Potato Yellow Mosaic Virus Research Articles

Surveys of virus diseases and molecular identification of viruses affecting pepper crops (Capsicum spp.) in southern Benin

Boosting the production of market garden products is a top priority for agricultural development in Benin. Chili pepper (Capsicum spp.), an economically important spice, is widely cultivated for its fruits in different parts of the country. Viral diseases are known to have a devastating impact on production. The objective of this study was to identify the viruses associated with pepper cultivation in southern Benin. Surveys and sample collections were conducted in five districts (Ouidah, Kpomassè, Sèmè, Cotonou, and Abomey-Calavi) from three departments (Atlantic, Littoral, and Ouémè) in September 2021. Disease incidence and severity of infection were assessed. Leaf samples from symptomatic and asymptomatic plants were collected randomly from farmers’ fields and were analyzed for viruses by RT-PCR using twelve primer pairs for different viruses sought. The overall high incidence of diseases varied according to the localities between 84.76% and 100% with an average of 94.46%. As for the severity of the disease, it varied significantly depending on the location of 3.24 (in Sèmè-Kpodji) to 2.56 (in Ouidah Cotonou) on average. The analysis of the data obtained by the detection of the presence of viruses in the various samples by RT-PCR shows the following occurrences: potato virus X (PVX) 77.36%, potato virus Y veinal necrosis strain (PVYn) 52.83%, cucumber mosaic virus (CMV) 47.17%, pepper vein virus (PeVYV) 32.08%, potato yellow mosaic virus (PYMV) 32.08%, Polerovirus 32.08%, Begomovirus 32.08%, tomato spoon yellow leaf (TYLCV) 18.87%, tomato spotted wilt virus (TSWV) 15.09%, pepper mottle virus (PepMoV) 11.32%, pepper mild mottle virus (PMMoV) 03.77%, and PVY 0.00% in the five districts surveyed during the periods under survey. Of the twelve groups of viruses searched for in the samples, eleven were found. Each of the samples is infected with one to seven of the twelve viruses sought. Mixed infections were common in most samples, and the high incidence suggests that the cultivars are highly susceptible to viral infections.

Genomic characterization and transmission efficiency by its vector Bemisia tabaci of a novel recombinant strain of potato yellow mosaic virus

Potato yellow mosaic virus (PYMV) is one of the most important begomoviruses infecting tomatoes in the Caribbean basin. Viruses of this group are transmitted by whiteflies of the Bemisia tabaci cryptic species complex. Within this complex, the whitefly referred to as Middle East-Asia Minor 1 (MEAM1) is globally spread and recognised as a highly efficient begomovirus vector. This study reports the whole genome of a PYMV isolate infecting tomatoes in Tachira state, Venezuela. The DNA-A of this isolate shared the highest nucleotide identity (93.5%) with a PYMV isolate from Solanum americanum. The PYMV isolate described here revealed a putative recombination event involving PYMV and tomato chlorotic leaf distortion virus. Additionally, the PYMV transmission by the whitefly MEAM1 was evaluated. At 60 days post inoculation, the transmission efficiency was 83.6, 88.2 and 100% when using one, five and 20 adults per plants, respectively.

Partial molecular characterization of begomoviruses isolated from weeds collected in tomato crops in the southeast of Valle del Cauca, Colombia

Weeds are usually considered as a source of new viruses but are often neglected during diversity studies. Previously eleven samples of weeds were collected along the edges of a tomato crop field located in four municipalities (Florida, Ginebra, Cerrito and Candelaria) in the Southeast of Valle del Cauca. These samples were positive for begomoviruses but their molecular characterization had not been done until now. For each sample, DNA fragments were cloned, sequenced and analyzed. Nucleotide sequence analysis of viral fragments showed the presence of six different begomoviruses: two virus isolated from Lantana camara, Desmodium sp. and Amaranthus dubius were previously described as potato yellow mosaic virus (PYMV) and passionfruit leaf distortion virus (PLDV), respectively; other four virus which were isolated from L. camara, A. dubius, Rivina humilis, Desmodium sp., Rhynchosia minima, Hybanthus attenuatus, Verbena sp., Croton hirtus and Caesalpinia sp., showed its highest nucleotide sequence identity (89%) with bean chlorotic mosaic virus (BChMV), datura leaf distortion virus (DaLDV) and rhynchosia golden mosaic Yucatan virus (RhGMYV). Cloned viruses fragments from these weeds could be new begomoviruses not previously reported before, this in accordance with the ICTV species demarcation criterion for the genus Begomovirus (≥91 % sequence identity). Mixed infections of begomoviruses in Desmodium sp. and A. dubius weeds also was found in this analysis. Finally, this paper reports by the first time to three alternative begomoviruses weeds hosts that infect tomato and passion fruit crops: A. dubius for PYMV, and L. camara and Desmodium sp. for PLDV, respectively.

