Progress 02/01/02 to 09/30/07
Outputs
OUTPUTS: We identified new viruses in Alabama. One study identified Brome mosaic virus in wheat and showed the vector to be the flea beetle. Another study identified five viruses in winter wheat with occurrence widespread throughout the state. A third study identified four viruses in commercial blackberry plantings, representing first time detection of viruses in Alabama-grown blackberries. We studied various aspects of virus infection in bell pepper. A synergistic disease was described in great detail involving Cucumber mosaic virus and Pepper mottle virus. A study identified viral (genome-linked protein gene) and host (Elongation factor 4E) genes involved in a resistance/susceptibility response. The full-length sequence was determined for the 9.5 Kb RNA genome of Pepper mottle virus, genus Potyvirus. A study showed that once virus moved out of the inoculated leaf, the rate and extent of movement and accumulation throughout the plant occurred independently of the source leaf. We
demonstrated that as pepper plants "mature", they become increasingly more resistant to infection by Cucumber mosaic virus but not to the potyvirus Pepper mottle virus. This age-related resistance appeared to result from an inhibition of virus movement from the inoculate leaf to young developing tissues. Biological control studies were performed using various plant growth-promoting rhizobacteria treatments. Protection was observed in tomato and Arabidopsis and molecular (mechanistic) studies were performed in an effort to understand the nature of the induced resistance. A persistent, severe outbreak of Cucumber mosaic virus in tomato has occurred in northern counties of Alabama. A three-way relationship was identified involving Cucumber mosaic virus- aphid vectors and fire ants. Fire ants were shown to protect aphids from natural predators in return for the sugary carbon source honeydew. The protection afforded the aphids allowed populations to increase thereby enhancing spread of
Cucumber mosaic virus. A population genetics study of the wild plant species, Mimulus guttatus (Yellow monkeyflower), was performed to understand its response to infection and disease development by Cucumber mosaic virus. The studies described above have led to numerous refereed publications in a broad range of scientific journals. Similarly, the research findings from the studies have been presented at numerous scientific and agriculturally-based meetings. Depending on the study, the primary recipient of the scientific findings may be other scientists, agricultural industries and national and local farmers.
PARTICIPANTS: Dr. Molly Jahn, a collaborator at Cornell University, played a critical role with the pepper research. Her program offered important molecular biology and host genetics expertise. Dr. Joe Kloepper, a collaborator at Auburn University, offered important direction and materials for biological control projects. His program is internationally recognized in the area of biological control of plant diseases. Dr. Micky Eubanks, a collaborator at Auburn University, played a key role in the virus ecology work, the population genetics project and especially as the lead person on the fire ant-aphid mutualism project. Dr. Kira Bowen, a collaborator at Auburn University, offered important expertise in modeling disease severity that allowed us to quantitate the synergistic disease expression of Cucumber mosaic virus and Pepper mottle virus in pepper. The list of publications includes names of many other collaborators. These individuals include graduate students, postdoctoral
researchers and extension personnel The research accomplished during the project period focused on projects at Auburn University; however, collaborators at other universities provided essential expertise.
TARGET AUDIENCES: The research accomplished during the project period was targeted to other researchers at universities, federal laboratories and industry. Some projects provided important information to horticulturists and extension personnel (university and state). The more applied projects have had results delivered to growers that used the information to reduce losses by plant viruses in their crops. The research findings have been delivered to undergraduate and graduate students through structured classroom courses, seminars and reading material. Presentations were also directed to grower groups.
