PCR–RFLP-based typing for differentiation of Tomato yellow leaf curl virus (TYLCV) genotypes from infected host plants in Korea

A polymerase chain reaction (PCR) using two sets of primers designed from published Tomato yellow leaf curl virus (TYLCV) genomes was developed to distinguish from the TYLCV-IL groups. The specificity of the two sets of primers was proven by testing against control TYLCV genomes and the symptomatic leaves of 34 different tomato cultivars naturally infected with TYLCV in greenhouses. One set for TYLCV-IL strain-specific primers (TYLCV-UNI-F and TYLCV-UNI-R) amplified full-length genome fragments from all the 34 tomato cultivars. Another set for TYLCV-IL group-II strain-specific primers (TYLCV-GPII-F and TYLCV-GPII-R) amplified target DNA fragments from only 9 tomato cultivars. Digestion by BglII and EcoRV of the PCR amplicons produced restriction fragment length polymorphism pattern that distinguished the TYLCV-IL group-I with two fragments from the TYLCV-IL group-II with no digested fragment. PCR coupled with BglII and EcoRV digestion confirmed that the 9 tomato cultivars were infected with the TYLCV-IL group-II and the remained 25 tomato cultivars were infected with the TYLCV-IL group-I.     

Molecular characterization and pathogenicity of tomato yellow leaf curl virus in China

Several tomato production regions in China were surveyed for tomato yellow leaf curl disease (TYLCD), and 31 tomato leaf samples showing TYLCD-like symptoms were collected. The partial or full-length genomes of these isolates were sequenced and tomato yellow leaf curl virus (TYLCV) was detected in Shanghai, Zhejiang, Jiangsu Shandong and Hebei provinces of China. The TYLCV isolates found in China share high sequence identity (>98%) and have more than 97% sequence identity with TYLCV-IL[IL:Reo] (X15656). Phylogenetic relationship analysis reveals that although with little genetic variability, they can form two groups and all the TYLCV isolates in China belong to the group I. An infectious clone of TYLCV-[CN:SH2] (AM282874) was constructed and agro-inoculated into Nicotiana benthamiana, N. tabacum Samsun, N. glutinosa, Solanum lycopersicum, Petunia hybrida, Cucumis sativus, Gossypium hirsutum, S. melongena, and Capsicum annuum. TYLCV-[CN:SH2] can induce severe leaf curling and stunting symptoms in these plants except C. sativus, G. hirsutum, S. melongena and C. annuum. We verified that TYLCV can trans-replicate tomato yellow leaf curl China virus DNA-β in N. benthamiana and S. lycopersicum and induced more severe symptoms with distortion and yellow vein.     

Molecular characterization of a distinct begomovirus infecting <Emphasis Type="Italic">Allamanda cathartica</Emphasis> in Guangdong,China

Virus isolate G10 was obtained from diseased allamanda plants showing leaf curl symptoms in Guangdong, China. The full-length nucleotide sequence of a DNA-A-like molecule of G10 was cloned and sequenced; it comprises 2755 nucleotides and has a typical begomovirus genome organization with six conserved open reading frames. When compared with the DNA-A sequences of other begomoviruses, the complete nucleotide sequence of DNA-A of G10 had the highest sequence identity (81.2%) to tomato leaf curl Guangdong virus (ToLCGuV) isolate G2. This is less than the 89% identity in the complete genome that has been defined as the threshold value for demarcation of species in the genus Begomovirus. The molecular data show that isolate G10 from allamanda in Guangdong, China is a distinct Begomovirus species, for which the name Allamanda leaf curl virus (AlLCV) is proposed. The GenBank accession number of the sequence reported in this paper is EF602306.     

