Presence Of Tomato Yellow Leaf Curl Virus Research Articles

The Influence of Visual and Olfactory Cues in Host Selection for Bemisia tabaci Biotype B in the Presence or Absence of Tomato Yellow Leaf Curl Virus

The silverleaf whitefly, Bemisia tabaci, is one of the most destructive agricultural pests in the world, vectoring a large number of devastating viruses, including Tomato Yellow Leaf Curl Virus (TYLCV). When selecting a host, B. tabaci is primarily influenced by a range of visual and olfactory cues. Therefore, elucidating how such cues become modified in the presence of whitefly-vectored begomoviruses is critical to better understanding the epidemiology of many economically important diseases. The goal of this study was to determine how both visual and odor cues interact in the presence of TYLCV. In Y-tube olfactometer assays, whiteflies were submitted to a range of isolated visual and olfactory cues to determine behavioral changes. B. tabaci choices were then compared to both stimuli combined in the presence or absence of TYLCV. Under visual stimuli only, B. tabaci exhibited a visual attraction to the color yellow, TYLCV-infected tomato leaves, and TYLCV-infected tomato volatiles. Attraction was the strongest overall when both visual and olfactory cues from TYLCV-symptomatic tomato plants were combined, as opposed to a single isolated cue. These results highlight the importance of both sensory stimuli during B. tabaci host selection in the presence of an associated begomovirus.

FIRST REPORT OF SOLANUM ELAEAGNIFOLIUM AS NATURAL HOST OF TOMATO YELLOW LEAF CURL VIRUS SPECIES (TYLCV AND TYLCSV) IN TUNISIA

Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) (genus Begomovirus, family Geminiviridae), as well as recombinant variants, were recently found in tomato in Tunisia (Mnari-Hattab et al., 2014). To identify sources of infection, tomato plants and Solanum elaeagnifolium, an invasive weed, were sampled and tested for the presence of TYLCV and TYLCSV. Genomic DNA was purified from leaf samples showing curling and yellowing and subjected to PCR using primers designed in the coat protein gene of TYLCV (Mnari-Hattab et al., 2014; Wyatt and Brown, 1996). A product of ca. 580 bp was obtained from four of six S. elaeagnifolium and six of six tomato samples tested. The nucleotide sequence of one amplicon from tomato and two amplicons from S. elaeagnifolium was obtained and deposited in GenBank as accession numbers KF990598, KF990599 and KF990600. The nucleotide sequence of Tunisian TYLCV isolates was 91.2 to 98.9% identical and shared 91 to 98.3% identity with a TYLCV isolate from Turkey (AJ867487). Multiplex PCR (Davino et al., 2008) was further used to identify virus species with the amplification of a 570 bp fragment for TYLCV and a 800 bp fragment for TYLCSV. Results showed two S. elaeagnifolium and four tomato plants infected with TYLCV or TYLCSV, and two S. elaeagnifolium and one tomato plant infected with both viruses. To the best of our knowledge, this is the first report of S. elaeagnifolium as a natural host of TYLCV and/or TYLCSV in Tunisia. These findings suggest S. elaeagnifolium as a reservoir for tomato yellow leaf curl virus disease.

Peroxidase Activity after Viral Infection and Whitefly Infestation in Juvenile and Mature Leaves of Solanum lycopersicum

AbstractWhitefly infestation and the begomoviruses that they transmit have been shown to affect the activities of plant defence proteins, but with no relation to heterophylly, a process of great importance underlying the overall biology of plants. Here, we have assessed the effects of Tomato yellow leaf curl virus (TYLCV) infection on Solanum lycopersicum peroxidase (POD) activity and have examined whether leaves of different ages exhibit differential POD activity in response to infection and infestation with Bemisia tabaci B biotype. We used leaf discs of two ages (juvenile and mature) with two different infection statuses (infected and healthy) to examine the activity of the tomato plant peroxidase using guaiacol as a substrate and taking exposure time into account. S. lycopersicum showed increased POD activity in the presence of TYLCV. The activity of the enzyme was higher in mature than in juvenile leaves. In general, both infected and healthy leaves exhibited greater POD activity during whitefly infestation. In the infested juvenile leaves, POD activity was much lower in the healthy leaves and increased gradually with period of exposure to B. tabaci B infestation. In contrast, the activity of the enzyme remained low in infested mature leaves in both the presence and absence of the virus even with increased exposure time. Determination of the distribution of an insect pest is critical for sampling and management. Leaf age is presumed to be associated with the within‐host distribution of the geminivirus vector B. tabaci. Juvenile leaves will usually attract more insects due to increased nutritional value and weaker defences. Our results highlight the importance of leaf age/position on the whitefly – host plant – geminivirus interactions and have important implications for sampling and control strategies.

