Incidence Of Tomato Yellow Leaf Curl Virus Research Articles

First Report of Tomato Yellow Leaf Curl Virus Infecting Pepper and Tomato in Oklahoma.

Tomato yellow leaf curl virus (TYLCV), (genus Begomovirus and family Geminiviridae) is one of the devastating viruses infecting tomatoes (Solanum Lycopersicon) and could have a significant impact on tomato production worldwide (Moriones and Navas-Castillo, 2000; Rybicki, 2015; Perez-Padilla et al. 2019). TYLCV was first reported in the United States (US) in 1997 in Florida (Polston et al. 1999) and since then it has been reported in several other states but not in Oklahoma (de Sa et al. 2008). Both pepper (Capsicum spp.) and tomato are grown in >50 counties of Oklahoma for fresh produce in the local market, and for processing industries. During a survey in 2021, pepper (bell pepper cv SV3964) and tomato (cv grand marshall) plants grown in a commercial field in Bixby, Oklahoma, showed typical virus-like symptoms including yellowing, leaf curling, cupping, twisting, and mottling (Fig. 1). Estimated disease incidence was 10% in both crops. In addition, whiteflies (Bemisia tabaci) were also observed on these plants. Twenty symptomatic samples from pepper (n=16) and tomato (n=4) plants, and four asymptomatic from pepper (n=2) and tomato (n=2) plants were collected and brought to the Plant Virology Lab at the University of Tulsa for further analysis Total RNA was extracted from all samples using the Spectrum Plant Total RNA Kit (Sigma-Aldrich, LOT: SLCG7913). RNA from two symptomatic samples, one each from pepper and tomato (named BX6 and BX11, respectively) were subjected to high-throughput sequencing (HTS) on the NextSeq 500/550 high-output kit v2.5 (Illumina, USA) at the genomic facility, Oklahoma State University (Stillwater, OK, USA). A total of 22,385,404 (average length 73.6 bp) and 19,012,605 (average length 73.7 bp) trim pair-end for both samples (BX6 and BX11) were assembled using CLC Genomics Workbench (v12.0.3) (Qiagen, Inc) and subjected to BLASTn analysis. The three contigs: 393 bp (coverage 363.24X), 670 bp (coverage 489.92X), and 990 bp (coverage 112.96X) for BX6 isolate, and four contigs: 393 bp (coverage 341.64X), 668 bp (coverage 457.23X), 814 bp (coverage 107.86X), and 990 bp (coverage 93.71X), for BX11 isolate, showed from 96 to 99% nucleotide (nt) identities with movement protein, capsid protein, C3, V2, C4, AC1, AC2, AC3 protein genes of the TYLCV isolates from Australia, China, Iran, Mexico, South Korea, and the US. The HTS data did not reveal any other viral sequence in these two samples. To further confirm the presence of TYLCV in these samples, three overlapping TYLCV-specific primer pairs (Supplementary Table 1) were designed based on the alignment of complete genome sequences of TYLCV isolates present in the Genbank. Total DNA was extracted from fresh leaf tissues of BX6 and BX11 samples using the Plant DNA Kit (Omega BIO-TEK,) and used in the PCR assay. The expected PCR products (814 bp, 1,085 bp and 1,068 bp) were generated from both samples providing further evidence of TYLCV infection. To obtain the complete genome sequence, these PCR amplified DNA fragments of both isolates were gel extracted and cloned using the pGEM-T® Easy Vector system. Three independent clones of each fragment were sequenced and analyzed by Sanger sequencing. The resulting consensus sequences were used in a BLASTn search against the GenBank and had the highest identities (99-99.2%) with TYLCV sequences. The overlapping consensus nt sequence of the BX6 isolate was 2,782 nt (Accession no ON321843), whereas that of BX11 was 2,777 nt (Accession no ON785706) showed 99.2% and 99.0% nt identities with the corresponding sequence of TYLCV isolates (KX347141 and KX347142) respectively from Australia. The nt identity between BX6 and BX11 was 99.7%. Further screening by PCR of the remaining 18 symptomatic field samples (pepper, n=15 and tomatoes, n=3) revealed TYLCV infection in two pepper and all three tomato samples consistent with the greater susceptibility of tomato. None of the asymptomatic pepper and tomato samples were positive for TYLCV. DNA from both BX6 and BX11 samples was also used in the rolling circle amplification (RCA) assay (TempliPhi Amplification Kit, Cytiva) and the presence of circular TYLCV DNA was detected. Our results demonstrated the presence of TYLCV infection in these symptomatic pepper and tomato plants. This is the first report of TYLCV infecting pepper or tomato in open fields in Oklahoma. Further surveys are needed to determine the incidence of TYLCV and the presence of its vector in other counties throughout Oklahoma.