Tomato leaf curl virus from Bangalore (ToLCV-Ban4): sequence comparison with Indian ToLCV isolates, detection in plants and insects, and vector relationships}

Summary.  Tomato leaf curl virus (ToLCV) is a whitefly (Bemisia tabaci) transmitted geminivirus (family Geminiviridae, genus Begomovirus) causing a destructive disease of tomato in many regions of India, East Asia and Australia. While ToLCV isolates from Australia and Taiwan have a single genomic component (designated DNA-A), those from Northern India have two components (DNA-A and DNA-B). The ToLCV isolates from Southern India (Bangalore) previously cloned seem to have a DNA-A-like monopartite genome. We have used degenerate DNA-A-specific PCR primers to clone the genome of a ToLCV isolate (named ToLCV-Ban4) from field-infected tomato plants growing in Bangalore, India, in 1997. Degenerate DNA-B-specific PCR primers have not allowed to amplify a putative DNA-B from infected tomato, at the time when DNA-B fragments were amplified from plants infected by known bipartite begomoviruses. The full-length 2759 nucleotide-long DNA-A-like viral genome was sequenced. Similarly to other monopartite ToLCV and TYLCV isolates, ToLCV-Ban4 contains six open reading frames, two on the virion strand and four on the complementary strand. Sequence comparisons indicated that ToLCV-Ban4 is similar to the other three isolates from Bangalore previously sequenced, and is closely related to ToLCV-Ban2 (approximately 91\% nucleotide sequence identity). Phylogenetic analysis showed that the ToLCV isolates from Bangalore constitute a group of viruses separated from those of Northern India. ToLCV-Ban4 was detected in tomato and in its whitefly vector Bemisia tabaci by one or by a combination of ELISA, Southern blot hybridization and PCR. Parameters of virus acquisition, retention and transmission by the whitefly vector were investigated in the laboratory. Single whiteflies were able to acquire ToLCV-Ban4 from infected tomato and to transmit the virus to tomato test plants, but five insects were necessary to achieve 100% transmission. Minimum acquisition access and inoculation access periods were 10 min and 20 min, respectively. A latent period of 6 h was required for B. tabaci to efficiently infect tomato test plants. Following a 24 h acquisition access period the insect retained its ability to infect tomato test plants for 12 days, but not for its entire life. In one insect/one plant inoculation tests, female whiteflies were more efficient (∼95%) than males (∼25%) in transmitting the virus. Received July 5, 1999 Accepted March 2, 2000     

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     

Molecular identification of a new begomovirus associated with mosaic disease of Jatropha curcas L. in Nigeria

We report the complete nucleotide sequence of DNA-A of a begomovirus naturally infecting Jatropha curcas L. in Nigeria. Symptoms observed on infected plants were severe mosaic, mottling and blistering of leaves. The virus, which we provisionally name “jatropha mosaic Nigeria virus” (JMNV), has a monopartite genome of 2,779 to 2,789 nucleotides. Pairwise comparisons of DNA-A sequences showed that JMNV had maximum nucleotide sequence identity (72%) with a strain of tomato yellow leaf curl virus. Since there are widespread infections of jatropha in Nigeria showing similar symptoms as those investigated in the present study, JMNV may represent a significant threat to a promising bioenergy crop.     

Application of Phi29 DNA polymerase in identification and full-length clone inoculation of tomato yellow leaf curl Thailand virus and tobacco leaf curl Thailand virus

Summary. Tomato plants grown in greenhouses in Thailand developed typical symptoms of a tomato yellow leaf curl Thailand virus (TYLCTHV) infection. After confirmation by ELISA, a Phi29 DNA polymerase approach was chosen for further molecular analysis of TYLCTHV. Total DNA purified from infected tomato leaves was subjected to rolling-circle amplification (RCA) of DNA-A and DNA-B of TYLCVTHV. In addition, a new monopartite geminivirus with a putative recombinant background was identified by RCA and tentatively named tobacco leaf curl Thailand virus (TbLCTHV). To confirm the composition of both geminiviruses, full-length clones were established and used for inoculation of Nicotiana benthamiana by particle bombardment or agroinfection. When TYLCTHV DNA-A and DNA-B were applied together by particle bombardment or agroinfection, severe stunting, yellowing, and leaf curling were observed. Whereas TYLCTHV DNA-A and TbLCTHV revealed no infection after'particle bombardment, similar symptoms in N. benthamiana, like leaf upward curling and yellowing were observed following agroinfection. DNA components of TYLCTHV DNA-A and DNA-B were excised from their respective plasmids, ligated, and amplified by Phi29 DNA polymerase. The ability of viral concatamere inoculation was evaluated in particle co-bombardment experiments on N. benthamiana. Thus, particle bombardment of RCA-derived multimeric products proved to be at least as effective as inoculation with a partial repeat construct and tenfold as effective as inoculation with excised unit-lengths of DNA-A and DNA-B of TYLCVTHV when using each DNA component in an amount of 5 ng.     

