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.     

A novel recombinant tomato-infecting begomovirus capable of transcomplementing heterologous DNA-B components

The genome of a tomato-infecting begomovirus from Ranchi, India, was cloned, sequenced and analysed. The viral genome shared 88.3% sequence identity with an isolate belonging to the species Tobacco curly shoot virus (TbCSV), and this virus should therefore be considered a member of a new species, tentatively named Tomato leaf curl Ranchi virus (ToLCRnV). The DNA-?? molecule, which had 74.5% sequence identity with tomato leaf curl Bangladesh betasatellite (ToLCBDB), is named tomato leaf curl Ranchi betasatellite (ToLCRnB). Phylogenetic analysis revealed that ToLCRnV is related to tomato leaf curl Bangladesh virus (ToLCBDV), tobacco curly shoot virus (TbCSV) and tomato leaf curl Gujarat virus (ToLCGV). An infectivity study with ToLCRnV established the monopartite nature of the viral genome, whereas inoculation with ToLCRnB resulted in increased symptom severity. ToLCRnV could transreplicate DNA-B of tomato leaf curl Gujarat virus (ToLCGV) and tomato leaf curl New Delhi virus (ToLCNDV), both in N. benthamiana and tomato, although DNA-B accumulation of was less than with the wild-type combinations. ToLCRnB could be efficiently replicated by DNA-A of both ToLCNDV and ToLCGV. A leaf disk assay suggests that DNA-A could transreplicate the homologous DNA-B and DNA-?? more efficiently than the heterologous one.     

Predominance of tomato leaf curl Gujarat virus as a monopartite begomovirus: association with tomato yellow leaf curl Thailand betasatellite

Tomato leaf curl is a serious malady in the state of Maharashtra, India, causing nearly 100 % yield loss. An extensive survey was done in the affected fields of tomato in the year 2008, and members of three species of begomoviruses were identified as causing the disease. More than 60 % of the samples from diseased plants were infected with tomato leaf curl Gujarat virus (ToLCGuV). Isolates collected from these fields differed from the Varanasi isolate of ToLCGuV in not having a DNA B component. Instead, they were like typical Old World monopartite begomoviruses in that they were associated with only one betasatellite, tomato yellow leaf curl Thailand betasatellite (TYLCTHB). ToLCGuV alone is readily infectious, expressing systemic symptoms in Nicotiana benthamiana and tomato. Co-inoculation of ToLCGuV with TYLCTHB, increased symptom severity and reduced the incubation time required for symptom expression. ToLCGuV successfully interacted with heterologous DNA B component of ToLCNDV [IN:Pun:JID:08], and co-inoculation of these two resulted in yellow mottling symptoms that were typical of DNA B.     

Tomato leaf curl Joydebpur virus: a monopartite begomovirus causing severe leaf curl in tomato in West Bengal

A begomovirus was isolated from tomato plants showing leaf curl and stunting symptoms in farmers’ fields near the district of Kalyani, West Bengal, India. Viral genomic components amplified by rolling-circle amplification were cloned and sequenced. The genome organization of this virus was found to be similar to those of Old World monopartite begomovirus, with DNA A and a betasatellite component. Neither alphasatellite nor DNA B component was detected. The begomovirus showed highest sequence identity of 93.6% to tomato leaf curl Joydebpur virus (ToLCJoV-[IN:Kal:Chi:06]) and was thus identified to be an isolate of ToLCJoV. The betasatellite isolated from these samples was identified as tomato leaf curl Joydebpur betasatellite. ToLCJoV-[IN:Kal:Tom:08] alone induced severe symptoms in Solanum lycopersicum, N. benthamiana and N. glutinosa plants, and its severity was enhanced when co-inoculated with the cognate betasatellite. ToLCJoV-[IN:Kal:Tom:08] trans-replicated four more non-cognate betasatellites and induced severe symptoms in N. benthamiana and tomato. Since DNA A replicated efficiently and caused systemic symptom expression, it is hypothesized that ToLCJoV is essentially a monopartite virus, which could have acquired a betasatellite from an unknown source.     

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.     