Management of Tomato Yellow Leaf Curl Virus (TYLCV) Infecting Tomato by using Calcium Rich Compounds

Bemisia tabaci (whitefly) transferred Tomato yellow leaf curl virus (TYLCV) disease is a significant constraint on tomato productivity. One technique for managing the condition is to spray calcium compounds (calcium carbonate, calcium chloride, calcium nitrate) onto tomatoes. According to the research findings, the incidence of TYLCV was lower in calcium compound sprayed plants than in control plants. The control group had the greatest TYLCV prevalence. Calcium carbonate-treated plants had the lowest TYLCV, followed by calcium nitrate-treated plants. Temperature and relative humidity were shown to be strongly linked with the population of whiteflies, the TYLCV vector in the tomato field. The expansion of TYLCV in tomatoes and the growth in whitefly populations were shown to have positive and substantial connections. In terms of plant height, fresh shoot weight, dried shoot weight, and root length, the three calcium compounds outperformed the others. Furthermore, the number of fruit/plants in the calcium carbonate spray was shown to be higher than in the control. With a few exceptions, calcium carbonate and calcium nitrate treatments were shown to be superior to calcium chloride treatments in terms of increasing growth and yield, contributing to character as well as yield.

The Establishment and Spread of a Newly Introduced Begomovirus in a Dry Tropical Environment Using Tomato Yellow Leaf Curl Virus as a Case Study.

Early detection of tomato yellow leaf curl virus (TYLCV) in a previously unaffected tomato production district in Australia allowed its spread to be evaluated spatially and temporally. The population dynamics of the TYLCV vector, Bemisia argentifolii (silverleaf whitefly, SLW), were also evaluated. The district is a dry tropical environment with a clear break to commercial production during the summer wet season. The incidence of TYLCV within crops and its prevalence through the district was influenced by weather, location, vector movements, and the use of Ty-1 virus-resistant hybrids. Rainfall had an important influence, with late summer and early autumn rain suppressing the levels of SLW and, by contrast, a dry summer supporting faster population growth. The use of Ty-1 hybrids appears to have reduced the incidence of TYLCV in this district. There was limited use of Ty-1 hybrids during 2013, and by season end, crops had moderate levels of SLW and high virus incidence. The 2015 and early 2016 season had high SLW populations, but TYLCV incidence was lower than in 2013, possibly due to the widespread adoption of the Ty-1 hybrids reducing virus spread. This study provides valuable epidemiology data for future incursions of begomoviruses, and other viruses spread by SLW.

Repelling whitefly (Bemisia tabaci) using limonene-scented kaolin: A novel pest management strategy

Despite intensive control efforts, whitefly Bemisia tabaci, remains a difficult pest to manage due to its wide host range and ability to easily switch feeding between crop hosts and surrounding weed hosts. To develop more economical management strategies, the combination of kaolin and limonene was tested as a natural organic repellent against whiteflies. Whitefly host selection was compared between kaolin and limonene-coated tomato and control plants using closed cage bioassays. Combining limonene and kaolin had an additive effect on repelling adult whiteflies compared with the control. Field trials were conducted during two fall seasons in Quincy, Florida. In the 2019 field trial, during dry conditions, tomatoes treated with kaolin + limonene (K + L) had a three to four-fold reduction in B. tabaci adult populations compared to controls and a two to three-fold reduction compared to kaolin-only and limonene-only treatments. In addition, infection with Tomato Yellow LeafCurlVirus (TYLCV) was at least two times lower on average in K + L treatments compared to the control. This translated to a two-fold increase in marketable yield of tomatoes harvested from K + L treatments. In fall 2020, due to wetter conditions we only observed a decrease in adult populations on plants in the K + L treatment compared to the control, yet no difference in TYLCV incidence between treatments. Limonene-scented kaolin's effectiveness as a whitefly repellent seems to depend largely on rainfall. In dry conditions, more effective control of whiteflies and of TYLCV was achieved.

