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2012 Vol. 11 No. 2 Previous Issue    Next Issue

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SPECIAL ISSUE: THE WHITEFLY BEMISIA TABACI SPECIES COMPLEX AND BEGOMOVIRUSES
EDITORIAL
SECTION 1: THE Bemisia tabaci CRYPTIC SPECIES COMPLEX
SECTION 2: Bemisia AND BEGOMOVIRUS TRANSMISSION
SECTION 3: MOLECULAR CHARACTERIZATION OF Bemisia tabaci
SECTION 4: CONTROL OF WHITEFLY AND WHITEFLY TRANSMITTED VIRUS DISEASES




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SPECIAL ISSUE: THE WHITEFLY BEMISIA TABACI SPECIES COMPLEX AND BEGOMOVIRUSES

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blank 2012, 11(2): 170-170.  DOI: 10.1016/S1671-2927(00)8533 Abstract ( )   PDF in ScienceDirect

EDITORIAL

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Special Issue Introduction - The Whitefly Bemisia tabaci Species Complex and Begomoviruses: Research Progress and Future Prospects LIU Shu-sheng, Linda L Walling, WANG Xiao-wei 2012, 11(2): 171-175.  DOI: 10.1016/S1671-2927(00)8534 Abstract ( )   PDF in ScienceDirect

SECTION 1: THE Bemisia tabaci CRYPTIC SPECIES COMPLEX

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Species Concepts as Applied to the Whitefly Bemisia tabaci Systematics: How Many Species Are There? LIU Shu-sheng, John Colvin , Paul J De Barro 2012, 11(2): 176-186.  DOI: 10.1016/S1671-2927(00)8535 Abstract ( )   PDF in ScienceDirect   The worldwide distribution and extensive genetic diversity of the whitefly, Bemisia tabaci, has long been recognized. However, the levels of separation within B. tabaci and the nomenclature of the various genetic groups have been a subject of debate. Recent phylogenetic analyses indicate that B. tabaci is a complex composed of 28 morphologically indistinguishable species. In this article, we first review the debate and difficulties associated with B. tabaci’s taxonomy and systematics, and argue for the need to apply the biological species concept in order to elucidate B. tabaci’s systematics. We summarize the accumulated genetic and behavioural data on reproductive incompatibilities evident amongst phylogenetic mtCOI groups of B. tabaci. Crossing studies have been conducted with 14 of the 28 putative species covering 54 reciprocal inter-species pairs, and observations on mating behaviour have been conducted for seven species pairs. Data from both crossing trials and behavioural observations indicate a consistent pattern of reproductive isolation among the putative species. We then discuss the technical and conceptual complexities associated with crossing experiments and behavioural observations designed to reveal reproductive incompatibility. Finally, we elaborate on a strategy for further clarifying the pattern of reproductive isolation between B. tabaci groups and propose future research directions on the systematics of this complex.

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The Bemisia tabaci Species Complex: Questions to Guide Future Research Paul J De Barro 2012, 11(2): 187-196.  DOI: 10.1016/S1671-2927(00)8536 Abstract ( )   PDF in ScienceDirect   Since 2007 we have began to consider the relationships between the different members of the Bemisia tabaci species complex in a more structured and systematic way. Much of these relationships has been infered from considerations of a portion of the mitochondrial cytochrome oxidase one (mtCOI) gene. While this is a quite limited approach which would benefit from the consideration of a much greater diversity of genetic material, it is the only publically available data that spans the diversity of the species complex. Despite the limitations, the phylogenetic reconstruction that can be derived from this data is useful and can be used as a basis to frame questions and construct testable hypotheses that will form the basis for future research. This study uses the largest available mtCOI dataset, consisting of 383 unique mtCOI haplotypes that spans the full diversity of the B. tabaci species complex as we currently know it, to make a range of observations which are then used to develop questions as guide for future research.