First Report of Tomato chlorosis virus Infecting Tomato in Georgia.

Tomato yellow leaf curl virus (TYLCV) and Tomato spotted wilt virus (TSWV) are prevalent in field-grown tomato (Solanum lycopersicum) production in Georgia. Typical TYLCV symptoms were observed during varietal trials in fall 2009 and 2010 to screen genotypes against TYLCV at the Coastal Plain Experiment Station, Tifton, GA. However, foliar symptoms atypical of TYLCV including interveinal chlorosis, purpling, brittleness, and mottling on upper and middle leaves and bronzing and intense interveinal chlorosis on lower leaves were also observed. Heavy whitefly (Bemisia tabaci (Gennadius), B biotype) infestation was also observed on all tomato genotypes. Preliminary tests (PCR and nucleic acid hybridization) in fall 2009 indicated the presence of TYLCV, TSWV, Cucumber mosaic virus, and Tomato chlorosis virus (ToCV); all with the exception of ToCV have been reported in Georgia. Sixteen additional symptomatic leaf samples were randomly collected in fall 2010 and the preliminary results from 2009 were used to guide testing. DNA and RNA were individually extracted using commercially available kits and used for PCR testing for ToCV, TYLCV, and TSWV. Reverse transcription (RT)-PCR with ToCV CP gene specific primers (4) produced approximately 750-bp amplicons from nine of the 16 leaf samples. Four of the nine CP gene amplicons were purified and directly sequenced in both directions. The sequences were 99.4 to 100.0% identical with each other (GenBank Accession Nos. HQ879840 to HQ879843). They were 99.3 to 99.5%, 97.2 to 97.5%, and 98.6 to 98.9% identical to ToCV CP sequences from Florida (Accession No. AY903448), Spain (Accession No. DQ136146), and Greece (Accession No. EU284744), respectively. The presence of ToCV was confirmed by amplifying a portion of the HSP70h gene using the primers HSP-1F and HSP-1R (1). RT-PCR produced approximately 900-bp amplicons in the same nine samples. Four HSP70h gene amplicons were purified and directly sequenced in both directions. The sequences were 99.4 to 99.7% identical to each other (Accession Nos. HQ879844 to HQ879847). They were 99.2 to 99.5%, 98.0 to 98.4%, and 98.9 to 99.3% identical to HSP70h sequences from Florida (Accession No. AY903448), Spain (Accession No. DQ136146), and Greece (Accession No. EU284744), respectively. TYLCV was also detected in all 16 samples by PCR using degenerate begomovirus primers PAL1v 1978 and PARIc 496 (3) followed by sequencing. TSWV was also detected in two of the ToCVinfected samples by RT-PCR with TSWV N gene specific primers (2) followed by sequencing. To our knowledge, this is the first report of the natural occurrence of ToCV in Georgia. Further studies are required to quantify the yield losses from ToCV alone and synergistic interactions between ToCV in combination with TSWV and/or TYLCV in tomato production in Georgia.

First Report of Tomato yellow leaf curl virus Co-infecting Pepper with Tomato chino La Paz virus in Baja California Sur, Mexico.