Natural incidence of bean viruses in the northwest of Iran

Bean is considered as one of the most important legumes around the world. Viral diseases are a major yield reducing factor in bean production. Bean samples with virus-like symptoms like severe or mild mosaic, vein banding, leaf curling, blistering and necrosis were collected from different bean fields in Urmia (Northwest of Iran) during the growing seasons of 2013 and 2014. Bean common mosaic virus (BCMV), Bean common mosaic necrosis virus (BCMNV), Bean yellow mosaic virus (BYMV), Cucumber mosaic virus (CMV), Tomato spotted wilt virus (TSWV), Tomato mosaic virus (ToMV) and Tomato yellow leaf curl virus (TYLCV) were detected by double antibody sandwich enzyme-linked-immunosorbent assay. Mixed infection of BCMV and BCMNV were found. BCMNV was the most frequent virus in this region whereas BYMV and TYLCV were each detected just in one sample. This is the first report of BCMNV, BCMV, BYMV, TSWV, TMV and TYLCV incidence on bean in Urmia, Iran.

Suppressive effect of acetylated glyceride (Bemidetach™EC) on Tomato yellow leaf curl virus transmitted by the whitefly Bemisia tabaci on greenhouse tomato plants

Acetylated glyceride (Bemidetach™EC)—a food additive—repels adult sweet potato whiteflies (Bemisia tabaci) and inhibits their mating behavior. We evaluated the effects of acetylated glyceride spraying of greenhouse-grown tomato plants on infestation with B. tabaci and the occurrence of Tomato yellow leaf curl virus (TYLCV) disease under commercial-like conditions. The abundance of adult B. tabaci was significantly reduced by three sprayings of acetylated glyceride, and the TYLCV incidence was significantly suppressed to less than 30% of that in the untreated control. These results suggest that acetylated glyceride sprays suppress the secondary spread of TYLCV in greenhouse-grown tomatoes by lessening B. tabaci adult density.

Reduced incidence of tomato yellow leaf curl virus and leafminer in a tomato cultivar in northern Thailand

Tomato yellow leaf curl virus (TYLCV), a whitefly-vectored begomovirus, is a major limiting factor for tomato production worldwide, including Thailand. Field evaluation of commercial tomato cvs. for resistance to the virus endemic in northern Thailand has not been reported. Experiments conducted in northern Thailand in 2011–2013 compared the field performance of three tomato cvs. from the US with a commonly grown Thai cultivar. There were few significant differences observed among the cvs. in marketable yield, and the severity of root-knot and root rot. However there were significant differences noted in TYLCV incidence; virus incidence ranged from 38 to 100% and 8–41% in experiments one and two, respectively. In both experiments ‘Husky Cherry Red’ from the US had the lowest TYLCV incidence, leafminer damage (Liriomyza sp.), and progression of foliar necrosis primarily caused by thrips feeding and possibly exacerbated by air pollution. TYLCV infection was confirmed by a simplified method of nuclear inclusion visualization with light microscopy in experiment one, and by virus inclusion detection and PCR in experiment two.