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The Effects of Space Dimension and Temperature on the Cross Mating of Three Cryptic Species of the Bemisia tabaci Complex in China LI Xiao-xi, LI Shao-jian, XUE Xia, Muhammad Z Ahmed, REN Shun-xiang, rew G S Cuthbertson , QIU Bao-li 2012, 11(2): 197-205.  DOI: 10.1016/S1671-2927(00)8537 Abstract ( )   PDF in ScienceDirect   The sweetpotato whitefly Bemisia tabaci (Homoptera: Aleyrodidae) is a destructive pest of agriculture and horticulture worldwide. Recent phylogenetic analysis using mitochondrial cytochrome oxidase 1 sequences indicates that this whitefly is a species complex including at least 24 morphologically indistinguishable but genetically distinct cryptic species. In this study, the inter-species crosses of Middle East-Asia Minor 1 (MEAM1), Mediterranean (MED) and Asia II 7 cryptic species, which were referred to as B, Q and Cv biotypes before, were conducted in two different devices, leaf cages (7 cm3) and cylinder cages (280 cm3), and at three temperatures of 22, 30 and 38°C. Results indicated that no female progeny were produced in the reciprocal cross between MEAM1×Asia II 7, between MED×Asia II 7 cryptic species neither in leaf cage nor in cylinder cages, while 0.81 and 1.37% of females in the offspring were recorded in the reciprocal cross between MEAM1×MED in leaf cage experiments. Approximately 0.95-0.98% female progeny were recorded in the reciprocal cross between MEAM1×MED at 30°C, 0.77% female progeny were recorded in the single cross direction between MEAM1 × MED at 22°C, and no female progeny were found in their reciprocal cross at 38°C in leaf cage. Our findings indicated that neither space dimension nor temperature have a significant effect on the hybridization of different B. tabaci cryptic species.

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Diversity and Genetic Differentiation of the Whitefly Bemisia tabaci Species Complex in China Based on mtCOI and cDNA-AFLP Analysis GUO Xiao-jun, RAO Qiong, ZHANG Fan, LUO Chen, ZHANG Hong-yu , GAO Xi-wu 2012, 11(2): 206-214.  DOI: 10.1016/S1671-2927(00)8538 Abstract ( )   PDF in ScienceDirect   The whitefly Bemisia tabaci are considered as a taxonomically complex that contained some destructive pests. Two of the most prevalent cryptic species are B. tabaci Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED). In an extensive field survey of the B. tabaci complex present throughout part of China from 2004 to 2007, we obtained 93 samples of B. tabaci from 22 provinces. We determined that these Chinese haplotypes included 2 invasive species (MEAM1 and MED), and 4 indigenous cryptic species (Asia II 1, Asia II 3, China 3 and Asia II 7) by sequencing mitochondrial cytochrome oxidose one gene (mtCOI). The diversity and genetic differentiation of a subset of 19 populations of B. tabaci were studied using cDNA amplified fragment length polymorphism (AFLP). Prior to 2007, MEAM1 was a dominant species in many provinces in China. By 2007, MED was dominant in 11 provinces. Both invasive and indigenous species were simultaneously found in some regions. Indigenous species of B. tabaci were found in six provinces in southern China. MED and MEAM1 have broad ranges of host plants, and indigenous species appeared to have much narrower host ranges. All Asia II 3 samples were found on cotton except one on aubergine. China 3 has more host plants than Asia II 3. Twelve samples of China 3 were collected from sweet potato, Japanese hop, squash and cotton. A total of 677 reproducible bands amplified with 5 AFLP primer combinations were obtained. The highest proportion of polymorphic bands was 98.7% and the lowest was 91.9%. Unweighted pair-group method analysis indicated that the clustering was independent of the different species. MED showed the lowest degree of similarity than the other species. The data indicate that both MEAM1and MED were rapidly established in China.