Impacts
The identification of viruses in crop plants allows us, as scientists, extension personnel and growers to be aware of threatening virus diseases. In each case, wheat or blackberry, different disease symptoms result from the particular viruses involved and methods had to be developed and improved for sample collection and detection. We have developed a large data base for processes leading to virus infection in bell pepper. In conjunction with these findings, we have evaluated and dissected new sources of resistance to virus infection. Each project requires development of new approaches or adaptation of previously used methodologies. With each new, deeper level of experimentation, the research appears to become more complicated as virus and host are teased apart at molecular levels. Management of insect-borne plant viruses is difficult if resistant varieties are not available. We have focused much effort on projects to evaluate different schemes to reduce or eliminate
losses due to virus infection. The work is complicated by an abundance of insect vectors, wild plant species that harbor virus and vector and changing weather conditions. The discovery of the mutualistic relationship between fire ants and aphids with that relationship leading to enhanced spread of virus provides further evidence of the complexity of virus pathosystems in nature. It also strengthens our realization of the many hurdles we need to overcome to develop broad spectrum, effective management strategies.
Publications
- Pernezny, K., Roberts, P., Murphy, J.F., and Goldberg, N. 2003. Compendium of Pepper Diseases. American Phytopathological Society Press, St. Paul, MN.
- Sikora, E.J., and Murphy, J.F. 2005. Identification and management of Cucumber mosaic virus in Alabama. Acta Horticulturae 695:191-194.
- Zehnder, G.W., Murphy, J.F., Sikora, E. and Kloepper, J.W. 2001. Application of rhizobacteria for induced resistance. European Journal of Plant Pathology 107:39-50.
- Murphy, J.F., Reddy, M.S., Ryu, C.M., Kloepper, J.W., and Li, R. 2003. Rhizobacteria-mediated growth promotion of tomato leads to protection against Cucumber mosaic virus. Phytopathology 93:1301-1307.
- Bowen, K.L., Murphy, J.F., Flanders, K.L. and Li, R. 2003. Incidence of viruses infecting winter wheat in Alabama. Plant Disease 87:288-293.
- Warren, C.E., and Murphy, J.F. 2003. The complete nucleotide sequence of Pepper mottle virus-Florida RNA. Archives of Virology 148:189-197.
- Turina, M., Omarov, R., Murphy, J.F., Bazaldua-Herandez-C., Desvoyes, B., and Scholthof, H.B. 2003. A newly identified role for Tomato bushy stunt virus P19 in cell-to-cell spread. Molecular Plant Pathology 4:67-72.
- Carr, D.E., Murphy, J.F., and Eubanks, M.D. 2003. The susceptibility and response of inbred and outbred Mimulus guttatus to infection by Cucumber mosaic virus. Evolutionary Ecology 17:85-103.
- Murphy, J.F., 2002. The relationship between virus source leaf and spread of infection through the stem of Capsicum sp. Archives of Virology 147:1789-1797.
- Sikora, E.J., Kemble, J., Zehnder, G.W., Goodman, R., Andrianifahanana, M., Bauske, E., and Murphy, J.F. 2002. Using on-farm demonstrations to promote integrated pest management practices in tomato production. Hortechnology 12:485-488.
- Garcia-Ruiz, H., and Murphy, J.F. 2001. Age-related resistance in bell pepper to Cucumber mosaic virus. Annals of Applied Biology 139:307-317.
- Coppler, L.B., Murphy, J.F., and Eubanks, M.D. 2007. Red imported fire ants (Hymenoptera: Formicidae) increase the abundance of aphids in tomato. Florida Entomologist 90:419-425.
- Ryu, C-M., Murphy, J.F., Reddy, M.S., and Kloepper, J.W. 2007. A two-strain mixture of Rhizobacteria elicits induction of systemic resistance against Pseudomonas syringae and Cucumber mosaic virus coupled to promote plant growth in Arabidopsis thaliana. Journal of Microbiology and Biotechnology 17:280-286.
- Eubanks, M.D., Carr, D.E., and Murphy, J.F. 2005. The effects of virus infection of Mimulus guttatus (Scrophulariaceae) on host plant quality for meadow spittlebugs, Philaenus spumarius (Hemiptera: Cercopidae). Environmental Entomology 34:891-898.
