Molecular characterization of a distinct bipartite begomovirus species infecting tomato in India

A distinct bipartite begomovirus was found associated with tomato plants showing yellowing, curling, and crumpling of the leaves, in a sub-temperate region in India. The complete DNA-A and DNA-B components were amplified through rolling circle amplification (RCA) using Φ-29 DNA polymerase and characterized. The DNA-A of the isolate was comprised of 2,756 nucleotides, encoding six open reading frames (ORFs) and DNA-B that of 2,725 nucleotides, encoding two ORFs. Genome organization of the isolate was typical of an old world bipartite begomovirus. Comparisons showed that DNA-A and its intergenic region (IR) have the highest sequence identity (86% and 84%, respectively) with the Tomato leaf curl New Delhi virus (ToLCNDV; DQ116885) and some other begomoviruses (>84%) reported from cucurbits and tomato. This data suggested that the isolate is a distinct begomovirus species for which a name Tomato leaf curl Palampur virus (ToLCPMV) is proposed. DNA-B showed the maximum sequence identity (73%) with Tomato leaf curl New Delhi virus-India-[Pakistan:Dargai:T5/6:2001] (AY150305). The common region (CR) of DNA-A and DNA-B showed 94% sequence similarity with each other. In the present study, phylogenetic relationship of this new species was also established with different begomoviruses reported from tomato and other begomoviruses showing highest homologies with complete DNA-A and DNA-B sequences. ToLCPMV is being reported from a sub-temperate region in India which was previously unaffected by begomoviruses and its whitefly vector. An erratum to this article can be found at     

Host-specific adaptation of diverse betasatellites associated with distinct Indian tomato-infecting begomoviruses

Tomato leaf curl viruses cause major crop loss hindering tomato cultivation worldwide. The ‘Old World’ begomoviruses are often associated with circular ssDNA satellite molecules called betasatellites. In the present study, replication compatibility of five different betasatellites with three distinct Indian tomato-infecting begomoviruses representing each of a monopartite, a mono-bipartite and a bipartite begomoviruses was studied. All the betasatellites could be trans-replicated by the begomoviruses in Nicotiana benthamiana plants, however, not uniformly in tomato. Tomato leaf curl Joydebpur betasatellite—Magrahat could not induce symptom with any of these begomoviruses in tomato, whereas only Tomato leaf curl Gujarat virus could trans-replicate Radish leaf curl betasatellite in this plant species. However, none of the betasatellites were found to complement the movement function of a bipartite begomovirus in tomato. Unlike tomato, the trans-replication/maintenance of betasatellites by these begomoviruses in N. benthamiana could be due to its compromised host defence machinery. Co-infection of betasatellites with these viruses did not enhance the helper virus accumulation, but the incubation period was reduced. The possible factors involved in this host-driven adaptability of betasatellites were also discussed.     

Evidence of local evolution of tomato-infecting begomovirus species in West Africa: characterization of tomato leaf curl Mali virus and tomato yellow leaf crumple virus from Mali

Tomato yellow leaf curl (TYLC) and tomato leaf curl (ToLC) diseases are serious constraints to tomato production in Mali and other countries in West Africa. In 2003 and 2004, samples of tomato showing virus-like symptoms were collected during a survey of tomato virus diseases in Mali. Three predominant symptom phenotypes were observed: (1) TYLC/ToLC (stunted upright growth and upcurled leaves with interveinal yellowing and vein purpling), (2) yellow leaf crumple and (3) broccoli or bonsai (severe stunting and distorted growth). Squash blot (SB) hybridization with a general begomovirus probe and/or SB/PCR analyses revealed begomovirus infection in plants with each of these symptom phenotypes and no evidence of phytoplasma infection. Sequence analysis of PCR-amplified begomovirus fragments revealed two putative new begomovirus species associated with the TYLC/ToLC and yellow leaf crumple symptom phenotypes, respectively. Full-length clones of these begomoviruses were obtained using PCR and overlapping primers. When introduced into N. benthamiana and tomato plants, these clones induced upward leaf curling and crumpling (the TYLC/ToLC-associated begomovirus) or downward leaf curl/yellow mottle (yellow leaf crumple-associated begomovirus) symptoms. Thus, these begomoviruses were named tomato leaf curl Mali virus (ToLCMLV) and tomato yellow leaf crumple virus (ToYLCrV). The genome organization of both viruses was similar to those of other monopartite begomoviruses. ToLCMLV and ToYLCrV were most closely related to each other and to tobacco leaf curl Zimbabwe virus (TbLCZV-[ZW]) and tomato curly stunt virus from South Africa (ToCSV-ZA). Thus, these likely represent tomato-infecting begomoviruses that evolved from indigenous begomoviruses on the African continent. Mixed infections of ToLCMLV and ToYLCrV in N. benthamiana and tomato plants resulted in more severe symptoms than in plants infected with either virus alone, suggesting a synergistic interaction. Agroinoculation experiments indicated that both viruses induced symptomatic infections in tomato and tobacco, whereas neither virus induced disease symptoms in pepper, common bean, small sugar pumpkin, African eggplant, or Arabidopsis. Virus-specific PCR primers were developed for detection of ToLCMLV and ToYLCrV and will be used to further investigate the distribution and host range of these viruses.     

