Tomato Spotted Wilt Tospovirus Research Articles

A versatile complementation assay for cell-to-cell and long distance movements by cucumber mosaic virus based agro-infiltration

Microinjection, bombardment or tobamovirus and potexvirus based assay has been developed to identify the putative movement protein (MP) or to characterize plasmodesma-mediated macromolecular transport. In this study, we developed a versatile complementation assay for the cell-to-cell and long distance movements of macromolecules by agro-infiltration based on the infectious clones of cucumber mosaic virus (CMV). The movement-deficient CMV reporter was constructed by replacing the MP on RNA 3 with ER targeted GFP. The ectopic expression of CMV MP was able to efficiently move the RNA3-MP::erGFP reporter from the original cell to neighboring cells, whereas CMV MP-M5 mutant was unable to initiate the movement. Importantly, the presence of CMV RNA1 and RNA2 can dramatically amplify the movement signals once the RNA3-MP::erGFP reporter moves out of the original cell. The appropriate observation time for this movement complementation assay was at 48–72hours post infiltration (hpi), whereas the optimal incubation temperature was between 25 and 28°C. The ectopic co-expression of MPs from other virus genera, NSm from tomato spotted wilt tospovirus (TSWV) or NSvc4 from rice stripe tenuivirus (RSV), could also facilitate the movement of the RNA3::erGFP reporter from the original cell into other cells. The chimeric mutant virus created by substituting the MP of CMV RNA3 with NSm from TSWV or NSvc4 from RSV move systemically in Nicotiana benthamiana plants by agro-infiltration. This agro-infiltration complementation assay is simple, efficient and reliable. Our approach provides an alternative and powerful tool with great potentials in identifying putative movement protein and characterizing macromolecular trafficking.

Nucleocapsid of Tomato spotted wilt tospovirus forms mobile particles that traffic on an actin/endoplasmic reticulum network driven by myosin XI‐K

A number of viral proteins from plant viruses, other than movement proteins, have been shown to traffic intracellularly along actin filaments and to be involved in viral infection. However, there has been no report that a viral capsid protein may traffic within a cell by utilizing the actin/endoplasmic reticulum (ER) network. We used Tomato spotted wilt tospovirus (TSWV) as a model virus to study the cell biological properties of a nucleocapsid (N) protein. We found that TSWV N protein was capable of forming highly motile cytoplasmic inclusions that moved along the ER and actin network. The disruption of actin filaments by latrunculin B, an actin-depolymerizing agent, almost stopped the intracellular movement of N inclusions, whereas treatment with a microtubule-depolymerizing reagent, oryzalin, did not. The over-expression of a myosin XI-K tail, functioning in a dominant-negative manner, completely halted the movement of N inclusions. Latrunculin B treatment strongly inhibited the formation of TSWV local lesions in Nicotiana tabacum cv Samsun NN and delayed systemic infection in N.benthamiana. Collectively, our findings provide the first evidence that the capsid protein of a plant virus has the novel property of intracellular trafficking. The findings add capsid protein as a new class of viral protein that traffics on the actin/ER system.

Stability Analysis of Incidence of Tomato Spotted Wilt in Virginia-Type Peanut Cultivars and Breeding Lines

ABSTRACT Tomato spotted wilt (TSW) caused by Tomato spotted wilt tospovirus (TSWV) has become a serious constraint to peanut (Arachis hypogaea L.) production in the Virginia-Carolina production area. Regression stability analysis was applied to TSW incidence data collected in 64 trials conducted over 17 years to determine if an array of 31 virginia-type cultivars and breeding lines exhibited variation in their reactions to increasing levels of general TSW intensity compared with the standard field-resistant cultivar Georgia Green and hirsuta-type line PI 576636. Eight cultivars (NC 7, NC 9, NC 10C, NC-V 11, NC 12C, Perry, Phillips, and Brantley) had mean effects greater than zero (P<0.01) while Bailey, four Bailey siblings, and N96076L, Bailey's resistant parent, all had mean effects less than zero (P<0.01). The deviations of the slope of regression on environmental index (β̂k) for four of the eight susceptible cultivars were greater than zero, indicating greater than average reaction to increased levels of TSW. The β̂k for Bailey indicated that its response to increasing levels of TSW was flat. PI 576636 was confirmed as a highly field-resistant line. The slopes of Georgia Green, the standard TSWV-resistant runner-type cultivar, the Bailey siblings and N96076L did not differ from the average of all lines. The correlation between mean effect and β̂k was r = 0.693, indicating that approximately half the variation in β̂k could be explained by mean effects. However, the regression analysis provided information useful in describing the TSW reactions of the lines and cultivars.