Chile peppers are among the most common and important crops in the State of Baja California Sur, Mexico, where diverse varieties of this crop are annually cultivated. The "chile ancho" (Capsicum annuum L. var. ancho poblano) is one of the most popular hot peppers that is exported fresh to the United States. During a survey in December of 2007 in an experimental field of the CIBNOR in El Carrizal, one of the principal farm districts in the state, a high incidence of yellowing, stunted growth with shortened internodes, foliage discoloration, malformation and crinkle, abortion of flowers, and reduction in size and quantity of fruit were noted in chile ancho. Symptoms and the presence of large populations of whiteflies in the field suggested a possible viral etiology of disease. The symptoms of disease were successfully transmitted by grafting from field plants to tomato and pepper test plants. Samples from both field and test plants were analyzed by scanning electron microscopy (SEM) and molecular techniques. SEM study revealed groups of geminate particles characteristic of begomoviruses (Geminiviridae) in phloem tissue of randomly selected symptomatic plants (four field and two test plants). Total DNA from 12 symptomatic plants (eight naturally infected and four test plants) was obtained by a modified Dellaporta method and analyzed by PCR using the begomovirus universal primers prRepDGR (2) and prC889 (3). Amplicons of ~1.4 kb were obtained from all plant samples and PCR products from four of them were cloned into pGEM-T Easy vector (Promega, Madison, WI) and subsequently analyzed by restriction fragment length polymorphism (RFLP) using EcoRI and HinfI. Two distinct restriction fragment patterns were observed among the cloned PCR products, indicating the occurrence of at least two viruses in the infected plant tissues. The four examined samples contained the same two begomoviruses according to the RFLP analysis data. The complete sequence of the genomic component A of those viruses was determined by PCR amplification of viral DNA with universal, degenerate primers previously described (2), the subsequent cloning of overlapped PCR products, and sequencing. The full-length DNA-A sequence was assembled and compared with viral sequences available at the GenBank database using BlastN and the ClustalV alignment method (MegAlign; DNASTAR, Madison, WI). The 2,781-bp complete genome sequence of one co-infecting monopartite begomovirus (Accession No. HM459851) displayed the highest identity (99%) with Tomato yellow leaf curl virus (TYLCV), isolate Guasave, Sinaloa (Accession No. FJ609655). The 2,609-bp DNA-A sequence of the second begomovirus exhibited the highest nucleotide identity (96%) with Tomato chino La Paz virus (ToChLPV)-[Baja California Sur] (Accession No. AY339619). The presence of TYLCV in this region of Mexico had not been previously reported nor was ToChLPV detected in pepper until now. To our knowledge, this is the first report of a mixed infection of pepper plants with TYLCV and a bipartite begomovirus in Baja California Peninsula. Since the high frequency of recombination events observed in begomovirus mixed infections involving TYLCV (1), it would be important to monitor the possible emergence of ToChLPV-TYLCV recombinants with higher potential virulence.

Identification of Tomato yellow leaf curl virus and Tomato mottle virus in Two Counties in Alabama.

During July 2005, approximately 23% of tomato plants (Solanum lycopersicum L. 'Sebring') in a commercial field in St. Clair County, Alabama showed symptoms of stunting, leaf deformation, mottling, and reduced leaf size, which resembled symptoms of Tomato yellow leaf curl virus (TYLCV). A high population of whiteflies (Bemisia tabaci) was observed in this field, and as the season progressed, 100% of the plants became symptomatic. During October 2006, similar symptoms in tomato were observed at low incidences (less than 10%) in a commercial greenhouse in Jefferson County. Two samples from St. Clair County and six from Jefferson County were collected and tested for the presence of a begomovirus by PCR using three pairs of primers, PAR1c496 and PAL1v1978, a degenerate primer pair designed to amplify regions of the begomovirus A component, PBL1v2040 and PCRc154, a degenerate primer pair that amplifies a hypervariable region of the begomovirus B component (3), and C473 and PTYC1v2406, which are specific to TYLCV (1,2). Primer pair PAR1c496 and PAL1v1978 produced two amplicons (1,360 and 1,159 bp) in all samples tested, which suggests the presence of a monopartite and bipartite begomovirus. Primer pair pBL1v2040 and PCRc154 produced a 678-bp amplicon that would be consistent with the presence of a bipartite begomovirus. Primer pair C473 and PTYC1v2406 produced an 850-bp amplicon that would be consistent with the presence of TYLCV. Sequence analysis revealed that the 1,360-bp amplicon had 98% sequence identity to isolates of TYLCV from Cuba (GenBank Accession No. AJ223505), the Dominican Republic (GenBank Accession No. (AF04715), Florida (GenBank Accession Nos. AF260331 and AY530931), Egypt (GenBank Accession No. AY594174), and Almeria (GenBank Accession No. AJ489258). The 1,159-bp amplicon had a 97 to 99% sequence identity to the A component of Tomato mottle virus (ToMoV) Florida (GenBank Accession Nos. L14460, EF028241, and M90495) and Puerto Rico (GenBank Accession No. AY965900). Each of the eight tomato samples were shown to be infected with TYLCV and ToMoV. Symptoms of plants infected with both viruses resembled those of TYLCV because the milder symptoms of ToMoV are masked in the field by the more severe symptoms of TYLCV. To our knowledge, this is the first report of ToMoV and TYLCV in the state of Alabama. Reference: (1) M. Ghanim et al. Virology 240:295, 1998. (2) M. K. Nakhla et al. Phytopathol. Mediterr. 32:163, 1993. (3) M. R. Rojas et al. Plant Dis. 77:340, 1993.