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Species Exclusion Between an Invasive and an Indigenous Whitefly on Host Plants with Differential Levels of Suitability LUAN Jun-bo, XU Jing, LIN Ke-ke, Myron P Zalucki , LIU Shu-sheng 2012, 11(2): 215-224.  DOI: 10.1016/S1671-2927(00)8539 Abstract ( )   PDF in ScienceDirect   The whitefly Bemisia tabaci has risen to international prominence since the 1980s due to the rapid spread around the globe by the two species B and Q within this species complex. The invasion of B has often been associated with the displacement of indigenous whiteflies. As the genetic structure of B. tabaci is diverse, more case studies of the competitive relationships between B and indigenous species of the whitefly species complex will help to understand further the mechanisms underlying the invasion of B. We examined the competitive interactions between B and ZHJ2, a widely distributed indigenous whitefly in Asia, on host plants with differential levels of suitability to the two species in the laboratory, and also tested the effect of insecticide application on the competitive relationships. Three species of plants were tested including cotton, a plant showing similar levels of suitability to both species, squash, a plant showing higher suitability to B than to ZHJ2, and kidney bean, a plant showing higher suitability to ZHJ2 than to B. In the case of no insecticide application, B displaced ZHJ2 on cotton, squash, and kidney bean by the 6th, 3rd and 10th generation, respectively. With the application of imidacloprid, the displacement of ZHJ2 by B on cotton occurred by the 5th generation. As the displacement progressed, the proportion of B females increased, and the proportion of ZHJ2 females decreased on cotton and squash. In contrast, on kidney bean the proportion of B females remained unchanged while that of ZHJ2 increased. These results show the strong capacity of the invasive B to displace ZHJ2, and indicate that host plants with differential levels of suitability to the two species may affect the speed but not the trend of displacement and insecticide application may accelerate the process of displacement.

SECTION 2: Bemisia AND BEGOMOVIRUS TRANSMISSION

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Back to Basics: Are Begomoviruses Whitefly Pathogens? Henryk Czosnek , Murad Ghanim 2012, 11(2): 225-234.  DOI: 10.1016/S1671-2927(00)8540 Abstract ( )   PDF in ScienceDirect   Begomoviruses and whiteflies have interacted for geological times. An assumed long-lasting virus-vector intimate relationship of this magnitude implies that the partners have developed co-evolutionary mechanisms that insure on one hand the survival and the efficient transmission of the virus, and on the other hand the safeguard of the insect host from possible deleterious effects of the virus. Several studies have indicated that viruses belonging to the Tomato yellow leaf curl virus (TYLCVs) family from China, Israel and Italy are reminiscent of insect pathogens. TYLCVs like all begomoviruses are transmitted in a circulative manner by the whitefly Bemisia tabaci. The survival of the virus in the haemolymph of B. tabaci is ensured by a GroEL homologue produced by a whitefly secondary endosymbiont. Following acquisition and transfer to non-host plants, the virus may remain associated with the insect for its entire 4-5 wk-long adult life. During this period, the ability of the insects to inoculate plants steadily decreased, but did not disappear. The long-term presence of TYLCVs in B. tabaci was associated with a decrease in the insect longevity and fertility. Viral DNA was transmitted to progeny, but seldom infectivity. TYLCV transcripts were found associated with the insects, raising the possibility of replication and expression in the vector. TYLCVs may spread amidst whiteflies during copulation. Functional genomics tools such as microarrays, deep sequencing, quantitative PCR and gene silencing allow revisiting the proposition that TYLCVs have retained, or acquired, some characteristics of an insect pathogen.

