, and this advantage of the B biotype over the non‐B biotypes may assist in its invasion and displacement of some indigenous biotypes in the field.     

Geminivirus transmission and biological characterisation of Bemisia tabaci (Gennadius) biotypes from different geographic regions

Eighteen populations of Bemisia tabaci, collected from different geographic locations (North & Central America, the Caribbean, Africa, the Middle East, Asia and Europe), were studied to identify and compare biological and genetic characteristics that can be used to differentiate biotypes. The morphology of the fourth instar/pupal stage and compound eye structures of adults were investigated using scanning electron microscopy and found to be typical of the species among all biotypes and populations studied. Setae and spines of B. tabaci larval scales from the same colony were highly variable depending on the host plant species or leaf surface characteristics. The location and the morphology of caudal setae, characteristic of all B. tabaci studied to date, were present in all colonies. However, differences in adult body lengths and in the ability to induce phy to toxic disorders in certain plant species were found between biotypes or populations. The recently identified “B” biotype, characterised by a diagnostic esterase banding pattern and by its ability to induce phytotoxic responses in squash, honeysuckle and nightshade was readily distinguished from non-“B” biotype populations. None of the non-“B” biotypes studied, were found to induce phytotoxic responses. Nine populations examined showed typical “B” biotype characteristics, regardless of country of origin. All tested populations, determined as “B” or “B”-like biotypes successfully mated with other “B” biotype colonies from different geographic areas. Non-“B” biotype colonies did not interbreed with other biotypes. The B. tabaci populations were tested for their ability to transmit 15 whitefly-transmitted geminiviruses (WTGs) from different geographic areas with a wide range of symptom types. All WTGs were transmitted by the “B” biotype colonies and by most non-“B” biotype colonies, with the exception of three viruses found in ornamental plants which were non-transmissible by any colony. Some non-“B” biotypes would not transmit certain geminiviruses and some geminiviruses were more efficiently transmitted than were others.     

Spatial Genetic Heterogeneity in Populations of a Newly Invasive Whitefly in China Revealed by a Nation-Wide Field Survey

Background

Even though introductions of exotic species provide ready-made experiments of rapid evolution, few studies have examined the genetic structure of an exotic species shortly after its initial introduction and subsequent spread. To determine the genetic structure of its populations during the initial introduction, we investigated the invasive sweet potato whitefly (Bemisia tabaci Q, commonly known as B. tabaci biotype Q) in China, which was introduced in approximately 2003. A total of 619 B. tabaci Q individuals in 20 provinces throughout China were collected and analyzed using five microsatellite loci.

Results

The introduced populations of B. tabaci Q in China represent eight genetic clusters with different geographic distributions. The populations in Yunnan Province, where B. tabaci Q was first detected, are genetically different from the other populations in China.

Conclusion

The introduced populations of B. tabaci Q in China have high spatial genetic heterogeneity. Additional research is required to determine whether the heterogeneity results from multiple introductions, rapid evolution following one or few introductions, or some combination of multiple introductions and rapid evolution. The heterogeneity, however, is inconsistent with a single introduction at Yunnan Province, where B. tabaci Q was first detected, followed by spread.     

Identification of biotypes and secondary endosymbionts of Bemisia tabaci in Korea and relationships with the occurrence of TYLCV disease

Bemisia tabaci is a species complex that consists of at least 24 genetically diverse biotypes. Here, we determined the biotypes of 27 populations collected in 17 different regions of Korea. Nucleotide sequence comparisons of cytochrome oxidase showed that 26 populations were Q biotype and that one population, the Goyang population, was B biotype. Further subgroup analysis of the Q biotype showed that all populations belonged to the Q1 subgroup, which originates from Western Mediterranean countries. Five endosymbiotic bacteria from various B. tabaci populations were analyzed by comparing rDNA sequences. Hamiltonella was detected in all the populations tested regardless of biotype. Cardinium was detected in all Q biotype populations but not in the B biotype population, while Rickettsia was detected in the B biotype population but not in Q biotype populations. Arsenophonus and Wolbachia were detected in 35% and 58% of Q biotype populations, respectively, but not in the B biotype population. Our results show that the endosymbiont profile is strongly associated with each biotype and with subgroups of the Q biotype. Survey of TYLCV disease from 2008 to 2010 indicated that this disease is widely spread in Korea. This study suggests that the rapid spread of TYLCV may be associated with endosymbiont infection, particularly Hamiltonella infection of B. tabaci.     

Feeding Experience of Bemisia tabaci (Hemiptera: Aleyrodidae) Affects Their Performance on Different Host Plants

The sweetpotato whitefly, Bemisia tabaci biotype B is extremely polyphagous with >600 species of host plants. We hypothesized that previous experience of the whitefly on a given host plant affects their host selection and performance on the plants without previous experience. We investigated the host selection for feeding and oviposition of adults and development and survival of immatures of three host-plant-experienced populations of B. tabaci, namely Bemisia-eggplant, Bemisia-tomato and Bemisia-cucumber, on their experienced host plant and each of the three other plant species (eggplant, tomato, cucumber and pepper) without previous experience. We found that the influence of previous experience of the whiteflies varied among the populations. All populations refused pepper for feeding and oviposition, whereas the Bemisia-cucumber and the Bemisia-eggplant strongly preferred cucumber. Bemisia-tomato did not show strong preference to any of the three host palnts. Development time from egg to adult eclosion varied among the populations, being shortest on eggplant, longest on pepper, and intermediate on tomato and cucumber except for the Bemisia-cucumber developed similarly on tomato and pepper. The survivorship from egg to adult eclosion of all populations was highest on eggplant (80-98%), lowest on pepper (0-20%), and intermediate on tomato and cucumber. In conclusion, the effects of previous experience of whiteflies on host selection for feeding and oviposition, development, and survivorship varied depending on host plants, and host plants play a stronger role than previous experience. Preference of feeding and oviposition by adults may not accurately reflect host suitability of immatures. These results provided important information for understanding whitefly population dynamics and dispersal among different crop systems.     

Occurrence of three genotypic clusters of Bemisia tabaci and the rapid spread of the B biotype in south India

The whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), is generally considered to have originated from the Indian subcontinent, although little information has so far been collected on the molecular diversity of populations present in this region. The genetic diversity of B. tabaci populations from Karnataka State, south India was analysed using the random amplified polymorphic DNA‐polymerase chain reaction (RAPD‐PCR) technique and partial mitochondrial cytochrome oxidase I (mtCOI) gene sequences (689 bases) of 22 selected samples. A total of 108 whitefly samples analysed by RAPD‐PCR produced 89 polymorphic bands, and cluster analyses grouped them according to their geographic origin into ‘north’ and ‘south’ Karnataka. Phylogenetic analysis of mtCOI gene sequences with reference B. tabaci sequences from other Asian countries divided them into three genotypic clusters. Each cluster was supported with high bootstrap values (82–100%) and the individuals belonging to each cluster shared high nucleotide identities (up to 100%). This indicated at least three distinct genotypes, apparently indigenous to India, which are also present in China, Malaysia, Nepal, Pakistan, and Thailand. These coexist with the B biotype, which was first reported in India in 1999, and has since spread rapidly to other states in south India. The B biotype was more common than the indigenous B. tabaci, in locations where it had been present for more than 2 years. This is reminiscent of the situation in the Americas during the early 1990s, where the B biotype replaced existing biotypes and caused unprecedented losses to agriculture.