- Eubanks, M.D., Carr, D.E., and Murphy, J.F. 2005. Defense against multiple enemies: Genetic variation in the response of plants to herbivore and virus attack. Evolutionary Ecology 19:15-27.
- Kang, B.C., Yeam, I., Frantz, J.D., Murphy, J.F., and Jahn, M.M. 2005. The pvr1 locus in pepper encodes a translation initiation factor eIF4E that interacts with Tobacco etch virus Vpg. The Plant Journal 42:392-405.
- Ryu, C.M., Murphy, J.F., Mysore, K.S., and Kloepper, J.W. 2004. Plant growth-promoting rhizobacteria systemically protect Arabidopsis thaliana against Cucumber mosaic virus by a novel signaling pathway. The Plant Journal 39:381-392.
- Sikora, E.J., Kemble, J., Zehnder, G.W., Goodman, R., Andrianifahanana, M., Bauske, E., and Murphy, J.F. 2001. Tomato IPM field demonstrations in Alabama. Journal of Extension 39:no page numbers in this journal. (See April 2001 issue: www.joe.org)
- Davis, M.A., Murphy, J.F., and Boyd, R.S. 2001. Nickel increases susceptibility of the Ni hyperaccumulater, Streptanthus polygaloides, to Turnip mosaic virus. Journal of Environmental Quality 30:85-90.
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Progress 01/01/06 to 12/31/06
Outputs
One study evaluated different kinds of inter-row cover crops (e.g. Serecia lespedeza or Sunn Hemp) for their ability to reduce aphid-borne virus incidence in pumpkin and associated yield losses relative to a conventional approach. Results were promising with significant reductions in virus accumulation in pumpkin plants grown with Serecia inter-row crops. A second study on inheritance of resistance to eight Potyviruses in a bell pepper genotype was performed. The source of resistance appears broad spectrum with varied levels of resistance depending on the virus and strain. A third study examined the relationship between aphid species, fire ants and weed species as components in a CMV epidemic in tomato. A strong correlation was detected among cotton aphids and their relationship with fire ants and two weed species. A fourth study focused on bell pepper plant response to different growth conditions and the relationship of these growth conditions to virus disease
severity. Results indicate that manipulation of components as simple as pot size can alter disease severity and host resistance to virus infection.
Impacts
Our efforts continue to address applied and basic aspects of plant virus and host interactions with an emphasis on reducing losses to virus disease. The field-based projects evaluate environmentally sound strategies to reduce losses. The greenhouse-laboratory projects complement the field projects attempting to understand the nature of virus-host interactions with results being incorporated into the field-based projects.
Publications
- Murphy, J.F. 2006. Applied aspects of induced resistance to plant virus infection. In: Natural Resistance Mechanisms Of Plants To Viruses. Chapter A1, pages 1-11. Springer Publishing, Netherlands. Editors: G. Loebenstein and J.P. Carr. 532 pages.
- Murphy, J.F., and Bowen, K.L. 2006. Synergistic disease in pepper caused by the mixed infection of Cucumber mosaic virus and Pepper mottle virus. Phytopathology 96:240-247.
- Carr, D.E., Murphy, J.F., and Eubanks, M.D. 2006. Genetic variation and covariation for resistance and tolerance to Cucumber mosaic virus in Mimulus guttatus (Phrymaceae): a test for costs and constraints. Heredity 96:29-38.
- Srivatsavai V.S.K., Huettel, R.N., and Murphy, J.F. 2006. Xiphinema spp., a putative vector for Brome mosaic virus (BMV), not associated with BMV-infected wheat plants in Alabama. Nematropica 36:269-272.
- Sikora, E.J., Murphy, J.F., and Burkett, J.E. 2006. Performance of virus resistant squash in Alabama. Journal of Vegetable Science 12:75-83.
- Murphy, J.F., and Eubanks, M.D. 2006. Integration of biological and plastic mulches to mantage Watermelon mosaic virus in squash. Cucurbitaceae Proceedings, pages 492-497.