Sequence characterization of Tomato leaf curl Sinaloa virus and <Emphasis Type="Italic">Tomato severe leaf curl virus</Emphasis>: Phylogeny of New World begomoviruses and detection of recombination

Summary. Diseases caused by begomoviruses (family Geminiviridae, genus Begomovirus) constitute a serious constraint to tomato production in Nicaragua. In this study, the complete nucleotide (nt) sequences of the DNA-A and DNA-B components were determined for the first time for Tomato leaf curl Sinaloa virus (ToLCSinV). In addition, the complete nt sequence was determined for the DNA-A component of two isolates of Tomato severe leaf curl virus (ToSLCV). The genome organization of ToLCSinV and ToSLCV was identical to the bipartite genomes of other begomoviruses described from the Americas. A phylogenetic analysis of DNA-A including 45 begomovirus species showed that the indigenous begomoviruses of the New World can be divided into three major clades and an intermediate group: AbMV clade, SLCV clade, “Brazil clade”, and BGYMV group. Phylogenetic analyses of the DNA-A and DNA-B components and their open reading frames indicated that ToLCSinV and ToSLCV belong to different clades: ToLCSinV to the AbMV clade, and ToSLCV to the SLCV clade. The two Nicaraguan isolates of ToSLCV showed a close relationship with ToSLCV from Guatemala (ToSLCV-[GT96-1]) and Tomato chino La Paz virus (ToChLPV), but differed significantly in the AV1 and AC1 regions, respectively. Computer-based predictions indicated that recombination with another begomovirus had taken place within AV1 of ToSLCV dividing this species into two strains. A high probability was also found that ToChLPV is involved in the evolution of ToSLCV.     

Differential pathogenicity among Tomato leaf curl Gujarat virus isolates from India

Tomato leaf curl Gujarat virus (ToLCGV) has been identified as one of the most destructive pathogens causing tomato leaf curl disease (ToLCD) in India. In the tomato growing regions of Dhanbad and Ramgarh, plants bearing severe symptoms of ToLCD such as leaf curling, leaf crinkling, yellowing and leaf rolling was observed in the farmer fields. The association of begomovirus in these samples was confirmed by PCR and the causal viruses were identified as the isolates of ToLCGV. However, association of cognate DNA B component could not be ascertained from these samples. Indeed, like other Old World begomoviruses, the present ToLCGV isolates were found to be associated with a particular betasatellite, Tomato yellow leaf curl Thailand betasatellite (TYLCTHB). Although DNA A of both ToLCGV isolates could alone infect tomato inducing systemic symptoms, the difference in virulence was observed. Co-inoculation of TYLCTHB reduced the incubation period without influencing the accumulation of helper virus DNA and hence, differential pathogenesis among ToLCGV isolates was governed by the helper component rather than betasatellite. ToLCGV infection with DNA B increases the accumulation of DNA A component of Dhanbad isolate but not of Ramgarh isolate. Results indicated that the begomovirus identified from Ramgarh sample was a mild strain of ToLCGV.     