Registration of ‘Titan’ Peanut

‘Titan’ (Reg. No. CV‐112, PI 660127) virginia‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea), which was developed and tested as VT 9506083‐3 by the Virginia Tech was released in May 2010. In Virginia, Titan was tested from 1997 to 2005 at several locations throughout the peanut‐growing area of Virginia, North Carolina, and South Carolina. In 2007 and 2008, it was tested in Virginia, North Carolina, and South Carolina in the Peanut Variety and Quality Evaluation trials. Titan is an extra‐large‐seeded peanut with an exceptionally high content of jumbo pods and super‐extra‐large kernels (SELK) in all tests performed from 1997 to 2008. It has the highest jumbo‐pod content of any cultivar available at this time with values ranging from 69 to 97% in all tests. Titan had 36–60% SELK content with seeds averaging 1437 mg/seed. Because of these characteristics, Titan is well suited for in‐shell‐peanut, gourmet, and green‐boiling products. On average, Titan produced a pod yield of 4700 kg ha−1 and was moderate susceptible to Cylindrocladium black rot (caused by Cylindrocladium parasiticum Crous, M.J. Wingf. & Alfenas), Sclerotinia blight (caused by Sclerotinia minor Jagger), and tomato spotted wilt (caused by Tomato spotted wilt tospovirus).

Registration of ‘Bailey’ Peanut

‘Bailey’ (Reg. No. CV‐111, PI 659502) is a large‐seeded virginia‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) with partial resistance to five diseases that occur commonly in the Virginia‐Carolina production area: early leaf spot (caused by Cercospora arachidicola Hori), late leaf spot [caused by Cercosporidium personatum (Berk. & M.A. Curtis) Deighton], Cylindrocladium black rot [caused by Cylindrocladium parasiticum Crous, M.J. Wingf. & Alfenas], Sclerotinia blight (caused by Sclerotinia minor Jagger), and tomato spotted wilt (caused by Tomato spotted wilt tospovirus). It also has partial resistance to southern stem rot (caused by Sclerotium rolfsii Sacc.). Bailey was developed as part of a program of selection for multiple‐disease resistance funded by growers, seedsmen, shellers, and processors. Bailey was tested under the experimental designation N03081T and was released by the North Carolina Agricultural Research Service (NCARS) in 2008. Bailey was tested by the NCARS, the Virginia Agricultural Experimental Station, and five other state agricultural experiment stations and the USDA‐ARS units participating in the Uniform Peanut Performance Tests. Bailey has an alternate branching pattern, an intermediate runner growth habit, medium green foliage, and high contents of fancy pods and medium virginia‐type seeds. It has approximately 34% jumbo and 46% fancy pods, seeds with tan testas and an average weight of 823 mg seed−1, and an extra large kernel content of approximately 42%. Bailey is named in honor of the late Dr. Jack E. Bailey, formerly the peanut breeding project's collaborating plant pathologist.

Normes OEPP/EPPO Standards Diagnostics Diagnostic

Normes OEPP/EPPO Standards Diagnostics Diagnostic

Normes OEPP/EPPO Standards Diagnostics Diagnostic

Normes OEPP/EPPO Standards Diagnostics Diagnostic

Registration of ‘AP‐4’ Peanut

‘AP‐4’ (Reg. No. CV‐106, PI 654070) peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar was developed by the University of Florida, Florida Agricultural Experiment Station, North Florida Research and Education Center (NFREC) near Marianna, FL. Tested under the experimental designation UF03325, AP‐4 was approved for release in 2007. AP‐4 was developed from a cross made in 1996 between a University of Florida breeding line (88 × OL3‐HO6‐) and the F1 (‘Andru 93’ × F435‐HO). Lines were advanced using single seed descent in the F2 to F4 generations and pedigree selection in the F5 and F6 generations. Seed from three F7 plants were bulked to form the line later designated UF03325. AP‐4 has larger‐than‐average runner‐type seeds and pods. The average weight of 100 sound mature kernels of AP‐4 was 71 g compared with 57 g for ‘Georgia Green’ (P < 0.0001), a typical runner‐type cultivar. The prostrate growth habit of AP‐4 is typical of runner‐type peanut cultivars. Release of AP‐4 was based on its pod yield and seed grade (total sound mature kernels [TSMK]). In 19 tests in Florida over 3 yr, the TSMK of AP‐4 averaged 77% compared with 73% for ‘AP‐3’ (P < 0.0001). AP‐3 is most noted for its high level of resistance to spotted wilt caused by Tomato spotted wilt tospovirus, but low TSMK has restricted its acceptance among farmers. AP‐4 has competitive pod yield potential and good resistance to spotted wilt. The improved TSMK of AP‐4 should provide improved revenue compared to AP‐3.

