Location: Crop Diseases, Pests and Genetics
2009 Annual Report
Objective 1: Determine the epidemiology of exotic, emerging, re-emerging, and invasive diseases in California, including (but not necessarily limited to) Xf-caused diseases of horticultural, agronomic, and ornamental crops. Objective 2: Determine the nature and mechanism(s) of susceptibility/resistance to Xf infection and subsequent disease development in horticultural and agronomic crops, including (but not necessarily limited to) Vitis species and Prunus species. Objective 3: Develop effective, economical, environmentally sound strategies to manage exotic, emerging, re-emerging, and invasive diseases, including (but not necessarily limited to) xylella diseases.
Clonal replicates of peach, almond and a hybrid created from them were challenge inoculated with X. fastidiosa. Seedlings from backcrosses of almond hybrid P63-61, almond cultivar Butte, and Prunus webbii have been transplanted to the field to provide future clonal replicates for X. fastidiosa inoculation assays. Plant samples collected in and near almond nurseries were assayed for X. fastidiosa infection to identify potential reservoir hosts that may serve as a source of primary inocula. To date, Xf was detected in Himalayan blackberry in an area highly infested by insect vectors. The role of alfalfa in the epidemiology of xylellae diseases was assessed. Results indicate that alfalfa may serve as a source of insect vectors but is not likely to represent a significant source of the pathogen. Simulation models were used to assess the effectiveness of different management techniques on X. fastidiosa spread. The model indicates that ecological differences among vectors dictate that management practices must be tailored to the specific vector associated with a given crop.
Development of a mechanistic model describing vector transmission of X. fastidiosa to plants continued. Confocal microscopy showed the major enzyme in glassy-winged sharpshooter (GWSS) saliva, beta 1,4-glucanase, is highly concentrated in the deepest, thinnest branches of the salivary sheath. Glucanase loosens and penetrates xylem cell walls, forming a tight bond between sheath and xylem. These results suggest that the enzyme is associated with GWSS access to the xylem and may play a key role in inoculation of X. fastidosa to plants. Mobile genetic elements of X. fastidiosa were characterized. A novel phage of the family Podoviridae was identified by electron microscopy. Sequence analysis indicated that phage DNA is integrated into the X. fastidosa genome. Complete sequence of a 25 kilobase pair plasmid resident in mulberry-infecting strains of X. fastidiosa was determined. The plasmid encoded a DNA transfer system, a plasmid maintenance system, and DNA replication functions. Surprisingly, the plasmid shared extensive sequence identity with a plasmid present in a symbiont of earthworms.
A new virus species infecting GWSS was purified and characterized. The genome of the new virus was completely sequenced and shown to be most closely related to rice dwarf virus. Surveys indicated that the virus is common in California.
Sisterson, M.S. 2008. Egg load dynamics of Homalodisca vitripennis. Environmental Entomology. 37(5):1200-1207(8).
Chen, J., Deng,, X., Liu,, S., Pu,, X., Li,, H., Civerolo, E.L. 2009. A phytoplasma related to Candidatus Phytoplasma asteri is associated with citrus showing Huanglongbing (yellow shoot disease) symptoms in Guangdong, P. R. China. Phytopathology. 99:236-242.
Lin, H., Doddapaneni,, H., Munyaneza, J.E., Civerolo, E.L., Venkatesan, S.G., Buchman, J.L., Stenger, D.C. 2009. Molecular characterization and Phylogenetic analysis of 16S rRNA from a new Candidatus Liberibacter strain associated with Zebra chip disease of Potato (Solanum tuberosum L.) and the potato psyllid. Journal of Plant Pathology. 91:215-219.
Yao, J., Lin, H., Vandeyne, A., Doddapaneni, H., Francis, M., Macedo Lemos, E., Civerolo, E.L. 2008. PrimerSNP: a web tool for whole-genome selection of allele-specific and common primers of phylogenetically-related bacterial genomic sequences. BMC Microbiology, 8:185doi:10.1186/1471-2180-8-185.