Molecular analysis of new isolates of Tomato leaf curl Philippines virus and an associated betasatellite occurring in the Philippines

Three new begomovirus isolates and one betasatellite were obtained from a tomato plant exhibiting leaf curl symptom in Laguna, the Philippines. Typical begomovirus DNA components representing the three isolates (PH01, PH02 and PH03) were cloned, and their full-length sequences were determined to be 2754 to 2746 nucleotides. The genome organizations of these isolates were similar to those of other Old World monopartite begomoviruses. The sequence data indicated that PH01 and PH02 were variants of strain B of the species Tomato leaf curl Philippines virus, while PH03 was a variant of strain A of the species Tomato leaf curl Philippines virus. These isolates were designated ToLCPV-B[PH:Lag1:06], ToLCPV-B[PH:Lag2:06], and ToLCPV-A[PH:Lag3:06], respectively. Phylogenetic analysis revealed that the present isolates form a separate monophyletic cluster with indigenous begomoviruses reported earlier in the Philippines. A betasatellite isolated from same sample belongs to the betasatellite species Tomato leaf curl Philippines betasatellite and designated Tomato leaf curl Philippines betasatellite-[Philippines:Laguna1:2006], ToLCPHB-[PH:Lag1:06]. When co-inoculated with this betasatellite, tomato leaf curl Philippines virus induced severe symptoms in N. benthamiana and Solanum lycopersicum plants. Using a PVX-mediated transient assay, we found that the C4 and C2 proteins of tomato leaf curl Philippines virus and the βC1 protein of ToLCPHB-[PH:Lag1:06] function as a suppressor of RNA silencing.     

Diversity and prevalence of Brazilian bipartite begomovirus species associated to tomatoes

Information on the distribution and prevalence of the economically destructive Begomovirus species and recombinant forms infecting fresh-market and processing tomato crops in Brazil is crucial in guiding breeding programs and also to understand the evolutionary mechanisms associated with the upsurge of so many species and quasi-species comprising this unique disease complex. An extensive survey was carried out over 3 years (between 2002 and 2004) aiming to study the diversity of begomoviruses in tomato plants, predominantly collected in central Brazil. Polymerase chain reaction (PCR) with degenerated primers was used to detect the begomoviruses in tomato leaf samples showing virus-like symptoms in commercial fields. Seven hundred and seventeen out of 2,295 samples were found to be PCR positive for a begomovirus infection. High quality sequences were obtained from a fragment encompassing the 5′ region of the coat protein (CP) gene and a segment of the intergenic region for 295 isolates from distinct geographic regions. Comparison analyses with those available in public databases enabled preliminary classification of the isolates into four previously described and/or proposed species: Tomato severe rugose virus (61%), Tomato golden vein virus (29.8%), Tomato mottle leaf curl virus (7.1%), Tomato yellow vein streak virus (0.7%), and two putative new species (1.4% of isolates). Within the prevailing species, we noted a relatively low degree of diversity, possibly indicating the existence of recent population founder effects and/or recent selective sweeps.     

Begomovirus genetic diversity in the native plant reservoir Solanum nigrum: Evidence for the presence of a new virus species of recombinant nature

We examined the native plant host Solanum nigrum as reservoir of genetic diversity of begomoviruses that cause the tomato yellow leaf curl disease (TYLCD) emerging in southern Spain. Presence of isolates of all the species and strains found associated with TYLCD in this area was demonstrated. Mixed infections were common, which is a prerequisite for recombination to occur. In fact, presence of a novel recombinant begomovirus was demonstrated. Analysis of an infectious clone showed that it resulted from a genetic exchange between isolates of the ES strain of Tomato yellow leaf curl Sardinia virus and of the type strain of Tomato yellow leaf curl virus. The novel biological properties suggested that it is a step forward in the ecological adaptation to the invaded area. This recombinant represents an isolate of a new begomovirus species for which the name Tomato yellow leaf curl Axarquia virus is proposed. Spread into commercial tomatoes is shown.     