Normes OEPP EPPO Standards Diagnostics Diagnostic

Normes OEPP EPPO Standards Diagnostics Diagnostic

The U.S. Breeding Program to Develop Peanut with Drought Tolerance and Reduced Aflatoxin Contamination

Abstract Aflatoxin contamination costs the U.S. peanut (Arachis hypogaea L.) industry over $20 million annually. The development of peanut cultivars with resistance to preharvest aflatoxin contamination (PAC) would reduce these costs. Screening techniques have been developed that can measure genetic differences in aflatoxin contamination and they have been used to identify accessions that exhibited relatively low PAC in multiple environments. Significant reductions in PAC have been identified in peanut genotypes with drought tolerance. These sources of resistance to PAC have been crossed with cultivars and breeding lines that have high yield, acceptable grade, and resistance to spotted wilt caused by Tomato spotted wilt tospovirus (TSWV). Due to the large environmental variation in PAC, breeding populations can only be evaluated in late generations when there is less heterozygosity and adequate numbers of seed are available for field testing using multiple replications. Evaluation of numerous breeding populations has identified several families and individual breeding lines with relatively low PAC, relatively high yield, and acceptable levels of resistance to TSWV. To increase breeding efficiency, studies on mechanisms of resistance to PAC are being conducted. The most promising mechanisms identified thus far are resistance to drought and resistance to the peanut root-knot nematode. Late generation breeding lines have been developed with resistance to drought, several of which also exhibited reduced aflatoxin contamination in multiple environments. Tifguard, the first cultivar with high levels of resistance to both TSWV and the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] was released from this program. Testing is ongoing to determine if this cultivar can be used to reduce aflatoxin contamination in nematode infested fields.

The Influence of Cultivar and Chlorimuron Application Timing on Spotted Wilt Disease and Peanut Yield

Abstract The effects of chlorimuron application timing on the development of spotted wilt disease of peanut caused by tomato spotted wilt tospovirus was studied in fifteen field trials in Georgia from 2000 through 2007. Chlorimuron at 9 g ai/ha was applied to new peanut cultivars at various intervals ranging from 60 to 105 days after emergence (DAE) under weed-free conditions. When averaged over chlorimuron application timings, AP-3, and Georgia-02C had less spotted wilt incidence than Georgia Green but only AP-3 produced yields equivalent to Georgia Green. AT-201 had significantly higher levels of spotted wilt and 44% lower yields when compared to Georgia Green. Spotted wilt incidence of Georgia-03L did not differ from Georgia Green but the yields of GA-03L were 24% lower than Georgia Green. Differential tolerance of peanut cultivars to chlorimuron was not observed. When averaged over cultivars, chlorimuron applied at 60–69 DAE, 70–79 DAE, or 90–99 DAE increased the incidence of spotted wilt by 6–9%. However, peanut yields were not reduced by any application of chlorimuron.

Registration of ‘Florida‐07’ Peanut

‘Florida‐07’ (Reg. No. CV‐104, PI 652938) peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar was developed by the University of Florida, Florida Agricultural Experiment Station, North Florida Research and Education Center near Marianna, FL. It was approved for release in 2006. Florida‐07 has larger‐than‐average runner market–type seeds and pods. The growth habit of Florida‐07 is prostrate, typical of runner‐type peanut cultivars. Under irrigation in Florida, it matures about 140 d after planting, which places it in the category of medium‐late relative maturity. Release of Florida‐07 was made on the basis of its excellent pod yield potential, competitive kernel grade (percentage total sound mature kernels), high‐oleic fatty acid oil chemistry, and resistance to spotted wilt (caused by Tomato spotted wilt tospovirus) and white mold (Sclerotium rolfsii Sacc.).