High genetic stability of potato yellow mosaic Panama virus infecting tomato in Panama

The relevant regions in Panama involved in commercial tomato production, including the Chiriqui, Veraguas, Herrera, Los Santos and Panama Oeste provinces, were surveyed for the distribution and genetic diversity of potato yellow mosaic Panama virus (PYMPV) in the growing seasons of 2011 and 2012. A total of 28 tomato plots were surveyed and 314 individual tomato plants were sampled. DNA was extracted from each plant for a subsequent rolling circle amplification (RCA) analysis, to confirm the presence of begomovirus infections. The samples displaying a positive RCA reaction were subsequently analysed by PCR with a specific primer pair to identify PYMPV. This virus was detected in samples collected in all the above-mentioned provinces. The population structure of PYMPV was assessed by single-strand conformation polymorphism (SSCP) analysis. In total, four distinct SSCP patterns were distinguished. Based on the geographical distribution and the different patterns obtained, 42 viral isolates were selected for cloning and sequencing. Sequences obtained were compared with the ancestral sequence of PYMPV reported in Panama in 1998. These sequences showed very low variability, with two lineages probably originated by a single introduction.

Fast detection by loop-mediated isothermal amplification (LAMP) of the three begomovirus species infecting tomato in Panama

Potato yellow mosaic Panama virus (PYMPV), Tomato leaf curl Sinaloa virus (ToLCSiV) and Tomato yellow mottle virus (TYMoV) of genus Begomovirus (family Geminiviridae) are the only three begomovirus species detected infecting tomato (Solanum lycopersicum L.) in Panama. PYMPV, ToLCSiV and TYMoV induce symptoms of stunting, yellowing, curling, distortion of leaves and reduction of fruit size and cause important economic loses. A loop-mediated amplification under isothermal conditions (LAMP) assay was developed for the individual detection of these three begomovirus species by using a set of three primer pairs specific per each one of them. Amplification products were visualized by gel electrophoresis or direct Gel-Red staining of DNA into the reaction tube. PYMPV, ToLCSiV and TYMoV were detected in total DNA extracts obtained from different plant tissues such as leaves, stems, flowers, fruits and roots of infected tomato plants collected in different production regions of Panama. LAMP sensitivity was similar to that of conventional PCR but, the first procedure was faster and cheaper than the last one. Moreover, all three viruses were successfully detected by LAMP and not by conventional PCR from sap extracts obtained from leaf tissues of infected tomato plants which were embedded into 3MM Whatman paper and stored several days, facilitating the samples processing as well as the material movement among different laboratories. Therefore, LAMP is a specific, rapid and cheap procedure to detect all three begomoviruses infecting tomato in Panama and it is suitable for field surveys and sanitation programs.

First report of Potato yellow mosaic virus infecting Solanum americanum in Venezuela

Potato yellow mosaic virus (PYMV) is one of the most important tomato begomoviruses in the Caribbean basin (Morales et al ., 2006). In Venezuela, a recent survey showed that PYMV is the most widespread and prevalent begomovirus in tomato…

Occurrence of Six Begomoviruses Infecting Tomato Fields in Venezuela and Genetic Characterization of Potato Yellow Mosaic Virus Isolates

Begomoviruses are one of the major pathogens in tomato crops worldwide. In Venezuela, six begomovirus species have been described infecting tomato: Potato yellow mosaic virus (PYMV), Euphorbia mosaic Venezuela virus (EuMVV), Merremia mosaic virus (MeMV), Tomato chlorotic leaf distortion virus (ToCLDV), Tomato yellow margin leaf curl virus (TYMLCV) and Tomato yellow leaf curl virus (TYLCV). In this study, the occurrence of these viruses was analysed by PCR in 338 tomato plants exhibiting virus-like symptoms. Sixty-three per cent of the plants were positive at least to one of the begomoviruses tested. PYMV and TYLCV were the most frequent viruses showing 39.6 and 23.7% occurrence, respectively. Phylogenetic analyses revealed two groups of PYMV isolates from several Caribbean Basin countries. The first group clustered isolates from several countries, including Venezuela, and the second group clustered only Colombian isolates. Due to the high prevalence of PYMV and TYLCV in Venezuela, it is suggested that the surveillance and control strategies currently applied in the country should be focused on these two begomoviruses.