Xanthium strumarium: a weed host of components of begomovirus–betasatellite complexes affecting crops

Xanthium strumarium is a common weed that often shows symptoms typical of begomovirus infection, such as leaf curling and vein thickening. The virus complex isolated from the weed consisted of two begomoviruses along with a betasatellite and an alphasatellite. The first begomovirus was shown to be an isolate of Cotton leaf curl Burewala virus, a new recombinant begomovirus species that is associated with resistance breaking in previously resistant cotton varieties in Pakistan, whereas the second was shown to be an isolate of Tomato leaf curl Gujarat virus (ToLCGV), a begomovirus previously reported to be bipartite. However, there was no evidence for the presence of the second genomic component, DNA B, of ToLCGV in X. strumarium. The betasatellite was shown to be an isolate of Tomato yellow leaf curl Thailand betasatellite, the first time this satellite has been identified in Pakistan. The alphasatellite associated with infection of X. strumarium was shown to be a species recently identified in potato and various weeds; Potato leaf curl alphasatellite. Although each component has been identified previously, this is the first time they have been identified in a single host. These findings reinforce the hypothesis that weeds are reservoirs of crop-infecting begomoviruses that may contribute to virus diversity by virtue of harboring multiple viruses and virus associated components, which may lead to interspecific recombination and component exchange.     

Complete sequences of tomato leaf curl Palampur virus isolates infecting cucurbits in Iran

Tomato leaf curl disease (TLCD) and and tomato yellow leaf curl (TYLCD) is caused by a number of begomovirus species that collectively threaten tomato production worldwide. We report here that an ongoing TLCD and TYLCD epidemic in Iran is caused by variants of tomato leaf curl Palampur virus (ToLCPMV), a newly proposed begomovirus species previously only detected in India. Besides infecting tomatoes, we identified ToLCPMV as the causal agent of a cucurbit disease that has devastated greenhouse cucumber and melon farms in Jiroft, southeastern Iran. We found no convincing evidence that the ToLCPMV DNA-B sequences have been derived through inter-species recombination, however, all of the currently sampled ToLCPMV DNA-A sequences are descendents of a sequence that probably arose through recombination between a ToLCNDV isolate and a currently unsampled geminivirus species that falls outside the ToLCNDV-ToLCPMV cluster. The increasing incidence of ToLCPMV in different cultivated species throughout Iran may signal the emergence of a serious new threat to agricultural production throughout the Middle East. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Complete nucleotide sequences of a distinct bipartite begomovirus, bitter gourd yellow vein virus, infecting Momordica charantia

Momordica charantia (Cucurbitaceae), a vegetable crop commonly cultivated throughout Pakistan, and begomoviruses, a serious threat to crop plants, are natives of tropical and subtropical regions of the world. Leaf samples of M. charantia with yellow vein symptoms typical of begomovirus infections and samples from apparently healthy plants were collected from areas around Lahore in 2004. Full-length clones of a bipartite begomovirus were isolated from symptomatic samples. The complete nucleotide sequences of the components of one isolate were determined, and these showed the arrangement of genes typical of Old World begomoviruses. The complete nucleotides sequence of DNA A showed the highest nucleotide sequence identity (86.9%) to an isolate of Tomato leaf curl New Delhi virus (ToLCNDV), confirming it to belong to a distinct species of begomovirus, for which the name Bitter gourd yellow vein virus (BGYVV) is proposed. Sequence comparisons showed that BGYVV likely emerged as a result of inter-specific recombination between ToLCNDV and tomato leaf curl Bangladesh virus (ToLCBDV). The complete nucleotide sequence of DNA B showed 97.2% nucleotide sequence identity to that of an Indian strain of Squash leaf curl China virus.     

Characterization and distribution of tomato yellow margin leaf curl virus, a begomovirus from Venezuela

A begomovirus causing mottling and leaf deformation in tomato from the State of Mérida was cloned and sequenced. The virus has a bipartite genome comprised of a DNA-A (2,572 nucleotides) and a DNA-B (2,543 nucleotides) with a genome organization typical of New World begomoviruses. Both components share a common region of 115 nucleotides with 98 % sequence identity. Phylogenetic analysis indicated that while no virus sequences were closely related, the A component was distantly related to those of two other tomato-infecting viruses, tomato leaf deformation virus and Merremia mosaic virus; and the DNA-B, to those of pepper huasteco yellow vein virus and Rhynchosia golden mosaic Yucatan virus. The DNA-A and DNA-B sequences were submitted to GenBank (accession no. AY508993 and AY508994, respectively) and later accepted by the International Committee on Taxonomy of Viruses as the genome of a member of a unique virus species with the name Tomato yellow margin leaf curl virus (TYMLCV). Tomato (Solanum lycopersicum L. ‘Fl. Lanai’) plants inoculated with cloned TYMLCV DNA-A and DNA-B became systemically infected and showed chlorotic margins and leaf curling. The distribution of TYMLCV in tomato-producing states in Venezuela was determined by nucleic acid spot hybridization analysis of 334 tomato leaf samples collected from ten states using a TYMLCV-specific probe and confirmed by PCR and sequencing of the PCR fragment. TYMLCV was detected in samples from the states of Aragua, Guárico, and Mérida, suggesting that TYMLCV is widely distributed in Venezuela.     