Registration of ‘DP‐1’ Peanut

The peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar DP‐1 (Reg. No. CV‐103, PI 633047) was developed by the University of Florida, Florida Agricultural Experiment Station and approved for release in 2002. Tested under the experimental designation UF97318, DP‐1 has runner market‐type seed and pod size with a runner growth habit. Under irrigation, it matures about 150 d after planting, which places it in the category of late relative maturity. Release of DP‐1 was based on its resistance to spotted wilt caused by tomato spotted wilt tospovirus, white mold caused by Sclerotium rolfsii Sacc., and late leaf spot caused by Cercosporidium personatum (Berk. & M.A. Curtis) Deighton, as well as competitive pod yield and grade characteristics.

Registration of ‘Tifguard’ Peanut

‘Tifguard’ (Reg. No. CV‐101, PI 651853) is a runner‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar released by the USDA‐ARS and the Georgia Agricultural Experiment Stations in 2007. Tifguard was developed at the University of Georgia Coastal Plain Experiment Station, Tifton, GA. Peanut cultivars are available that have high resistance to the peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] or spotted wilt caused by tomato spotted wilt tospovirus (TSWV). However, no cultivars exist that have resistance to both pathogens. Our research objective was to combine resistance to both pathogens in a single cultivar. Breeding populations were developed by hybridizing the TSWV‐resistant ‘C‐99R’ with the nematode‐resistant ‘COAN’. Selection for nematode resistance was conducted using standard greenhouse screening techniques. Selection for TSWV resistance was conducted in the field with natural virus infection. A breeding line (C724‐19‐15) was selected that had high resistance to both pathogens. Tifguard exhibited higher resistance to TSWV and higher yield than standard check cultivars when grown in fields with little or no nematode pressure. Because of its high level of resistance to both TSWV and M. arenaria, Tifguard had significantly higher yield than all others entries when grown in two locations with high pressure from both pathogens. This cultivar should be valuable for peanut growers who have to deal with both pathogens.

A rapid and efficient inoculation method for Tomato spotted wilt tospovirus

A rapid and efficient method of inoculation for Tomato spotted wilt tospovirus (TSWV) was achieved by applying the inoculum with a device consisting of a spray gun, an atomizer and a CO 2-powered sprayer. The inoculum contained infected leaf sap prepared in 0.1 M phosphate buffer, pH 7.0, 0.2% sodium sulfite and 0.01 M 2-mercaptoethanol (1 g: 10 ml) and 1% each of Celite 545 and Carborundum 320 grit. The spray application of chilled inoculum at the rate of 1.1 ml/plant and at an air pressure of 4.1 bar resulted in systemic infection nearly to a 100% of the tobacco ( Nicotiana tabacum) plants inoculated. The inoculation procedure was successfully applied to two other important host species of TSWV, peanut ( Arachis hypogaea) and tomato ( Lycopersicon esculentum), where 75.0–100% and 72.2–91.6% plants developed systemic infection, respectively. The approach facilitated a much faster inoculation of test plants with TSWV as it was estimated to be about 50 times quicker (depending on the plant species) than the hand inoculation. The procedure is suitable for rapid and simultaneous inoculation of a large number of test plants with TSWV and should facilitate screening of germplasm and breeding lines for virus resistance.

Development of Near‐Isogenic Peanut Lines with and without Resistance to the Peanut Root‐Knot Nematode

Peanut (Arachis hypogaea L.) cultivars are available that have high resistance to the peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] or tomato spotted wilt, caused by tomato spotted wilt Tospovirus (TSWV); however, no cultivars exist that have resistance to both pathogens. The objective of this research was to combine resistance to both pathogens in a single genotype. During the course of this research, we also had the opportunity to develop near‐isogenic lines with and without nematode resistance. Such near‐isogenic lines can be valuable research tools to obtain a better understanding of the interaction of nematodes with other pathogens of peanut. Breeding populations were developed by hybridizing the TSWV‐resistant cultivar C‐99R with the nematode‐resistant cultivar COAN. Selection for nematode resistance was conducted using standard greenhouse screening techniques. Selection for TSWV resistance was conducted in the field with natural virus infection. A breeding line (C724‐19‐15) was selected that had high resistance to both pathogens. A near‐isogenic line (C724‐19‐25) susceptible to the peanut root‐knot nematode was also developed. Both breeding lines exhibited higher resistance to TSWV and higher yield than standard check cultivars when grown in fields with little or no nematode pressure.