Molecular Characterization of Two Distinct Begomovirusesfrom Papaya in China

Six papaya samples showing downward leaf curling were collected in Guangdong and Guangxi provinces, China. The result of TAS-ELISA showed they were all infected by geminiviruses. Comparison of partial DNA-A sequences reveals that these virus isolates can be classified into two groups. Group I includes isolates G2, G4, G5, G28 and G29 from Guangxi province, while isolate GD2 from Guangdong province belongs to Group II. The complete DNA-A sequence of G2 and GD2 were characterized. Sequence comparisons showed that the DNA-A of G2 and GD2 were most closely related to that of Ageratum yellow vein China virus-[Hn2] and Ageratum yellow vein virus, respectively, with 83.4 and 75.2% nucleotide sequence identity, while DNA-A sequence between G2 and GD2 had only 73.4% sequence identity. The molecular data suggests that G2 and GD2 are two distinct begomoviruses, for which the name Papaya leaf curl China virus (PaLCuCNV) for G2 and Papaya leaf curl Guangdong virus (PaLCuGDV) for GD2 are proposed. Comparison of individual encoded proteins showed the coat protein of G2 and GD2 shared highest amino acid sequence identity (97.7 and 94.2%, respectively) with that of Pepper leaf curl virus-[Malaysia] (PepLCV-[MY]), suggesting the CP of these viruses may have identical ancestor.     

Pathogenicity and insect transmission of a begomovirus complex between tomato yellow leaf curl virus and Ageratum yellow vein betasatellite

Tomato yellow leaf curl virus (TYLCV) and Ageratum yellow vein betasatellite (AYVB) are members of the genus Begomovirus (family Geminiviridae). TYLCV and AYVB have been found in Japan over the last 15 years, and are associated with tomato leaf curl and the tomato yellow leaf curl diseases (TYLCD). AYVB is also associated with some monopartite begomoviruses. We have cloned both TYLCV and AYVB and demonstrated that TYLCV can trans-replicate with AYVB in Nicotiana benthamiana and tomato plants. A mixed infection of TYLCV and AYVB induced more severe symptoms of upward leaf curl, stunting, vein thickening, and swelling compared with TYLCV infection alone. The symptoms induced by infection of AYVB included a rise in abnormal cell proliferation, and pigmentation around leaf vein tissues. This is the first study to show that a complex of TYLCV and AYVB can be transmitted by vector insects among tomato plants. These results indicate that TYLCV possesses the potential to induce severe TYLCD by associating with AYVB.     

Association of a satellite DNA β molecule with mesta yellow vein mosaic disease

The yellow vein mosaic disease infected mesta samples exhibited positive amplification with different primers specific for coat protein (CP) gene of DNA-A molecule of begomoviruses and full-length DNA β molecule. The amplified product of a full-length DNA β and the CP gene of two different isolates were cloned and sequenced. The DNA β molecule was 1,354 nt in length having highest sequence identity (86.1%) with two reported DNA β molecules of Indian isolates of begomovirus infecting cotton (accession number DQ191161 and AJ316038). Highest sequence identity (85.5%) of βC1 gene product was found with that encoded by DNA β associated with begomovirus infecting tomato (AJ316035), originating from Pakistan. The predicted βC1 protein consisted of 118 amino acids. The nucleotide sequences of the CP genes from both was 771 nt in length and showed sequence identity with CP genes of begomoviruses infecting tomato (82.2–92.4%), tobacco (AY007616, 94.2%) and Croton (AJ507777, 93.9%). The highest percentage sequence identity (97.6%) of the CP gene product was found with that encoded by DNA-A of two isolates of begomovirus infecting tomato (AJ810364 and AJ810357). The predicted CP consisted of 256 amino acids. The results indicate for the first time that the begomovirus associated with mesta yellow vein mosaic disease contains DNA β molecule along with DNA-A in its genome. The phylogenetic tree also indicated that the DNA β molecule reported here is distinct from other known geminiviruses or nanovirus components.     

