Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: Epidemiology and Management of Pierce's Disease and Other Maladies of Grape

Location: Crop Diseases, Pests and Genetics Research

2013 Annual Report

1a. Objectives (from AD-416):
The overall goal of this project is to mitigate losses due to Xylella fastidiosa-caused diseases during crop production and to develop effective, sustainable disease and insect-vector management strategies by characterizing host-pathogen-vector-environment interactions of these complex pathosystems. Specific objectives for the project are outlined below: Objective 1: Characterize genomic and biological diversity of Xylella fastidiosa strains. Objective 2: Elucidate molecular interactions of Xylella fastidiosa with horticultural and model plant hosts that result in disease susceptibility or resistance. Objective 3: Determine biological/ecological/transmission properties of Xylella fastidiosa vectors. Objective 4: Develop and assess strategies to manage diseases caused by Xylella fastidiosa.

1b. Approach (from AD-416):
Pierce’s disease (PD) is an economically important disease affecting US grape production. PD is caused by the xylem-limited bacterium Xylella fastidiosa (Xf), a generalist pathogen also causing disease in numerous horticultural crops and landscape ornamentals. In California, prevalence and incidence of PD increased following introduction and establishment of the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis. Presently, PD is managed in California via an area-wide surveillance and insecticide application program aimed at suppressing GWSS populations in citrus (the most common feeding/oviposition host) and urban landscape plants. Development of an integrated management program for PD requires detailed knowledge of host-pathogen-vector-environment interactions. Such knowledge is limited for this complex pathosystem involving multiple hosts and vectors, a genetically diverse pathogen, and a non-uniform agro-ecosystem. The project objectives are designed to address knowledge gaps in the biology, ecology, and genetics of Xf, sharpshooter vectors, and host plants. Genomic diversity, as well as the evolutionary, biological and epidemiological relationships among Xf strains will be characterized. The genetic and molecular basis of host-pathogen-vector interactions will be determined to better understand PD development and epidemiology. Biotic and abiotic factors that affect sharpshooter ecology and pathogen transmission mechanisms/efficiency will be identified. The nature, basis, and mechanism(s) of host resistance to Xf will be identified, characterized, and incorporated into advanced grape selections. New information and products will facilitate mitigation of PD losses, with the ultimate goal of developing an environmentally friendly, integrated management strategy that may augment or replace the area-wide surveillance and insecticide application program.

3. Progress Report:
FY13 research focused on Xylella fastidiosa (Xf), the bacterium responsible for Pierce’s disease (PD) of grapes, and sharpshooter insects that transmit Xf. The research was performed in the context of four objectives dealing with genetic analyses of Xf and grapes, Xf-host plant interactions, sharpshooter ecology/biology/transmission, and PD resistance/control. Progress on Objective 1 (Characterize genomic and biological diversity of Xf strains) included genome sequencing of Xf strains from red oak and muscadine grapes. Comparison of these two Xf genomes with previously sequenced strains is ongoing. Greenhouse experiments designed to evaluate the potential of Xf strains from olive to cause PD were initiated. Genome sequencing of Xf strains from olive has commenced. Progress on Objective 2 (Elucidate molecular interactions of Xf with horticultural and model plant hosts that result in disease susceptibility or resistance) focused on i) Xf genes associated with virulence/pathogenicity, and ii) genetic differences among grapevines that are resistant or susceptible to PD. Gene structure/function studies were conducted with two toxin-antitoxin systems that regulate Xf growth and biofilm formation. Xf proteins of unknown function were evaluated as potential virulence factors in plants using a transient expression system. A seedling population derived from a cross between PD-susceptible and PD-resistant grapes was evaluated for differences in gene expression. Resulting profiles were compared to identify expression patterns specific to PD-resistance. Gene sequences specific to PD-resistant seedlings were used to design DNA-based assays for marker-assisted selection. Progress on Objective 3 (Determine biological/ecological/transmission properties of Xf vectors) focused on sharpshooters. A blue green sharpshooter colony was established to use as a model system for Electrical Penetration Graph (EPG) monitoring of feeding in relationship to Xf inoculation. Preliminary EPG assays identified waveforms representing key behaviors. A protocol to estimate egg maturation rates of individual glassy-winged sharpshooter (GWSS) females was developed. Experiments to determine the effects of plant sap chemistry on GWSS egg maturation rates were initiated. Two compounds released by GWSS-infested grapevines were shown to be attractive to a GWSS egg parasitoid. Chemicals emitted by red-tip photinia, an alternative GWSS host, also are being analyzed to identify parasitoid attractants. Progress on Objective 4 (Develop and assess strategies to manage diseases caused by Xf) focused on breeding and cultural control. Crosses were performed in both table grapes and raisins to combine fruit quality with PD resistance. Additional crosses combined PD resistance with powdery mildew (PM) resistance; resistant seedlings were transplanted to the field. A new PD-evaluation field plot was established in Monte Alto, TX with 13 advanced table grape selections. Rootstock effects on susceptibility of scions to PD were evaluated. PD-susceptible scions grafted onto rootstock ‘101-14MG’ were more tolerant to Xf infection than when grafted onto other rootstocks.

4. Accomplishments

Review Publications
Voegel, T.M., Doddapaneni, H., Cheng, D., Lin, H., Stenger, D.C., Kirkpatrick, B., Roper, C. 2013. Identification of a response regulator involved in surface attachment, cell-cell aggregation, exopolysaccharide production and virulence in the plant pathogen, Xylella fastidiosa. Molecular Plant Pathology. 14:256-264.

