Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2004
Publication Date: 6/20/2004
Citation: Yokomi, R.K. 2004. Transmissibility and genotype analysis of Central California isolates of Citrus tristeza closterovirus. Phytopathology 94:S-131.
Technical Abstract: To ascertain the threat posed by Citrus tristeza closterovirus (CTV) in Central California, spread of CTV was monitored from 1997 to 2003 in selected CTV 'hot spots'. In Tulare Co. where CTV eradication stopped in 1996, incidences up to 42% were found with annual spread rates from 1.6 to 3.6%. In Kern Co. where eradication continues, incidence in a plot in a 4-year-old orchard went from 0 to 5% over a 3-year period before infected trees were eradicated. Fifty field isolates were collected and vector transmissibility examined using standardized conditions and 5 to 10 Aphis gossypii per receptor plant. The isolates fell into two broad transmission categories: low (zero to 8%) and moderately high (16 to 64%) which remained consistent for an isolate (e.g. always high or always low). Nearly all isolates characterized had the same genotype as the T30 mild strain from Florida. A few isolates had a non-standard genotype. Aphid transmission did not result in genotype pattern changes, although some sequence variations did occur with some aphid transmitted sub-isolates. These results show that significant reservoirs of CTV now exist, some isolates are highly aphid transmissible, and the genotype of most local isolates is associated with a mild CTV strain. Efforts are now underway to sequence isolates of high and low transmissibility in an attempt to determine which gene(s) control vector transmission