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.     

Tomato chlorotic leaf distortion virus,a new bipartite begomovirus infecting <Emphasis Type="Italic">Solanum lycopersicum</Emphasis> and <Emphasis Type="Italic">Capsicum chinense</Emphasis> in Venezuela

Virus isolate T217L was obtained from a diseased tomato (Solanum lycopersicum) plant showing leaf deformation and chlorotic mottle symptoms near Maracaibo in the state of Zulia, Venezuela. Full-length DNA-A and DNA-B molecules of T217L were cloned and sequenced. The genome organization of T217L was identical to the bipartite genomes of other begomoviruses described from the Americas. Characteristic disease symptoms were reproduced in S. lycopersicum and Capsicum annum plants inoculated using the cloned viral DNA-A and DNA-B components, confirming disease aetiology. A sequence analysis of DNA-A showed that the T217L isolate has the highest sequence identity (84%) with sida yellow mosaic Yucatan virus (SiYMYuV), sida golden mosaic Honduras virus (SiGMHV) and bean dwarf mosaic virus (BDMV) isolates. This is less than the 89% identity in the DNA-A component that has been defined as the threshold value for the demarcation of species in the genus Begomovirus. The molecular data show that isolate T217L belongs to a novel tentative begomovirus species, for which the name tomato chlorotic leaf distortion virus is proposed. TCLDV was also detected in symptomatic C. chinense plants growing near the T217L-infected plant.     

Making a friend from a foe: expressing a GroEL gene from the whitefly <Emphasis Type="Italic">Bemisia tabaci</Emphasis> in the phloem of tomato plants confers resistance to tomato yellow leaf curl virus

Summary Some (perhaps all) plant viruses transmitted in a circulative manner by their insect vectors avoid destruction in the haemolymph by interacting with GroEL homologues, ensuring transmission. We have previously shown that the phloem-limited begomovirus tomato yellow leaf curl virus (TYLCV) interacts in vivo and in vitro with GroEL produced by the whitefly vector Bemisia tabaci. In this study, we have exploited this phenomenon to generate transgenic tomato plants expressing the whitefly GroEL in their phloem. We postulated that following inoculation, TYLCV particles will be trapped by GroEL in the plant phloem, thereby inhibiting virus replication and movement, thereby rendering the plants resistant. A whitefly GroEL gene was cloned in an Agrobacterium vector under the control of an Arabidopsis phloem-specific promoter, which was used to transform two tomato genotypes. During three consecutive generations, plants expressing GroEL exhibited mild or no disease symptoms upon whitefly-mediated inoculation of TYLCV. In vitro assays indicated that the sap of resistant plants contained GroEL-TYLCV complexes. Infected resistant plants served as virus source for whitefly-mediated transmission as effectively as infected non-transgenic tomato. Non-transgenic susceptible tomato plants grafted on resistant GroEL-transgenic scions remained susceptible, although GroEL translocated into the grafted plant and GroEL-TYLCV complexes were detected in the grafted tissues.     

Sweet pepper confirmed as a reservoir host for tomato yellow leaf curl virus by both agro-inoculation and whitefly-mediated inoculation

Tomato yellow leaf curl virus (TYLCV), a member of the genus Begomovirus, has a single-stranded DNA genome. TYLCV can induce severe disease symptoms on tomato plants, but other hosts plants such as cucurbits and peppers are asymptomatic. A full-length DNA clone of a Korean TYLCV isolate was constructed by rolling-circle amplification from TYLCV-infected tomatoes in Korea. To assess relative susceptibility of sweet pepper varieties to TYLCV, 19 cultivars were inoculated with cloned TYLCV by agro-inoculation. All TYLCV-infected sweet peppers were asymptomatic, even though Southern hybridization and polymerase chain reaction analysis showed TYLCV genomic DNA accumulation in roots, stems, and newly produced shoots. Southern hybridization indicated that TYLCV replicated and moved systemically from agro-inoculated apical shoot tips to roots or newly produced shoots of sweet peppers. Whitefly-mediated inoculation experiments showed that TYLCV can be transmitted to tomatoes from TYLCV-infected sweet peppers. Taken together, these results indicate that sweet pepper can be a reservoir for TYLCV in nature.     