Evaluation of Round and Roma-type Tomato Varieties and Advanced Breeding Lines Resistant to Tomato Yellow Leaf Curl Virus in Florida

Tomato yellow leaf curl virus (TYLCV) is considered to be the most damaging tomato (Solanum lycopersicum) virus worldwide. Management of TYLCV has relied primarily on insecticidal control targeting the vector sweetpotato whitefly [SPW (Bemisia tabaci)]. However, resistance of the SPW to insecticides; increased length of the growing season, due in part to increased plantings of grape tomato; and asymptomatic hosts of TYLCV such as pepper (Capsicum annuum) have increased the need for wider use of TYLCV-resistant (TYLCV-R) varieties. The objective of this study was to evaluate horticultural characteristics of commercially available TYLCV-R varieties/advanced breeding lines of round and Roma-type tomato varieties in Florida. Sweetpotato whitefly populations and incidence of TYLCV were greater in 2007 than 2008. Under high TYLCV pressure, most of the TYLCV-R varieties/advanced breeding lines produced higher yield than susceptible varieties. In contrast, no clear advantage was found by using TYLCV-R varieties under low TYLCV pressure. Additionally, TYLCV-R varieties produced a high percentage of unmarketable fruit due to rough blossom end scars (BES), zippering, catfacing, sunscald, yellow shoulders, off shapes, and radial or concentric cracking compared with susceptible varieties in both years. Visual assessment of TYLCV-R varieties/advanced breeding lines for horticultural traits showed that ‘Security 28’, Sak 5443, and ‘Shanty’ were the best overall varieties/advanced breeding lines based on participants combined score rating, although ‘Tygress’ and Sak 5808 performed best based on empirical evaluation (numerical data) of total marketable yields and low unmarketable yield.

Insect symbiont facilitates vector acquisition, retention, and transmission of plant virus.

Tomato yellow leaf curl virus (TYLCV) was first detected in China in 2006, following the introduction of Bemisia tabaci Q into China in 2003. Since then, the incidence of TYLCV in tomato fields in China has greatly increased as has the abundance and distribution of Q whiteflies containing the bacterial symbiont Hamiltonella with high frequency. This suggested that the symbiont Hamiltonella might associate with the transmission efficiency of TYLCV by the whitefly vector. Here we report the first evidence that the Hamiltonella is closely associated with the acquisition, retention, and transmission efficiency of TYLCV by the whitefly vector. Our findings combined with the outbreaks of TYLCV following the introduction of Q, provided an explanation for why Hamiltonella is being maintained at a relatively high level in Chinese B. tabaci Q and also have implications for disease and vector management.

초고속 Real-time PCR을 이용한 Tomato yellow leaf curl virus의 신속진단

Tomato yellow leaf curl virus (TYLCV), transmitted exclusively by the whitefly (Bemisia tabaci) in a circulative manner is one of the most important virus in tomato. Since the first report of TYLCV incidence in Korea in 2008, the virus has rapidly spread nationwide. TYLCV currently causes serious economic losses in tomato production in Korea. Early detection of TYLCV is one of the most important methods to allow rouging of infected tomato plants to minimize the spread of TYLCV disease. We have developed an ultra-rapid and sensitive real-time polymerase chain reaction (PCR) using a new designed real-time PCR system, GenSpectorTM TMC-1000 that is a small and portable real-time PCR machine requiring only a reaction volume on microchips. The new system provides ultra-high speed reaction (30 cycles in less than 15 minutes) and melting curve analysis for amplified TYLCV products. These results suggest that the short reaction time and ultra sensitivity of the GenSpector-based real-time PCR technique is suitable for monitoring epidemics and pre-pandemic TYLCV disease. This is the first report for plant virus detection using an ultra-rapid real-time PCR system.

Whitefly Population Dynamics and Evaluation of Whitefly-Transmitted Tomato Yellow Leaf Curl Virus (TYLCV)-Resistant Tomato Genotypes as Whitefly and TYLCV Reservoirs