A new begomovirus–betasatellite complex is associated with chilli leaf curl disease in Sri Lanka

Leaf curl disease of chilli (LCDC) is a major constraint in production of chilli in the Indian subcontinent. The objective of this study was to identify the begomovirus species occurring in chilli in Sri Lanka, where the LCDC was initially recorded in 1938. The virus samples were collected from the North Central Province, the major chilli growing region in Sri Lanka with a history of epidemic prevalence of LCDC. The virus could be readily transmitted by Bemisia tabaci to chilli, tomato and tobacco, where vein clearing followed by leaf curl developed. The genome analysis of two isolates obtained from two distantly located fields showing 100 % LCDC, revealed that the DNA-A genome (2754 nucleotides) shared 89.5 % sequence identity with each other and 68.80–84.40 % sequence identity with the other begomoviruses occurring in the Indian subcontinent. The closest identity (84.40 %) of the virus isolates was with Tomato leaf curl Sri Lanka virus (ToLCLKV). The results support that a new begomovirus species is affecting chilli in Sri Lanka and the name Chilli leaf curl Sri Lanka virus (ChiLCSLV) is proposed. Recombination analysis indicated that ChiLCSLV was a recombinant virus potentially originated from the begomoviruses prevailing in southern India and Sri Lanka. The genome of betasatellite associated with the two isolates consisted of 1366 and 1371 nucleotides and shared 95.2 % sequence identity with each other and 41.50–73.70 % sequence identity with the other betasatellite species. The results suggest that a new begomovirus betasatellite, Chilli leaf curl Sri Lanka betasatellite is associated with LCDC in Sri Lanka. This study demonstrates a new species of begomovirus and betasatellite complex is occurring in chilli in Sri Lanka and further shows that diverse begomovirus species are affecting chilli production in the Indian subcontinent.     

Two genetically related begomoviruses causing tomato leaf curl disease in Togo and Nigeria differ in virulence and host range but do not require a betasatellite for induction of disease symptoms

Tomato leaf curl disease (ToLCD) has emerged as a major constraint on tomato production in some parts of West Africa. In this study, begomoviruses associated with ToLCD in Togo and Nigeria were characterized, as well as a betasatellite associated with the disease in Togo. The genome organization of both viruses is typical of Old World monopartite begomoviruses. Sequence analysis revealed that the begomovirus from Togo is a variant of tomato leaf curl Kumasi virus (ToLCKuV) from Ghana, and it is designated ToLCKuV-[Togo:Pagouda:2006] (ToLCKuV-[TG:Pag:06]). The begomovirus from Nigeria has a recombinant genome, composed of sequences of ToLCKuV (major parent) and a cotton leaf curl Gezira virus (CLCuGV)-like virus, and possesses an unusual non-reiterated replication-associated protein (Rep) binding site. Moreover, because the sequence has <89% identity with those of previously characterized begomoviruses, it is a new species and is designated tomato leaf curl Nigeria virus-[Nigeria:Odogbo:2006] (ToLCNGV-[NG:Odo:06]). The cloned DNAs of ToLCKuV-TG and ToLCNGV were infectious and induced leaf curl symptoms in tomato plants, but ToLCNGV was comparatively more virulent. Both viruses also induced stunted growth and leaf curl symptoms in other solanaceous species (various Nicotiana spp. and Datura stramonium), whereas ToLCNGV but not ToLCKuV-TG induced symptoms in common bean plants. The betasatellite associated with ToLCD in Togo is genetically distinct (i.e., <78% nucleotide sequence identity with previously identified betasatellites) and is designated tomato leaf curl Togo betasatellite-[Togo:Pagouda:2006] (ToLCTGB-[TG:Pag:06]). Replication and systemic spread of ToLCTGB in tomato was mediated by ToLCKuV-TG and ToLCNGV; however, the betasatellite had no effect on disease symptoms induced by either begomovirus. In contrast, ToLCTGB increased symptom severity induced by both viruses in Nicotiana spp. and D. stramonium. Thus, although ToLCTGB increased symptom severity in a host-dependent manner, it does not appear to play a role in ToLCD and may have been present with ToLCKuV-TG as a reassortant.     

