|Yokomi, Raymond - Ray|
Submitted to: International Organization of Citrus Virologists Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 8/20/2007
Publication Date: 10/17/2007
Citation: Yokomi, R.K., Polek,, M., Grafton-Cardwell,, B., O'Connell,, N. 2007. Rapid Assessment of the Citrus Tristeza Virus Isolates Detected in Spring 2007 at the Lindcove Research and Extension Center, Exeter, California. In: Proceedings of the 17th Conference of International Organization of Citrus Virologists, October 22-26, 2007, Adana, Turkey. p. 58. Interpretive Summary:
Technical Abstract: Citrus tristeza virus (CTV) was detected in at least 50 trees at the 71 ha Lindcove Research and Extension Center (LREC) near Exeter, Calif. in spring 2007. In the previous 3 years, 3, 1, and 5 trees were infected. The purpose of this research was to assess the aphid transmissibility and molecular genotype of the isolates found at the LREC. Samples from 10 representative infected-trees were collected on May 21, 2007, prior to their removal. ELISA confirmed that all samples were infected. Field flush from 9 source plants were placed in water, caged and exposed to lab-reared cotton aphids for a 24 h virus acquisition period. The aphids were then transferred to Mexican lime seedlings (10 aphids/plant) for a 24 h inoculation period. Transmission was obtained from 5 of the 9 source trees. A 12.5% transmission efficiency was observed from the 5 trees where transmission was achieved. Although fast, this procedure underestimated transmissibility since conditions for virus acquisition could not be optimized. RT-PCR and the multiple molecular marker analysis showed that the genotype of CTV was T30, the typical signature of a mild Florida isolate. Mexican lime index plants showed extremely mild symptoms. CTV disease spread in a 4-year-old, 8 ha plot ~16 km south of the LREC increased from 0.2, 7 and 94% from 2005 to 2007. These data show that CTV isolates capable of rapid spread by aphid vectors now occur. With increased inoculum pressure in this area and abundant vector populations observed, rapid CTV spread will continue due to the absence of infected tree removals.