Begomoviruses Infecting Tomato Crops in Panama

AbstractThe key regions in Panama involved in open field‐ and greenhouse‐grown commercial tomato production, including the Chiriquí, Veraguas, Herrera, Los Santos, Coclé and Panama Oeste provinces, were surveyed for the incidence and distribution of begomoviruses in the growing seasons of 2011 and 2012. The surveys took place in 14 of the 51 districts of the above‐mentioned provinces and comprised all relevant tomato production areas of the provinces. A total of 28 tomato plots were surveyed. The exact location of each plot was geo‐referenced using a hand‐held Global Positioning System unit. In total, 319 individual tomato plants (181 in 2011 and 138 in 2012) were sampled. Plants displayed diverse combinations of virus‐like symptoms of different severity, including necrosis, yellowing, mosaic, mottling, rolling, curling, distortion and puckering of leaves, reduced leaf size, and stunted growth. DNA was extracted from each plant for a subsequent polymerase chain reaction (PCR) analysis, using two sets of degenerate primers able to detect members of the genus Begomovirus. The samples displaying a positive reaction were subsequently analysed with specific primer pairs to identify the affecting begomoviruses. A total of 42.3% of all collected samples showed a positive signal to PCRs. Three begomovirus species were detected with the species‐specific set of primers; in particular, in the samples obtained in 2011, Potato yellow mosaic Panama virus (PYMPV), Tomato leaf curl Sinaloa virus (ToLCSiV) and Tomato yellow mottle virus (TYMoV) were detected, while in the 2012 samples, only PYMPV and ToLCSiV were found. To our knowledge, this is the first reported incidence of ToLCSiV and TYMoV in Panamanian tomato crops.

A novel synthetic quantification standard including virus and internal report targets: application for the detection and quantification of emerging begomoviruses on tomato.

BackgroundBegomovirus is a genus of phytopathogenic single-stranded DNA viruses, transmitted by the whitefly Bemisia tabaci. This genus includes emerging and economically significant viruses such as those associated with Tomato Yellow Leaf Curl Disease, for which diagnostic tools are needed to prevent dispersion and new introductions. Five real-time PCRs with an internal tomato reporter gene were developed for accurate detection and quantification of monopartite begomoviruses, including two strains of the Tomato yellow leaf curl virus (TYLCV; Mld and IL strains), the Tomato leaf curl Comoros virus-like viruses (ToLCKMV-like viruses) and the two molecules of the bipartite Potato yellow mosaic virus. These diagnostic tools have a unique standard quantification, comprising the targeted viral and internal report amplicons. These duplex real-time PCRs were applied to artificially inoculated plants to monitor and compare their viral development.ResultsReal-time PCRs were optimized for accurate detection and quantification over a range of 2 × 109 to 2 × 103 copies of genomic viral DNA/μL for TYLCV-Mld, TYLCV-IL and PYMV-B and 2 × 108 to 2 × 103 copies of genomic viral DNA/μL for PYMV-A and ToLCKMV-like viruses. These real-time PCRs were applied to artificially inoculated plants and viral loads were compared at 10, 20 and 30 days post-inoculation. Different patterns of viral accumulation were observed between the bipartite and the monopartite begomoviruses. Interestingly, PYMV accumulated more viral DNA at each date for both genomic components compared to all the monopartite viruses. Also, PYMV reached its highest viral load at 10 dpi contrary to the other viruses (20 dpi). The accumulation kinetics of the two strains of emergent TYLCV differed from the ToLCKMV-like viruses in the higher quantities of viral DNA produced in the early phase of the infection and in the shorter time to reach this peak viral load.ConclusionsTo detect and quantify a wide range of begomoviruses, five duplex real-time PCRs were developed in association with a novel strategy for the quantification standard. These assays should be of a great interest for breeding programs and epidemiological surveys to monitor viral populations.