De Mello Varani, A., Souza, R., Nakaya, H., De Lima, W., De Almeida, L., Kitajima, E., Chen, J., Civerolo, E.L., Vasconcelos, A., Van Sluys, M. 2008. Origins of the Xylella fastidiosa prophage-like regions and their impact in genome differentiation. PLoS One. 3(12):e4059. doi:10.1371/journal.pone.0004059.
Stenger, D.C., Sisterson, M.S., Krugner, R., Backus, E.A., Hunter, W.B. 2009. A New Phytoreovirus Infecting the Glassy-Winged Sharpshooter (Homalodisca vitripennis). Virology. 386:469-477.
Krugner, R., Groves,, R.L., Johnson,, M.W., Flores,, A.P., Hagler, J.R., Morse,, J.G. 2009. Seasonal Population Dynamics of Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) in Sweet Orange Trees Maintained under Continuous Deficit Irrigation. Journal of Economic Entomology. 102(3):960-973.
Sisterson, M.S. 2009. Transmission of Insect-Vectored Pathogens: Effects of Vector Fitness as a Function of Infectivity Status. Environmental Entomology. 38:345-355.
Sandanayaka, W., Backus, E.A. 2008. Quantitative comparison of stylet penetration behaviors of glassy-winged sharpshooter, Homalodisca vitripennis, on four crop plants important in New Zealand and the USA. Journal of Economic Entomology. 98:787-813.
Deng,, X., Chen, J., Li,, H. 2008. Sequestering and characterization of sequence of a ribosomal RNA operon (rrn) from “Candiatus Liberibacter asiaticus”. Molecular and Cellular Probes. 22:338-340.
Ledbetter, C.A., Chen, J., Livingston, S., Groves, R.L. 2009. Wintercuring of Prunus dulcis cv ‘Butte,’ P. webbii and their interspecific hybrid in response to Xylella fastidiosa infections. Euphytica. Available: http://www/springerlink.com/content/80775k3135586p81/fulltext.html
Cheng, D.W., Lin, H., Walker,, M., Stenger, D.C., Civerolo, E.L. 2009. Effects of Grape Xylem Sap and Cell Wall Constituents on In Vitro Growth, Biofilm Formation, and Cellular Aggregation of Xylella fastidiosa. European Journal of Plant Pathology. 125:213-222.
Krugner, R., Johnson, M.W., Daane, K.M., Morse, J.G. 2008. Olfactory responses of the egg parasitoid, Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae), to host plants infested by Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae). Biological Control. 47:8-15.
Doddapaneni, H., Liao,, H., Lin, H., Bai,, X., Zhao,, X., Civerolo, E.L., Irey,, M., Coletta-Filho,, H., Pietersen,, G. 2008. Comparative phylogenomics and multi-gene cluster analyses of the CitrusHuanglongbing (HLB)-associated bacterium Candidatus Liberibacter. BMC Research Notes, 1:72.
Sisterson, M.S., Yacoub,, R., Montez,, G., Grafton-Cardwell, E., Groves,, R.L. 2008. Distribution and Management of Citrus in California: Implications for Management of Glassy-winged Sharpshooter. Journal of Economic Entomology. 101:1041-1050.
Riaz, S., Tenscher, A.C., Graziani, R., Krivanek, A.F., Ramming, D.W., Walker, M. 2009. Using Marker-Assisted Selection to Breed Pierce’s Disease-Resistant Grapes. American Journal of Enology and Viticulture. 60(2):199-207.
Cabrera-La Rosa,, J., Johnson,, M., Chen, J., Civerolo, E.L., Groves,, R. 2008. Seasonal Population Dynamics of Draeculacephala minerva (Hemiptera: Cicadellidae) and Transmission Efficiency of Xylella fastidiosa. Journal of Economic Entomology. 101(4):1105-1113.