Mixed infection by two West African tomato-infecting begomoviruses and ageratum leaf curl Cameroon betasatellite in tomato in Cameroon

Begomovirus isolates ToF3B2 and ToF3B17 and betasatellite isolate SatBToF3 were obtained from the same infected tomato plant showing begomovirus disease symptoms in Fontem, Cameroon. The full-length nucleotide sequences of ToF3B2, ToF3B17 and SatBToF3 were cloned and sequenced and were determined to be 2,797 nt, 2,794 and 1,373 nt long respectively. When compared with other begomovirus and betasatellite sequences, ToF3B2 was 93.5 % identical to Tomato leaf curl Togo virus, ToF3B17 was 95 % identical to Tomato leaf curl Cameroon virus and SatBToF3 was 92 % identical to Ageratum leaf curl Cameroon betasatellite (ALCCMB), respectively. The identification of ALCCMB in Ageratum and now in tomato strongly suggests Ageratum may be an alternative host to these viruses and that ALCCMB is non host specific and may cause severe diseases when transmitted to other crops.     

Genetic diversity and distribution of a distinct strain of Chili leaf curl virus and associated betasatellite infecting tomato and pepper in Oman

Tomato and pepper are widely grown in Oman for local consumption. A countrywide survey was conducted during 2010–2011 to collect samples and assess the diversity of begomoviruses associated with leaf curl disease of tomato and pepper. A virus previously only identified on the Indian subcontinent, chili leaf curl virus (ChLCV), was found associated with tomato and pepper diseases in all vegetable grown areas of Oman. Some of the infected plant samples were also found to contain a betasatellite. A total of 19 potentially full-length begomovirus and eight betasatellite clones were sequenced. The begomovirus clones showed >96% nucleotide sequence identity, showing them to represent a single species. Comparisons to sequences available in the databases showed the highest levels of nucleotide sequence identity (88.0–91.1%) to isolates of the “Pakistan” strain of ChLCV (ChLCV-PK), indicating the virus from Oman to be a distinct strain, for which the name Oman strain (ChLCV-OM) is proposed. An analysis for recombination showed ChLCV-OM likely to have originated by recombination between ChLCV-PK (the major parent), pepper leaf curl Lahore virus and a third strain of ChLCV. The betasatellite sequences obtained were shown to have high levels of identity to isolates of tomato leaf curl betasatellite (ToLCB) previous shown to be present in Oman. For the disease in tomato Koch's postulates were satisfied by Agrobacterium-mediated inoculation of virus and betasatellites clones. This showed the symptoms induced by the virus in the presence of the betasatellite to be enhanced, although viral DNA levels were not affected. ChLCV-OM is the fourth begomovirus identified in tomato in Oman and the first in Capsicum. The significance of these findings is discussed.     

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.     

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.     

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.     

Role of betasatellite in the pathogenesis of a bipartite begomovirus affecting tomato in India

Betasatellites are commonly associated with tomato leaf curl disease caused by begomoviruses in India. This study demonstrates the role of a betasatellite in the pathogenesis of tomato leaf curl New Delhi virus (ToLCNDV), a bipartite begomovirus affecting tomato in India. For infection, accumulation, systemic movement and disease induction by ToLCNDV, co-infection by the associated betasatellite was not essential, as the DNA A alone of ToLCNDV could infect tomato and Nicotiana benthamiana and induce mild symptoms, but DNA B or Cotton leaf curl Multan betasatellite (CLCuMB) was required for development of typical leaf curl symptoms. The symptoms were most severe in plants infected with all three components, indicating a role of the betasatellite in the pathogenesis of ToLCNDV. The plants infected with ToLCNDV DNA A alone had limited accumulation of viral DNA, which increased by many times in plants co-infected with DNA B or/and betasatellite. However, the plants infected with all three components accumulated 20 times less betasatellite DNA than the plants infected with DNA A and betasatellite. The increase in the amount of viral DNAs was also reflected in the commensurate increase in symptom severity and transmissibility by whitefly, Bemisia tabaci.     

Complete nucleotide sequence of a begomovirus and associated betasatellite infecting croton (Croton bonplandianus) in Pakistan

The complete sequences of a begomovirus and an associated betasatellite isolated from Croton bonplandianus originating from Pakistan were determined. The sequence of the begomovirus showed the highest level of nucleotide sequence identity (88.9%) to an isolate of papaya leaf curl virus and thus represents a new species, for which we propose the name Croton yellow vein virus (CYVV). The sequence of the betasatellite showed the highest levels of sequence identity (82 to 98.4%) to six sequences in the databases that have yet to be reported, followed by isolates of tomato leaf curl Joydebpur betasatellite (48.7 to 52.5%). This indicates that the betasatellite identified here (and the six sequences in the databases) is an isolate of a newly identified species for which the name Croton yellow vein mosaic betasatellite (CroYVMB) is proposed. For the begomovirus, an analysis of the sequence indicates that it has a recombinant origin.     