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Bemisia tabaci Phylogenetic Groups in India and the Relative Transmission Efficacy of Tomato leaf curl Bangalore virus by an Indigenous and an Exotic Population R V Chowda-Reddy, M Kirankumar, Susan E Seal, V Muniyappa, Girish B Val, M R Govindappa, John Colvin 2012, 11(2): 235-248.  DOI: 10.1016/S1671-2927(00)8541 Abstract ( )   PDF in ScienceDirect   Bemisia tabaci adults from various host-plant species were collected from 31 regions across India. 266 B. tabaci samples were first screened by RAPD-PCR to examine molecular variability and to select individuals with different fingerprints. Host-plant and region of collection were then used to select 25 individuals for PCR amplification and sequencing of their partial mitochondrial cytochrome oxidase subunit one (mtCOI) genes. Pairwise comparisons with mtCOI consensus sequences showed that the majority of these samples had <3.5% sequence divergence from groups currently termed Asia I, Asia II-5, Asia II-7, and Asia II-8. The biotype-B B. tabaci from India clustered into the Middle East-Asia Minor 1 group. A new group of B. tabaci from Coimbatore, collected from pumpkin, was related most closely to the Asia I group (6.2% sequence divergence from the consensus Asia I sequence). To increase our understanding of the epidemiology of tomato leaf curl disease (ToLCD) and the key B. tabaci genetic groups involved in virus spread, the indigenous Asia I and the exotic biotype-B population from South India were used to carry out transmission experiments using Tomato leaf curl Bangalore virus (ToLCBV). The acquisition access periods (AAP), inoculation access periods (IAP), latent periods (LP), and ToLCBV transmission efficiencies of the two populations were compared and the biotype-B had the more efficient transmission characteristics. These results are discussed in relation to recent changes in the epidemiology of tomato leaf curl disease in South India.

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Homopteran Vector Biomarkers for Efficient Circulative Plant Virus Transmission are Conserved in Multiple Aphid Species and the Whitefly Bemisia tabaci Michelle Cilia, Michael Bereman, Tara Fish, Michael J MacCoss , Stewart Gray 2012, 11(2): 249-262.  DOI: 10.1016/S1671-2927(00)8542 Abstract ( )   PDF in ScienceDirect   Plant viruses in the families Luteoviridae and Geminiviridae are phloem restricted and are transmitted in a persistent, circulative manner by homopteran insects. Using fluorescence 2-D difference gel electrophoresis to compare the proteomes of F2 genotypes of Schizaphis graminum segregating for virus transmission ability, we recently discovered a panel of protein biomarkers that predict vector competency. Here we used aphid and whitefly nucleotide and expressed sequence tag database mining to test whether these biomarkers are conserved in other homopteran insects. S. graminum gene homologs that shared a high degree of predicted amino acid identity were discovered in two other aphid species and in the whitefly Bemisia tabaci. Selected reaction monitoring mass spectrometry was used to validate the expression of these biomarkers proteins in multiple aphid vector species. The conservation of these proteins in multiple insect taxa that transmit plant viruses along the circulative transmission pathway creates the opportunity to use these biomarkers to rapidly identify insect populations that are the most efficient vectors and allow them to be targeted for control prior to the spread of virus within a crop.

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Monoclonal Antibodies Against the Whitefly-Transmitted Tomato Yellow Leaf Curl Virus and Their Application in Virus Detection WU Jian-xiang, SHANG Hai-li, XIE Yan, SHEN Qing-tang , ZHOU Xue-ping 2012, 11(2): 263-268.  DOI: 10.1016/S1671-2927(00)8543 Abstract ( )   PDF in ScienceDirect   Tomato yellow leaf curl virus (TYLCV) is a species of the family Geminiviridae, causing serious yield losses in tomato production. The coat protein (CP) gene of TYLCV isolate SH2 was expressed in Escherichia coli BL21 (DE3) using pET- 32a as the expression vector. The recombinant protein was purified through Ni+-NTA affinity column and used to immunize BALB/c mice. Three hybridoma cell lines (2B2, 2E3 and 3E10) secreting monoclonal antibodies (MAbs) against TYLCV CP were obtained by fusing mouse myeloma cells (Sp 2/0) with spleen cells from the immunized BALB/c mouse. The titers of ascitic fluids of three MAbs ranged from 10-6 to 10-7 in indirect-ELISA. Isotypes and subclasses of all the MAbs belonged to IgG1, κ light chain. Triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) showed that the MAb 3E10 could react with five begomoviruses infecting tomato, while the other two (2B2 and 2E3) mainly reacted with TYLCV. TAS-ELISA was set up using the MAb 3E10, and the established method could successfully detect virus in plant sap at 1:2 560 (w/v, g mL-1). Detection of field samples showed that begomoviruses were common in tomato crops in Zhejiang Province, China.