Sweetpotato whitefly, Bemisia tabaci (Gennadius), and whitefly-transmitted tomato yellow leaf curl virus (TYLCV) are major threats to tomato production in the southeastern United States. TYLCV was introduced to Florida from the Caribbean islands and has spread to other southern states of the United States. In Georgia, in recent years, the incidence of TYLCV has been steadily increasing. Studies were conducted to monitor population dynamics of whiteflies in the vegetable production belt of Georgia, to evaluate TYLCV-resistant genotypes against whiteflies and TYLCV, and to assess the potential role of resistant genotypes in TYLCV epidemiology. Monitoring studies indicated that the peak incidence of whiteflies varied seasonally from year to year. In general, whitefly populations were not uniformly distributed. Tomato genotypes exhibited minor differences in their ability to support whitefly populations. TYLCV symptoms were visually undetectable in all but one resistant genotype. The infection rates (visually) in susceptible genotypes ranged from 40 to 87%. Greenhouse inoculations with viruliferous whiteflies followed by polymerase chain reaction (PCR) indicated that up to 100% of plants of resistant genotypes were infected, although predominantly symptomless. TYLCV acquisition by whiteflies from TYLCV-infected genotypes was tested by PCR; TYLCV acquisition rates from resistant genotypes were less than from susceptible genotypes. Nevertheless, this difference did not influence TYLCV transmission rates from resistant to susceptible genotypes. Results emphasize that resistant genotypes can serve as TYLCV and whitefly reservoirs and potentially influence TYLCV epidemics.

Squash as a trap crop to protect tomato from whitefly-vectored tomato yellow leaf curl

The silverleaf whitefly, Bemisia argentifolii Bellows & Perring [also known as biotype B of the sweetpotato whitefly, B. tabaci (Gennadius)], is a key pest of tomato in southern Florida. Most damage by the whitefly is inflicted indirectly through the transmission of plant viruses, the most damaging of which is Tomato yellow leaf curl virus (TYLCV). Trap crops may be one means of reducing whitefly populations and TYLCV incidence in tomato. Because squash is more attractive to whitefly adults than tomato, it was evaluated as a trap crop in three field experiments conducted during the spring and fall of 2000 and the spring of 2001. Four, 15.25 m long rows of tomato were surrounded by 1.5 m of either squash or tomato and were transplanted about 3 weeks after the squash was seeded. The numbers of whitefly adults and nymphs and the incidence of plants with symptoms of tomato yellow leaf curl (TYLC) were determined weekly. The squash was harvested weekly to promote flowering, and fungicides were applied weekly for preventive control of fungal pathogens. In all experiments, a greater cumulative proportion of plants with symptoms of TYLC were observed on tomato plants surrounded by tomato, compared to tomato plants surrounded by squash. In general greater cumulative numbers of whitefly adults and nymphs were observed on tomato plants surrounded by tomato than on tomato plants surrounded by squash. Therefore, growing squash as a trap crop could be a useful cultural manipulation in managing the silverleaf whitefly and TYLC on tomato, although the management tactic may be more applicable to small-scale farm operations.

Tomato yellow leaf curl virus in the Dominican Republic: Characterization of an Infectious Clone, Virus Monitoring in Whiteflies, and Identification of Reservoir Hosts

ABSTRACT Epidemics of tomato yellow leaf curl disease (TYLCD) in the Dominican Republic in the early to mid-1990s resulted in catastrophic losses to processing tomato production. As part of an integrated management approach to TYLCD, the complete nucleotide sequence of a full-length infectious clone of an isolate of Tomato yellow leaf curl virus (TYLCV) from the Dominican Republic (TYLCV-[DO]) was determined. The TYLCV-[DO] genome was nearly identical in sequence (>97%) and genome organization to TYLCV isolates from Israel and Cuba. This established that TYLCV-[DO] is a bonafide TYLCV isolate (rather than a recombinant virus, such as isolates from Israel [Mild], Portugal, Japan, and Iran), and provided further evidence for the introduction of the virus from the eastern Mediterranean. A reduction in the incidence of TYLCV in the northern and southern processing tomato production areas of the Dominican Republic has been associated with the implementation of a mandatory 3-month whitefly host-free period (including tomato, common bean, cucurbits, eggplant, and pepper). Monitoring TYLCV levels in whiteflies, by polymerase chain reaction with TYLCV-specific primers, established that the incidence of TYLCV decreased markedly during the host-free period, and then gradually increased during the tomato-growing season. In contrast, TYLCV persisted in whiteflies and tomato plants in an area in which the host-free period was not implemented. Surveys for TYLCV reservoir hosts, conducted to identify where TYLCV persists during the host-free period, revealed symptomless infections in a number of weed species. The implications of these findings for TYLCV management in the Dominican Republic are discussed.