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.     

Molecular characterization and pathogenicity of a carrot (Daucus carota) infecting begomovirus and associated betasatellite from India

The yellow mosaic pattern and shortening of leaf petiole are common disease symptoms associated with begomovirus infection in carrot. DNA from field infected carrot leaves was analyzed by rolling circle amplification and sequencing. The results established the presence of ageratum enation virus (AEV), which is referred to here as ageratum enation virus-carrot (AEV-Car). Symptomatic ageratum (Ageratum conyzoides) plants, growing adjacent to the carrot fields, also showed the presence of AEV (AEV-Age). Ageratum yellow leaf curl betasatellite (AYLCB) was also detected in the AEV infected carrot and ageratum samples. AEV-Car and AEV-Age are 95–97% identical in their DNA sequences, represent groups of isolates from the respective plant hosts (carrot and ageratum). Agroinoculation using infectious clones of AEV-Car plus AYLCB or AEV-Age plus AYLCB in carrot, ageratum, tobacco (Nicotiana tabacum) and tomato (Solanum lycopersicum) produced yellow mosaic and curling symptoms in leaves of inoculated plants. Agroinoculation of the two isolates together, along with the betasatellite (AEV-Car plus AEV-Age plus AYLCB) resulted in the enhancement of symptoms in comparison to the plants inoculated with single isolate. Plants with more severe symptoms showed a higher level of viral DNA accumulation, suggesting synergistic interactions between the two isolates of AEV.     

Identification of a disease complex involving a novel monopartite begomovirus with beta- and alphasatellites associated with okra leaf curl disease in Oman

Okra leaf curl disease (OLCD) is an important viral disease of okra in tropical and subtropical areas. The disease is caused by begomovirus-satellite complexes. A begomovirus and associated betasatellite and alphasatellite were identified in symptomatic okra plants from Barka, in the Al-Batinah region of Oman. Analysis of the begomovirus sequences showed them to represent a new begomovirus most closely related to cotton leaf curl Gezira virus (CLCuGeV), a begomovirus of African origin. The sequences showed less than 85 % nucleotide sequence identity to CLCuGeV isolates. The name okra leaf curl Oman virus (OLCOMV) is proposed for the new virus. Further analysis revealed that the OLCOMV is a recombinant begomovirus that evolved by the recombination of CLCuGeV isolates with tomato yellow leaf curl virus-Oman (TYLCV-OM). An alpha- and a betasatellite were also identified from the same plant sample, which were also unique when compared to sequences available in the databases. However, although the betasatellite appeared to be of African origin, the alphasatellite was most closely related to alphasatellites originating from South Asia. This is the first report of a begomovirus-satellite complex infecting okra in Oman.     

Molecular characterization of Chilli leaf curl virus and satellite molecules associated with leaf curl disease of Amaranthus spp

Amaranthus, collectively known as amaranth, is an annual or short-lived perennial plant used as leafy vegetables, cereals and for ornamental purposes in many countries including India. During 2011, leaf samples of Amaranthus plants displaying leaf curling, leaf distortion, leaf crinkling and yellow leaf margins were collected from Banswara district, Rajasthan in India. Full-length clones of a monopartite begomovirus, a betasatellite and an alphasatellite were characterized. The complete nucleotide sequence of the isolated begomovirus features as a typical ‘Old World’ begomovirus with the highest nucleotide per cent identity with Chilli leaf curl virus and hence, considered as an isolate of Chilli leaf curl virus. The complete nucleotide sequences of betasatellite and alphasatellite possess maximum nucleotide identity with Tomato yellow leaf curl Thailand betasatellite and Chilli leaf curl alphasatellite, respectively. This is the first report of the association of chilli-infecting begomovirus and satellite molecules infecting a new host, Amaranthus, causing leaf curl disease.     