Recent evolution of a novel begomovirus causing tomato leaf curl disease in the Al-Batinah region of Oman

For last two decades, begomoviruses (family Geminiviridae) have been a major constraint for tomato production in Oman, particularly in the Al-Batinah region, the major agricultural area of Oman. Farms in the Al-Batinah region were surveyed during January-March and November-December in 2012 and January-February in 2013. Leaf samples of tomato plants showing typical leaf curl disease symptoms were collected and analyzed for begomoviruses. Out of fifteen begomovirus clones sequenced, seven were shown to be tomato yellow leaf curl virus strain Oman (TYLCV-OM); three, chili leaf curl virus strain Oman (ChLCV-OM); and one, tomato leaf curl Oman virus (ToLCOMV) – viruses that have previously been shown to occur in Oman. Four sequences were shown to have relatively low percent identity values to known begomoviruses, with the highest (86 %) to isolates of pepper leaf curl Lahore virus, indicating that these should be included in a new species, for which the name “Tomato leaf curl Al Batinah virus” (ToLCABV) is proposed. Although the betasatellite tomato leaf curl betasatellite (ToLCB; 7 full-length sequences isolated) was identified with some isolates of ChLCV-OM, TYLCV-OM and ToLCOMV, it was not identified in association with any of the ToLCABV isolates. Analysis of the sequences of the TYLCV-OM and ToLCOMV isolates characterized here did not show them to differ significantly from previously characterized isolates of these viruses. The three isolates of ChLCV-OM characterized were shown to have a recombination pattern distinct from earlier characterized isolates. ToLCABV was shown to have resulted from recombination between ChLCV-OM and ToLCOMV. A clone of ToLCABV was infectious by Agrobacterium-mediated inoculation to Nicotiana benthamiana and tomato, inducing symptoms typical of those seen in tomato in the field. Additionally, ToLCABV was shown to be able to interact in planta with ToLCB, resulting in a change in symptom phenotype, although the betasatellite did not appear to affect viral DNA levels.     

Diversity and distribution of begomoviruses infecting tomato in India

Summary. Leaf curl begomoviruses cause serious yield losses to Indian tomato crops. Total DNAs were extracted from leaves of 69 tomato plants and 34 weeds or neighbouring crops collected from all the major tomato producing areas of India. Eighty-one of the 103 samples were positive by PCRs using begomovirus genus-specific primers. Coat protein (CP) genes from 29 samples were PCR amplified, cloned and sequenced. Phylogenetic analyses of the CP sequences revealed five different tomato leaf curl begomovirus (TLCB) clusters each <88% identity to the others. Four clusters represented known Indian TLCBs, whereas one cluster contained sequences originating from Haryana State with most identity (89%) to the provisional Begomovirus species Croton yellow vein mosaic virus.Sixty-five begomovirus positive samples were characterised further by PCR with DNA-, DNA-B, four Indian TLCB species, PALIc1960/PARIv722 (universal begomovirus primers), and by sequencing. The majority of samples represented monopartite TLCBs associated with DNA- components. All four known TLCBs appeared to be present throughout India. TLCBs were also present in chilli, cowpea, okra and tobacco crops, as well as in some common weeds. Papaya leaf curl virus and Pepper leaf curl Bangladesh virus sequences were detected in tomato. Mixed begomovirus infections, a prerequisite for recombination, were evident in 13 samples.     

Tomato yellow leaf curl Thailand virus-[Y72] from Yunnan is a monopartite begomovirus associated with DNAβ

Previous studies have shown that isolates of tomato yellow leaf curl Thailand virus (TYLCTHV) originated from Thailand are bipartite begomoviruses, while all the seven TYLCTHV isolates found in China are associated with DNAβ molecules. In this study, infectious clones of TYLCTHV isolate Y72 (TYLCTHV-[Y72]) and its DNAβ were constructed to verify the bipartite or monopartite nature of TYLCTHV. Agroinoculation showed that TYLCTHV-[Y72] alone was able to induce significant symptoms in Nicotiana benthamiana, Nicotiana glutinosa, and Solanum lycopersicum plants, but co-inoculation with its associated satellite DNAβ produced more severe symptoms, which is similar to tobacco curly shoot virus. Southern blot results showed that TYLCTHV DNAβ could increase the virus accumulation in systemically infected tissues. Thus, TYLCTHV-[Y72] is a monopartite begomovirus, which may represent an evolutionary intermediate between the begomoviruses requiring DNAβ and begomoviruses dispensable of DNAβ. Wei Guo and Xiuling Yang contributed equally to this paper.     