SECTION 3: MOLECULAR CHARACTERIZATION OF Bemisia tabaci

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A Roadmap for Whitefly Genomics Research: Lessons from Previous Insect Genome Projects Owain Rhys Edwards , Alexie Papanicolaou 2012, 11(2): 269-280.  DOI: 10.1016/S1671-2927(00)8544 Abstract ( )   PDF in ScienceDirect   Due to evolving molecular and informatics technologies, modern genome sequencing projects have more different characteristics than what most biologists have become accustomed to during the capillary-based sequencing era. In this paper, we explore the characteristics that made past insect genome projects successful and place them in the context of next-generation sequencing. By taking into account the intricacies of whitefly biology and the community, we present a roadmap for whitefly-omics, which focuses on the formation of an international consortium, deployment of informatic platforms and realistic generation of reference sequence data.

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Next Generation Transcriptome Sequencing and Quantitative Real-Time PCR Technologies for Characterisation of the Bemisia tabaci Asia 1 mtCOI Phylogenetic Clade Susan Seal, Mitulkumar V Patel, Carl Collins, John Colvin , David Bailey 2012, 11(2): 281-292.  DOI: 10.1016/S1671-2927(00)8545 Abstract ( )   PDF in ScienceDirect   A programme of functional genomics research is underway at the University of Greenwich, UK, to develop and apply genomics technologies to characterise an economically-important but under-researched Bemisia tabaci (Hemiptera: Aleyrodidae), the Asia 1 mtCOI phylogenetic group. A comparison of this putative species from India with other important B. tabaci populations and insect species may provide targets for the development of more effective whitefly control strategies. As a first step, next-generation sequencing (NGS) has been used to survey the transcriptome of adult female whitefly, with high quality RNA preparations being used to generate cDNA libraries for NGS using the Roche 454 Titanium DNA sequencing platform. Contig assemblies constructed from the resultant sequences (301 094 reads) using the software program CLC Genomics Workbench generated 3 821 core contigs. Comparison of a selection of these contigs with related sequences from other B. tabaci genetic groups has revealed good alignment for some genes (e.g., HSP90) but misassemblies in other datasets (e.g., the vitellogenin gene family), highlighting the need for manual curation as well as collaborative international efforts to obtain accurate assemblies from the existing next generation sequence datasets. Nevertheless, data emerging from the NGS has facilitated the development of accurate and reliable methods for analysing gene expression based on quantitative real-time RT-PCR, illustrating the power of this approach to enable rapid expression analyses in an organism for which a complete genome sequence is currently lacking.

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cDNA Cloning of Heat Shock Protein Genes and Their Expression in an Indigenous Cryptic Species of the Whitefly Bemisia tabaci Complex from China YU Hao, WAN Fang-hao , GUO Jian-ying 2012, 11(2): 293-302.  DOI: 10.1016/S1671-2927(00)8546 Abstract ( )   PDF in ScienceDirect   Thermal adaptation plays a fundamental role in shaping the distribution and abundance of insects, and heat shock proteins (Hsps) play important roles in the temperature adaptation of various organisms. To better understand the temperature tolerance of the indigenous ZHJ2-biotype of whitefly Bemisia tabaci species complex, we obtained complete cDNA sequences for hsp90, hsp70, and hsp20 and analyzed their expression profiles under different high temperature treatments by real-time quantitative polymerase chain reaction. The high temperature tolerance of B. tabaci ZHJ2-biotype was determined by survival rate after exposure to different high temperatures for 1 h. The results showed that after 41°C heat-shock treatment for 1 h, the survival rates of ZHJ2 adults declined significantly and the estimated temperature required to cause 50% mortality (LT50) is 42.85°C for 1 h. Temperatures for onset (Ton) or maximal (Tmax) induction of hsps expression in B. tabaci ZHJ2-biotype were 35 and 39°C (or 41°C). Compared with previous studies, indigenous ZHJ2- biotype exhibits lower heat temperature stress tolerance and Ton (or Tmax) than the invasive B-biotype.