Rashed, A., Wallis, C.M., Paetzold, L., Workneh, F., Rush, C.M. 2013. Zebra Chip disease and potato biochemistry: Tuber physiological changes in response to ‘Candidatus Liberibacter solanacearum’ infection over time. Phytopathology. 103:419-426.

Son, Y., Backus, E.A., Johnson, M., Groves, R. 2012. Pattern of stylet penetration activity by Homalodisca vitripennis (Hemiptera: Cicadellidae) adults in relation to environmental temperature and light conditions. Environmental Entomology. 41(5):1215-1230.

Rogers, E.E., Stenger, D.C. 2012. A conjugative 38kB plasmid is present in multiple subspecies of Xylella fastidiosa. PLoS One. 7:e52131.

Lin, H., Han, C., Lou, B., Liu, B., Bai, X., Deng, C., Civerolo, E.L., Gupta, G. 2013. Complete genome sequence of chinese strain of ‘Candidatus Liberibacter asiaticus’. Genome Announcements. 1(2):e00184-13.

Lin, H., Coletta-Filho, H.D., Han, C.S., Lou, B., Civerolo, E.L., Machado, M.A., Gupta, G. 2013. Draft genome sequence of “Candidatus Liberibacter americanus” bacterium associated with citrus huanglongbing in Brazil. Genome Announcements. 1(3):e00275.13.

Sisterson, M.S. 2012. Host selection by a phytophagous insect: the interplay between feeding, egg maturation, egg load, and oviposition. Arthropod-Plant Interactions. 6:351-360.

Serikawa, R., Rogers, M., Backus, E.A. 2012. Effects of soil-applied imidacloprid on Asian citrus psyllid (Hemiptera: Psyllidae) feeding behavior. Journal of Economic Entomology. 105(5):1492-1502.

Lightle, D., Dossett, M., Backus, E.A., Lee, J.C. 2012. Location of the mechanism of resistance to Amphorophora agathonica (Hemiptera: Aphididae) in red raspberry. Journal of Economic Entomology. 105:1465-1470.

Jin, S., Chen, Z., Backus, E.A., Sun, X.L., Xiao, B. 2012. Characterization of EPG waveforms for the tea green leafhopper, Empoasca vitis Göthe (Hemiptera: Cicadellidae), on tea plants and their correlation with stylet activities. Journal of Insect Physiology. 58:1235-1244.

Krugner, R., Hagler, J.R., Groves, R.L., Sisterson, M.S., Morse, J.G., Johnson, M.W. 2012. Plant water stress effects on the net dispersal rate of the insect vector Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) and movement of its egg parasitoid, Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae). Environmental Entomology. 41(6):1279-1289.

Hagler, J.R., Blackmer, F., Krugner, R., Groves, R.L., Morse, J.G., Johnson, M.W. 2013. Gut content examination of the citrus predator assemblage for the presence of Homalodisca vitripennis remains. Biocontrol. 58:341-349.

Dey, K.K., Lin, H., Borth, W.B., Melzer, M.J., Hu, J. 2012. A highly sensitive single-tube nested PCR assay for the detection of Pineapple mealybug wilt associated virus-2 (PMWaV-2). Journal of Virological Methods. 183(2):215-218.

Nwugo, C.C., Lin, H., Duan, Y., Civerolo, E.L. 2013. The effect of 'Candidatus Liberibacter asiaticus' infection on the proteomic profiles and nutritional status of pre-symptomatic and symptomatic grapefruit (Citrus paradisi) plants. Biomed Central (BMC) Plant Biology. Available:

Deng, X., Gao, Y., Chen, J., Pu, X., Kong, W., Li, H. 2012. Current situation of "Candidatus Liberibacter asiaticus" in Guangdong, P.R. China, where citrus huanglongbing was first described. Journal of Integrative Agriculture. 11:424-429.

Lin, H., Islam, M., Morano, L., Groves, R., Bextine, B., Civerolo, E.L., Walker, M. 2013. Genetic variation of Xylella fastidiosa associated with grape vines in two major viticulture regions in the United Sates: California and Texas. Journal of Plant Pathology. 95(2):329-337.

Walse, S.S., Krugner, R., Tebbets, J.S. 2012. Postharvest treatment of strawberries with methyl bromide to control spotted wing drosophila, Drosophila suzukii. Journal of Asia-Pacific Entomology. 15:451-456.

Sisterson, M.S., Stenger, D.C. 2013. Roguing with replacement in perennial crops: modeling conditions for successful disease management. Phytopathology. 103:117-128.

Krugner, R., Ledbetter, C.A., Chen, J., Shrestha, A. 2012. Phenology of Xylella fastidiosa and its vector around California almond nurseries: An assessment of plant vulnerability to almond leaf scorch disease. Plant Disease. 96(10):1488-1494.

Nwugo, C.C., Duan, Y., Lin, H. 2013. Study on citrus response to huanglongbing highlights a down-regulation of defense-related proteins in lemon plants upon 'Ca Liberibacter asiaticus' infection. PLoS One. 8(6):e67442.

Wallis, C.M., Wallingford, A.K., Chen, J. 2013. Xylella fastidiosa infection effects on xylem sap and tissue phenolics in different grapevine cultivars. Physiological and Molecular Plant Pathology. 84:28-35.

Nandety, R., Fofanov, V., Koshinsky, H., Stenger, D.C., Falk, B. 2013. Small RNA populations for two unrelated viruses exhibit different biases in strand polarity and proximity to terminal sequences in the insect host Homalodisca vitripennis. Virology. 442:12-19.

Last Modified: 10/18/2017
Footer Content Back to Top of Page