Progress 07/01/02 to 06/30/07
Outputs
An average of 4,000 samples per year of peach budwood was tested by ELISA for the presence of Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), and Plum pox virus. PNRSV and PDV were detected in a few of the samples tested and the trees from which these samples originated were excluded as sources of budwood. Plum pox was not detected in any of the samples tested. The graft transmissible agents associated with the bloom delay caused by Ta Tao 5 peach have been partially characterized. Complete sequence for the isolate of PLMVd present in the cultivar has been described. The complete sequence of the isolate of apple chlorotic leaf spot virus that infects Ta Tao 5 has also been described. The foveavirus present in Ta Tao 5 has been identified as Asian prunus virus 3 (APV-3) and 3 kb of the genomic sequence of this virus have been determined. Initial data from a trial of the cultivar Springprince chip bud inoculated with mixtures of PLMVd, ACLSV, and APV-3,
and a second trial using the cultivar Juneprince, show visible differences among treatments but there are as yet no consistent tangible differences. ELISA to detect Watermelon mosaic virus was completed on several hundred samples of cantalope as part of a project to develop IPM strategies that might ameliorate the impact of this virus on yield. Watermelon mosaic virus was detected but no useful information on the relationship between the incidence of the virus, and proposed controls using IPM strategies was obtained. A survey of blackberry cultivars growing in 4 U pick operations in Upstate South Carolina documented a significant incidence of plants displaying symptoms typically associated with infection by viruses. At one location all plants were "symptomatic". PCR testing detected Blackberry yellow vein associated virus (BYVaV) in the cultivar Apache at all locations. The presence of Tomato ringspot virus, Tobacco ringspot virus, and Raspberry bushy dwarf virus was not detected by
PCR although plants showing symptoms typical of virus infection but that did not contain BYVaV were sampled and tested. The complete sequences of 2 potexviruses that infect ornamental species (Hydrangea ringspot virus [HdRSV] and Nandina mosaic virus [NAMV]) were completed and deposited in GenBank. A novel carlavirus isolated from Ligustrum was characterized and named Ligustrum necrotic ringspot virus. The complete genomic sequence of this virus was deposited with GenBank. The sequence of the complete genome of a new and distinct species within the genus Ilarvirus, Blackberry chlorotic ringspot virus has been described. Complete genomic sequences for two other ilarviruses , Parietaria mottle virus and Humulus japonicas latent virus have also been described and deposited in GenBank.
Impacts
The Southeastern Budwood program has been in operation for 7 years. A number of orchards established using budwood from blocks tested in 2001 are used as sources of budwood in the program. These have been tested for 5 years subsequent to establishment. None of the 3 viruses has been detected in these plantings, indicating that the program is effective. Morover, there is, as yet, no suggestion of spread into these blocks from adjacent infected trees. Nandina mosaic virus was shown not to be a distinct potexvirus but to be an isolate of another distinct potexvirus, Plantago asiatica mosaic virus this allows a reassessment of the taxonomy of the genus Potexvirus. The identification of a previously unreported carlavirus in Ligustrum may explain some of the symptoms of disease observed on this host that are not associated with either fungal or bacterial disease. The genomic sequences of ilarviruses are being used to reassess the taxonomy of this viral genus and solve
problems associated with the identification of ilarviruses. All the sequence data collected has allowed the development of detection methods involving PCR. This sensitive method can be utilized in efforts to index plant material and provide virus-tested material for propagation. The identification of BYVaV virus in blackberry in South Carolina paves the way for research into this problem in conjunction with colleagues from Arkansas and Oregon.
Publications
- Tzanetakis, I.E., Martin, R.R., Scott, S.W.. 2007 Strawberry necrotic shock virus and Blackberry chlorotic ringspot virus: Evolution of Ilarvirus Subgroup 1.. American Society for Virology Annual Meeting, Corvallis 2007.
