Tomato Leaf Curl Virus Disease Research Articles

Purple standard tomato and cherry tomato crosses could enhance phytonutrient contents and tolerance to tomato leaf curl virus disease

ABSTRACT Intermating between genetically diverse tomatoes could provide information on the underlying biology as a source of new alleles for phytonutrient contents and tomato leaf curl virus (ToLCV) disease tolerance in cherry tomato [Solanum lycopersicum var. cerasiforme (Dunnal) A. Gray]. The study determined combining ability effects, heterosis and gene action for conditioning 19 quantitative traits involving crosses between anthocyanin rich (Aft gene) tomato (Solanum lycopersicum L.) lines and 7 breeding lines of nutritionally rich cherry tomato [S. lycopersicum var. cerasiforme (Dunnal) A. Gray]. An overwhelming response of non-additive gene action in controlling expression of most traits was evident. Purple tomato line “Bidhan Purple” and the cherry tomato lines “Cherry Round Yellow Big Fruit” and “18/ToCVAR-2” could be potential genitors for cherry tomato breeding. Based on combining ability, average heterosis, and mean performance, the promising hybrids: “Alisha Craig Aft ×18/TOCVAR-2,” “Bidhan Purple × 18/TOCVAR-2” and “Alisha Craig Aft × Cherry Round Yellow Big Fruit” were identified in terms of phytonutrient contents and ToLCV disease tolerance. Partial, to over-dominance, reaction in inheritance of most traits reflects the genetic basis of heterosis. Promising cherry tomato hybrids could be exploited following appropriate testing or could be used in segregating generations to produce line-bred cultivars that are ToLCV disease-tolerant and high in phytonutrient contents.

Morphological characterization and molecular validation for ToLCV resistance (Ty-2 and Ty-3 genes) in tomato (Solanum lycopersicum)

An experiment was conducted during the rainy (kharif) season of 2019 and 2020 at ICAR-Indian Agricultural Research Institute, New Delhi to identify the potential genotypes having good horticultural traits along with strong and durable resistance against ToLCV disease of tomato (Solanum lycopersicum L.). A diverse set of 30 tomato genotypes carrying different Ty genes were screened out at phenotypic and genotypic level. First appearance/symptom of tomato leaf curl virus (ToLCV) disease was recorded in Pusa 120 only after 16 days of transplanting (DAT). Within 30 days of transplanting most of the genotypes, viz. Pusa 120, DT12, DT16, DT6 and Pusa Sheetal recorded 80 to 100 PDI (per cent disease incidence) and they were rated as highly susceptible to ToLCV. While at 90 DAT ToLCVincidence (≤15%) was observed in DT2, DT8, DT17, DT20 and DT30 and were categorized a resistant. None of the genotype was found as highly resistant. Four genotypes, viz. DT2, DT10, DT20 and DT30 showed presence of both resistant genes Ty-2 and Ty-3 at genotypic level. These promising genotypes will be useful as parental material to develop lines/hybrids carrying multiple genes against both monopartite and bipartite viruses for strong and durable resistance against ToLCV disease.

Double cross hybrids could substantially supersede single cross hybrids for yield, fruit quality and tolerance to tomato leaf curl virus disease

ABSTRACT Recombination of commercially available hybrids could produce desirable segregants that act as sources of new alleles for tomato breeding. Seven commercial single cross (SC) hybrids of tomato (Solanum lycopersicum L.) were crossed in a half diallel fashion to obtain 21 double cross hybrids (DC) to estimate combining ability, mode of gene action and extent of heterobeltiosis for fruit yield, processing qualities and tomato leaf curl virus (ToLCV) disease severity traits. Predominance of non-additive gene action occurred in the control for all characters except for total soluble solids (TSS) content in fruit that was conditioned by both additive and non-additive gene action. Improvement of most traits in DC hybrids over SC hybrids occurred. Maximum heterotic effect in DC hybrids was for vitamin C content followed by lycopene content, fruit yield per plant, titratable acidity content, number of fruit per plant and percent disease index of ToLCV. Two good combiners, ‘PAN-1286’ and ‘Devi’ among SC hybrids were identified based on general combining ability effects and average performance. Commercial exploitation of DC hybrids, ‘TO-1458 × L-37’ and ‘NS-501 × TO-1458’ following multilocational testing in the tropics and subtropics might be useful. High yielding, ToLCV disease tolerant DC hybrids could be exploited in segregating generations to identify elite multi-parent advanced generation inter-cross (MAGIC) populations.