Tomatoes showing yellow leaf curl symptoms in the island of Grenada exhibit an infection with Tomato yellow leaf curl virus either alone or in combination with Potato yellow mosaic virus

In March 2007, severe symptoms of leaf curling and yellowing resembling tomato yellow leaf curl disease were observed on tomato ( Solanum lycopersicum ) plants with a very high incidence in six sites on Grenada Island (Fig. 1; Table 1).…

Molecular characterization and experimental host range of an isolate of Macroptilium golden mosaic virus that infects Wissadula amplissima in Jamaica

Partial genome sequences for the tentative begomovirus Macroptilium golden mosaic virus (MGMV) have been previously reported and were originally obtained for an isolate that infected Macroptilium lathyroides in Jamaica. In this study, we PCR-amplified, cloned and determined the sequence for the complete genome of isolates of MGMV that we found infecting Wissadula amplissima collected from August Town and Spanish Town, Jamaica. Sequence analysis confirmed that MGMV is a distinct begomovirus species, based on the ICTV 89% rule for species demarcation. MGMV shared its highest nucleotide identity at 79% for DNA-A component and 66% for DNA-B component to Corchorus yellow spot virus [Mexico:Yucatan:2005]. The names Macroptilium golden mosaic virus [Jamaica1:Wissadula:AugustTown] (MGMV [JM1:Wd:AT]) and Macroptilium golden mosaic virus [Jamaica1:Wissadula:SpanishTown] (MGMV [JM1:Wd:ST]) are proposed herein for the MGMV isolates from August Town and Spanish Town, respectively. The genome organization of MGMV [JM1:Wd:AT] and MGMV [JM1:Wd:ST] is characteristic of Western Hemisphere bipartite begomoviruses. Excluding the replication enhancer protein (REn), all proteins encoded by the MGMV [JM1:Wd:AT] and MGMV [JM1:Wd:ST] genomes are most similar to their counterparts in Western Hemisphere begomoviruses. The REn proteins of MGMV [JM1:Wd:AT] and MGMV [JM1:Wd:ST], share greatest similarity to the REn protein of Corchorus yellow vein virus [Vietnam:Hoa Binh:2000], a New World-like begomovirus identified in Asia. Phylogenetic reconstruction places MGMV in a clade containing Potato yellow mosaic virus. Results of an experimental host range study indicated that MGMV [JM1:Wd:AT] can infect kidney bean, hot pepper and tomato.

Molecular characterization and phylogenetic relationships of Desmodium leaf distortion virus (DeLDV): a new begomovirus infecting Desmodium glabrum in Yucatan, Mexico

The complete DNA-A component sequence of Desmodium leaf distortion virus (DeLDV, Begomovirus) isolated in Yucatan was determined to be 2569 nucleotides (nt) in length, and it was most closely related to Cotton leaf crumple virus-California (CLCrV-[Cal]), at 76%. The complete DNA-B component sequence was 2514 nt in length, and shared its highest nucleotide identity (60%) with Potato yellow mosaic Trinidad virus (PYMTV). Phylogenetic analyses group the DeLDV DNA-A component in the SLCV clade, whereas, the DeLDV DNA-B was grouped with the Abutilon mosaic virus clade, which also contains PYMV, suggesting that the DeLDV components have distinct evolutionary histories, possibly as the result of recombination and reassortment.

Vector and graft inoculations of Potato yellow mosaic virus reveal recessive resistance in Solanum pimpinellifolium

AbstractTransmission of Potato yellow mosaic virus (PYMV) (bipartite begomovirus) to tomato by 50 Bemisia tabaci biotype B individuals was observed when the acquisition access period (AAP) was at least 3 h and the inoculation access period (IAP) at least 30 min. The transmission efficiency increased with the access period to reach 92% transmission after a 48‐h IAP and 48‐h AAP. The transmission efficiency decreased when whiteflies were fed on PYMV non‐host plant between AAP and IAP. According to these results, we inoculated nine Solanum accessions with 50 whiteflies (48‐h APP and 48‐h IAP) to assess their resistance level. Four of these accessions with various levels of resistance were graft inoculated with PYMV. Although none of the accessions were immune, we observed a high level of resistance to PYMV in Solanumpimpinellifolium LA2187‐5 (no symptoms after vector or graft inoculation) and in Solanum chilense LA1969 (no symptoms after vector inoculation and one plant with symptoms after graft inoculation). Inheritance of LA2187‐5 resistance, investigated in F1 and F2 populations, appeared to be recessive. Fewer plants were infected by PYMV in S. pimpinellifolium LA1478 after vector inoculation than after graft inoculation. We hypothesised that this was because of vector resistance, which could also be effective against other begomoviruses.

