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United States Department of Agriculture

Agricultural Research Service

Research Project: CHARACTERIZATION & EPIDEMIOLOGY OF CITRUS TRISTEZA VIRUS & OTHER INVASIVE & EMERGING GRAFT-TRANSMISSIBLE DISEASES OF CITRUS IN CALIFORNIA

Location: Crop Diseases, Pests and Genetics

Title: Genetic Diversity of Citrus tristeza Virus Isolates Collected Recently in California

Authors
item Yokomi, Raymond
item Saponari, Maria -
item Metheney, Paul -
item Polek, Marylou -
item Vidalakis, Georgios -

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 2009
Publication Date: August 1, 2009
Citation: Yokomi, R.K., Saponari, M., Metheney, P., Polek, M., Vidalakis, G. 2009. Genetic Diversity of Citrus tristeza Virus Isolates Collected Recently in California. Phytopathology 99:S147.

Technical Abstract: Surveys conducted over the past several years show a dramatic increase in Citrus tristeza virus (CTV) incidence in several locations in Central California. Our objective was to assess genetic diversity of current CTV field populations and determine their phylogenetic relationships with representative isolates from collections established over the past 40 years at the Citrus Clonal Protection Program, Riverside, CA and the Central California Tristeza Eradication Agency, Tulare, CA. Over 385 field isolates were assessed by reverse transcription (RT-polymerase chain reaction (PCR), multiple molecular marker analysis, single strand conformational polymorphism and sequencing of the coat protein (CP) and other relevant genes, and quantitative RT-PCR with strain-specific probes. More than 90% of the field isolates had the mild strain T30-like genotype and 37 field isolates contained a non-standard (NS) CTV genotype. Since 2000, field surveys have not detected severe CTV genotypes in either CTV eradicative or non-eradicative pest control districts in Central California. The NS isolates reacted with the CTV monoclonal antibody MCA13 but were typed as mild in biological characterization tests. CP sequence of the NS isolates were most similar to Poncirus trifoliata resistant-breaking CTV strains. Tests are underway to determine if these isolates replicate in P. trifoliata or its hybrids. Sequence comparisons showed that NS genotype isolates have been occasionally intercepted in California since 1993. Knowledge of CTV population structure and dynamics are being used to design more effective strategies to mitigate diseases caused by severe strains of CTV.

Last Modified: 7/28/2014
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