- Flanders, K., Herbert, A., Buntin, D., Johnson, D., Murphy, J.F., Chapin, J., and Hagan, A. 2006. Barley yellow dwarf in small grains in the Southeast. Alabama Cooperative Extension System Circular ANR-1082, 10 pages.
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Progress 01/01/05 to 12/31/05
Outputs
A source of resistance to potyviruses was evaluated for mechanistic studies and inheritance of resistance. The resistance to two strains of PepMoV, PVY and four strains of TEV varied with virus and strain. The more resistant response involved lack of detection in the inoculated leaf with no systemic infection. The least resistant response involved systemic infection but with a delay and significantly reduced accumulation of virus in non-inoculated leaves. The resistance is inherited as a single, recessive gene. Other studies correlated CMV-induced symptoms in pepper with virus accumulation and physiological parameters, surveys for BMV infection of Alabama-grown wheat and characterization of a mutualistic relationship between red-imported fire ants, aphids and incidence of CMV in fresh-market tomato.
Impacts
The identification and characterization of a source of broad-spectrum resistance in bell pepper to viruses in the genus Potyvirus has great potential for the pepper industry. Potyviruses pose a serious threat to pepper production. Their transmission by aphids in a non-persistent manner results in extremely limited opportunities to manage these viruses. A single gene conferring genetic resistance to multiple potyviruses may provide growers with an important element of protection.
Publications
- Cooper, L.B., Murphy, J.F., and Eubanks, M.D. 2005. Effects of ant-aphid mutualisms on epidemics of plant viral diseases. Annual meeting for Ecology Society of America, Montreal, Canada. (August)
- Srivatsavai, S., Murphy, J.F., and Huettel, R.N. 2005. Is the dagger nematode a vector of Brome mosaic virus in Alabama? Society of Nematologists Annual Meeting, Ft. Lauderdale, FL.
- Srivatsavia, S.K., Murphy, J. F., Flanders, K., and Huettel, R. N. 2005. Flea Beetles as a vector for Brome Mosaic Virus in Alabama. Annual meeting for Entomology Society of America, Ft. Lauderdale, FL. (December)
- Cooper, L.B., Murphy, J.F., and Eubanks, M.D. 2005. Fire ants may promote epidemics of aphid-vectored plant viruses. Annual meeting for Entomology Society of America, Ft. Lauderdale, FL. (November)
- Sikora, E.J., and Murphy, J.F. 2005. Identification and management of Cucumber mosaic virus in Alabama. Acta Horticulturae 695:191-194 (special issue from the International Symposium On Tomato Diseases, June 2004, Orlando, FL).
- Kang, B.C., Yeam, I., Frantz, J.D., Murphy, J.F., and Jahn, M.M. 2005. The pvr1 locus in pepper encodes a translation initiation factor eIF4E that interacts with Tobacco etch virus VPg. The Plant Journal 42:392-405.
- Eubanks, M.D., Carr, D.E., and Murphy, J.F. 2005. The effects of virus infection of Mimulus guttatus (Scrophulariaceae) on host plant quality for meadow spittlebugs, Philaenus spumarius (Hemiptera: Cercopidae). Environmental Entomology 34:891-898.
- Eubanks, M.D., Carr, D.E., and Murphy, J.F. 2005. Variation in the response of Mimulus guttatus (Scrophulariaceae) to herbivore and virus attack. Evolutionary Ecology 19:15-27.
- Sikora, E.J., and Murphy, J.F. 2005. First Report of Bean pod mottle virus in soybean in Alabama. Plant Disease 89:108.