Lamium amplexicaule (Lamiaceae): a weed reservoir for tomato yellow leaf curl virus (TYLCV) in Korea

After the first identification of tomato yellow leaf curl virus (TYLCV) in the southern part of Korea in 2008, TYLCV has rapidly spread to tomato farms in most regions of Korea. From 2008 to 2010, a survey of natural weed hosts that could be reservoirs of TYLCV was performed in major tomato production areas of Korea. About 530 samples were collected and identified as belonging to 25 species from 11 families. PCR and Southern hybridization were used to detect TYLCV in samples, and replicating forms of TYLCV DNA were detected in three species (Achyranthes bidentata, Lamium amplexicaule, and Veronica persica) by Southern hybridization. TYLCV transmission mediated by Bemisia tabaci from TYLCV-infected tomato plants to L. amplexicaule was confirmed, and TYLCV-infected L. amplexicaule showed symptoms such as yellowing, stunting, and leaf curling. TYLCV from infected L. amplexicaule was also transmitted to healthy tomato and L. amplexicaule plants by B. tabaci. The rate of infection of L. amplexicaule by TYLCV was similar to that of tomato. This report is the first to show that L. amplexicaule is a reservoir weed host for TYLCV.     

Further characterization of tomato-infecting begomoviruses in Brazil

Tomato cultivation in Brazil is threatened by a number of tomato-infecting viruses belonging to the genus Begomovirus of the family Geminiviridae. Here, we report the full DNA-A sequences of three Brazilian begomoviruses: a potentially new tomato-infecting viruses, tomato interveinal chlorosis virus (ToICV), and two previously proposed begomoviruses for which only partial DNA-A sequences are available in the databases: tomato mottle leaf curl virus (TMoLCV) and tomato golden vein virus (TGVV). The complete sequences of the DNA-B components of TMoLCV and TGVV and the DNA-A components of a number of tomato severe rugose virus variants are also presented. Collectively, all of the analyzed sequences were phylogenetically clustered within the two major groups of Brazilian tomato-infecting begomoviruses.     

Infection of tomato by the tomato yellow leaf curl virus: susceptibility to infection,symptom development,and accumulation of viral DNA

Summary Symptom development in tomato plants following whitefly-mediated inoculation with tomato yellow leaf curl virus (TYLCV) was related to the occurrence of viral DNA using a specific DNA probe. Although disease symptoms were first observed 15 days post-inoculation, viral DNA could be detected 7 days earlier. TYLCV-DNA concentrations reached an optimum 4 days before symptoms appeared. The highest concentrations of TYLCV-DNA were found in rapidly growing tissues (shoot apex, young leaves, roots) and in the stems; the lowest concentrations were found in the older leaves and cotyledons. Plants were also inoculated on specific sites. Young leaves and apices were the best targets for virus inoculation. In these tissues, the viral DNA replicated at the site of inoculation and was transported first to the roots, then to the shoot apex and to the neighboring leaves and the flowers. Inoculation through the oldest leaves was inefficient.     

Strains of a new bipartite begomovirus, pepper yellow leaf curl Indonesia virus, in leaf-curl-diseased tomato and yellow-vein-diseased ageratum in Indonesia