Identification of whitefly (Bemisia tabaci) proteins interacting with Tomato leaf curl Bangalore virus coat protein gene using Y2H system

Tomato leaf curl Bangalore virus (ToLCBV) (Geminiviridae) causes the economically important tomato leaf curl virus disease (ToLCVD), and is transmitted by the whitefly, Bemisia tabaci (Gennadius) (Aleyrodidae: Hemiptera). Successful transmission of the virus by the insect requires safe translocation of the virus through different barriers inside the vector. During the translocation, the viral coat protein will interact with many whitefly proteins, while a few of them are beneficial to virus (e.g. heat shock proteins) but some may be harmful (e.g. whitefly immune proteins). We carried out the yeast two hybrid (Y2H) assays to identify the proteins of the B.tabaci Asia 1 genetic group interacting with ToLCBV coat protein (CP). The Y2H assay initially identified a total of 425 putative interacting whitefly proteins on a low stringent selection media, and they were reduced to 324 when the yeast colonies were grown on a high stringent media, and of which about 274 colonies produced single bands in colony PCR experiments while the remaining colonies produced multiple bands. Further, high selection pressure assays confirmed a total of 102 whitefly proteins interacting with ToLCBV CP and these included the heat shock proteins (HSPs) 70 kDa, GroEL, nucleoproteins, vitellogenins, apolipophorins, 40 s ribosomal proteins, sorbitol dehydrogenase, dipeptidyl peptidase, E3 ubiquitin, annexin, GTP cyclohydrolase, tropomyosin, salivary secreted proteins, succinate dehydrogenase, lachesins, enolase and others. The identified proteins could be potential targets for novel whitefly control strategies such as using RNAi or insecticide target sites for developing future disease and whitefly control strategies.

Evaluation of tomato genotypes for resistance to whitefly (Bemisia tabaci Gennadius) and tomato leaf curl virus in eastern India

Tomato production in the tropics is threatened by whitefly infestation and tomato leaf curl virus (ToLCV) causing severe economic losses. No stable resistance to these biotic challenges has been identified in eastern India. Therefore, initial screening of 19 advance breeding lines of tomato was carried out during the year 2016–17. Based on the whitefly population per leaf and tomato leaf curl disease severity, eight tomato genotypes were selected for final screening during the year 2017–18. Morphological leaf traits and biochemical parameters in tomato leaf were assessed in selected genotypes and considered as potential mediators of resistance. Significant variation was observed for whitefly infestation and ToLCV disease severity among the tomato genotypes tested. Higher leaf trichome density with narrow and thinner leaves and higher total phenol content in leaf emerged as reliable morphological and biochemical markers for early selection of tomato genotype resistant to whitefly and ToLCV disease. The resistance of tomato genotypes 2016/Res-1, 2015/Res-5, 2014/Res-1 and 2014/Res-4 to both whitefly and ToLCV disease is based on antixenotic properties and they could be utilized in future breeding to enhance stable resistance against these biotic challenges.

Horticultural evaluation of advance breeding lines possessing different combinations of Ty and Ph genes in tomato (Solanum lycopersicum L.)