First Report of Tomato yellow leaf curl virus in Mississippi.

Tomato yellow leaf curl virus (TYLCV) is a begomovirus (family Geminiviridae) that causes severe chlorosis, stunting, and cupping of leaves in tomato (Lycopersicon esculentum) throughout the world. The disease was first reported in the United States in Florida in 1997 (2). In 2000, TYLCV was confirmed as the cause of severe chlorosis, stunting, and cupping of leaves in tomato in Louisiana (3). In January of 2001, mild symptoms consistent with TYLCV were observed in a greenhouse-tomato production operation in east-central Mississippi. Whiteflies (Bremisia tabaci) were present in the greenhouse during the previous month, but in relatively low numbers. Symptom severity slightly increased over time with chlorosis in the terminal, reduction in terminal leaf size, and upward cupping of leaves observed. Approximately 4% of plants in the greenhouse developed symptoms. Yield reductions are thought to be negligible since the tomato plants harbored most fruit for that growing season. Terminal growth was halted, and no additional flower production was observed. No symptoms were observed on mature fruit; however, fruit set after leaf symptoms developed remained stunted. A representative sample of symptomatic tissue was submitted to an independent lab (Agdia, Inc., Elkhart, IN), screened for whitefly-transmitted geminiviruses, and the results were positive. Additional symptomatic tomato tissue was submitted to the University Diagnostics Lab, University of Florida, Gainesville, and was observed for viral inclusion bodies. This test was positive for TYLCV based on morphology of virus particles located in the nucleus of tomato cells (1). Total DNA was extracted from the symptomatic plants for polymerase chain reaction (PCR) assay (2). Results from the PCR assay indicated the presence of TYLCV in symptomatic tomato tissue. The strain of the virus was not determined. To our knowledge, this is the first report of TYLCV in Mississippi.

Tomato curly stunt virus, a New Begomovirus of Tomato Within the Tomato yellow leaf curl virus-IS Cluster in South Africa.

Tomato yellow leaf curl virus (TYLCV) causes a serious disease of tomato in many countries throughout the world. Preliminary reports suggested that TYLC disease was present in 1997 in South Africa. In 1998 140 ha of tomato fields in the Onderberg area were assessed for possible presence of TYLCV. Symptoms like those caused by TYLCV isolates in Israel were observed in most fields, and disease incidence ranged from <1 to 50%. Yield losses in individual plants ranged from negligible to 100% and appeared related to the age of the plants at time of infection. Two isolates of the suspect virus were experimentally transmitted from symptomatic tomato to virus-free, glasshouse-grown tomato seedlings by colony. Field and colony whiteflies were identified as the Bemisia tabaci based on mt COI sequence analysis (1). Attempts to transmit the suspect begomovirus by sap inoculation between tomato plants were unsuccessful. Polymerase chain reaction (PCR) amplification with degenerate PCR primers (2) that permit detection of the coat protein gene (AV1) and the common region (CR) of other begomoviruses yielded an amplicon of the expected size (2,100 bp), suggesting begomovirus association with diseased tomato plants. Nucleotide (nt) sequence analysis of AV1 for both tomato isolate AF261885 indicated that they were indistinguishable and shared less than 78% sequence identity with other well-studied begomoviruses, indicating a distinct, previously undescribed begomovirus species. AV1 sequence comparisons also revealed that its closest relatives were members of the TYLCV cluster, which includes South African cassava mosaic virus (77.4%) (AF11785), East African cassava mosaic virus (77.3%) (AJ006459), and TYLCV-IS (76.2%) (X15656). The theoretical Rep binding element in the CR, TCGGT, was identical to TYLCV-IS and Cotton leaf curl virus-Pakistan (AJ002448) (AJ002449). Here, we provisionally designate this new tomato-infecting begomoviral species, Tomato curly stunt virus from South Africa (ToCSV-SA).