Reservoir Weed Hosts of Tomato Yellow Leaf Curl Begomovirus from Tanzania

A survey was initiated to detect tomato yellow leaf curl virus (TYLCV) and identify its reservoir weed hosts in six regions (Arusha, Morogoro, Dodoma, Iringa, Kilimanjaro and Dar es Salaam) in Tanzania. Three farms were randomly selected in each region. Assessment of TYLCV incidence was done by relating the number of infected tomato plants to the total number of plants assessed along a diagonal in five quadrants measuring 4m ‐ 4m in size (one at each corner of the farm and one at the centre). Disease severity was scored on a scale of 0 to 4 (where 0 = no symptoms and 4 = very severe symptoms). Within and outside each farm, weeds showing TYLCV-like symptoms were collected and either squash-blotted, dot-blotted or both on nylon membranes. The membranes were hybridized with DIG-labelled probe synthesized for the detection of TYLCV from Sardinia (TYLCV-Sar) following standard protocols. Selected plant species were experimentally inoculated with screenhouse cultures of TYLCV representative isolates from the six regions using Bemisia tabaci to determine their host status. Results indicated that TYLCV incidence and severity were significantly higher (P = 0.05) in Dodoma region than the rest of the regions. In Iringa region, the incidence and severity of TYLCV were the lowest of all regions. TYLCV was detected in 12 of the 17 dot-blotted samples and in all the 21 squashed samples using the non-radioactively labelled riboprobes. Similarly, five plant species (Capsicum annuum, Datura stramonium, Lycopersicon esculentum, Nicotiana glutionsa and N. tabacum) tested in the screenhouse were infected by the six TYLCV isolates used. It is recommended that weeds within and outside tomato farms be removed to eliminate or reduce sources of virus inoculum. The dot and squash blot techniques are convenient for field detection of the virus, and are especially useful for the detection of early and latent infections so that management strategies can be initiated and implemented.

Effect of Imidacloprid on Incidence of Tomato yellow leaf curl virus.

Confidor, an imidacloprid insecticide, was used in two applications at four rates (47.6, 71.4, 95.2, and 119 g a.i./ha) for indirectly controlling Tomato yellow leaf curl virus (TYLCV) in field plantings of tomato. This spray regimen was compared with standard applications of cypermethrins at 10- to 15-day intervals throughout the growing season. In three field trials, a combination of integrated pest management (IPM) practices and two applications of Confidor at the two highest rates immediately after planting and 6 weeks later, protected tomato plants against the disease until 12 weeks after sowing. All rates of Confidor reduced disease incidence compared with standard chemical control applied in an integrated strategy, and quantitative efficacy increased with increase of insecticide rate. In the three seasons, the mean incidence of TYLCV 12 weeks after sowing was 42.7% in plots not adopting IPM compared with 15.7% in those that did. Disease incidence was reduced by Confidor treatments to 2.2 to 17%. Confidor-treated plots consistently had higher yields than control plots, and the yields decreased with the decrease in the rate of Confidor application. Confidor offers several advantages over standard applications of cypermethrins to control TYLCV. When applied immediately after planting, its long-lasting systemic activity protected the crop against the disease during early stages of growth. In addition, it reduced the number of sprays and increased tomato yield.

Outbreak of Tomato yellow leaf curl virus (Family Geminiviridae) in Georgia.