- Tzanetakis, I.E., Martin, R.R., Scott, S. 2007. The Nucleotide Sequence of Blackberry chlorotic ringspot and Strawberry necrotic shock viruses. Phytopathology 97: American Phytopathological Society Annual Meeting, San Diego
- Liu, Z., Scorza, R., Hily, J-M., Scott, S.W., and James D. 2007. Engineering Resistance to Multiple Prunus Fruit Viruses Through Expression of Chimeric Hairpins. Journal of the American Society for Horticultural Science 132: 407-414.
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Progress 01/01/06 to 12/31/06
Outputs
Over 3,000 samples of peach budwood were tested by ELISA for the presence of Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), and Plum pox virus. PNRSV and PDV were detected in a few of the samples tested and the trees from which the samples were excluded as sources of budwood. Plum pox was not detected in any of the samples tested. The graft transmissible agents associated with the bloom delay caused by Ta Tao 5 peach have been partially characterized. Complete sequence for the isolate of PLMVd present in the cultivar has been described. Over 2 kb of sequence from a trichovirus (potentially ACLSV) and over 3 kb of sequence for the foveavirus present in Ta Tao 5 have been determined. Initial data from a trial of the cultivar Springprince chip bud inoculated with mixtures of PLMVd, ACLSV, and the foveavirus show differences among treatments but there are as yet no consistent differences.
Impacts
The budwood screening program continues to provide a source of virus-tested budwood to nurseries in Tennessee and hence to growers in South Carolina. The absence of PPV in particular provides reassurance to producers that they are not at risk from this devastating virus. The sequences of the trichovirus and foveavirus present in Ta Tao 5 allow a tentative identification of these viruses. This knowledge allows decisions as to whether graft inoculation of trees using Ta Tao 5 germplasm can be recommended as a means of delaying bloom in peach, while not having a negative impact on the stone fruit producing industry as a whole, to be made.
Publications
- Jones, A.T. Mcgavin, W.J., Gepp, V, Scott, S.W. and Zimmerman, M.T. 2006. Purification and properties of Blackberry chlorotic ringspot, a new virus species in Subgroup 1 of the genus Ilarvirus found naturally infecting blackberry in the UK. Annals of Applied Biology : 149 125 - 135
- Scott, S.W., Zimmerman, M.T. Rankin D. 2006. Complete sequence of the RNA 1 and RNA 2 of Parietaria mottle virus. Archives of Virology 151: 1895 - 1898. DOI 10.1007/s00705-006-0803-2
- Scott, S.W., Zimmerman, M.T. 2006. The complete nucleotide sequence of the genome of Humulus japonicus latent virus. Archives of Virology 151: 1683 - 1687. DOI 10.1007/s00705-006-0771-6
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Progress 01/01/05 to 12/31/05
Outputs
Over 4,000 samples of peach budwood were tested by ELISA for the presence of Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), and Plum pox virus. PNRSV and PDV were detected in a few of the samples tested and the trees from which the samples were excluded as sources of budwood. Plum pox was not detected in any of the samples tested Attempts to purify the foveavirus associated with Ta Tao 5 peach (Asian prunus virus 1- Candresse) have proved unsuccessful. Alternative approaches involving the extraction of dsRNA have been more successful but attempts to clone and sequence the virus using dsRNA as the source material have yet to succeed. ELISA to detect Watermelon mosaic virus was completed on several hundred samples of cantalope as part of a project to develop IPM strategies that might ameliorate the impact of this virus on yield. ELISA to detect Hosta virus X has been completed for samples from the Plant Problem Clinic and for one large propagator in
South Carolina.
Impacts
The budwood screening program continues to provide a source of virus-tested budwood to nurseries in Tennessee and hence to growers in South Carolina. The absence of PPV in particular provides reassurance to producers that they are not at risk from this devastating virus. The testing of cantalopes for the presence of Watermelon mosaic virus allows strategies to be developed that offer growers the opportunity to manage the disease and the economic losses associated with infection by this virus using IPM approaches. Testing of hosta material for the presence of Hosta virus X allows growers to make decisions about the sources from which they buy hosta material for large scale propagation.