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p38 MAPK is a Component of the Signal Transduction Pathway Triggering Cold Stress Response in the MED Cryptic Species of Bemisia tabaci LI Fang-fang, XIA Jun, LI Jun-min, LIU Shu-sheng , WANG Xiao-wei 2012, 11(2): 303-311.  DOI: 10.1016/S1671-2927(00)8547 Abstract ( )   PDF in ScienceDirect   Cold stress responses help insects to survive under low temperatures that would be lethal otherwise. This phenomenon might contribute to the invasion of some Bemisia tabaci cryptic species from subtropical areas to temperate regions. However, the molecular mechanisms regulating cold stress responses in whitefly are yet unclear. Mitogen-activated protein kinases (MAPKs) which including p38, ERK, and JNK, are well known for their roles in regulating metabolic responses to cold stress in many insects. In this study, we explored the possible roles of the MAPKs in response to low temperature stresses in the Mediterranean cryptic species (the Q-biotype) of the B. tabaci species complex. First, we cloned the p38 and ERK genes from the whitefly cDNA library. Next, we analyzed the activation of MAPKs during cold stress in the Mediterranean cryptic species by immuno-blotting. After cold stress, the level of phospho-p38 increased but no significant change was observed in the phosphorylation of ERK and JNK, thus suggesting that the p38 might be responsible for the defense response to low temperature stress. Furthermore, we demonstrated that: i) 3 min chilling at 0°C was sufficient for the activation of p38 MAPK pathway in this whitefly; and ii) the amount of phosphorylated p38 increased significantly in the first 20 min of chilling, reversed by 60 min, and then returned to the original level by 120 min. Taken together, our results suggest that the p38 pathway is important during response to low temperature stress in the Mediterranean cryptic species of the B. tabaci species complex.

SECTION 4: CONTROL OF WHITEFLY AND WHITEFLY TRANSMITTED VIRUS DISEASES

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Bemisia tabaci Biotype Dynamics and Resistance to Insecticides in Israel During the Years 2008-2010 Svetlana Kontsedalov, Fauzi Abu-Moch, Galina Lebedev, Henryk Czosnek, A Rami Horowitz , MuradGhanim 2012, 11(2): 312-320.  DOI: 10.1016/S1671-2927(00)8548 Abstract ( )   PDF in ScienceDirect   The sweetpotato whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is an extremely polyphagous insect pest that causes significant crop losses in Israel and worldwide. B. tabaci is a species complex of which the B and Q biotypes are the most widespread and damaging worldwide. The change in biotype composition and resistance to insecticide in Israel was monitored during the years 2008-2010 to identify patterns in population dynamics that can be correlated with resistance outbreaks. The results show that B biotype populations dominate crops grown in open fields, while Q biotype populations gradually dominate crops grown in protected conditions such as greenhouses and nethouses, where resistance outbreaks usually develop after several insecticide applications. While in previous years, Q biotype populations were widely detected in many regions in Israel, significant domination of the B biotype across populations collected was observed during the year 2010, indicating the instability of the B. tabaci population from one year to another. Reasons for the changing dynamics and the shift in the relative abundance of B. tabaci biotype, and their resistance status, are discussed.

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Characterisation of Neonicotinoid and Pymetrozine Resistance in Strains of Bemisia tabaci (Hemiptera: Aleyrodidae) from China RAO Qiong, XU Yong-hua, LUO Chen, ZHANG Hong-yu, Christopher M Jones, Greg J Devine, KevinGorman , Ian Denholm 2012, 11(2): 321-326.  DOI: 10.1016/S1671-2927(00)8549 Abstract ( )   PDF in ScienceDirect   Four strains of the Q biotype and one of the B biotype of the whitefly Bemisia tabaci collected from China were characterised for resistance to four neonicotinoid insecticides and pymetrozine. Q biotype strains showed moderate to strong resistance to imidacloprid, thiamethoxam and acetamiprid, but little or no cross-resistance to dinotefuron. Resistance to neonicotinoids was consistently associated with resistance to pymetrozine, despite the latter having a distinct (though unresolved) mode of action. The single B biotype strain proved largely susceptible to all the insecticides investigated. Resistance in the Q biotype strains was associated with over-expression of a cytochrome P450 monooxygenase gene, CYP6CM1, whose substrate specificity presumably accounts for the observed cross-resistance profiles.