Agro-statistics, India is the second largest tomato producer only after China in the world. Tomato crop is grown round the year due to wider adaptability but production is adversely affected due to high incidence of tomato leaf curl virus and late blight diseases. These pathogens have enormous capacity to generate new forms and control of these pathogen are mainly achieved by chemical approaches which is not safe for environment as well as for human beings and also add an extra cost in tomato production. Therefore resistance breeding is best approach to manage these types of diseases along with improvement of yield and quality parameters. Five genes viz. Ty-1, Ty-2, Ty-3, Ph-2 and Ph-3 were tried to pyramid from different parent through hybridization to achieve resistance against tomato leaf curl virus and late blight diseases. In this study, 122 advance breeding lines of tomato were evaluated in 2016-17 and 2017-18, through phenotypic and genotypic screening to identify best lines having resistance to both the diseases with better horticultural traits. Punjab Chhuhara cultivar was used as common susceptible check to both the diseases while PVB-4 and LBR-10 were used as resistant checks for tomato leaf curl virus and late blight disease, respectively. Out of 122 lines evaluated, 12 lines were found to be having resistance against both the diseases with different combination of Ty and Ph genes. Among them, four lines viz. TW-4-5G-12, TW-5-1E-7, PR-DH-15-7-11 and PR-DH-28-11G-13 having resistant to both diseases and produces 3.14, 3.90, 2.74 and 3.84 yield kg plant-1 which is more than all the three standard checks. These resistant lines could be evaluated in multi-locations for their commercial exploitation.

Molecular detection and management of tomato leaf curl virus with Pseudomonas fluorescens and chitosan

Tomato production is affected by various fungal, bacterial and viral diseases that attribute to considerable yield losses. Among all the diseases of tomato, Tomato Leaf Curl Virus (ToLCV) disease is cited to be the most devastating both in terms of quantitative and qualitative yield losses. Often, the loss reaches to the extent of 100% during summer throughout India. The virus associated with tomato leaf curl disease was detected by PCR using coat protein specific primers. The present investigations were carried out with potent Pseudomonas fluorescens isolates alone and along with elicitor molecule chitosan to determine its ability to control ToLCV in tomato. Different formulations of P. fluorescens and chitosan were evaluated for controlling ToLCV and growth promotion of tomato. It was found that the application of P. fluorescens isolates Pf1 and Pf2 @ 5kg/ha in combination with chitosan @ 5% reduces the severity of the ToLCV disease by 80 – 90 %. Application of chitosan and P. fluorescens alone caused 60 – 70% reduction in severity of ToLCV disease. Moreover, the plants inoculated with the chitosan based formulation of P. fluorescens isolates Pf1 and Pf2 recorded maximum plant height, fruit number and yield/plant over the control in potted condition. The results, thus, indicate that addition of chitosan has enhanced the biocontrol efficacy of P. fluorescens against ToLCV.

Diallel Analysis for Morphological and Biochemical Traits in Tomato Cultivated under the Influence of Tomato Leaf Curl Virus

Eloquent information about the genetic basis of inheritance is important for any breeding program. Therefore, a diallel study was conducted under the influence of tomato leaf curl virus (TLCV) disease, using the eleven advanced lines of tomato. Firstly, information regarding percent disease index (PDI) was determined via artificial screening with viruliferous whiteflies. Later, these lines were crossed in a half diallel mating design to produce fifty-five one-way hybrids. These hybrids and parental genotypes were evaluated for morphological and biochemical traits under open field conditions. Using the Griffing approach (Method II and Model I), the basis of the inheritance of traits was determined. Furthermore, a Bayesian model was applied to the total yield descriptor. Correlation data indicated that total yield was not correlated with any other trait. The significant general combining ability (GCA) and specific combining ability (SCA) values indicate exploitable genetic variation. The broad-sense heritability values were larger than narrow-sense heritability, showing that selection will be efficient for the improvement of these traits. Hybrid combinations H23, H42 and H49 can be considered efficient for the selection of multiple traits, including yield. Overall, this study provides useful information regarding the genetics of important traits of tomato under TLCV infestation.