Relative Distribution and Incidence of Viruses Associated with Disease Outbreaks in Tomato Fields in Trinidad

Tomato production in Trinidad has suffered considerable losses in yield and fruit quality due to infections of hitherto surmised etiology. In order to develop strategies for controlling viral diseases in tomato, the relative distribution and incidence of seven viruses that commonly infect tomato were determined. Of the 362 samples tested, Potato yellow mosaic Trinidad virus (PYMTV) was found in every farm except two and was present at relatively high incidence throughout the country. Tobacco mosaic virus (TMV) and Tobacco etch virus (TEV) were found in fewer farms and at lower incidences while the other viruses were absent. Single infections of either virus were more common than double infections and multiple infections were rare but present. The results indicated that PYMTV is the predominant and most important viral pathogen in tomato production systems in Trinidad; however, begomovirus disease management strategies will also have to accommodate controls Accepted for publication 10 January 2006. Published 9 March 2006.

Potato leaf curl – a new disease of potato in northern India caused by a strain of Tomato leaf curl New Delhi virus

A severe leaf curl disease has been observed since 1999 in potato ( Solanum tuberosum ) crops in northern India. The affected plants were severely stunted with apical leaf curl and crinkled leaves and a conspicuous mosaic. Garg et al . (2001) showed that, using polyclonal antibodies to Indian cassava mosaic virus in immunospecific electron microscopy, a begomovirus was associated with this disease. This report describes that the leaf curl disease in potato is caused by a strain of Tomato leaf curl New Delhi virus (ToLCNDV). The begomovirus from a severely affected potato plant was sap-transmitted to Nicotiana benthamiana seedlings in which it induced severe leaf distortion and stunting 15 days post-inoculation. Meristem-derived plantlets of potato cv. Kufri Anand inoculated with sap from infected N. benthamiana leaves developed yellow mottling, mosaic and leaf curl symptoms. Double-stranded viral replicative DNAs were purified from infected potato and N. benthamiana plants and cloned at Hind III, BamH I, Xba I and Pst I sites in the vector pUC18. The clones at the Xba I and Pst I sites had a unit genome length insert ( ∼ 2·7 kb) which hybridized with the viral replicative forms from the infected plants. The nucleotide sequence of the Xba I and Pst I clones corresponded to the DNA A (accession no. AY286316) and B (accession no. AY158080) components of the begomovirus causing the disease. Comparison of the complete nucleotide sequence of DNA A revealed that it has 93–95% identity with that of ToLCNDV isolates and < 75% identity with other Tomato leaf curl virus isolates and Potato yellow mosaic virus . A whitefly-transmitted begomovirus of potato has not been reported previously in India, probably as potato crops on the north Indian plains have been cultivated during winter months when whitefly populations are low. However, in recent years, potato crops have been planted earlier and this has resulted in a sufficient build-up of whitefly populations that might have led to the emergence of a new disease in potato. This is the first observation of a begomovirus causing a severe disease of potato in India. The nucleotide sequence data indicate that the cause is a virus closely related to ToLCNDV which, unlike the strain infecting potato, is not sap-transmissible and is not known to infect potato naturally. Therefore, it is likely that a new strain of ToLCNDV has emerged that infects a new host, potato.

Characterization and genetic diversity of Potato yellow mosaic virus from the Caribbean

The begomovirus Potato yellow mosaic virus (PYMV) is responsible of significant yield losses in tomato in Guadeloupe. Four field isolates from Guadeloupe were analyzed in term of their host range using three inoculation methods (mechanical, grafting and insect vector), sequences analysis of PCR fragments and phylogenetic analysis of an infectious clone, PYMV-[GP]. Capsicum annuum, Datura stramonium, Nicotiana benthamiana, N. tabacum 'Xanthi NC', Petunia hybrida, and Solanum tuberosum were found to be hosts. All isolates from Guadeloupe, Martinique, Puerto Rico and the Dominican Republic were closely related to PYMV-[GP]. Sequence identity between PYMV-[GP] and PYMV-Ve from Venezuela and PYMTV from Trinidad and Tobago clearly confirmed that it is a new strain of PYMV.

