|Yokomi, Raymond - Ray|
|RATTNER, RACHEL - Cooperative Agricultural Support Services|
|HAJERI, SUBHAS - Central California Tristeza Eradication Agency|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/13/2021
Publication Date: 10/6/2022
Citation: Yokomi, R.K., Rattner, R., Hajeri, S. 2022. Estimated incidence and genotypes of CTV in Southern California. California Citrus Conference. Citrus Research Board.
Technical Abstract: A survey was conducted in 2021 to determine the incidence and strains of citrus tristeza virus (CTV) in major citrus-growing counties in California. A hierarchical subsample (HS) method was used where an HS sample is a collection of four leaves per tree from four adjacent trees (a quadrat) and the leaves combined and processed as one sample for CTV tested by Enzyme-linked immunosorbent assay (ELISA). The number of HS samples collected was proportional to the county’s citrus acreage. ELISA-positive samples were further analyzed by Immunocapture Reverse Transcription qPCR with CTV strain-specific primer/probes. Only results from Imperial, Riverside, San Bernardino, and San Diego Counties are presented here. Samples from these counties were collected in spring (May and June) when CTV titer is highest as CTV titer decreases with high temperatures. From a total of 37,090 acres (A) of citrus from the four counties, 1,600 samples were collected from a combined area of 555.3 A which represents 1.5% of the citrus acreage. No CTV was found in Imperial County, but San Bernardino and San Diego Counties had 77.8% and 82.3% CTV-positive trees, respectively. CTV incidence in Riverside County was lower at 37.4% but that was dependent on location with Arlington Heights area with 73% CTV-positive trees. Infection was also cultivar-dependent among orange, grapefruit, lemon, and mandarin cultivars tested with CTV infections of 77.9%, 21.4%; 0%, and 0%, respectively. The T30 genotype was the most common strain at 49.5% but when mixtures with RB, S1, and VT were added, T30 was detected in 93.7% of the CTV-positive trees. The VT strain was also commonly found alone or in mixtures. T36NS strains represented by S1 and RB genotypes were also present as mixtures with T30 and VT genotypes. The T36 strain was rare in this survey. This data will be used in an Environmental Assessment of CTV in California. This research was supported by CRB 5300-210.