Publications
- Hughes, P.L., Lawrence, J.E., and Scott, S.W. 2005. The complete nucleotide sequence of Hydrangea ringspot virus. Archives of Virology 150: 2339-2345 DOI 10.1007/s00705-005-0594-x
- Hughes, P.L., Harper, F., Zimmerman, M.T., and Scott, S.W. 2005. Nandina mosaic virus is an isolate of Plantago asiatica mosaic virus. European Journal of Plant Pathology 113: 309-313. DOI 10.1007/s10658-005-0624-2
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Progress 01/01/04 to 12/31/04
Outputs
The budwood screening program has continued and tested approximately 3,500 trees for the presence of Plum pox virus, Prunus necrotic ringspot virus and Prune dwarf virus. The program has been in operation for 4 years. This year new orchards established using budwood from blocks tested in 2001 have been tested for the first time. None of the 3 viruses was detected in any of these 7 new orchards, indicating that the program is effective. The detection of the foveaviruses in oriental germ plasm has been improved. Initial assays using primers designed by Candresse gave erratic results. Adoption of a lower temperature for reverse transcription (37C) has improved the reliability of detection for both the foveavirus found in this germ plasm and Apple chlorotic leafspot virus. A survey of blackberry cultivars growing in 4 U pick operations in Upstate South Carolina documented a significant incidence of plants displaying symptoms typically associated with infection by viruses.
At one location all plants were "symptomatic". PCR testing detected Blackberry yellow vein associated virus (BYVaV) in the cultivar Apache at all locations. The presence of Tomato ringspot virus, Tobacco ringspot virus, and Raspberry bushy dwarf virus was not detected by PCR although plants showing symptoms typical of virus infection but that did not contain BYVaV were sampled and tested. Watermelon mosaic virus was again detected in cucurbits using ELISA but no useful information on the relationship between the incidence of the virus, and proposed controls using IPM strategies were obtained. The complete sequences of 2 potexviruses that infect ornamental species (Hydrangea ringspot virus [HdRSV] and Nandina mosaic virus [NAMV] )were completed and submitted to GenBank (accessions AY707100 and AY800279, respectively). Nandina mosaic virus was shown not to be a distinct potexvirus but to be an isolate of another distinct potexvirus, Plantago asiatica mosaic virus. A carlavirus closely
related to Lily symptomless virus has been isolated from Ligustrum. The host range of Lily symptomless is reported to be restricted to members of the Lliliaceae. Thus this virus may be a previously unreported species of carlavirus. The sequence of the complete genome of Blackberry chlorotic ringspot virus has been described. This ilarvirus is a member of subgroup 1 and although related to Strawberry necrotic shock virus appears to be a new and distinct species within the genus Ilarvirus.
Impacts
The budwood screening program continues to provide a source of virus-tested budwood to nurseries in Tennessee and hence to growers in South Carolina. The absence of PPV in particular provides reassurance to producers that they are not at risk from this devastating virus. The improved ability to detect the unnamed foveavirus in oriental germplasm allows us to refine our identification of the agent specifically associated with bloom delay. The detection of BYVaV in the cultivar Apache in South Carolina adds support for recommendations that growers plant material from the clean stock program for blackberry being operated by Arkansas and North Carolina. The description of the sequences of HdRSV and NaMV allows for the development of sensitive molecular methods for screening asexually propagated material of hydrangea and nandina potentially infected with these viruses.