Interaction of tomato yellow leaf curl virus with diverse betasatellites enhances symptom severity

The complete nucleotide sequence was determined for a begomovirus isolated from tomato exhibiting leaf curling and yellowing symptoms in Tochigi Prefecture in Japan. The genome organization of this virus was similar to those of other Old World monopartite begomoviruses. Neither a DNA betasatellite nor a DNA-B component was detected. It had the highest total nucleotide sequence identity (99%) with tomato yellow leaf curl virus-Israel[Japan:Tosa:2005] (TYLCV-IL[JR:Tos:05]) and TYLCV-Israel[Japan:Haruno:2005] (TYLCV-IL[JR:Han:05]). Its coat protein V1 also showed an identical amino acid sequence with those of TYLCV-IL[JR:Tos:05] and TYLCV-IL[JR:Han:05]. Thus, the begomovirus was determined to be an isolate of TYLCV-IL designated as TYLCV-Israel[Japan:Tochigi:2007] (TYLCV-IL[JR:Toc:07]). We investigated the interaction of TYLCV-IL[JR:Toc:07] with two known satellites associated with tomato yellow dwarf disease in Japan, tobacco leaf curl Japan betasatellite [Japan:Ibaraki:2006] and honeysuckle yellow vein mosaic betasatellite [Japan:Nara:2006], as well as with tomato leaf curl Philippines betasatellite [Philippines:Laguna1:2008], in tomato and Nicotiana benthamiana plants. TYLCV-IL[JR:Toc:07] trans-replicated these betasatellites, inducing more severe tomato yellow leaf curl disease-related symptoms than TYLCV-IL[JR:Toc:07] alone.     

Detection and characterization of a new betasatellite: variation in disease symptoms of tomato leaf curl Pakistan virus-India due to associated betasatellite

A begomovirus and its associated betasatellites were amplified and sequenced from tobacco plants affected with leaf curl disease. The begomovirus was identified as a new strain of tomato leaf curl Pakistan virus (ToLCPKV), which is referred to here as ToLCPKV-India. A previously known betasatellite [tomato leaf curl Patna betasatellite (ToLCPaB)] and a new betasatellite were also found in leaf-curl-affected samples. The use of infectious clones of ToLCPKV-IN plus ToLCPaB for agroinoculation led to typical leaf curl, while ToLCPKV-IN together with the new betasatellite resulted in curling and chlorosis of leaves. Based on these disease symptoms, we propose to name the new betasatellite tobacco leaf chlorosis betasatellite (TbLChB).     

Isolation and molecular characterization of a distinct begomovirus and its associated betasatellite infecting Hedyotis uncinella (Hook. et Arn.) in Vietnam

A begomovirus isolate VN1 associated with symptomatic Hedyotis uncinella Hook. et Arn. from Vietnam was characterized. The virus, which we provisionally name H. uncinella yellow mosaic virus (HUYMV), has a monopartite genome of 2,749 nucleotides (nts). Pairwise comparisons of DNA-A sequences showed that HUYMV had a maximum nt sequence identity with Soybean crinkle leaf virus (SbLCV) and Premna leaf curl virus (PLCuV) at 82.1 and 81.9 %, respectively, which are less than the 89 % identity in the complete genome, which has been used as the threshold value for demarcation of species in the genus Begomovirus, the family Geminiviridae. One recombination event was detected for HUYMV, which involves an unknown begomovirus as the major parent and Tomato leaf curl Philippines virus (ToLCPV) as the minor parent, with nt 2163 and nt 2452 as the beginning and ending breakpoints, respectively. A betasatellite was found to be associated with HUYMV. The betasatellite showed the highest nt sequence identity (70 %) with Tomato leaf curl Philippine betasatellite—[Philippines:Laguna2:2006]. The name H. uncinella yellow mosaic betasatellite [Vietnam: Binh Dinh: 2013] was proposed for the betasatellite.     

Tomato leaf curl Bangalore virus (ToLCBV): infectivity and enhanced pathogenicity with diverse betasatellites

Genomic components of a begomovirus isolated from tomato plants showing leaf curl and stunting symptoms in farmer’s fields at Hessarghatta village near Bangalore, India, were cloned by rolling-circle amplification. The virus was identified as a variant of strain C of the species Tomato leaf curl Bangalore virus and designated as Tomato leaf curl Bangalore virus-C[India:Hessarghatta:2008], ToLCBV-C[IN:Hess:08]. The betasatellite isolated from these samples belongs to the betasatellite species Tomato leaf curl Bangalore betasatellite. ToLCBV-C[IN:Hess:08] induced severe symptoms in Nicotiana benthamiana and Solanum lycopersicum plants when co-inoculated with the cognate betasatellite, Tomato leaf curl Bangalore betasatellite–[India:Hessarghatta:2008], ToLCBB-[IN:Hess:08] and with two other non-cognate betasatellites, Cotton leaf curl Multan betasatellite–[India:SriGanganagar:2002] and Luffa leaf distortion betasatellite–[India:Luffa:2004].