Breeding tomato for leaf curl virus resistance

The tomato line IC 613995 was bred for resistance to the begomovirus that causes Tomato leaf curl virus (ToLCV) disease and was recommended for commercial cultivation in the Punjab state under the name Punjab Varkha Bahar-4 (PVB 4). ToLCV resistance of IC 613995 was confirmed through whitefly mediated inoculation trials and under natural disease pressure in the field, including three years of on-station trials, four multi-location trials and 19 on-farm trials. The line IC 613995 produced an average fruit yield of 611.42 q (61.14 tons) ha−1 which was 16% higher than the check ‘PVB 2’ and 22% higher than commercial hybrid ‘NS 524’. Fruits of ‘IC 613995’ are firm and round with an average weight of 90 g. It showed mild ToLCV severity symptoms and symptom appearance was delayed until 45 days post inoculation in the whitefly-mediated trial. The variety is expected to help farmers grow tomato when ToLCV pressure is high and help stabilize tomato supplies and prices.

Heterosis and resistance against tomato leaf curl virus disease in tomato (Solanum lycopersicum L.)

Eight genetically diverse genotypes of tomato (Solanum lycopersicum L.) were used to produce 28 F1 crosses in a diallel pattern excluding reciprocals during 2011–12 and these F1 and parents were evaluated during two consecutively years (2012–13 and 2013–14) to identify heterotic hybrids of tomato with resistance to tomato leaf curl virus disease (ToLCVD). The promising hybrid Pant T-3 × Punjab Chhuhara (25.86%) and Pant T-3 × H-24 (60.11%) produced highest heterosis for number of fruits per plant and total yield per plant, respectively. Five hybrids viz. Arka Meghali × Azad T-5, Pant T-3 × H-88-78-1, Pant T-3 × H-24, H-88-78-1 × H-24 and H-24 × Sel7 were observed to be having field resistance for ToLCVD, and these resistant hybrids could be used in breeding programmes for developing virus resistant cultivars.

Effect of climate change on tomato leaf curl virus (ToLCV) disease in tomato

Effect of climate change on tomato leaf curl virus (ToLCV) disease in tomato

Marker assisted selection of Ty-2 and Ty-3 carrying tomato lines and their implications in breeding tomato leaf curl disease resistant hybrids

Tomato leaf curl virus disease caused by whitefly-transmitted begomoviruses is a serious tomato production constraint in tropical and subtropical regions of the world. Use of genetic resistance for diseases caused by begomoviruses is an important component of sustainable disease management approaches. To date, six introgressions (Ty genes) derived from different tomato wild species that confer resistance to tomato leaf curl disease have been identified. Among these, dominant Ty-2 and partially dominant Ty-3 are important for the development of resistant hybrids because of their gene action. In the present study we report marker assisted selection of tomato lines carrying Ty-2 and Ty-3 genes and the effect of combining these in tomato hybrids using agroinoculation. The response of lines and hybrids with the Ty-2 gene indicated ineffectiveness of Ty-2 to infection by a bipartite tomato leaf curl virus. The Ty-3 gene showed dosage effect with partial resistance in heterozygous state. However, the level of resistance in hybrids with the combination of Ty-2 and Ty-3 genes was higher and similar to homozygous Ty-3 plants. The Ty-2 gene in either homozygous or heterozygous state enhanced the level of resistance of plants with heterozygous Ty-3. Thus, tomato hybrid breeding programs can be benefited by using tomato lines carrying Ty-2 and Ty-3 resistance genes. The combined results of evaluation of horticultural performance, field resistance and agroinoculation tests demonstrated that the set of tomato lines developed in this study could be useful resources for achieving higher level of resistance in tomato hybrids.