A betasatellite-dependent begomovirus infects ornamental rose: characterization of begomovirus infecting rose in Pakistan

The Begomovirus genus of the family Geminiviridae comprises the largest group of geminiviruses. The list of begomoviruses is continuously increasing as a result of improvement in the methods for identification. Ornamental rose plants (Rosa chinensis) with highly stunted growth and leaf curling were found in Faisalabad, Pakistan. Plants were analyzed for begomovirus infection, through rolling circle amplification and PCR methods. Based on complete genome sequence homologies with other begomoviruses, a new begomovirus species infecting the rose plants was discovered. In this paper, we propose a new species name, Rose leaf curl virus (RoLCuV), for the virus. RoLCuV showed close identity (83 %) with Tomato leaf curl Pakistan virus, while associated betasatellite showed 96 % identity with Digera arvensis yellow vein betasatellite (DiAYVB), justifying a new isolate for the betasatellite. Recombination analysis of newly identified begomovirus revealed it as a recombinant of tomato leaf curl Pakistan virus from its coat protein region. The infectious molecules for virus/satellite were prepared and inoculated through Agrobacterium tumefaciens to N. benthamiana plants. RoLCuV alone was unable to induce any level of symptoms on N. benthamiana plants, but co-inoculation with cognate betasatellite produced infection symptoms. Further investigation to understand the trans-replication ability of betasatellites revealed their flexibility to interact with Rose leaf curl virus.     

Molecular characterization and experimental host range of an isolate of <Emphasis Type="Italic">Wissadula golden mosaic St. Thomas virus</Emphasis>

Partial genome segments of a begomovirus were previously amplified from Wissadula amplissima exhibiting yellow-mosaic and leaf-curl symptoms in the parish of St. Thomas, Jamaica and this isolate assigned to a tentative begomovirus species, Wissadula golden mosaic St. Thomas virus. To clone the complete genome of this isolate of Wissadula golden mosaic St. Thomas virus, abutting primers were designed to PCR amplify its full-length DNA-A and DNA-B components. Sequence analysis of the complete begomovirus genome obtained, confirmed that it belongs to a distinct begomovirus species and this isolate was named Wissadula golden mosaic St. Thomas virus-[Jamaica:Albion:2005] (WGMSTV-[JM:Alb:05]). The genome of WGMSTV-[JM:Alb:05] is organized similar to that of other bipartite Western Hemisphere begomoviruses. Phylogenetic analyses placed the genome components of WGMSTV-[JM:Alb:05] in the Abutilon mosaic virus clade and showed that the DNA-A component is most closely related to four begomovirus species from Cuba, Tobacco leaf curl Cuba virus, Tobacco leaf rugose virus, Tobacco mottle leaf curl virus, and Tomato yellow distortion leaf virus. The putative Rep-binding-site motif in the common region of WGMSTV-[JM:Alb:05] was observed to be identical to that of Chino del tomate virus-Tomato [Mexico:Sinaloa:1983], Sida yellow mosaic Yucatan virus-[Mexico:Yucatan:2005], and Tomato leaf curl Sinaloa virus-[Nicaragua:Santa Lucia], suggesting that WGMSTV-[JM:Alb:05] is capable of forming viable pseudo-recombinants with these begomoviruses, but not with other members of the Abutilon mosaic virus clade. Biolistic inoculation of test plant species with partial dimers of the WGMSTV-[JM:Alb:05] DNA-A and DNA-B components showed that the virus was infectious to Nicotiana benthamiana and W. amplissima and the cultivated species Phaseolus vulgaris (kidney bean) and Lycopersicon esculentum (tomato). Infected W. amplissima plants developed symptoms similar to symptoms observed under field conditions, confirming that this virus is a causal agent of Wissadula yellow mosaic disease in W. amplissima.