Tomato yellow leaf curl virus (TYLCV) of the family Geminiviridae is a serious production constraint to tomato (3). In the southeastern United States the virus has been largely confined to Florida. The disease appeared in the southern most Georgia county (Decatur) in 1998, at an incidence rate of less than 1% (2). During the fall of 1999, tomato plants showing symptoms indicative of TYLCV were observed in commercial fields in Grady, Colquitt, and Lowndes counties and the experimental plots of the Coastal Plain Experiment Station in two locations in Tift County, GA. The 12-acre commercial field in Grady County had a disease incidence of 15%. In Tift County, in both experimental plots (≈5 miles apart), TYLCV incidence ranged from 15 to 20%. Bemisia argentifolii populations in southern Georgia, based on the observed high incidence of silverleaf symptoms in squash and the intensity of adult migrations during August and September, were the highest in more than 5 years. TYLCV infection was verified by polymerase chain reaction (PCR) amplification with degenerate primers (5'-GCC CAC ATY GTC TTY CCN GT-3' and 5' -GGC TTY CTR TAC ATR GG-3') specific to the DNA A component (4). A simplified and faster DNA extraction procedure was used to obtain PCR-ready templates. Leaf tissue was homogenized in 300 μl of extraction buffer (1), followed by one phenol and one chloroform/ isoamyl alcohol (24:1) extraction. The supernatant was purified using a QiaPrep MiniPrep purification kit (Qiagen, Valencia, CA) and was used in PCR amplification. The procedure yielded highly consistent PCR-quality template. The resulting ≈1.3-kb PCR product was cloned in pGEM-T vector (Promega Corp., Madison, WI) and completely sequenced. Sequence comparisons indicated 98% identity with known TYLCV isolates from Spain (GenBank Accession no. AJ223505), the Dominican Republic (GenBank Accession no. AF024715), and Israel (GenBank Accession no. X15656). Using PCR followed by restriction digestion analysis, three symptomatic plants from one field each in Colquitt and Lowndes counties were TYLCV positive. The higher incidence of TYLCV in the Georgia counties of Tift and Grady and its concurrent occurrence in Colquitt and Lowndes counties indicates its rapid spread in the southeastern United States.

Tomato performance and incidence of tomato yellow leaf curl (TYLC) virus as affected by type of mulch

Five mulch types, i.e. silver plastic, black plastic, paper, white/black plastic and black/white plastic, were evaluated in terms of their effect on tomato growth, yield, fruit quality and incidence of tomato yellow leaf curl (TYLC) virus. Highest early marketable yields were obtained from the silver, white/black and black/white plastic mulches. Total marketable yields were significantly increased by all the mulch treatments. Both the silver and white/black plastic mulches were superior to other treatments in early and total fruit counts. Average weight per fruit was similar for all treatments and was acceptable in the Jordanian market. While incidence of sunscald increased significantly, blossom end rot (BER) incidence, seasonal cracking and shoot dry weight were not affected by the mulch treatments. Incidence of TYLC virus was reduced by the silver plastic mulch.

Efficacy of three trap crops against whitefly to manage tomato yellow leaf curl virus

doi:10.3329/bjar.v33i3.1610 Bangladesh J. Agril. Res. 33(3) : 515-517, September 2008

Status of Tomato Yellow Leaf Curl Virus in Tomato in the Western Hills of Nepal

Tomato cultivation in rainy season is being endangered and is becoming less profitable because of tomato yellow leaf curl virus (TYLCV) infection. Studies were conducted at Agriculture Research Station, Lumle to assess the incidence of TYLCV and associated yield losses in various commercial tomato growing pockets of the western hills during the period of 1995 and 1997. The studies revealed a high incidence of the disease in most tomato growing pockets and yield losses of 40% or even higher have been reported in some areas like Risingpatan, Tanahun and Kudule, of western hills of Nepal. Laboratory analysis of the diseased samples by Asian Vegetable Research and Development Center revealed the presence of three different strains of TYLCV: Banglore I, Banglore II and Sri Lanka in the western hills. The TYLCV vector, whitefly (Bemisia tabaci Gen.), was found active throughout the crop growing period in some commercial tomato growing pockets. Therefore, research on the development of effective TYLCV management technology is needed to sustain rainy season tomato cultivation in the western hills of Nepal.Key words: Bemisia tabaci; Lycopersicon esculentum; Tomato; Yellow leaf curl virus; WhiteflyDOI: http://dx.doi.org/10.3126/narj.v4i0.4856Nepal Agriculture Research Journal Vol. 4&5, 2001/2002Page: 1-4Uploaded date: 8 June, 2011