Marker assisted gene pyramiding for enhanced Tomato leaf curl virus disease resistance in tomato cultivars

The present research is aimed towards molecular marker assisted pyramiding Tomato leaf curl virus (ToLCV) disease resistance genes into two ToLCV susceptible tomato (Solanum lycopersicum L.) cvs. Pbc and H-86 (resistance genes recipient parents). Resistance gene donors were EC-538408 (Solanum chilense) and EC-520061 (S. peruvianum) in the case of cv. Pbc, and EC-520061 (S. peruvianum) and H-24 (S. lycopersicum) in the case of cv. H-86. A ToLCV resistance gene associated co-dominant simple sequence repeat (SSR) marker SSR-218 was used to discriminate between homozygotes and heterozygotes at the seedling stage prior to pollination, which enabled the rejection of nontarget back crosses and pyramiding progenies of the crosses PbcxEC-520061 and H-86xEC-520061, whereas SSR-306 was used for the cross PbcxEC-538408. Ty-2 gene cleaved amplified polymorphic sequences (CAPS) marker was used for the cross H-86xH-24. Out of 279 pyramiding progenies of the cross PbcxEC-538408/PbcxEC-520061, total 91 plants showed the presence of both resistance allele 1 and 2 along with both susceptibility alleles, and in 243 pyramiding progenies of the cross H-86xEC-520061/H-86xH-24, total 82 plants showed the presence of both resistance allele 1 and Ty-2 along with both susceptible alleles. The pyramiding lines that carried both pyramided resistance genes were resistant to tomato leaf curl disease throughout its life cycle.

Pyramiding Ty‐2 and Ty‐3 genes for resistance to monopartite and bipartite tomato leaf curl viruses of India

Breeding resistance to whitefly‐transmitted begomoviruses is an important goal of tomato breeding programmes worldwide. So far, resistance to begomoviruses in tomato has been achieved using wild species, and at least five resistance genes (Ty genes) have been studied. The present study was undertaken to combine Ty‐2 and Ty‐3 and to determine the effect of pyramiding on infection of tomato by three diverse begomovirus species. The diagnostic ability of the markers linked to Ty genes was assessed and marker‐assisted selection was used to develop pyramided tomato lines from the crosses between Ty stocks. Five stable pyramided tomato lines that differ in fruit morphology and yield potential were developed. The horticultural performance of pyramided lines in field trials showed that the yield and horticultural traits are well maintained in the plants. The response of these lines was assessed using agroinoculation and field tests in a disease hotspot. The pyramided lines and Ty‐3‐carrying lines exhibited a high level of resistance to the monopartite and two bipartite begomoviruses tested. The pyramided tomato lines developed in this study could be important genetic resources for sustainable tomato production in areas affected by tomato leaf curl virus disease. The combined results of disease resistance tests also showed that Ty‐3 is critical for achieving broad‐spectrum resistance. The limitations of relying on a single gene and the importance of pyramiding are discussed in the light of available evidence on frequent recombination in begomoviruses.

Selection of tomato genotypes resistant to tomato leaf curl virus disease using biochemical and physiological markers

SUMMARYA total of 34 tomato genotypes (24 F1+10 parents) were tested for resistance to tomato leaf curl virus (ToLCV) disease by various whitefly inoculation techniques under field and insect-proof glasshouse (mass and cage) conditions. Of the ten tomato parental lines, two accessions [EC-520061 (Solanum habrochaites) and EC-521080 (Solanum pimpinellifolium)] were identified as highly resistant while four accessions (EC-520049, EC-528372, WIR-5032 and WIR-3957) of wild species were resistant to ToLCV. Out of the 24 F1 crosses, PBC×EC-520061, H-86×EC-520061, H-24×EC-520061 and DVRT-2×EC-520061 were found to be highly resistant against ToLCV disease. Biochemical (total phenol and total sugar concentration) and physiological (chlorophyll content and leaf area index) parameters were also used in healthy and disease-inoculated leaves of ten parents and six F1 hybrids to test the conformity of ToLCV-resistant and susceptible disease reactions. The results showed that among the 16 genotypes (10 parents+6 F1), EC-520061, EC-520049, PBC×EC-520061 and H-86×EC-520061 were stable for both biochemical and physiological markers while EC-521080 showed higher accumulations of total phenol and sugar concentrations and reduced leaf size between healthy and disease-inoculated leaves. The present study demonstrates the importance of the whitefly inoculation technique and biochemical and physiological markers in virus resistance screening programmes, and identifies a potential source of resistance to the ToLCV in Solanum species.