First Report of Tomato yellow leaf curl virus in Tomato in Guadeloupe.

In September 2001, symptoms of stunting and chlorotic curled leaves of reduced size were observed on tomato plants in Guadeloupe. These symptoms were different from those described for Potato yellow mosaic virus, which has been present since 1993, but similar to those described for Tomato yellow leaf curl virus (TYLCV). Samples from symptomatic plants were collected and analyzed by polymerase chain reaction (PCR). Primers PC1 (5'-TGACTATGTCGAAGCGACCAGG-3') and PC2 (5'-CGACATTACAGCCTCAGACTGG-3') were designed to amplify a 950-bp fragment within the coat protein gene (CP) of TYLCV-IL species (2). Primer pair MP16/MP82 (3) amplified a 550-bp fragment from the conserved nonanucleotide sequence (TAATATTAC) to the 5' end of the CP gene. Products of expected sizes were obtained with both pairs of primers from all symptomatic samples but not from uninfected samples. A 950-bp and a 550-bp PCR product were cloned into a pGEM-T Easy Vector (Promega, Madison, WI) and sequenced with plasmid specific primers (SP6 and T7). Sequences were compared with those available in the NCBI database using BlastN. Fifteen of the sequences that gave the highest score with BlastN were aligned with the Guadeloupe sequences using Clustal W. The nucleotide sequence of the 950-bp fragment (GenBank Accession No. AY319645) shared at least 97% sequence identity with that of TYLCV from Israel (EMBL Accession No. X15656), Puerto Rico (GenBank Accession No. AY134494), Cuba (EMBL Accession No. AJ223505), and the Dominican Republic (GenBank Accession No. AF024715). Similar percentages of identity were obtained with the 550-bp sequence (GenBank Accession No. AY319646). These results confirm that a begomovirus belonging to the species TYLCV-Israel is infecting tomato in Guadeloupe. To our knowledge, this is the first report of TYLCV in this region of the Caribbean. Puerto Rico is the closest location from which TYLCV was previously reported (1). In May 2002, typical TYLCV symptoms were observed in all tomato production areas at an incidence of 80 to 100%.

Tomato mottle Taino virus pseudorecombines with PYMV but not with ToMoV: implications for the delimitation of cis- and trans-acting replication specificity determinants.

Over the last decade, the tomato production in Cuba has been affected by new whitefly-associated diseases. In addition to the well-documented presence of Tomato yellow leaf curl virus (TYLCV) along the island, the occurrence of bipartite begomoviruses has also been reported. One of them, tentatively named Tomato mottle Taino virus (ToMoTV), has now been cloned and characterized at the molecular level. Its genomic organization is similar to other bipartite geminiviruses. Phylogenetic analyses placed ToMoTV in a subcluster with other geminiviruses isolated in the Caribbean Basin: Tomato mottle virus (ToMoV), Bean dwarf mosaic virus, Abutilon mosaic virus, Sida golden mosaic virus and Potato yellow mosaic virus (PYMV). Biolistic inoculation of tobacco and tomato plants with cloned viral DNA showed that ToMoTV pseudorecombines with PYMV-GP as predicted by the identity of their iterative elements, whereas it does not show the same ability with ToMoV, even when their replication-associated proteins (Rep and REn) show the highest percentage of similarity. A comparative analysis of Rep proteins from begomoviruses that are able to produce viable reassortants suggests that some key elements for virus replication specificity are located in the first ten amino acids of this protein.

Potato yellow mosaic virus: a synonym of tomato yellow mosaic virus.