- Murphy, J.F. 2005. Cucumber mosaic virus infection of bell pepper leads to distinct systemic symptom phases that correlate in apparent severity with virus titer levels. American Phytopathological Society Annual Meeting, Austin, TX Phytopathology
- Cooper, L.B., Murphy, J.F., and Eubanks, M.D. 2005. Effects of ant- aphid mutualisms on the incidence of Cucumber mosaic virus in fresh-market tomato. American Phytopathological Society Annual Meeting, Austin, TX Phytopathology
- Srivatsavai, S., Murphy, J.F., and Huettel, R.N. 2005. Brome mosaic virus (BMV) in Alabama. American Phytopathological Society Annual Meeting, Austin, TX Phytopathology
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Progress 01/01/04 to 12/31/04
Outputs
Our understanding of the virus infection of bell pepper plants has progressed on several fronts. First, potyvirus movement to young tissues in pepper plants has been shown to occur through internal phloem. We recently identified connecting channels that allow passage from leaf petiole internal phloem to stem internal phloem. Second, we have identified and characterized a synergistic disease response in pepper caused by co-infection of CMV and PepMoV. Third, detailed studies have been conducted on symptom development in pepper caused by CMV and include correlation of virus accumulation with symptom type and physiological response of leaf tissues to virus infection. Fourth, we have continued to evaluate virus disease outbreaks in vegetebles in the State, with an emphasis on the ecology of CMV in the tomato epidemic in Blount County.
Impacts
Our knowledge of the infection processes in pepper have led to important collaboations to define host resistance responses and develop new sources of resistance to plant viruses. Our efforts to study to ecology of viruses in natural enviroments will allow us to identify and target key links in the disease cycle in an effort to reduce losses caused by insect-borne plant viruses.
Publications
- Ryu, C.M., Murphy, J.F., Mysore, K.S., and Kloepper, J.W. 2004. Plant growth-promoting rhizobacteria systemically protect Arabidopsis thaliana against Cucumber mosaic virus by a novel signaling pathway. The Plant Journal 39:381-392.
- Cooper, L., J.F. Murphy, and M.D. Eubanks. Implications of a fire ant-aphid mutualism on the spread of aphid-vectored viruses. Southeastern Branch of the Entomological Society of America Meeting, Savannah, Georgia, March 2004.
- Cooper, L., J.F. Murphy, and M.D. Eubanks. Effects of ant-aphid mutualisms on herbivore populations and spread of aphid-vectored viruses. Ecological Society of America, Portland, Oregon, August 2004.
- Cooper, L., J.F. Murphy, and M.D. Eubanks. Implications of a fire ant-aphid mutualism on the spread of aphid-vectored viruses. Entomological Society of America Meeting, Salt Lake City, Utah, November 2004
- Cooper, L.B., J.F. Murphy, and Eubanks, M.D. 2004. Implications of a fire ant-aphid mutualism on the spread of aphid-vectored viruses. Annual Meeting for the Entomology Society of America.
- Sikora, E.J., and Murphy, J.F. 2004. Identifiction and management of Cucumber mosaic virus in Alabama. Presented at the International Symposium on Tomato Diseases, Orlando, FL.
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Progress 01/01/03 to 12/31/03
Outputs
In a study to determine the pathway of movement of plant viruses through pepper plants, we showed using confocal laser scanning microscopy that virus moved into the stem of plants via both internal and external phloem. This occurred in both susceptible and resistant genotypes of pepper indicating that the block in movement in the stem of Avelar pepper plants was not associated with loading of virus in the inoculated leaf. We also identified channels that connect neighboring phloem bundles that allow virus to move into phloem that feeds upper young tissues. In a survey for virus diseases in soybean crops, the beetle transmitted Bean pod mottle virus was detected in more than 50% of the 1,200 samples tested. Two other viruses also tested for included Soybean mosaic virus and Alfalfa mosaic virus; however, no samples contained detectable amounts of these viruses.
Impacts
The identification of channels connecting internal phloem bundles may explain a crucial step in the virus movement process leading to systemic infection. Identification of Bean pod mottle virus infecting Alabama-grown soybean is new information and important with regard to the recent emergence of this virus posing a threat to the soybean industry on a national level.