Dynamics of Defense-Related Components in Two Contrasting Genotypes of Tomato Upon Infection with Tomato Leaf Curl New Delhi Virus

Tomato leaf curl virus (ToLCV) disease is a serious threat for tomato cultivation in the tropics and subtropics. Despite serious efforts no immune commercial varieties or F(1) hybrids are available till date. In this study, the interaction between Solanum lycopersicum and ToLCV was characterized on molecular and biochemical basis. RNA silencing mediated by short interfering RNA (siRNA) and reactive oxygen species (ROS) has been proposed as central components of plant adaptation to several stresses. A comparative RNA interference study between two contrasting tomato genotypes, LA1777 (tolerant) and 15SBSB (susceptible) infected with Tomato Leaf Curl New Delhi Virus (ToLCNDV) revealed relatively higher accumulation of siRNA in the leaves of tolerant genotype. In LA1777, ToLCNDV produced chlorotic as well as necrotic areas at the inoculation sites 5-10 days post-inoculation. Caspase-9- and caspase-3-like activities were significantly increased in response to ToLCNDV infection in LA1777 at inoculated region. Activities of antioxidant enzymes involved in the detoxification of ROS were examined in both systemic and localized area of infection, and their expression level was further validated through quantitative real-time PCR of the corresponding transcripts. Expression patterns of three genes encoding pathogenesis-related proteins showed higher accumulation in tolerant genotype. Tolerance against the ToLCNDV in LA1777 can be attributed to the higher siRNA accumulation, localized cell death, altered levels of antioxidant enzymes and activation of pathogenesis-related genes at different durations of virus infection. Based on these direct and indirect evidences, we have proposed a putative mechanism for ToLCNDV tolerance in the tolerant genotype.

MicroRNAs as biomarkers in Tomato Leaf Curl Virus (ToLCV) disease

MicroRNAs are approximately 21- 25 nt long RNA species that are critical regulators of transcriptome across the eukaryotes. Growing number of evidences clearly supports their involvement in plant leaf development. ToLCV infection severely affects the morphology of mature tomato leaves. To investigate the mechanism underlying the virus- host interaction, we focussed our studies on expression of microRNAs and the irrespective targets under normal and ToLCV infection. We have cloned Myb33, ARF4 homolog, Argonaute1, Apetala2, SBP transcription factor and RBOH from tomato and checked their expression by RT-PCR. Our work suggests that miR159 is upregulated while miR164 and miR171 are downregulated under viral infection. Our studies shed light on the impact of ToLCV infection on host transcriptome.

Development of tomato hybrids resistant to tomato leaf curl virus disease in South India

Resistance to tomato leaf curl virus disease (ToLCVD) in tomato (Solanum lycopersicum) is scarce but was developed recently in three open pollinated (OP) varieties (Sankranthi, Nandi and Vybhav), which are now available for cultivation in South India. Hybrids with superior yield capabilities, however, are a preferred choice of cultivation by farmers but hybrids are highly susceptible to ToLCVD. In order to develop virus resistant tomato hybrids, the three OPs were crossed with 12 tomato genotypes with superior agronomic characteristics. From the crosses, 20 hybrids were selected (named BLRH-1 to BLRH-20, Bangalore leaf curl virus-resistant hybrid) and evaluated for their resistance to ToLCVD at the University of Agricultural Sciences, Bengaluru, South India, both through whitefly-mediated inoculations in the glasshouse and natural infection in the field during summer 2005. Their growth and fruit yield parameters were compared against the popularly grown hybrids and OPs. Differences occurred between hybrids in disease incidence, spread, symptom severity and fruit yield. Of the 20 hybrids evaluated, 11 were found resistant to ToLCVD in the field, but only three (BLRH-3, BLRH-9 and BLRH-16) remained resistant when challenged with high virus inoculum pressure in the glasshouse through whitefly-mediated inoculations. None of the six commercially available hybrids tested was found resistant to ToLCVD. An examination of the extent of heterosis in resistant hybrids for both quantitative and qualitative characters over the popularly grown hybrid, US-618, indicated a major improvement in virus resistance, yield and fruit quality. All the twenty hybrids yielded significantly more than US-618, and of these, BLRH-3 and BLRH-16 were considered the best with yields over ca. 60 t/ha and resistant to virus both in the glasshouse and field.