Publications
- Fry, C., Zimmerman, M.T., and Scott, S.W. 2004. Occurrence of Colombian datura virus in the terrestrial orchid Spiranthes cernua. Journal of Phytopathology 152: 200-203
- Scott, S.W., 2004. Diseases caused by phytoplasmas. In Southeastern Peach Grower's Handbook, Eds, Horton, D. and Johnson, D. http://www.ent.uga.edu/Peach/peach_handbook/hbk.htm
- Scott, S.W., 2004. Viruses of peach In Southeastern Peach Grower's Handbook, Eds, Horton, D. and Johnson, D. http://www.ent.uga.edu/Peach/peach_handbook/hbk.htm
- Jones, A.T. and Scott, S.W. 2004. Elm mottle Virus. CMI/ AAB Virus descriptions no 404. http://www.dpvweb.net/dpv/showdpv.php?dpvno=404
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Progress 01/01/03 to 12/31/03
Outputs
Four new source blocks were added to the budwood program. 3,456 potential sources of budwood were tested for the presence of Plum pox virus (PPV), Prunus necrotic ringspot virus (PNRSV), and Prune dwarf virus (PDV). PPV was not detected in any of the samples. PDV was identified in 4 samples and PNRSV was present in approximately 10% of the samples. Sources of Phony disease (Xylella fastidiosa) were identified in preparation for developing a test to screen budwood for the presence of this disease. A correlation between the vein clearing expressed on chip bud-inoculated seedlings of the peach roostock cultivar Okinawa and the presence of an as yet unnamed foveavirus in some 16 different peach cultivars of Oriental origin was established using PCR to detect the presence of the virus. Collaborative work with researchers in Oregon has detected the newly reported Blackberry yellow vein associated virus (BYVAV), a Crinivirus, in many of the blackberry plants growing
in South Carolina and which are displaying symptoms of viral infection. Despite unusually heavy rainfall, which inhibited aphid movement, non-statistically significant trends were observed in the incidence of Watermelon mosaic virus (WMV) under different IPM treatments. Viral incidence was much greater, and crop yield much lower, on plots established with black mulch than in plots established with reflective mulch. Plots surrounded by a cover crop also showed a lower incidence of viral infection.
Impacts
The budwood screening program continues to provide a source of virus-tested budwood to nurseries in Tennessee and hence to growers in South Carolina. The absence of PPV in particular provides reassurance to producers that they are not at risk from this devastating virus. The detection of the unnamed foveavirus in ornamental germplasm adds to the body of knowledge on the relationship between Ta Tao germplasm and bloom delay and should allow identification of the agent specifically associated with bloom delay. The detection of BYVAV in South Carolina may explain the inability to detect the nepoviruses thought to be causing the symptoms typically associated with virus infection in Rubus. The use of reflective mulch and cover crops offers promise for an effective control of WMV.
Publications
- Scott, S.W., Zimmerman, M.T., and Ge, X., 2003. Viruses in subgroup 2 of the genus Ilarvirus share both serological relationships and characteristics at the molecular level. Archives of Virology 148: 2063-2075. DOI: 10.1007/s00705-003-0148-z
- Rao, S., Carner, G.R., Scott, S.W., Omura, T., and Hagiwara, K. 2003. Comparison of the amino acid sequences of RNA-dependent RNA polymerases of cypoviruses in the family Reoviridae. Archives of Virology 148: 209-219.
- Hughes, P.L. and Scott, S.W. 2003. First report of Tomato ringspot virus in butterfly bush (Buddleia davidii L.). Plant Disease 87: 102. Publication no. D-2002-1106-03N
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Progress 01/01/02 to 12/31/02
Outputs
Mechanical inoculations of peach germplasm accessions of Asian origin to the herbaceous host Nicotiana occidentalis 37B indicate the presence of viruses in many accessions. Although some of the viruses are the commonly occurring Prunus necrotic ringspot virus , Prune dwarf virus, and Apple chlorotic leaf spot virus others are novel and presently resist characterization. PCR assays designed to amplify Foveaviruses (a relatively recently discovered group of viruses that infect stonefruits) have been unsuccessful. Other attempts to determine the identity of the viruses are under way. Mechanical inoculation of total RNA isolated from the blackberry cultivar, Apache, to Nicotiana tabacum has caused stunting and yellowing of the herbaceous host. Although the plant is surviving, attempts to transmit the virus to other plants of N. tabacum and to other herbaceous host species have proved unsuccessful.
Impacts
The research to date has provided viral isolates in herbaceous material which should facilitate identification and characterization of these novel viruses.
Publications
- No publications reported this period
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