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African Cassava Whitefly, Bemisia tabaci, Resistance in African and South American Cassava Genotypes Christopher AOmongo, Robert Kawuki, Antony C Bellotti, Titus Alicai, Yona Baguma, M N Maruthi, Anton Bua , John Colvin 2012, 11(2): 327-336.  DOI: 10.1016/S1671-2927(00)8550 Abstract ( )   PDF in ScienceDirect   The whitefly, Bemisia tabaci, is a major pest of cassava, particularly in Africa where it is responsible both for the transmission of plant viruses and, increasingly, for direct damage due to feeding by high populations. To date, there have been no practical solutions to combat this emerging problem, due to the inability of the subsistence farmers that grow cassava to afford expensive inputs such as insecticides. A programme of research was carried out linking institutes in Africa, the UK and South America, to identify possible resistance sources in cassava to the whitefly, Bemisia tabaci. The South American genotype MEcu 72 and several Ugandan cassava landraces including Ofumba Chai, Nabwire 1 and Mercury showed good levels of resistance to B. tabaci. Field and screen-house experiments showed that all of the improved, high-yielding cassava mosaic disease (CMD) resistant cassava genotypes assessed were highly susceptible to B. tabaci and supported high populations of all life stages. These data support the hypothesis that the continuing high populations of cassava B. tabaci in Uganda are due, in part, to the widespread adoption of CMD-resistant cassava varieties during the CMD pandemic. They also show that the whitefly, Aleurotrachelus socialis, resistance present in the South American cassava genotypes could have broader applicability in the Old World.

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Socio-Economic and Scientific Impact Created by Whitefly-Transmitted, Plant- Virus Disease Resistant Tomato Varieties in Southern India John Colvin, N Nagaraju, Carlos Moreno-Leguizamon, R M Govindappa, T B Manjunatha Reddy, SA Padmaja, Neena Joshi, Peter M Hanson, Susan E Seal , V Muniyappa 2012, 11(2): 337-345.  DOI: 10.1016/S1671-2927(00)8551 Abstract ( )   PDF in ScienceDirect   Research carried out to assess the impact of open-pollinated Tomato leaf curl virus (ToLCV)-resistant tomatoes and hybrids on the livelihoods of resource-poor farmers in Southern India is described and discussed. Three high-yielding ToLCV-resistant tomato varieties were developed initially using conventional breeding and screening techniques involving inoculation by ToLCV-viruliferous whitefly, Bemisia tabaci. In 2003 and 2004, respectively, these varieties were released officially by the Karnataka State Seed Committee and the Indian Ministry of Agriculture through notification in the Gazette of India. From 2003 to 2005, eleven seed companies bought breeder seed of the ToLCV-resistant varieties and used them to begin breeding F1 hybrids from them. Socio-economic studies carried out to assess the benefits obtained from growing the ToLCV-resistant varieties found that farmers could gain up to 10 times the profit by growing the ToLCV-resistant varieties compared to the pre-existing ToLCV-susceptible varieties. Adoption of ToLCV-resistant tomatoes was also associated with reduced pesticide use. Extra income from tomato sales was prioritised by farmers to pay for children’s education, better nutrition and medicines. In a joint effort with the commercial seed sector in India, a promotional field day was organised in 2007. As well as the three ToLCV-resistant varieties, 62 ToLCV-resistant hybrid tomatoes were exhibited during a farmer-field day by 17 commercial seed companies and several public institutes. Tomatoes with ToLCV-resistance are now grown widely in South India and seeds of the three open-pollinated varieties have been distributed to more than 12 countries. In 2007, a conservative estimate of the financial-benefit to cost of the research ratio was already more than 837:1.