The complete nucleotide sequences of begomoviruses from pepper with leaf curl and yellowing symptoms, tomato with leaf curl symptoms, and ageratum with yellow vein in Indonesia were determined. On the basis of genome organization and sequence homology, they were proposed to belong to a new species, Pepper yellow leaf curl Indonesia virus (PepYLCIV), which includes the new strains PepYLCIV-Tomato and PepYLCIV-Ageratum. These viruses had bipartite genomes. Pepper virus DNAs from Indonesia (PepYLCIV, PepYLCIV-Tomato and PepYLCIV-Ageratum DNA-As) were noticeably distinct, forming a separate branch from the viruses infecting pepper. Considerable divergence was observed in the common region (CR) of the genomic components of PepYLCIV (77%), PepYLCIV-Tomato (82%) and PeYLCIV-Ageratum (75%). A stem-loop-forming region and a Rep-binding motif were identical in the CR of the three viruses. The CRs of PepYLCIV-Ageratum DNA-A was approximately 10 nucleotides longer than that of PepYLCIV DNA-A and PepYLCIV-Tomato DNA-A. A similar insertion was also found in the CR of PepYLCIV-Ageratum DNA-B. PepYLCIV DNA-A alone was infectious in pepper and Nicotiana benthamiana plants, and association with DNA-B increased symptom severity.     

Molecular characterization of tomato-infecting begomoviruses in Thailand

Bipartite geminiviruses infecting tomatoes in Thailand were detected by polymerase chain reaction (PCR) using CPA5/CPA2 primers. Products derived from PCR-amplified full-length DNA-A and DNA-B of TYLCV collected from Chiang Mai, Nong Khai, and Sakon Nakhon were cloned and sequenced. DNA-A from Chiang Mai was 2747 nts long; Nong Khai, 2744 nts; and Sakon Nakhon, 2747 nts, and those of DNA-B from Chiang Mai were 2750 nts long; Nong Khai, 2749 nts; and Sakon Nakhon, 2749 nts. The genomes of these virus isolates were organized like those of other begomoviruses. The DNA-A had two ORFs in the virion sense and four ORFs in the complementary sense. The DNA-B had two ORFs in the virion sense and one ORF in the complementary sense. Nucleotide sequences of DNA-A of TYLCV from Chiang Mai, Nong Khai, and Sakon Nakhon were closely related to those of Tomato yellow leaf curl Thailand virus (TYLCTHV) and Tomato yellow leaf curl Thailand virus-[Myanmar] (TYLCTHV-[MM]) with nucleotide sequence identity ranging from 89% to 95%. Based on sequence comparisons and phylogenetic analyses, these three virus isolates studied were identified as new strains of TYLCTHV and named Tomato yellow leaf curl Thailand virus-Chiang Mai (TYLCTHV-[CM]The GenBank accession codes for DNA-A of TYLCTHV-[CM], -[NK], and -[SK] are , and , respectively. The GenBank accession codes for DNA-B of TYLCTHV-[CM], -[NK], and -[SK] are , , and , respectively.), Nong Khai (TYLCTHV-[NK] and Sakon Nakhon (TYLCTHV-[SK]).     

Molecular characterization and phylogenetic relationships of two new bipartite begomovirus infecting malvaceous plants in Yucatan,Mexico

Sida acuta and Corchorus siliquosus plants showing yellow mosaic and yellow vein symptoms, respectively, were collected in the Yucatan Peninsula, Mexico. Total DNA was isolated from both plant species and used for the amplification, cloning, and sequencing of the Begomovirus genome. Nucleotide comparison of the complete DNA-A component isolated from S. acuta and C. siliquosus confirmed the presence of two distinct begomoviruses species. Based on phenotypic symptoms observed in infected field plants, the names Sida yellow mosaic Yucatan virus (SiYMYuV) and Corchorus yellow vein Yucatan virus (CoYVYuV) were proposed. The SiYMYuV DNA-A shared the highest nucleotide identity (86%) with the Okra yellow mosaic Mexico virus (OkYMMV). The complete DNA-B component shared the highest nucleotide identity (80%) with CoYVYuV. The CoYVYuV DNA-A shared the highest nucleotide identity (84%) with SiYMYuV. The 166-nt common region (CR) sequence for the DNA-A and DNA-B components of SiYMYuV shared a high nucleotide identity of 99%, and the 151 nt of CoYVYuV CR shared 95% of nucleotide identity. The organization and the iterated sequence of the putative AC1 binding site (located within the common region) of both isolates, were similar to that of the begomoviruses of the Western Hemisphere. Phylogenetic analyses placed the DNA-A and DNA-B of SiYMYuV and CoYVYuV in the clade containing the Abutilon mosaic virus (AbMV).