Evaluation of the National Plant Germplasm System's Garlic Collection for Seven Viruses

Garlic (Allium sativum L. and A. longicuspis Regel.) germplasm maintained by the USDA-ARS Western Regional Plant Introduction Station (WRPIS) was screened for four viruses commonly infecting garlic [Garlic common latent carlavirus (GCLV), Leek yellow stripe potyvirus (LYSV), Onion yellow dwarf potyvirus (OYDV), and Shallot latent carlavirus (SLV)] plus three others [Iris yellow spot tospovirus (IYSV), Tobacco rattle tobravirus (TRV), and Tomato spotted wilt tospovirus (TSWV)]. Over 200 accessions were rated for the incidence of symptomatic plants during two production seasons, in July 2005 and June 2006. In both years, incidence of symptomatic plants ranged from less than 10% to 100% in individual accessions. Laboratory testing of selected accessions showed that the accessions were predominantly infected with OYDV (60% of infections), followed by GCLV (25%) and LYSV (15%). Accepted for publication 26 June 2008. Published 19 September 2008.

Reaction of Peanut Cultivars to Tomato Spotted Wilt Virus (TSWV) Under Field Conditions and Their Response to Mechanical Inoculation by TSWV Under Greenhouse Conditions

Spotted wilt virus disease caused by Tomato spotted wilt tospovirus (TSWV) has become a limiting factor in peanut (Arachis hypogaea L.) production in the Southwest region of the U.S. Selected peanut cultivars (Okrun, Southwest Runner, Tamrun-98, Tamrun-96, Georgia Green, Tamrun OL-02, Tamrun OL-01, and Georgia Hi Oleic) were evaluated for reaction to TSWV in field plots in 2001, 2002, and 2003. Field plots were located near Pearsall, TX, where TSWV is endemic. In 2001, at 72 days post planting (DPP), incidence of TSWV was significantly (P , 0.05) higher in Southwest runner, Okrun, and Tamrun98 than the other cultivars except Tamrun OL-02 in the test. In 2002, disease incidence of TSWV was low and thus only one reading was taken at 135 DPP where the cultivars Georgia Green and Georgia Hi Oleic exhibited the least incidence of spotted wilt. In 2003, at 58 DPP, Georgia Green, and Georgia Hi Oleic showed the lowest incidence of spotted wilt compared with other cultivars. The response of the eight peanut cultivars to TSWV following mechanical inoculation with TSWV at three plant ages was evaluated under greenhouse conditions. Disease severity index (DSI) and plant growth parameters such as root length, root volume, plant height, and fresh weight were determined. ELISA values (as indicative of the relative presence of TSWV), and relative water content were also determined to show the impact of TSWV infections in inoculated plants. Reductions in most plant growth parameters were observed when plants were inoculated with TSWV at five days post-planting, than twelve and nineteen days post-planting inoculation. Positive values of correlation coefficient (CC) between DSI and root volume or root length in the cultivars Georgia Hi Oleic, Georgia Green, Tamrun-96 and Tamrun OL-01 indicate resistance or tolerance to mechanical inoculation with TSWV. Negative values of CC between DSI and root length or root volume in the cultivars Tamrun-98, Tamrun OL-02, Southwest Runner, and Okrun provide evidence for their susceptibility to TSWV. Comparison of results obtained from the field with those from greenhouse evaluations suggest that Georgia Hi Oleic, Georgia Green, Tamrun-96 and Tamrun OL-01 cultivars are useful as potential tools for management of TSWV in peanut for the Southwestern United States.

Effect of Mechanical Inoculation of Tomato spotted wilt tospovirus Disease on Disease Severity and Yield of Greenhouse Raised Tomatoes

Effect of Mechanical Inoculation of Tomato spotted wilt tospovirus Disease on Disease Severity and Yield of Greenhouse Raised Tomatoes

Incidence of Thrips and Tomato Spotted Wilt Tospovirus in Flue-Cured Tobacco Protected from Early Season Insect Pest Infestations

Incidence of Thrips and Tomato Spotted Wilt Tospovirus in Flue-Cured Tobacco Protected from Early Season Insect Pest Infestations