First Report of Tomato leaf curl New Delhi virus Infecting Tomato in Bangladesh

Tomato is an important cash crop for resource-poor farmers and accounts for 20% of the 2 million t of vegetables grown annually in Bangladesh. Tomato cultivation is affected by Tomato leaf curl virus (ToLCV), which can cause as much as 100% yield loss. Plants exhibiting typical ToLCV disease symptoms of yellowing, severe leaf curling, and stunting were collected at Jessore, Bangladesh during September 2003. The putative virus was transmitted from tomato to tomato by the whitefly Bemisia tabaci. In two separate experiments, 100% transmission was achieved by using 10 viruliferous B. tabaci adults for each of the 20 test plants that was confirmed by comparing the symptoms on test and virus source plants. Total DNAs were extracted from the symptomatic leaves, and the putative viral genomes were amplified by polymerase chain reaction by using the Deng A and B primers (1). Sequences generated from these primers were used to design virus-specific primers that were used to obtain complete viral sequences. Full-length DNA-A (2,740 nt; GenBank Accession No. AJ875157) and DNA-B (2,688 nt; GenBank Accession No. AJ875158) sequences of a bipartite Tomato leaf curl New Delhi virus from Jessore (ToLCNDV-[Jes]) were obtained, which were most similar to the corresponding sequences of ToLCNDV-(Lucknow) (GenBank Accession No. Y16421) at 95.7% and Tomato leaf curl Gujarat virus-(Varanasi) (Gen-Bank Accession No. AY190291) at 90.6% nt identities, respectively. DNA-A sequences had only 73.2% nt identity with the previously reported monopartite Tomato leaf curl Bangladesh virus (GenBank Accession No. AF188481) (2), confirming the occurrence of mono- and bipartite bego-moviruses in Bangladesh. The virus diversity poses a challenge for ToLCVD management in Bangladesh.

Resistance of tomato and sweet-pepper genotypes to Tomato leaf curl Bangalore virus and its vector Bemisia tabaci

The primary objective of this study was to identify sources of resistance to Tomato leaf curl Bangalore virus—Bangalore strain 4 (ToLCBV-[Ban4]) and its whitefly vector Bemisia tabaci (Gennadius) in tomato and sweet-pepper genotypes, because resistant cultivars did not exist. A total of 25 wild and cultivated tomato and nine sweet-pepper genotypes obtained from the Asian Vegetable Research and Development Centre, Taiwan and local cultivars were screened at the University of Agricultural Sciences, Bangalore, India, both by whitefly-mediated inoculation of virus in the glasshouse and natural infection in the field. Resistance to virus was assessed by disease incidence, symptom severity and DNA hybridisation tests. Resistance to B. tabaci was measured by counting the number of eggs, nymphs and pupal cases on the tomato genotypes. The wild species Lycopersicon peruvianum INRA sel. and L. chilense LA 1969 were resistant to ToLCBV-[Ban4] but highly susceptible to whiteflies, whereas L. hirsutum LA 1777 was resistant to both the virus and the vector. Among the L. esculentum genotypes, H-24, FL 744-6-9, FL 699 and FL 699 sp + were tolerant to ToLCBV-[Ban4], but were susceptible to whiteflies. Of the nine pepper genotypes inoculated with the virus, only five became infected, at low incidence levels and none were suitable for the development of B. tabaci. Use of tomato lines with resistance to both the virus and the vector offer the best way of controlling these related problems, and the prospects for tomato leaf curl virus disease management in South India are discussed.