Tomato yellow mosaic was first described in 1963, as a disease caused by a geminivirus transmitted by the whitefly Bemisia tabaci in Venezuela. In 1981 and 1985, Tomato yellow mosaic virus (ToYMV) was reported to occasionally infect potato plants growing in the proximity of tomato plantings affected by this virus. Despite these previous reports, a virus isolated from yellow mosaic-affected potato plants in Venezuela, was described in 1986 as a "new geminivirus" called potato yellow mosaic virus (PYMV). In recent years, different geminiviruses related to PYMV have been described from tomato fields in Venezuela and other countries in the Caribbean Basin, including Panama. Comparative nucleotide and amino acid sequence analyses of a 1698 bp fragment amplified from the common region and part of the AV1 and AC1 ORFs of ToYMV from Venezuela, yielded 95.7% sequence identity with the corresponding regions of PYMV. Nucleotide and amino acid sequence identities between ToYMV and PYMV, were 96.3% and 95.1% for AC1, and 95.7% and 100% for AV1, respectively. The identity of the nucleotide sequence for the common region of ToYMV and PYMV was 96.5%. Comparative sequence analyses conducted with ToYMV and other tomato begomoviruses present in the Caribbean region, showed only distant relationships. It is concluded here that PYMV is a synonym of ToYMV.

Introduction of the Exotic Tomato yellow leaf curl virus-Israel in Tomato to Puerto Rico.

Thirty-five-day-old tomato plants (cultivar Florasette) exhibited yellow leaf curling, stunting, and extremely reduced fruit set in spring 2001, in Guanica, Puerto Rico (PR). Twenty percent disease incidence was observed in this field and, 8 weeks later, 75% of the plants showed symptoms. These symptoms were distinct from those caused by other tomato-infecting begomoviruses reported previously from PR, namely Merremia mosaic virus, Tomato mottle virus (ToMoV), and Potato yellow mosaic virus (1). A colony of the B biotype of Bemisia tabaci (Genn.) was used to transmit the suspect virus from symptomatic plants collected in the field and established in the greenhouse in Rio Piedras, PR. The suspect virus was transmitted readily to tomato cultivar Roma (10 of 10 plants), and symptoms were like those observed in the field. Symptoms also were reminiscent of those described for several Old World begomoviruses, referred to as Tomato yellow leaf curl virus (TYLCV). Total nucleic acids were isolated from three symptomatic field samples and three greenhouse-inoculated tomato plants showing typical disease symptoms. Extracts were analyzed by polymerase chain reaction (PCR) with primers AV2466 and AC1145 to amplify a begomoviral fragment (approximately 1.1 bp) that contains a portion of the intergenic region and the viral coat protein gene (CP) (2). Amplicons were cloned, and their nucleotide sequences were determined. A comparison of CP with other well-studied begomoviral nucleotide sequences revealed that the CP sequences for field isolates 1 to 6 shared 99.7 to 100% identity with each other and 99.9 to 100% identity with TYLCV from Israel (TYLCV-IL; accession no. X76319) as well as TYLCV-IL isolates discovered in the Dominican Republic (DO; accession no. AF024715) and, subsequently, in Florida. TYLCV-specific PCR primers (forward) 5'-GAATTCCGCCTTTAA-TTTG-3' and (reverse) 5'-GAATTCCCACTATCTTTCTC-3' were used to amplify the complete viral genome form a PR field isolate. An expected-sized amplicon of approximately 2.8 kb was obtained, and the nucleotide sequence of two cloned amplicons was determined. Genome organization revealed a predicted precoat open reading frame of 351 bp, which is characteristic of other Old World begomoviruses, including TYLCV-IL. Nucleotide comparisons indicated that the PR isolate shared 99% nucleotide sequence identity with TYLCV-IL (first reported from Israel) and introduced TYLCV-IL isolates in DO and Florida, thereby confirming the introduction of TYLCV-IL into PR. TYLCV-IL was first identified several years ago in the Western Hemisphere, and the virus has been reported in five offshore locations and three continental U.S. states since its initial introduction into the DO in the early 1990s. Considering the extreme virulence of TYLCV-IL compared with most New World tomato-infecting begomoviruses, this introduction, which likely occurred from a nearby Caribbean country or Florida, has the potential to destroy the fresh-market tomato industry in PR, which supplies tomatoes to the continental United States during the winter months. There is compelling evidence for the routine movement of tomato seedlings from the continental United States to this location in PR throughout the last 10 years, including the previous introduction of ToMoV (1). These incidences and others indicate the need for those in infected areas to take precautions to avoid further spread of this highly damaging virus in and adjacent to the Caribbean region.