Publications
- Warren, C.E., and Murphy, J.F. 2003. The complete nucleotide sequence of Pepper mottle virus-Florida RNA. Archives of Virology 148:189-197.
- Turina, M., Omarov, R., Murphy, J.F., Bazaldua-Herandez-C., Desvoyes, B., and Scholthof, H.B. 2003. A newly identified role for Tomato bushy stunt virus P19 in cell-to-cell spread. Molecular Plant Pathology 4:67-72.
- Carr, D.E., Murphy, J.F., and Eubanks, M.D. 2003. The susceptibility and response of inbred and outbred Mimulus guttatus to infection by Cucumber mosaic virus. Evolutionary Ecology 17:85-103.
- Murphy, J.F., and Bowen, K.L. 2003. Defining synergy in plant virus infections in bell pepper. Phytopathology 93:S64.
- Hatcher, W.L., Dute, R.R., and Murphy, J.F. 2003. The nature of Capsicum annuum cv. Avelar resistance to systemic infection by Pepper mottle virus. Phytopathology 93:S34.
- Kloepper, J.W., Reddy, M.S., Ryu, C-M., and Murphy, J.F. 2003. Induction of host defenses and plant growth promotion by Bacillus spp. Phytopathology 93:S117.
- Pernezny, K., Roberts, P., Murphy, J.F., and Goldberg, N. 2003. Compendium of Pepper Diseases. American Phytopathological Society Press.
- Murphy, J.F., Reddy, M.S., Ryu, C.M., Kloepper, J.W., and Li, R. 2003. Rhizobacteria-mediated growth promotion of tomato leads to protection against Cucumber mosaic virus. Phytopathology 93:1301-1307.
- Bowen, K.L., Murphy, J.F., Flanders, K.L. and Li, R. 2003. Incidence of viruses infecting winter wheat in Alabama. Plant Disease 87:288-293.
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Progress 01/01/02 to 12/31/02
Outputs
Studies directed at understanding plant virus movement in pepper plants and the nature of resistance of the cultivar Avelar are underway. We showed that the infection process of the stem of pepper plants is independent of the source leaf, once virus is delivered to the stem from the source leaf. Avelar's resistance to systemic infection by Pepper mottle virus (Florida strain)(PepMoV-FL) is not due to a block in loading in the inoculated leaf but appears to occur in the stem. We cloned and sequenced the genome of PepMoV-FL and compared the sequence with that of PepMoV-CA and other potyviruses. The RNA genome sequence of FL and CA strains was 93% homologous, with Potato virus V and Potato virus Y having only 61-63% homology. Biocontrol research in tomato involving PGPR formulations that enhance plant growth showed that the enhanced growth protected plants from infection from Cucumber mosaic virus (CMV). The PGPR-treated tomato plants were developmentally similar to
plants that were at least ten days older and they responded to inoculation with CMV in a similar manner to the older plants.
Impacts
Identification of a specific portion of the virus movement pathway in pepper plants, along with determination of the viral determinants associated with this movement process, will offer a target for resistance strategies in pepper plants. The enhanced growth observed with new PGPR formulations will significantly reduce the window of time during which young plants are in the field and vulnerable to infection by plant viruses.
Publications
- Murphy, J.F., 2002. The relationship between virus source leaf and spread of infection through the stem of Capsicum sp. Archives of Virology 147:1789-1797.
- Sikora, E.J., Kemble, J., Zehnder, G.W., Goodman, R., Andrianifahanana, M., Bauske, E., and Murphy, J.F. 2002. Using on-farm demonstrations to promote integrated pest management practices in tomato production. Hortechnology 12:485-488
- Bowen, K.L., Flanders, K.L. Mask, P. and Murphy, J.F. 2002. Risk index for Barley yellow dwarf virus and Cereal yellow dwarf virus of wheat in Alabama. Pp. 106-107 in Barley Yellow Dwarf Disease: Recent Advances and Future Strategies, M. Henry and A. McNab, eds. Mexico, D.F.: CIMMYT.
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